Systematics, Environment, and Biogeography of Some Late Cambrian and Early Ordovician Trilobites From Eastern New York State

GEOLOGICAL SURVEY PROFESSIONAL PAPER 834

Systematics, Environment, and Biogeography of Some Late Cambrian and Early Ordovician Trilobites From Eastern New York State

By MICHAEL E. TAYLOR and ROBERT B. HALLEY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 834

The environmental setting and regional significance of two trilobite assemblages from shelf deposits of the fVhitehall Formation in the southern Champlain Valley

UNITED STATES GOVERNl\1ENT PRINTING OFFICE, WASHINGTON 197 4 UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress catalog-card No. 73-60031 S

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.35 (paper covers) Stock Number 2401-02459 CONTENTS

Page Page Abstract 1 Systematic paleontology ------­ 18 Introduction 1 Introductory statement ------­ 18 Objectives ------­ 1 Class Trilobita Walch, 1771 ------­ 19 Geologic setting ------­ 1 Family Catillicephalidae Raymond, 1938 --­ 19 Previous work ------­ 2 Genus Acheilops Ulrich, 1931 ------­ 19 Fossil collections ------­ 2 Genus Stenoc.hilina Ulrich, 1931 ------20 Acknowledgments --_------2 Family Heterocaryonidae Hupe, 1953 ______21 Biostratigraphy ------4 Genus Bowmania Walcott, 1925 ------­ 21 Composition of Whitehall fauna ------­ 4 Family Mis,sisquoiidae Hupe, 1953 ------­ 22 Trilobites ---_ ------4 Genus Missisquoia Shaw, 1951 ------22 4 Gastropods ______- --__ ------Family Plethopeltidae Raymond, 1925 ____ _ 23 4 Other fossils ------Genus Plethometopus Ulrich, 1931 23 4 Age and correlations ------­ Genus Plethopeltis Raymond, 1913 ---­ 25 Problems and methods ------4 Family Ptychaspididae Raymond, 1924 ---­ 26 6 Saukia Zone ------­ Subfamily Ptychaspidinae Longacre, Missisquoia Zone ------­ 6 26 Symphysurina B Zone ( ?) ------8 1970 ------Genus Euptychaspis Ulrich, 1931 ----- 26 Cambrian-Ordovician boundary ------­ 8 Subfamily Saukiinae Ulrich and Resser, 1933 27 Summary ------9 27 Environmental setting ______----- 9 Genus Calvinella Walcott, 1914 ------­ Petrology ______Genus Ulrich and Resser, 9 Prosaukia 28 Inferred environments ------10 1933 ------Biofacies distribution ------12 Family Solenopleuridae Angelin, 1854 ------31 Genus Hystricurus Raymond, 1913 ----- 31 ~odels ------12 ~ethods of analysis ------13 Description of fossil localities ------32 Assemblages similar to Whitehall fauna ______13 References cited ______--__ ---- 33 Assemblages dissimilar to Whitehall fauna ____ _ 16 Index ------37

ILLUSTRATIONS

[Plates foHow index]

PLATE 1. Plethopeltis, Acheilops, Stenochilina, and Plethometopus. 2. "Calvinella," Euptychaspis, BoH)mania, and "Prosaukia." 3. Missisquoia and Hystricurus. 4. Photomicrographs of petrographic thin sections.

Page FIGURE 1. Geologic map showing fossil localities discussed in text ------­ 3 2. Columnar section showing typical repetition o.f components in limestones of the lower Whitehall Forma- tion ------10 3-5. Photograph showing- 3. Sharp vertical contact between crossbedded grainstone and finer grained clotted thrombolitic fabric ------10 4. Domal stromatolites in the lower part of the Whitehall Formation ------· 11 5. Domal thrombolite in the lower Whit·ehall Formation ------­ 11 6. Map showing the general location of principal areas of North America from which Saukia. Zone faunas have been reported ------­ 14 III IV CONTENTS TABLES

Page TABLE 1. The occurrence of identified taxa in samples studied and the inferred biostratigraphic zonal assignment__ 5 2. Comparison of the biostratigraphic ranges of trilobite species and genera from the Whitehall Formation with occurrences in the central Great Basin, central Texas, and south-central Oklahoma ______7 3. Known occurrences of trilobite sp,ecies recognized from the Saukia Zone at Whitehall, N.Y ------16 4. Known North American occurrences of trilobite genera recognized from the Saukia Zone at Whitehall, N.Y ------17 SYSTEMATICS, ENVIRONMENT, AND BIOGEOGRAPHY OF' SOME LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES FROM EASTERN NEW YORK STATE

By MICHAEL E. TAYLOR and RoBERT B. HALLEY 1

ABSTRACT INTRODUCTION

The Whitehall Formation in Washington County, eastern OBJECTIVES New York Sta:te, has yielded two assemblages of trilobites, gastropods, and other fossHs, which are assigned to the Late Cambrian and Early Ordovician fossils from Saukiella serotina Subzone of the Saukia Zone (Late Cam­ the Whitehall area of Washington County, eastern brian, Trempealeauan Stage) and to the M issisquoia Zone (Early Ordovician, Canadian Series). These occurrences New York State, were studied to : ( 1) provide a suppor,t D. W. Fisher's interpretation that the Cambrian­ more refined biostratigraphic classification of the Ordovician boundary, as currently recognized in North Whitehall Formation than has been previously possi­ America, is within the Whitehall Formation. ble, (2) document the environmental setting of the The lower part of the Whitehall contains domal s1tromato­ Whitehall faunas, and (3) determine the biofacies lites, thrombolites, and lime grainstones interpreted to have formed in supvatidal, intertidal, and shallow-subtidal marine relationship of the Whitehall Late Cambrian faunas environments. The vagile epibenthic fauna probably occupied relative to other known areas in North America. warm-water, nearshore, shallow-subtidal habitats char­ Study of the sedimentary environments of the acterized by sustained moderate to high turbulence. Some Whitehall Formation was begun by Halley as part limestone beds contain length-slow chalcedony which is thought to be an indicator of general hypersalinity or widely of a graduate research project at Brown University fluctuating salinity conditions in the environment of deposi­ (Halley, 1971a). During the course of his fieldwork, tion. Halley collected fossils and made preliminary identi­ Comparison of the Trempealeauan taxa from the White­ fications of the trilobites. The fossils were later sent hall with other occurrences in North America suggests that to Taylor in February 1971 for examination and the fauna is part of a shelf biofacies commonly occurring in are,as of shallow-water carbonate deposition. The shelf­ proved similar to some currently being studied from carbonate biofacies contrasts markedly with Trempealeauan the Great Basin (Taylor, 1971). In this report Tay­ trilobite ass,emblages that occupied sites of basinal sedimen­ lor has taken responsibility for taxonomic, biostrati­ tllltion. graphic, and biogeographic aspects and Halley, for The Whitehall faunas s,tudied contain 12 species of trilo­ bites, 2 of which are indeterminate; at least 10 species of stratigraphic occurrence, description, and environ­ gastropods; Matthevia sp.; 2 species of Ribeiria, including mental analysis of rocks of the Whitehall Formation. Ribeiria cf. R. nuculiti/ormis Cleland, 1900; and 1 hyoli­ thoid. Formal descriptions of trilobite's are given. Seven GEOLOGIC SETTING trilohiEarth and Space Sciences, State University of New York, Stony Brook, NY 11790. of Cambrian-Ordovician miogeosynclinal carbonate 1 2 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE and terrigenous clastic rocks which crop out between crops in the vicinity of Whitehall and collected two Precambrian rocks of the Adirondack Mountains to samples (7098-CO, 7099-CO) from the upper part the west and the Cambrian-Ordovician Taconic se­ of the type section at Skene Mountain (fig. 1). quence on the east (Theokritoff, 1964; Fisher, 1969). Search of U.S. Geological Survey fossil collections General geologic setting of the area is shown on the in Washington, D.C., yielded several samples from Adirondack Sheet of the Geologic Map of New York the Whitehall area that proved relevant to this (lsachsen and Fisher, 1971), and the regional tec­ study. They include one sample collected by C. D. tonic significance of the Whitehall area has been Walcott ( 418e), probably early in the 1900's, and recently discussed by Rodgers (1970). The general several collections made by E. 0. Ulrich, Josiah location of the area studied and the geographic and Bridge, and Rudolph Ruedemann in 1931 (470b, geologic setting are shown in figure 1. 470b1J 473f). The general geographic and geologic setting of the samples is shown in figure 1. Detailed PREVIOUS WORK locality information is given on page 32. The stratigraphy of the Whitehall area was de­ Trilobites illustrated in this report are in the col­ scribed by Rodgers (1937). He named the Whitehall lections of the Department of Paleobiology, U.S. Formation for an easterly dipping sequence of inter­ Museum of Natural History (USNM), Washington, bedded sandstone, dolostone, and limestone cropping D.C. Silicon rubber positive replicas of the illus­ out on Skene Mountain at the east edge of the village trated specimens and representative nonillustrated of Whitehall, Washington County, N.Y. (fig. 1). material have been deposited in the New York State The base of the formation is exposed on the west Museum, Albany, N.Y. All other nonillustrated ma­ side of Skene Mountain about 120 feet below the terial is in the trilobite collections of the U.S. Geo­ crest (D. W. Fisher, written commun., 1972), and logical Survey, Washington, D.C. the top is exposed east of Skene Mountain (Rodgers, 1937) in the shallow valley occupied by Norton Road ACKNOWLEDGMENTS (Washington County Route 9A). Wheeler (1942) formally recognized two members The authors especially wish to thank Donald W. of the Whitehall Formation, a lower Hoyt Member Fisher for making available unpublished data on and an upper Skene Member. Fisher (1956, 1968, the Cambrian-Ordovician rocks and fossils of the 1969) summarized the stratigraphy and rock-nomen­ Whitehall area and for his generosity in allowing clatural history of the Whitehall area and is current­ us to publish a geologic index map prepared from ly engaged in detailed stratigraphic studies of Cam­ his unpublished field data. Ellis L. Yochelson is brian and Ordovician rocks in the region (D. W. thanked for providing gastropod identifications and Fisher, written commun., 1971). John Pojeta, Jr., for identifying Ribeiria nuculiti­ Cambrian fossils from the Whitehall area were formis Cleland. John H. Shergold originally pointed described by Walcott (1912b) from possibly what out the general similarity between Missisquoia and are now termed the Potsdam and Ticonderoga For­ Parakoldinioidia. Taylor wishes to thank A. J. mations. The described fossils are older than those Rowell for several stimulating discussions on Late reported here. Wheeler (1941, 1942) was apparently Cambrian biogeography. the first to report Trempealeauan fossils from the Halley thanks Conrad D. Gebelein, Donald W. Whitehall area, but his discoveries were never Fisher, and A. R. Palmer for guidance in the field documented. and Leo F. Laporte who supervised thesis research which led, in part, to the present report. The New FOSSIL COLLECTIONS York Geological Survey provided field funds to Hal­ Fossil collections used in this study came from ley during 1970. three general sources. Robert B. Halley collected Persons to whom we are grateful for reading several fossil samples from the Whitehall Formation various versions of the manuscript and offering use­ at Crossman quarry (H-1) and Warner Hill (H-2, ful suggestions include: A. K. Armstrong, D. W. H-3), north of the village of Whitehall, N.Y., dur­ Fisher, J. F. Mello, A. R. Palmer, R. A. Robison, ing 1970. The senior author spent several days dur­ R. J. Ross, Jr., J. H. Shergold, J. H. Stitt, and E. L. ing fall 1971 examining Whitehall Formation out- Yochelson. INTRODUCTION 3

EXPLANATION

>­ AUTOCHTHONOUS SEQUENCE !{ D BEDROCK COVERED 6 Unconformity = rs :. A FORT CASSIN FORMATION :~ Disconformity ~ 8--- --i FORT ANN FORMATION

kf£n1 CUTTING FORMATION Disconformity ~ Upper part} WHITEHALL il EEill ~~:;~::~OG:OF::T~::N ~ 1::::::\:1 POTSDAM SANDSTONE s:: Nonconformity ~~{ l;:;::J METAMORPHICROCKS d

ALLOCHTHONOUS SEQUENCE 43°32'30" Thrust or reverse fault - Sawteeth + . TACONIC SEQUENCE on upper plate. Dashed where [8] approximately located Contact - Dashed where D TACONIC MELANGE approximately located ~ Quarry Inferred fault ,/6 Strike and dip of beds Normal fault ~ Hachures on TTTT relatively downdropped side 470b X Foss~'llocality 0 1 MILE VT

0 L/2 1 KILOMETER Whitehall 1~'~'~'~1-LI ______~I area CONTOUR INTERVAL 100 FEET ~

FIGURE !.-Geologic map showing fossil localities discussed in text. Detailed locality description are given on pages 32 and 33. Geology is generalized from unpublished geologic maps made available through the courtesy of D. W. Fisher, New York State Museum and Science Service, Albany, N.Y. Base from Whitehall and Thorn Hill, New York-Vermont 772-minute quadrangles. 4 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

BIOSTRATIGRAPHY Sample 470bl from the hill between Skene Moun­ tain and Crossman quarry and samples 7098-CO COMPOSITION OF WHITEHALL FAUNA and 7099-CO from Skene Mountain contain Missis­ The fauna here reported from the Whitehall For­ quoia typicalis Shaw. The·se samples all contain mation consists of 12 species of trilobites, two of abundant and abraded trilobite debris, but M. typi­ which are indeterminate, at least 10 species of gas­ calis is the only trilobite taxon recognized. tropods, fragmentary material referred to the prob­ Sample H-2 from the southwest side of Warner lematical mollusk Matthevia, one indeterminate hyo­ Hill contains Hystricurus millardensis Hintze and lithoid, and several bivalved fossils assigned to three specimens questionably assigned to M issis­ Ribeiria sp. and Ribeiria cf. R. nuculitiformis Cle­ quoia typicalis Shaw. Hystricurus was not recog­ land. Formal systematic descriptions are given for nized in any other Whitehall samples studied. the trilobites. All taxa recognized are listed in table GASTROPODS 1 except those from locality 418e, which is discussed below. Gastropods were not studied in detail. However, identifications kindly provided by E. L. Yochelson TRILOBITES (written commun., Dec. 1971 and Oct. 1972) and data on associations are given in table 1. Fossil sample H-3 from the Whitehall Formation on the north end of Warner Hill contains the most OTHER FOSSILS diverse trilobite assemblage of those samples studied. Hyolithoids occur rarely in sample H-3, and frag­ The sample contains Acheilops masonensis Winston mentary material attributed to M atthevia occurs in and Nicholls, "Calvinella" prethoparia Longacre, sample 4 70b. Several bivalved fossils attributed to Euptychaspis typicalis Ulrich, Plethopeltis sp. in­ Ribeiria sp. occur in sample 4 70b, and John Poj eta, det., and "Prosaukia" spinula Taylor, n. sp. Sample Jr. (oral commun., 1972), identified Ribeiria cf. R. H-1 from Crossman quarry is similar in taxonomic nuculitiformis Cleland from sample 7098-CO. These composition but lacks Plethopeltis and Acheilops fossils were not studied in detail. masonensis and includes Bowmania cf. B. pennsyl­ vanica Rasetti. Sample 473f, probably collected near AGE AND CORRELATIONS Crossman quarry, contains Euptychaspis typicalis, Plethometopus obtusus Rasetti, Plethometopus sp. PROBLEMS AND METHODS A, and cf. "Prosaukia" spinula. Locality 470b, from Biostratigraphic studies in the Upper Cambrian the low hill between Skene Mountain and Crossman and Lower Ordovician of Washington County, N.Y., quarry, contains Acheilops masonensis, Euptychas­ are complicated by discontinuous outcrops resulting pis sp. indet., and "Prosaukia" spinula. from faulting and by vegetation and soil cover. As Inspection of table 1 shows that samples H-3, a result, it is commonly necessary to study fossils H-1, 4 73f, and 4 70b are similar in taxonomic com­ from isolated exposures or single horizons which are position but are not identical. The geographic difficult to relate to one another. This general prob­ proximity and taxonomic overlap suggests that dif­ lem has been compounded in rocks of latest Cam­ ferences between localities may reflect only sampling brian age (Trempealeauan Stage) by the general differences at approximately the same biostrati­ lack of a practicable biostratigraphic scale for sub­ graphic horizon. Alternatively, the differences in dividing the sequence. Trilobite zonal schemes for taxonomic composition could reflect differences in the type area of the Late Cambrian Trempealeauan species range in the local stratigraphic sequence or Stage in the Upper Mississippi .Valley (Howell and local environment~l factors. The latter alternatives others, 1944; Raasch, 1951; also see Nelson, 1953) cannot be ruled out at p;·esent. have not been successfully applied to other regions Sample 418e, from northeast of Whitehall (exact because oflack of systematic treatment of much of locality unknown), contains Stenochilina sp. A, in the fauna and perhaps because of biofacies association with the gastropods ?Schizopea sp. and differences. Dirachopea sp. Stenochilina was not found in any In recent years, research in highly fossiliferous other Whitehall samples, so its occurrence relative to sections of latest Cambrian (Trempealeauan Stage) other samples cannot be inferred at present. and earliest Ordovician carbonate rocks outside the BIOSTRAT1GRAPHY 5

TABLE 1.-The occurrence of identified taxa in samples studied and the inferred biostratigraphic zonal assignment [The stratigraphic sequence of samples is inferred from an interpretation of tr:lobite species associations compared with occurrences in other areas (s_ee text). Explana.tion _of s~mbols: ::<, established occurrence, identification definite; cf., established occurrence, identification tentative; ?, esta­ blished occurrence, IdentificatiOn questwnable. Mollusks were identified by Ellis L. Yochelson (written commun., December 1971, October 1972]

Series ------Upper Cambrian Lower Ordovician Formation ------Whitehall Part ------___ ----_____ ----- Lower part Upper part

Zone ------Saukia M issisquoia

Subzone ------Saukiella Saukiella Saukiella Corbinia pyrene iunia serotina apopsis Not established I 0 0 Not 0 0 Not recognized reco!Plized ... I I Fossil locality ------..Q ..Q 00 0 0 t­ t­ "'0 0 .... "'<11 "'t- "'t-

Trilobites: Acheilops masonensis Winston X X and Nicholls. Bowmania cf. B. pennsylvanica X Rasetti. "Calvinella" prethoparia Longacre X X Euptychaspis typicalis Ulrich ---­ X X X Euptychaspis sp. indet ------­ X Hystricurus millardensis Hintze __ ·------X Missisquoia typicalis Shaw ------X X X ? Plethometopus obtusus Rasetti __ _ X Plethometopus sp. A ------­ X Plethopeltis sp. indet ------­ X "Prosaukia" spinula Taylor, n. sp _ X X cf. X 1 Stenochil,ina sp. A ------Gastropods: Dirachopea sp ------­ X X High-spired gen. and spp. indet __ X X X X Low-spired gen. and sp. indet __ _ X ?Lytospira sp ------­ X ?Matherella sp ------­ X "Murchisonia" sp ------­ ? X Pleurotomariacean gen. indet ----­ X Schizopea sp. A ------­ X X Schizopea sp. B ------­ ? X ?Sinuopea sp ------X Other mollusks: Hyolithoid ------­ X Matthevia sp ------­ X Ribeiria cf. R. nuculitiformis X Cleland. Ribeiria sp. indet ------X

10ccurs in sample 418e, see text. Upper Mississippi Valley region has focused on the ( 1971) showed that a similar fourfold subdivision problem of developing a regionally practicable bio­ of the Saukia Zone can be recognized in the east­ stratigraphic scheme for correlation. This research, central Great Basin, and Derby and others (1972) largely a result of the efforts of Prof. W. Charles have recognized some of the subzones in southern Bell and his students, has resulted in a fourfold Alberta, Canada. biostratigraphic subdivision of the Trempealeauan The Whitehall faunas show a strong biogeographic ( =Saukia Zone) based on local ranges and associa­ similarity to faunas from Oklahoma, Texas, and the tions of trilobite species in the Wilberns Formation Great Basin (discussed under "Biofacies Distribu­ of central Texas (Bell and Ellinwood, 1962; Winston tion)." As a consequence, it is possible to infer a and Nicholls, 1967). Longacre (1970) refined and subzonal assignment for the Whitehall samples by provided additional information on the Texas fossil comparing taxonomic associations with relative sequence, and Stitt (1971) established a similar ranges of the same taxa in known sequences. The zonal scheme for the limestones of the Fort Sill and relative ranges of Whitehall species that also occur Signal Mountain Formations of south-central Okla­ in the Great Basin, central Texas, and south-central homa. Independent concurrent work by Taylor Oklahoma, are given in table 2 as are the ranges of

527-763 0 - 7-± - 2 6 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

genera common to.. the three regions. M atthevia, and Pelagiella. Of these molluscan taxa, only M atthevia and one specimen questionably as­ SAUKIA ZONE signed to M atherella were recognized in the White­ hall samples studied. Relative ranges of species within the Saukia Zone The Hoyt fauna from Saratoga County, N.Y., con­ as recognized in the Great Basin, central Texas, and tains trilobite forms that do not occur in the de­ south-central Oklahoma, provide a basis for infer­ scribed faunas from Oklahoma, Texas, or the Great ring the age of the Whitehall trilobites. Inspection of Basin. As a result, it is not now possible to assign table 2 shows that relative ranges of most taxa the Hoyt fauna to any of the subzones of the Saukia overlap in the Saukiella serotina Subzone of the Zone. Therefore, although faunas from the Hoyt Saukia Zone. The comparison is strongest with sam­ Limestone and lower Whitehall Formation can be ple H-3 from Warner Hill. Samples H-3 and H-1 assigned to the Trempealeauan Stage, it is not yet could be assigned to the Saukiella junia Subzone, but possible to document on paleontological evidence this alternative seems less likely because of the oc­ which parts of these two formations are currence of ucalvinella" prethoparia, a species ap­ synchronous. parently restricted to the Saukiella serotina Sub­ Lochman (1946) described and illustrated Pro­ zone. saukia briarcliffensis and Plethometopus knopfi Inspection of the relative ranges of genera (table from the Briarcliff Dolomite near Pine Plains in 2) shows that most are too long ranging to be of Dutchess County, N.Y. The fauna can be assigned to value in subdividing the Saukia Zone. ucalvinella" the Saukia Zone, but further refinement in classifi­ may be an exception, as its known occurrence is re­ cation cannot be made at present. stricted to the Saukiella serotina Subzone in these Dwight (1886a, b; 1887) reported a rich collec­ areas. However, this apparent restriction is proba­ tion of trilobites from outcrops near Poughkeepsie, bly a reflection of the occurrence of a group of forms Dutchess County, N.Y., which he (1887, p. 208) similar to "C." prethoparia in the three areas. Cal­ correlated with the Hoyt fauna at Saratoga Springs vinella s. l. is a very broadly circumscribed genus (then called "Potsdam limestone"). Apparently the which needs comprehensive reevaluation before em­ Poughkeepsie fauna has been neither described nor phasis can be placed on the occurrence of the genus illustrated so that further comparison cannot be alone. (See further discussion under "Systematic made at present. Descriptions.") Bird and Rasetti (1968) listed several occurrences Sample 418e contains Stenochilina, a genus of of probable Trempealeauan fossils from the Taconic catillicephalid trilobite that occurs in association sequence of Columbia County, eastern New York with Saukia Zone faunas reported from the Cono­ State. Examination of the material showed that the cocheague Limestone of Maryland (Rasetti, 1959, p. collections contain no genera or species in common 383) and the Eminence Dolomite of southeastern with the Whitehall fauna. The Taconic localities con­ Missouri (Ulrich, 1930, p. 215). These occurrences tain genera typical of the Hungaia magnifica fauna establish the Trempealeauan age of the sample, but (Bird and Rasetti, 1968, p. 45), but the full sig- data are insufficient to assign it to a subzone. nificance of the occurrences must await formal de­ Saukia Zone trilobites have been described and il­ scription of the fossils. lustrated by Walcott (1879, 1912b) from the Hoyt Limestone near Saratoga Springs, N.Y. Some addi­ MISSISQUOIA ZONE

tional Late Cambrian fossils from the Saratoga Sample 470b11 from the low hill between Skene Springs area were illustrated by Rasetti (1946) and Mountain and Crossman quarry, samples 7098-CO by Fisher and Hanson (1951). Our Late Cambrian and 7099-CO from the upper part of the Whitehall collections from the Whitehall Formation were com­ Formation on Skene Mountain, and questionably pared with the material in the U.S. National Muse­ sample H-2 from Warner Hill, contain Missisquoia um collections studied by Walcott ( 1912b). The typicalis Shaw in association with abundant gastro­ examination showed that available collections from pods. (See table 1.) Missisquoia typicalis was origi­ the two areas contain no trilobite species in common. nally described from the Highgate Formation of The mollusks reported by Walcott (1912b) from the northwestern Vermont (Shaw, 1951, 1955, 1958). Hoyt include species of Triblidium, JU atherella, Subsequently, the species was reported from the BIOSTRATIGRAPHY 7

TABLE 2.-Comparison of the biostratigraphic ranges of trilobite species and genera from the Whitehall Formation with occurrences in the central Great Basin, central Texas, and south-central Oklahoma [No attempt has been made to depict differences between regioJU> in local range within Cambrian subzones or Early Ordovician zones] Explan'ation of symbols: E9 Great Basin (Hintze, 1952; Taylor 1971. * Centra.! Texas (Winston and Nicholls, 1967; Longacre, 1970). C South-central Oklahoma (Stitt, 1971).

Epoch ------Late Cambrian Early Ordovician Symphy- Zone ______---_ ------Saukia Missi8quoia surina B

Subzone ------Saukiella Saukiella Saukiella Corbinia pyrene junia serotina apopsi8 Not established Species: E9 Acheilops masonensis Winston and Nicholls 0 0 * E9 * Bowmania pennsylvanica Rasetti ------0 0 *0 0 "Calvinella" prethoparia Longacre ------E9 *E9 Euptychaspis typicalis Ulrich ------*0 0 E9 Hystricurus millardensis Hintze ------0 E9 * Missisquoia typicalis Shaw ------*0 Plethometopus obtusus Rasetti ------*0 * 0 Plethometopus sp. A ------"Prosaukia" spinula Taylor, n. sp ------Stenochilina sp. A ------Gener~ E9 E9 E9 Acheilops Ulrich ______0 * 0 * ? E9 E9 Bowmania Walcott ------0 0 0 0 *E9 "Calvinella" Walcott 0 EB E9 *(f) Euptychaspis Ulrich ------* *0 * 0 (f) (f) Hystricurus Raymond 0 E9* * Missisquoia Shaw ------0 ? E9 EB * Plethometopus Ulrich 0* * *0 *0 Plethopeltis Raymond ______--______--- E9 E9 0 E9 "Prosaukia" Ulrich and Resser ------* 1* 0 Stenochilina Ulrich 1 Also reported in pre-Saukiclla pyrene beds. Wilberns Formation of central Texas (Winston and subjacent Corbinia apopsis Subzone of the Saukia Nicholls, 1967). Winston and Nicholls (p. 72) Zone and a superjacent zone consisting of an associa­ showed that part of the Wilberns Formation con­ tion of species of Clelandia, Hystricurus, Jujuyaspis, tains an assemblage of trilobites consisting of species Homagnostus, and Symphysurina. Winston and of Homagnostus, Hystricurus, Symphysurina, High­ Nicholls (1967) considered the latter association gatella, Missisquoia, and Parabolinella. The associa­ most similar to the Symphysurina B Zone of Ross tion, named the Missisquoia Zone, occurs strati­ (1951) and Hintze (1952). graphically between faunas characteristic of the N orford ( 1969) reviewed the known distribution 8 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE of some Early Ordovician trilobites in North Ameri­ because: ( 1) species of Symphysurina seem to occur ca and concluded that the Missisquoia and Symphy­ earlier in central Texas and south-central Oklahoma surina Zones of Winston and Nicholls (1967) to­ in association with Missisquoia typicalis, and (2) gether probably represent Zone A of Ross (1951). Lochman and Wilson (1967, p. 893) reported that Evidence for this interpretation is the reported oc­ an undescribed species of Apoplanias may be pres­ currence of Hystricurus cf. H. sp. D of Ross in both ent in association with Saukia Zone assemblages in the Missisquoia and Symphysurina zones of Winston central Montana. and Nicholls. H ystricurus sp. D of Ross is other­ In summary, the known biostratigraphic occur­ wise known from Zone A of Ross (1951, p. 29) near rences of M issisquoia typicalis are restricted to the the base of the Garden City Formation in south­ Missisquoia Zone as originally defined in North eastern Idaho. This evidence is considered tenuous, America. The upper Whitehall occurrences are ten­ and we prefer to recognize the Missisquoia Zone as tatively assigned to the zone on this basis. originally defined by Winston and Nicholls (1967). SYMPHYSURINA B ZONE(?) Stitt (1971) studied the biostratigraphy of Late Cambrian and Early Ordovician trilobites in the Sample H-2 from the upper part of the Whitehall western Arbuckle Mountains of south-central Okla­ Formation at Warner Hill contains H ystricurus homa. He reported a trilobite association that in­ millardensis Hintze, Missisquoia typicalis Shaw ( ?) , cludes species of Hystricurus, Symphysurina, Mis­ and several poorly preserved gastropods. Hystricur­ sisquoia (including M. typicalis), Apoplanias, us millardensis was originally reported from the Homagnostus, and Plethopeltis, which he assigned Symphysurina B Zone in the southern House Range to the Missisquoia Zone. The Mi.~sisquoia Zone as­ area of west-central Utah (Hintze, 1952). Subse­ semblage occurs in the Signal Mountain Limestone· quently, the species was recognized in the Symphy­ where it is underlain by assemblages assigned to the surina Zone of central Texas (Winston and Nicholls, Corbinia apopsis Subzone. Beds immediately above 1967) and south-central Oklahoma (Stitt, 1971). the M issisquoia Zone are only sparsely fossiliferous, This apparent restriction of H. millardensis to the so that the top of the zone is poorly defined in Symphysurina B Zone provides limited evidence for Oklahoma. inferred presence of the zone in the upper part of the The Missisquoia Zone also occurs in the uppermost Whitehall Formation. Alternatively, the absence of Symphysurina and presence of Missisquoia typi­ part of the Notch Peak Limestone in the southern calis ( ?) in sample H-2 is suggestive of the Missis­ House Range of west-central Utah (Taylor, unpub. quoia Zone. Sample H-2 is tentatively assigned to data, 1971) . The Notch Peak contains an associa­ the Missisquoia Zone for this reason, although fur­ tion of species of Highgatella, Hystricurus, JJ!issis­ ther collecting at Warner Hill is necessary to verify quoia (including M. typicalis), and Symphysurina, the zonal assignment. which overlies Corbinia apopsis Subzone assem­ blages. The Notch Peak Limestone is conformably CAMBRIAN-ORDOVICIAN BOUNDARY overlain by the House Limestone, in the lower part The base of the Ordovician System in North of which Hintze (1952) originally established the America has been traditionally recognized by the presence of the Symphysurina B Zone in western lowest occurrence of Symphysurina (Ross, 1951; Utah. Hintze, 1952; Bell and others, 1956; Palmer, 1971a; Derby, Lane, and Norford (1972) reported a Lochman, 1971), even though the position of the Missisquoia Zone fauna from the Survey Peak For­ boundary probably differs from that in the classic mation in the southern Rocky Mountains of Alberta. areas of Europe (Whittington and Williams, 1964; The listed fauna contains species of Apoplanias, Whittington, 1966). The M1:ssisquoia Zone contains Missisquoia (tentatively referred to M. typicalis), the earliest known occurrence of Symphysurina in Highgatella, and a large number of nontrilobite taxa. North America (Winston and Nicholls, 1967; Stitt, Derby, Lane, and Norford (1972) redefined the 1971; Taylor, 1971), although not at the base (Der­ Missisquoia Zone to coincide with the biostrati­ by and others, 1972), and is therefore tentatively graphic interval between the first occurrence of accepted here as the earliest trilobite assemblage Apoplanias and the first occurrence of Symphysurina zone of the Ordovician System in North America. As in the Survey Peak Formation. The regional prac­ so recognized, the Cambrian-Ordovician boundary ticability of this redefinition remains to be proved falls within the Whitehall Formation in Washington ENVIRONMENTAL SETTING 9

County, N.Y. (Fisher, 1968, 1969), rather than at parts of North America (see "Biofacies Distribu­ the base (Rodgers, 1937; Fisher, 1962) or top tion") adds credence to the interpretation that fos­ (Wheeler, 1942; Flower, 1964) of the formation, as sils were not transported great distances before had previously been thought. Available biostrati­ burial. (Also see Mudge and Yochelson, 1962, p. graphic data are not sufficiently refined at present 108.) Such recurrent associations of vagile epiben­ to determine how closely the boundary between lower thic taxa may be considered parautochthonous faun­ and upper parts of the formation approximates the ules. However, the inferred correlation between a systemic boundary. particular faunule and a particular environment SUMMARY should be accepted only cautiously because of the possibility that bioclastic debris accumulated near, The age of fossil samples from the Whitehall For­ but not necessarily in, the precise microenvironment mation in eastern New York is inferred from the occupied by the living organisms. known range of species in biostratigraphic se­ In spite of the tenebrous influence of biostrati­ quences in other areas. On this basis, samples can nomic factors, the fossil-enclosing rocks are thought be grouped into two taxonomic assemblages. The to contain the best independent evidence currently older assemblage from the lower part of the White­ available for deducing the physical environment oc­ hall is assigned to the Saulciella serotina Subzone of cupied by the fossils. Comparisons can be made be­ the Late Cambrian Saulcia Zone, and the younger as­ tween observed depositional features of the White­ semblage from the upper part of the Whitehall is hall and those of recent and other ancient carbonate assigned to the earliest Ordovician Missisquoia Zone. sediments and rocks to provide a basis for infer­ The Corbinia apopsis Subzone, which normally oc­ ences concerning some aspects of the environment in curs between the Saulciella serotina Subzone and which the Whitehall organisms lived. Thus, here we Missisquoia Zone, has not yet been recognized in review those aspects of the limestones, based on New York State. Biostratigraphic classification of Halley's (1971a) detailed study, which might have the Whitehall fossil samples is shown in table 1. particular relevance to the environmental setting of the Whitehall fauna, rather than present a de­ ENVIRONMENTAL SETTING tailed petrographic description of the Whitehall Fossils described in this paper were collected from Formation. limestones within the Whitehall Formation or from loose blocks presumed to be derived from the White­ PETROLOGY hall. The fossils mostly occur as poorly sorted bio­ The bulk of the limestones examined from the clastic debris in beds composed of ooid-skeletal lime Whitehall consist of grainstones and boundstones (in grainstone. All fossils studied represent vagile epi­ the carbonate rock classification of Dunham, 1962). benthos that were presumably highly susceptible to These are the predominant lithologies of the ex­ post-mortem transport and mixing that could poten­ posures at Crossman quarry (fig. 2), the upper tially obscure original natural spatial relationships slopes of Warner Hill, Skene Mountain, and Tub between organisms and environments. The frag­ Mountain. (See fig. 1.) Constituent particles of the mented condition of most trilobite exuviae is usually grainstones in order of decreasing abundance are evidence that some mechanical degradation occurred ooids, lithoclasts, pelletoidal grains, quartz grains, before burial. However, the very poor sorting and and trilobite and gastropod fragments. (See pl. 4.) common association of a wide variety of grain Chert, length-slow chalcedony, pyrite, dolomite, and shapes with presumably different hydrodynamic chlorite are minor (less than 1 percent) diagenetic properties suggests that distances of post-mortem minerals present. The Whitehall grainstones occur transport were probably short, perhaps on the order as individual beds or as fill betw2en boundstone of tens of feet rather than thousands of feet or miles. structures (fig. 3). Beds composed entirely of grain­ This conclusion is consistent with the findings of stone are 2-24 inches thick, uniform in thickness for Ginsberg (1956), who showed that the bulk of skele­ the length of outcrop (as much as 100 yards), and tal carbonate grains in the Florida reef tract coarser often have either low-angle crossbedding or planar than one-eight of a millimeter accumulate in the sub­ bedding. environment in which the grains originate. The fact Boundstones of the Whitehall Formation are that taxonomic associations similar to those in the thought to be cryptalgal structures (Aitken, 1967; Whitehall can be recognized in widely scattered Halley, 1971b) formed by the sediment-binding and 10 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

are spar rich and are not grain supported (pl. 4, EXPLANATION ... (\ . {\ fig. 5). The second type of nonlaminated cryptalgal 'Q.' ·r.·:·'l(, • • •• LIMESTONE COMPONENTS structure consists of lime mudstone mounds without • •• Q. .·,..., •• "". • • • •G!. • clastic textures. These structures are less common "( .. I"n" ISKELETAL GRAINS and also have clotted fabric. However, the light-gray clots in mudstone mounds are internally grain-filled fenestrae as much as 1 inch long in the largest di­ ~OOIDS mension. Some fenestrae have spar-filled geopetal surfaces (pl. 4, fig. 4). The matrix of nonlaminated D PELLETS AND LITHOCLASTS mounds is finely crystalline to aphanocrystalline, dark gray to black, the finer grained patches being ~ QUARTZ SAND GRAINS darker in color value. Individual grains are rarely recognized in lime mudstone mounds outside of the ~ CHERT AND CHALCEDONY grain-filled fenestrae. The Whitehall grainstones and three types of

• ;, .. .. • • 0 ~ 0 STROMATOLITES boundstones recur vertically in beds a few inches to • • 0 0 0 • • •• several feet thick (fig. 2). This phenomenon was • • • 0 • 0 •• 0

•• 0 • • 0 • interpreted (Halley, 197la) to have been produced THROMBOLITES • . . r'\ • I6P3I by oscillations of the strandline. . o:Q. o~Q· ~ ·. · r"\ · · . · __._Fossil locality H-1 1 METER 0 0 • .6. . • • .' . • t2 FEET INFERRED ENVIRONMENTS ·.8·. The depositional environments of the Whitehall ·~ t.J.ilj I Formation may be inferred from comparisons with I .. recent and ancient carbonate deposits. Domal high­ 0 relief stromatolites have been reported forming to­ 0 day in the intertidal zone of Hamelin Pool, a FIGURE 2.-Columnar section showing typical repetition of hypersaline lagoon in Shark Bay, Western Australia components in limestones of the lower Whitehall Forma­ (Logan, 1961; Logan and others, 1964; Davies, tion, exposed on the east •side of Crossman quarry 8-20 1970). Surface relief of the Shark Bay algal stroma­ feet above the quarry floor. Photomicrographs of thin tolites has been correlated with water turbulance. sections showing .the various lithic types are given on High-relief forms are typical in the low intertidal plate 4, figures 1- 6. zone of exposed headlands, whereas low-relief forms

(or) carbonate-precipitating activities of nonskele­ tal algae. Domal stromatolites are cryptalgal struc­ tures characterized by convex-upward laminations. Layers within the Whitehall domal stromatolites have a clastic texture, and the laminated fabric is produced by variations in grain size (pl. 4, fig. 6). Relief of Whitehall stromatolites ranges from 0 to 18 inches, as evidenced by tracing single laminations around the structures (fig. 4). Two distinctly different types of nonlaminated cryptalgal structures (thrombolites of Aitken, 1967) occur in the Whitehall. The most common type forms both beds and individual mound structures with as much as 12 inches of surface relief (fig. 5). Fabric observed in outcrop appears clotted whereas in thin FIGURE 3.- Sharp vertical contact between lo•w-angle cross­ section the texture is clastic with clots formed by bedded grainstone to the left, and finer grained clotted thrombolil!ic fabric to the right. Lower Whitehall Forma­ variations in grain packing. Clots that appear light tion, Crossman quarr y. Lens 0ap is 3 inches (7.5 em) in gray in outcrop are grain supported; darker clots diameter. ENVIRONMENTAL SETTING 11

and Buchanan, 1965). In the Whitehall, the associa­ tion of pellet and ooid grainstone around the bases of stromatolites suggests deposition in a relatively high-energy, low intertidal environment. Occasion­ ally, crossbed sets of grainstone, which overlie stromatolites, dip in opposite directions, and the resulting "herringbone" fabric is thought to be typical of shallow subtidal and low intertidal sites of deposition (Klein, 1972, p. 400). Oolite and other mud-free grainstones indicate sustained moderate to high turbulence in warm and probably clear water. Ooid formation requires fre­ quent agitation of the sand-sized grains, and other spar-rich grain-supported rocks suggest that mud was winnowed from the sediment by frequent agita­ FIGURE 4.-Domal stromatolites in the lower part of the tion. Evidence was not found for diagenetic altera­ Whitehall Formation, Crossman quarry. Relief on these particular forms decreases upward so that the upper tion (neomorphism) of micrite to pseudospar in the few inches are nearly fl·at laminated. Lens cap is 3 inches thin sections and acetate peels made of Whitehall (7.5 em) in diameter. limestones (Halley, 1971a). Hypersalinity or highly fluctuating salinity in the Whitehall depositional environment may be sug­ and flat-laminated sediments (incipient cryptalga­ gested by the abundance of high-relief domal laminates) occur in high-intertidal and supratidal stromatolites and by the presence of length-slow sites and on tidal flats along protected shorelines chalcedony. Recent high-relief domal stromatolites (Logan, 1961, p. 529; Hoffman and others, 1969; are uniquely associated with hypersaline environ­ Davies, 1970, p. 181). Low-relief stromatolites and ments in Shark Bay, Western Australia (Logan, flat-laminated sediments also characterize the high 1961, p. 518; Hoffman and others, 1969; also com­ intertidal zone of south Florida (Ginsburg and oth­ pare Logan and others, 1970, fig. 7B; Logan and ers, 1954; Gebelein and Hoffman, 1969); Andros Cebulski, 1970, fig. 6). Island, Bahamas (Shinn and others, 1969, p. 1211- Folk and Pittman (1971) recently presented 1216) ; and the Abu Dhabi along the Persian Gulf strong evidence that length-slow chalcedony forms (Kendall and Skipwith, 1968). These features, when recognized in ancient rocks, can be used to infer near-sea-level or tidal-flat deposition. Many modern studies have successfully applied these modern ana­ logues to the interpretation of ancient carbonate en­ vironments (for example, Roehl, 1967; Laporte, 1967). By analogy with recent patterns of occur­ rence, stromatolites and cryptalgalaminates in the lower part of the Whitehall Formation are inferred to have formed under conditions of tidal-flat deposition. Recent carbonate fabrics analogous to thrombo­ lites have not been reported. However, Aitken (1967, p. 1176) inferred from studies in Cambrian and Ordovician rocks of Alberta that thrombolites may have formed in low intertidal and shallow subtidal sites, possibly under hypersaline conditions. FIGURE 5.-Domal thrombolite in the lower Whitehall For­ Low-angle and planar crossbedded carbonate mation, Crossman quarry. A 6-inch-long (15 em) pen sands are characteristically found in low intertidal placed in the lower right corner of photograph is at the contact between a thrombolite (left) and planar-bedded and shallow subtidal sites in the Bahamas (Imbrie grains.tone (right). Dark material is chert. 12 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE predominantly in association with evaporitic de­ with intertidal lithologies, and it is thus presumed posits. The relatively low solubility and persistence that the animals lived in nearby shallow subtidal of length-slow chalcedony in carbonate deposits that habitats. lack more obvious evidence for evaporites suggest In summary, the Whitehall fossils represent a that occurrence of the mineral may be used as an vagile epibenthic fauna that probably lived in a indicator of evaporitic conditions. Length-slow chal­ nearshore subtidal habitat characterized by warm cedony occurs in the Whitehall Formation as void fill and clear marine waters. The habitat probably ex­ within some fenestrae of nonelastic thrombolites (pl. perienced sustained moderate to high turbulence and 4, fig. 3) and as cements in some grainstones. How­ may have had a high range of salinity or generally ever, the time of emplacement of the Whitehall chal­ hypersaline conditions. The geographic site of de­ cedony is unknown so that it is not now possible to position was probably on the landward edge of a differentiate between an early diagenetic origin in carbonate shelf of unknown width. contact with primary hypersaline marine waters, or late diagenetic origin from hypersaline waters BIOFACIES DISTRIBUTION flushed through the Whitehall beds from other MODELS evaporitic horizons. It may be noteworthy however, that almost half Two major facies models have been proposed to the examples of length-slow chalcedony cited by explain the distribution of North American Cam­ Folk and Pittman (1971, p. 1052-1053) are from brian trilobite faunas. The first was presented by Cambrian and Ordovician carbonate rocks, many of Lochman and Wilson (1958) who recognized three which are stromatolitic. Thus, the association of biofacies "realms" which were thought to be con­ domal stromatolites and length-slow chalcedony in centrically arranged around the North American the Whitehall Formation may be tentatively accepted craton and tectonically controlled. Lochman (1970, as evidence of hypersaline conditions. Absence of 1971) recently reviewed and updated the earlier remains of infaunal organisms and echinoderms model for part of the North American area. In the from the Whitehall rocks is consistent with hyper­ latter studies, Lochman recognized two major bio­ saline conditions in the depositional environment. facies: (1) A "cratonic" biofacies, consisting of The geographic setting of the Whitehall cryptalgal "Pacific province" assemblages occurring in cratonal limestones was probably the inner, landward (era­ and miogeosynclinal sites, and (2) an "extracra­ tonal) side of the carbonate shelf. (See "Biofacies tonic" biofacies, consisting of "Atlantic province" Distribution.") Shoreline deposits of the Whitehall assemblages which occur in outer miogeosynclinal are associated with well-rounded quartz sand grains. and eugeosynclinal areas. The Whitehall Saukia The quartz grains are diagenetically etched, and Zone fauna is near the outer limits of the cratonic parts of the grain edges have been replaced by cal­ biofacies as interpreted by Lochman (1970, fig. 7) cite. Diagenetic alteration of grain surfaces pre­ for New York State. cludes an interpretation of the transport mode of Palmer (1960, 1965, 1968, 1969, 1971a, b, 1972a, these grains (Margolis, 1968, p. 255). However, the 1973) has developed a second model of Cambrian presence of quartz sand in the Whitehall indicates trilobite- and sediment-distribution patterns that is that these deposits were not isolated from a clastic based on the recognition of three more or less coinci­ source, here probably the exposed craton. The quartz dent biofacies and lithofacies belts concentrically sand suggests that Whitehall shorelines were proba­ arranged around the North American craton. The bly near the exposed cratonal margin rather than on model differs from that of Lochman and Wilson by carbonate islands which may have existed near the placing greater emphasis on sedimentary deposition­ outer edge of the shelf. Field evidence for the width al patterns and contained fossils, rather than on geo­ of the Whitehall carbonate shelf is inconclusive be­ tectonic criteria. Palmer's lithofacies belts have been cause the seaward edge is obscured by the allocht­ termed: (1) an "inner detrital belt," characterized honous Taconic sequence a few miles east of the by terrigenous clastic rocks dominated by quartzose study area (Theokritoff, 1964; fig. 1, this report). and feldspathic sandstone, glauconitic sandstone, The frequency with which evidence of shorelines and varying amounts of shale and carbonate rocks, is found in the Whitehall sections indicates that the (2) a "carbonate belt" characterized by generally contained faunas probably lived relatively near high-mechanical-energy coarse-textured bioclastic shore. No fossils were found uniquely associated sparry limestones, oolitic and pisolitic limestones, BIOFACIES DISTRIBUTION 13 high-relief stromatolites, massive accumulations of are unevenly developed. Some areas have been sub­ light-colored lime mudstone and dolomite, and (3) jected to intensive collecting and systematic study an "outer detrital belt" characterized by dark­ (for example, central Texas and Oklahoma), where­ colored shales, siltstones, and intercalated thinly as some other areas have a variety of problems, such bedded limestones which are commonly pyritic and as relatively incomplete systematic study (for ex­ carbonaceous. Each lithofacies belt has been postu­ ample, Upper Mississippi Valley) and early sys­ lated to contain a particular trilobite fauna charac­ tematic work that needs reevaluation (for example, terized by differences in relative abundance and par­ New Jersey and, in part, Vermont) ; in some areas, ticular associations of genera and species (Palmer, faunas are known only from lists (for example, 1968, 1969). The model reflects a broad shallow­ Taconic sequence of New York and western New­ water depositional shelf with inner-shelf terrigenous foundland). These factors limit the reliance that can clastic environments grading seaward to outer-shelf be placed on numerical analyses of biogeographic carbonate shoals and tidal flats, which in turn grade distribution patterns. However, it seems useful to oceanward to basinal (below maximum effective examine distribution patterns, even though possible wave base) sedimentary environments. interpretation is limited at present. Palmer's model seems to have greater heuristic Simpson's (1960, p. 301) index of faunal resem­ value than the earlier model (Lochman and Wilson, blance ( IFR) is used here to determine the degree 1958; Lochman, 1970, 1971) for several reasons: of apparent biofacies similarity between the Saukia (1) The model separates rocks and contained faunas Zone trilobite fauna at Whitehall and at other North from the a priori genetic implications of the geotec- American sites (fig. 6). IFR is calculated from the tonic categories "cratonal shelf," "miogeosyncline," equation IFR=C/NX100, where C equals the num­ and "eugeosyncline." The sedimentary model im­ ber of taxa in common between two samples and N plies a more or less continuous transition of environ­ equals the number of taxa in the smaller of two sam­ ments from shoreline to continental shelf margin, ples. IFR values were calculated for both species and rather than a sharp division into cratonal and mio­ genera that occur at Whitehall. Results are shown geosynclinal sedimentary environments. Sloss in tables 3 and 4. (1960) has stressed the similarity of early Paleo­ Simpson (1960) has discussed the advantages and zoic sedimentary sequences in cratonal and miogeo­ disadvantages of his index in paleontological studies synclinal sites in the Western United States, and and Mello and Buzas (1968), and Cheetham and data presented by Lochman (1971, figs. 21-24) show Hazel (1969) have compared the index with other that Trempealeauan sedimentary facies patterns are numerical indexes. In general, IFR minimizes ef­ not closely correlated with geosynclinal areas, (2) fects of differences in sample size (Simpson, 1960, the model can be applied to critical analyses of the p. 301) and tends to emphasize similarity (Cheet­ relative influence of eustatic and epeirogenetic ham and Hazel, 1969, p. 1135). IFR can become factors in the regional control of lithofacies distribu­ strongly biased when large discrepancies exist in tion, and (3) the model is more reflective of infer­ sample size. When the number of taxa in the smaller red Cambrian paleogeography and thus is more easi­ sample (N) approaches the number in common (C) ly compared with recent geographic conditions. between two samples, excessively high IFR values Therefore, it may provide a regional framework for result. However, calculated values provide an ob­ studies of paleoecology, adaptive radiation in space jective and explicit basis for discussion of regional and time, and more detailed analyses of the signifi­ faunal similarities if limitations are recognized and cance of biogeographic distribution patterns. differences in IFR are cautiously interpreted.

METHODS OF ANALYSIS ASSEMBLAGES SIMILAR TO WHITEHALL FAUNA

An historically meaningful biogeographic (bio­ Analysis of species-level faunal resemblance with facies) analysis ideally should be based on critically the Whitehall Saukia Zone fauna shows a range in studied taxa to insure that concepts of all opera­ IFR values from 25 to 63 for the east-central Great tional taxonomic units are consistently applied Basin (Notch Peak and Whipple Cave Formations), throughout the area to be analyzed. The present state Llano region of central Texas (Wilberns Forma­ of knowledge of North American Saukia Zone trilo­ tion), Arbuckle Mountains of Oklahoma (Signal bite faunas falls short of this ideal. Taxonomic data Mountain Formation), and the central Appalachian

527-763 0 - 74 - 3 14 L·ATE GAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

EXPLANATION .A Basinal facies (outer detrital belt) e Outer-shelf facies (carbonate belt) X Inner- shelf facies (inner detrital belt)

----l .r---. I -r-·----~----·- i I I I I I I ! I I I \ ! \ '•2

Ciao

0 200 400 600 800 1000 MILES

0 200 400 600 800 1000 KILOMETERS

0 0 (\J BIOFACIES DISTRIBUTION 15 region ( Conococheague Limestone) . Faunal resem­ as commonly containing oolites, flat-pebble conglom­ blance at the generic level shows an increase in de­ erates and "cryptozoan" beds. Detailed data on the gree of similarity ranging from 63 to 87 for the fauna and lithologic characteristics of the Kitta­ same areas; high resemblance is also shown with the tinny Limestone of New Jersey are few so that fauna of the Mount Wilson area of Alberta (Mis­ further study is needed to clarify the faunal and taya and Survey Peak formations), the Eminence environmental relationships with other Upper Cam­ region (Eminence Dolomite) of Missouri, the Upper brian sites. Mississippi Valley (Trempealeauan Stage), and per­ The widespread distribution, high degree of faun­ haps northwestern New Jersey (Kittatinny Lime­ al similarity, and association with grossly similar stone). sedimentary environments suggests that the White­ Lithologic analysis of containing rocks provides hall Saukia Zone fauna is part of a near-sea-level evidence for the existence of a shallow-water carbon­ shelf carbonate biofacies that seems to be oriented ate bank in some of those areas showing high IFR concentrically around the North American Late values with the Whitehall Saukia Zone fauna. Cambrian cratonal region. Studies of Upper Cambrian rocks in the Mount Wil­ The Saukia Zone fauna from the Upper Mississip­ son area of Alberta (Aitken and N orford, 1967; pi Valley area shows a high degree of generic-level Aitken, 1967) and in central Texas (Ahr, 1971) similarity (IFR = 87) with the carbonate shelf bio­ show that in those areas the Saukia Zone interval facies typified by the Whitehall fauna, even though is characterized by coarse-textured skeletal grain­ terrigenous clastic deposition dominates that area stones, oolitic and pisolitic grainstones, flat-pebble (Nelson, 1956; Lochman, 1971). Such a high degree conglomerates, and both laminar and nonlaminar of faunal similarity is inconsistent with the Palmer algal boundstones. The characteristics of these di­ model of distinct inner detrital belt and carbonate verse rock suites are consistent with those here de­ belt biofacies. The discrepancy cannot be critically scribed for the Whitehall Formation and are thought evaluated at present because taxonomic information to reflect origin in shallow subtidal to tidal-flat on the Upper Mississippi Valley Trempealeauan environments. (See, for example, Laporte, 1971.) fauna is available only for the relatively large trilo­ Detailed petrographic studies have not been made ' bites of the families Dikelocephalinae and Saukiinae, in the other areas. However, field studies of strata whereas the presence of most other taxa are only containing the Saukia Zone fauna in th9 east-central known from faunal lists (Nelson, 1951; Raasch, Great Basin (Taylor, 1969, 1971) report an abun­ 1951). On the other hand, the low IFR value be­ dance of flat-pebble conglomerate, skeletal and oolitic tween Whitehall (carbonate shelf facies) and north­ grainstones, and laminar and nonlaminar limestone eastern and southwestern Montana (Lochman, mounds that may prove similar to those described by 1964a; Grant, 1965) (detrital shelf facies) suggests Aitken (1967) from Alb9rta and Ahr (1971) from that some faunal differences may be present between central Texas. Stitt (1971) reported similar rock these two areas. Further taxonomic work is needed types in the Signal Mountain Limestone of south­ to elucidate biofacies differences and similarities be­ central Oklahoma, and the Conococheague Limestone tween outer and inner shelf sites during Trempe­ has been characterized (Wilson, 1952; Sando, 1957) aleauan time.

FIGURE 6.-Map showing the general location of principal (13) central Appalachian Mountains, Conococheague For­ areas of North America from which Saukia Zone faunas mation, and (14) central Appalachian Mountains, Fred­ have been reported. See text for discussion. Sources of erick and Grove Formations (Rasetti, 1959); (15) north­ data: (1) East-central Alaska (Palmer, 1968); (2) Mount western New Jersey (Howell, 1945) and observations, this Wilson, Alberta (Derby and others, 1972); (3) McCone report; (16) Taconic sequence, eastern New York State County, Mont. (Lachman, 1964a); (4) southwestern Mon­ (Bird and Rasetti, 1968); (17) Saratoga Springs, N.Y. tana (Grant, 1965); (5) central Nevada and (6) eastern (Walcott, 1912b), and observations, this report; (18) Nevada-western Utah (Taylor, 1971); (7) Marathon basin, Whitehall, N.Y., this report; (19) St. Albans area, Ver­ Texas (Wilson, 1954, 1956); (8) Oaxaca, Mexico (Robison mont (Raymond, 1924, 1937; Clark and Shaw, 1968), and and Pantoja-Alor, 1968); (9) Llano uplift, Texas (Long­ some taxonomic reassignments, this report; (20) Levis acre, 1970); (10) Arbuckle Mountains, Okla. (Stitt, 1971); area, Quebec (Rasetti, 1944, 1945, 1963); (21) Broom (11) Eminence region Missouri (Ulrich, 1930); (12) Point, western Newfoundland (Kindle and Whittington, Upper Mississippi Valley (Nelson, 1951; Raasch, 1951) ; 1959). 16 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

TABLE 3.-Known occurrences of trilobite species rec.ognized from the Saukia Zone at Whitehall, N.Y.

[Simpson's (1960) index of faunal resemblance (IFR) is a rough measure of the degree of apparent biogeographic similarity between Whitehall and other areas where the species are known. Data-source numbers in parentheses are explained in fig. 6. Explanation of symbols: x. estab- lished occurrence; -, not known to occur; ?, questionable identification; *, insufficient data for computation. See text for discussion of each area]

;;- ; ;: e CD ~ ~ 'tl ..c:l ~ ..!<: =ell .a ~ ::a ~ lll .... lllO= ""0 ~ =· ... ~ ~ =~ ::: c:i' =-- :s 0 = ].- ]~ !it ~ ..... ""Ql ~ Ql C"' ~ ' 0 g ::ae~~ ::a~ ~ ;- z ...... ~ gj ., Ql Ql ri Area .a :; s Ql 0 =ell 'tl >< m· s:: > ~ ~ E e = t = .., Ql lll s::""o:!O o:lO Ql ,..Q 10 s:: 00 s:: ~ > "" (.) $"" ::a s:: E-t :c;~ .... "" !it Ql ~ 0 ·s. Ql Ql "' > gj lll"' ~"' ] =· (.) Ql -5c.? (.) ~ < ::a "' 0 0 al'tl z ri i ~ 'tl 'tl (.) E-t s:: s:: Ql ~ !it s:: s:: "' "' ·~ ~ ~& s:: Ql= ·c ..,· ~ ~ ·~ 0 'i ~§ ~ al a ~ ,..Q :( Po~ 0' A "" = 0 ~ "'~ i s:: ri $"" "' "' ::;: p...c:l Po~ $"" rJJ lll Ql 0 ::;: ""Ql ~ ·c; gj z z s:: Ql (.) <(.) < .... al s:: i Ql 0 :a 0 ~ ~ ~ ~ (.) "" c; s:: ri ~ s:: -(.) !it bel ,..Q ""al .., !it (.) Ql c;~ Ql § -:3 0 ~ Ql "'o ·a "' ., "' s:: -E .b $"" ~ "" -:3 0 .s s ~ 0 s:: .!3 A .b§ .b~ (.) ~ (.) ~ s:: "' >< < 8 0 0 Ql ""al "' ~ s A ~0 ~~ ""0 al "'"" ,.3 "> r.:1"' ::a ::a rJJ 0 ~ ::;: 0"' ~"' < r.:1 ~ o-- o-- z E-t rJJ"' rJJ ~ j:'Q""

Acheilops masonensis Winston and Nicholls __ X X X Bowmania cf. B. pennsylvanica Rasetti ------X X X ? "Calvinella" prethoparia Longacre ------? X Euptychaspis typicalis Ulrich ------X X X X X Plethometopus obtusus Rasetti ------X X - X X X Plethometopus sp. A ------"Prosaukia" spinula Taylor, n. sp ------Stenochilina sp. A ------25 Index of faunal resemblance (IFR) ------0 * 0 * 0 to 0 0 63 50 13 * 37 13? 13 * 0 0 13 * 37?

ASSEMBLAGES DISSIMILAR TO WHITEHALL FAUN A area of Alaska ; central Nevada (in part) ; the Mara­ thon region of Texas; the Frederick and Grove For­ Faunas from many areas analyzed have low IFR mations of Maryland; the Taconic sequence of east­ values with the Whitehall fauna at the species level. ern New York; the St. Albans area, Vermont; Levis, Causes of the low degree of similarity are probably Quebec; and western Newfoundland. The occur­ multiple and perhaps in large part influenced by the rence of the Hungaia fauna seems to be related to varying quality and quantity of taxonomic informa­ basinal sedimentary environments or shelf-edge car­ tion and field collecting in the different areas. For bonates that may occur as subsequent or penecon­ this reason, comparisons of generic occurrences temporaneous allochthonous debris flows into basin­ should be evaluated cautiously. al environments (Kindle and Whittington, 1958, p. Low IFR values, ranging from 0 to 37, were cal­ 340; also see Bird and Dewey, 1970, fig. 7a). culated for generic occurrences between the White­ The low IFR value between the Trempealeauan hall fauna and the Eagle area of Alaska ; McCone fauna at Saratoga Springs and Whitehall is an enig­ County, Mont. ; southwestern Montana; central N e­ ma that cannot be satisfactorily explained at present. vada; the Marathon region, Texas; Oaxaca, Mexico; The Hoyt trilobite fauna is dissimilar to all other de­ the Frederick and Grove Formations of Maryland; scribed faunas except for the occurrence of the Saratoga Springs, N.Y.; the Taconic sequence of ubiquitous Plethometopus, Plethopeltis, and "Pro­ eastern New York; the St. Albans area of Vermont; saukia" (a species not closely related to the White­ Levis, Quebec; and western Newfoundland (table hall form). The differences between the Hoyt and 4). Several Saukia Zone occurrences which have low Whitehall faunas may be a result of difference in IFR values with the Whitehall fauna are similar to age, but if this is true one might expect to find the one another and are characterized by the so-called Hoyt fauna in the carbonate facies of Saukia sub­ Hungaia magnifica fauna (Rasetti, 1944, 1945, zones in the relatively well known sections in Okla­ 1963), which is thought to characterize North homa, Texas, and the Great Basin. However, the American "outer detrital belt" (basinal) sites fauna has not been discovered in these areas in spite (Palmer, 1969, 1972b). Such areas include the Eagle of a considerable amount of collecting. This suggests BIOFACIES DISTRIBUTION 17

TABLE 4.-Known North American occurrences of trilobite genera recognized from the Saukia Zone at Whitehall, N. Y.

[Simpson's (1960) index of faunal resemblance (,IFR) is a rough measure of the degree of apparent biogeographic similarity between White­ hall and other areas of occurrence. Data-source numbers given in parentheses are explained in fig. 6. Explanation of symbols: X established occurrence; -, not known to occur; ?, questionable identification; *, insufficient data for computation. See text for discussion of' each area]

Area

... ·c;1: ~

0s 0 j:Q'"'

Acheilops Ulrich ------­ X X X X X ? Bowmania Walcott ------­ X X X X X ? ? "Calvinella" Walcott ------­ X X X X X X ? Euptychaspis Ulrich ------­ X X X X X X X Plethometopus Ulrich ------­ X X X X XX X X X X X X X X Plethopeltis Raymond ------­ X X X X X X X ? X "Prosaukia" Ulrich and Res,ser ------­ X X X X X X X X Stenochilina Ulrich ------X X ? 13 37 25 Index of faunal resemblance (IFR) ------0 50 13 0 0 87 0 0 87 87 75 75 63 to to 0 37 to 13 25 25? 87? 37? that the Hoyt fauna probably reflects environmental was less in the Hoyt depositional environment than conditions different from those reflected by the in that of the Whitehall Formation. Such environ­ Whitehall fauna. mental differences could account for faunal dissimi­ Halley (1971a) noted that although the Hoyt and larity between the two areas. However, further parts of the Whitehall Formations contain similar study in the Saratoga Springs area is needed to depositional textures, the Hoyt differs in possessing clarify the causes of faunal dissimilarity between a high content of carbonaceous residue and dolo­ the Hoyt, Whitehall, and other carbonate belt sites mite and lacks chert and length-slow chalcedony. in North America. Also, the Hoyt fauna contains representative ele­ The McCone County area of Montana (Lochman, ments of a greater number of phyla than does the 1964a) has only one genus reported in common with Whitehall. Walcott (1912b) reported gastropods, the Whitehall area. The site is characterized by trilobites, and inarticulate brachiopods from the intercalated terrigenous shale and limestone-pebble Hoyt, and Halley (1971a) found echinoderm and conglomerate (Lochman and Wilson, 1967), sug­ dasycladacean algal fragments. (See pl. 4, figs. 7, gesting, together with the faunal evidence, that the 8.) Inarticulate brachiopods, dasycladacean algae, area was part of an inner shelf facies. and echinoderm plates were searched for but not Grant (1965, p. 88) reported Trempealeauan fos­ identified from the Whitehall limestones. The ab­ sils from part of the Snowy Range Formation in sence of echinoderms from the Whitehall samples southeastern Montana and adjacent Wyoming, and the absence of length-slow chalcedony from the which he assigned to the Illaenurus Zori"e. The zone Hoyt suggest that the Hoyt fauna may have lived in contains no species or genera in common with the a more normal saline environment than the White­ Whitehall assemblages. However, the Illaenurus hall fauna. Although no quantitative estimate of the Zone is probably early Trempealeauan in age salinity fluctuations of the two areas can presently (Grant, 1965; Longacre, 1970) so that differences be made, it is reasonable to infer that either the between it and Whitehall could be due to temporal magnitude or the periodicity of salinity fluctuations rather than environmental factors. 18 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

Faunas described from Oaxaca, Mexico, differ est faunal change occurs between the outer-shelf markedly from both the Hungaia magnifica biofacies carbonate biofacies and the offshelf basinal biofacies. and the inner shelf biofacies which also shows low Further understanding of possible causes of ob­ IFR values. The Oaxaca fauna may be classified as served patterns of trilobite distribution will proba­ basinal facies, but it is most similar to described bly result from greatly needed detailed sedimento­ faunas from Argentina and the Tremadocian facies logical studies of the rocks enclosing the various of eastern Canada, Great Britain, and Scandinavia faunas and from taxonomic studies of trilobites (Robison and Pantoja-Alor, 1968, p. 772) rather from those areas for which available data are in­ than the North American basinal H ungaia magnifica sufficient or obsolete. biofacies. The methods used here for measuring faunal re­ SYSTEMATIC PALEONTOLOGY semblance do not allow quantitative conclusions INTRODUCTORY STATEMENT concerning the homogeneity or heterogeneity of the Trilobite morphological terminology used in the Saukia Zone biofacies belts. Estimates of homogenei­ systematic descriptions follows the "Treatise on ty or heterogeneity rely on subjective evaluation of Invertebrate Paleontology, Part 0" (Harrington faunal lists, published formal taxonomic studies, and and others, 1959) except that nomenclature for museum collections. glabellar furrows and lobes follows Henningsmoen On the basis of the published and newly described (1957, p. 13) : lateral glabellar furrows are num­ faunal evidence, however, (Taylor, and other 1971, bered forward from the posterior end, beginning unpub. data), the Upper Cambrian carbonate-shelf with SO (occipital furrow) and proceeding S1, S2, facies seems to have a relatively homogeneous trilo­ S3, and S4 ; lateral glabellar lobes are also numbered bite fauna. In contrast, North American basinal forward from the posterior end beginning with LO facies sites seem to be occupied by at least two (occipital lobe), and proceeding L1, L2, L3, and L4. faunas, the Hungaia magnifica biofacies and the Henningsmoen's system is preferred here over the Tremadocian faunas described from Mexico (Robi­ Treatise system because it usually results in an son and Pantoja-Alor, 1968), and perhaps a third economy of words without loss of precision in tele­ -the Hedinaspis fauna-in Alaska (Palmer, 1968) graphic descriptions, and it lacks the ambiguity of and the central Great Basin (Taylor, 1971, and the 1p, 2p, and so forth, system advocated in the other unpub. data). Treatise by providing separate notation for lobes Rowell and McBride (1972a, c), Rowell, McBride, and furrows. and Palmer (1973) recently made a quantitative Economy of words in systematic descriptions is study of Trempealeauan trilobite distribution in also made possible by the use of several other terms North America using multivariate-analysis tech­ in Henningsmoen's system (1957, p. 12-14). These niques applied to nearly all the available trilobite terms, together with the Treatise equivalent in pa­ data. Some results of their study were the recog­ rentheses, are as follows : Preocular suture (anterior nition of a "North American faunal province" that section of facial suture), postocular suture (posteri­ is divisible into two "subprovinces," a restricted or section of facial suture) , anterior fixigena (an­ shelf subprovince (inner-shelf detrital and outer­ terior area of fixigena), interocular fixigena (palpe­ shelf carbonate facies of this report) and a shelf bral area of fixigena), posterior fixigena (posterior margin-open ocean subprovince (basinal facies of area of fixigena), and ocular incisure (no Treatise this report) . The analysis by Rowell, McBride, and term). Palmer (1973) supports earlier suggestions (Rowell The terms "corner angle," "inner spine angle," and McBride, 1972b) that faunas of the marginal and "outer spine angle" (Henningsmoen, 1957) are shelf-open ocean (Tremadocian of Mexico and simple and useful for describing angles in the genal H edinaspis basinal biofacies of this report) are corner region of librigenae. The term "eye socle" is geographically heterogeneous and have affinities used, following Shaw and Ormiston (1964), in pref­ with either Asia or Europe. erence to "eye platform." Many terminological differences exist between the Gill (1949, p. 572) proposed that the term "proso­ report by Rowell, McBride, and Palmer ( 1973) pon" be used in place of "ornament" in the descrip­ and this one. However, an important conclusion to tion of surface appearance of fossil specimens to be made at this time is the general agreement that deemphasize the nonfunctional connotation of the for the North American Trempealeauan, the great- term ornament. (Also see Wright, 1950; Gill, 1951.) SYSTEMATIC PALEONTOLOGY 19

The surface appearance of trilobites is highly vari­ interocular fixigena and have faint but complete able. Some forms have surface sculpture consisting palpebral furrows and lunate palpebral lobes which of anastomosing ridges, bertillion pattern, and other are centered posterior to the glabellar midpoint and features of uncertain functional significance, where­ opposite the S1 furrows. as others have various kinds of perforate tubercles The type collection of A. dilatus could not be or surface pits that probably were functionally located in the USNM collections, nor could any other related to sensory setae in the living animal. An specimens be located among material from the type added difficulty arises in description of the surface locality (102j, old series). This constitutes a dilem­ appearance of molds and casts. For example, fea­ ma as A. dilatus is the type species of the genus. The tures visible on internal molds of exoskeletal parts problem is compounded by the fact that the original are a negative replica of the inner, or visceral, sur­ material was collected from residual cherts near face of the exoskeleton. "Ornament" seems particu­ Eminence, Mo. Thus, topotype material cannot be larly incongruous in the description of such features. objectively recollected. Fortunately, the concept of Therefore, Gill's usage of prosopon has been adopted Acheilops seems sufficiently well characterized on here as a descriptive term for the surface appear­ the basis of Ulrich's original description and Win­ ance of fossils. In trilobite descriptions, this usage ston and Nicholls' description of A. masonensis; is applicable to inner and outer actual surfaces, in­ designation of a neotype does not seem necessary at ternal and external molds, and internal and external present. casts of exoskeleton parts. Acheilops norwalkensis is similar to A. dilatus as Class TRILOBITA Walch, 1771 illustrated and described by Ulrich ( 1930, p. 219, Family CA TILLICEPHALIDAE Raymond, 1938 pl. 19, figs. 21, 22). Two differences can be noted in Genus ACHEILOPS Ulrich, 1931 comparison with Ulrich's description of A. dilatus. Ackeilops Ulrich in Bridge, 1931, p. 218; Kobayashi, 1942, He described the palpebral regions of A. dilatus as p. 174; Rasetti, 1954, p. 611; Winston and Nicholls, being ''apparently always without furrows (s) .'' 1967, p. 77. However, as pointed out by Winston and Nicholls Type species.-Acheilops dilatus Ulrich in Bridge, (1967, p. 77), the furrows are shown in Ulrich's 1931, by original designation. illustrations (1930, pl. 19, figs. 20-22) of the types. Diagnosis.-Catillicephalid trilobites with palpe­ In Ulrich's (1930, p. 219) original discussion of bral lobes that range in length from approximately A. dilatus, he referred to a form, not mentioned by 0.3 to 0.4 of cranidial length (exsagittal (exsag.)) name, from Monroe County, Wis., which differs and center posterior to the cranidial midpoint oppo­ from A. dilatus in having a "greater longitudinal site Sl. Posterior fixigenae are subparallel sided. convexity of the anterior half of the glabella." This Frontal area and anterior fixigenae are absent. probably refers to A. norwalkensis and seems to be Discussion.-Winston and Nicholls (1967, p. 77) the only morphological difference between it and A. discussed the characteristics of Acheilops and gave dilatus that can be detected from the information reasons for its inclusion in the Catillicephalidae. and material currently available. Their classification is followed here. Acheilops masonensis Winston and Nicholls There are apparently three nominal species of Plate 1, figures 4, 5 Acheilops: Acheilops dilatus, the type species from near Eminence, Mo. ; Acheilops masonensis Winston Acheilops masonensis Winston and Nicholls 1967, p. 77, pl. 11, figs. 23-25; Longacre, 1970, p. 15, pl. 6, fig. 19; and Nicholls, 1967, from the Wilberns Formation Stitt, 1971, p. 15, pl. 7, fig. 5. of central Texas; and Acheilops norwalkensis Ul­ rich and Resser, 1930, from Monroe County, Wis. Material available.-One cranidium and one libri­ Acheilops norwalkensis was illustrated (Ulrich and gena from locality 470b and one cranidium from Resser, 1930, pl. 21, fig. 8) but apparently never locality H-3. described. However, the name is available under the Description of Whitehall material.-Cranidium rules of the International Code on Zoological Nomen­ subtrapezoidal in outline, strongly convex sagittally. clature (1964), Article 12, by indication. The slab Glabella expanded anteriorly, basal width 0.8 length. illustrated by Ulrich and Resser contains two cra­ Axial glabellar furrows deeply impressed. Two pairs nidia attributable to Acheilops. Both have axial lateral glabellar furrows. S1 shallow, geniculate. S2 glabellar furrows, which diverge in the region of the shallow, nearly transverse, not connected across 20 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE midline. Occipital ring simple, slightly convex, pos­ bral lobe ( exsag. length/cranidial length 0.3 rather terior edge rounded, medial region not preserved. than 0.4), and axial glabellar furrows that are sub­ Occipital furrow deep. Frontal area not differenti­ parallel rather than divergent in the interocular fixi­ ated from glabella. Anterior border and border fur­ genal region. row absent. Anterior fixigena. absent. Interocular Occurrence.-Saukiella serotina Subzone, locali­ fixigena lunate, poorly differentiated from palpebral ties H-3 and 470b, Washi~gton County, N.Y. lobes. Postocular fixigena subparallel sided, length Genus STENOCHILINA Ulrich, 1931 (transverse (tr.)) 0.8 occipital lobe length (tr.). Stenochilina Ulrich in Bridge, 1931, p. 215. Rasetti, 1954, Palpebral lobes large, nearly flat, lunate, length p. 606; Rasetti, in Harrington and others, 1959, p. (exsag.) 0.3 cranidial length, centered opposite Sl. 0285. Palpebral furrow faintly developed on posterior one- Type species.-Stenochilina spinifera Ulrich in third of palpebral region. Preocular facial sutures Bridge, 1931, by original designation. strongly divergent, coursing coincident with anteri­ Diagnosis.-Glabella subparallel sided, rounded to or parts of axial glabellar furrows. Postocular facial bluntly rounded anteriorly; frontal area narrow, sutures transverse, nearly straight. lacking anterior border; palpebral lobes anterior to Librigena length approximately four times width, glabellar midpoint, centered opposite L2 lobe, below nearly vertical in life position. Genal field not differ­ level of interocular fixigena; occipital spine present entiated from border. Eye socle with attached holo­ or absent; prosopon coarsely granular. chroal visual surface. Genal spine short, bluntly Discussion.-Rasetti's (1954, 1959) diagnosis of pointed. Stenochilina is slightly modified to accommodate fea­ Prosopon consists of closely spaced coarse gran­ tures observed in Stenochilina sp. A from New York. ules on the .external surface except in furrows and The principal change is to include forms that lack branching ridges on the anterior lobe of the glabella an occipital spine. and librigena. Rasetti (1954, p. 606) restricted Stenochilina to Discussion.-A cheilops mason en sis has been re­ S. spinifera, the type species from the Trempealeau­ ported from the Saukiella serotina and Corbinia an near Eminence, Mo. Stenochilina spinifera has apopsis Subzones in the Wilberns Formation of cen­ also been reported from the Conococheague Forma­ tral Texas (Winston and Nicholls, 1967; Longacre, tion in Washington County, Md. (Rasetti, 1959, p. 1970). In the original description, Winston and 383). Nicholls (1967) noted that some specimens at­ Stenochilina is most similar to Triarthropsis from tributed to A. masonensis have shallow lateral gla­ which it differs in the presence of larger, well­ bellar furrows, whereas others possess rather deeply defined, anteriorly located palpebral lobes and coarse impressed furrows. The Whitehall specimens are granular prosopon. most similar to the shallow-furrowed Texas forms (see Longacre, 1970, pl. 6, fig. 19) except tha.t they Stenocbilina sp. A are more coarsely granular and the palpebral fur­ Plate ·1, figures 6-10 rows are present only on the posterior part of the Material available.-Eight cranidia from locality palpebral region. 418e (old series). Stitt (1971) reported A. masonensis from the Description.-Cranidium subtrapezoidal in out­ Saukiella junia and Saukiella serotina Subzones in line, moderately convex. Glabella subparallel sided, the Signal Mountain Formation of south-central nearly straight sided, basal width about 0.9 length, Oklahoma. The New York form differs from the anteriorly truncate. Axial glabellar furrow deep; specimen illustrated by Stitt (1971, pl. 7, fig. 5) in preglabellar furrow deep, slightly depressed at mid­ having shallower lateral glabellar furrows. Stitt line. Two pairs lateral glabellar furrows, deeply im­ noted that some forms hig4 in the range of A. ma­ pressed. S1 bifurcate, posterior segment geniculate, sonensis in Oklahoma possess coarser granules than faintly connected to SO in large specimens; anterior earlier forms. This phenomenon is similar to that segment connected across midline. S2 deeply im­ shown by the New York specimen. pressed, connected across midline. S3 · absent. S4 The New York material differs from A. nor­ present or absent; if present, short, oblique back­ walkensis (on USNM 72700) from Monroe County, wards, straight. Occipital ring composite, lacks Wis., in having an incomplete rather than complete medial spine or node. Occipital furrow deeply im­ palpebral furrow, relatively shorter (exsag.) palpe- pressed. Frontal area sagittally convex, length about SYSTEMATIC PALEONTOLOGY 21

0.1 cranidiallength, anterior border absent. Anteri­ Bowmania d. B. pennsylvanica Rasetti or fixigena slope anterolaterally about 45° from Plate 2, figures 12-14 horizontal. Interocular fixigena width 0.3 adjacent Bowmania pennsylvanica Rasetti, 1959, p. 395, pl. 55, figs. glabellar width. Posterior fixigena subparallel sided, 1-5, text fig. 1; Longacre, 1970, p. 56, pl. 6, figs. 4, bent posteriorly, about 0.8 occipital lobe width (tr.). 5; Stitt, 1971, p. 21, pL 7, fig. 10. Eye ridge absent. Palpebral lobe length (exsag.) Material available.-One cranidium from locality approximately 0.5 glabellar length, lunate, flat, be­ low level of interocular fixigena, centered anterior H-1. to glabellar midpoint opposite L2. Preocular facial Description of Whitehall material.-Cranidium sutures divergent then converging evenly to sagittal subrectangular in outline, strongly convex sagittally. line forming rounded anterolateral corners of an­ Glabella parallel sided, strongly convex sagittally terior fixigena. Postocular facial sutures strongly and transversely, basal width 0.85 length, length 0.7 divergent, slightly convex, forming nearly trans­ cranidial length (excluding occipital ring). Axial verse character-state. glabellar furrows deep, anterior glabellar furrow Librigena, thorax, and pygidium unknown. less deep, convex anteriorly. Two pairs lateral gla­ Prosopon consists of evenly spaced coarse per­ bellar furrows. S1 deep, straight, short, oblique forate ( ?) granules and closely spaced fine granules backwards. S2 deep, pitlike. Occipital ring simple, in furrows and interspersed between coarse straight. Occipital furrow deep, straight, bent for­ granules. ward laterally. Frontal area convex, strongly down­ Discussion.-Stenochilina sp. A differs from the sloping, length (sagittal (sag.)) 0.3 cranidial holotype of S. spinifera in the absence of an occipital length. Anterior border convex, length (sag.) 0.4 spine, in having a relatively shorter frontal area preglabellar field length, well defined by deep anteri­ (length/cranidiallength 0.10 rather than 0.07 in the or border furrow. Anterior fixigena downsloping to holotype), a more straight-sided glabella, and in near vertical anterolaterally. Interocular fixigena the presence of diminutive S4 furrows on some upsloping from axial glabellar furrow. Posterior individuals. fixigena not preserved. Eye ridge well developed, Material from the Conococheague Limestone of curved slightly backward toward palpebral lobe, Maryland was assigned to S. spinifera by Rasetti abutts glabella anterior to S2. Palpebral lobes poor­ (1959, p. 383, pl. 52, figs. 15, 16). The specimens are ly preserved, slightly raised, centered opposite similar to the New York material in having near­ S2 ( ?) . Preocular facial sutures strongly divergent, ly straight-sided glabellae and diminutive S4 fur­ directed downward anterolaterally to near vertical. rows (shown in Rasetti's fig. 15). The only signifi­ Postocular facial sutures not preserved. cant difference between the New York and Maryland Prosopon consists of scattered coarse perforate forms seems to be the presence of an occipital spine granules on the raised parts of the glabella, fixi­ in the latter. genae, anterior border, and occipital lobe; closely The New York material is placed in open nomen­ spaced fine granules on the raised parts of the gla­ clature because of uncertainty as to the precise loca­ bella, fixigenae, anterior border, and occipital lobe; tion of the original collecting site and because the and closely spaced fine pits on the anterior fixigenae available specimens are few and rather poorly and preglabellar field. preserved. Discussion.-Rasetti ( 1959) originally described Occurrence.-Saukia Zone, locality 418e, Wash­ Bowmania pennsylvanica from cranidia collected at ington County, N.Y. the type locality ("cca") in the Conococheague Lime­ stone, Franklin County, Pa. He also tentatively as­ Family HETEROCARYONIDAE Hupe, 1953, emended Clark and Shaw, 1968 signed some forms to the taxon from near Frederick, Genus BOWMANIA Walcott. 1925 Md. Rasetti designated a holotype and two paratype Bowmania Walcott, 1925, p. 73; Rasetti, in Harrington and others, 1959, p. 0517. cranidia for B. pennsylvanica. Examination of the types shows that the preglabellar-field prosopon of Type species.-Arethusina americana Walcott, the paratypes differs from that of the holotype. The 1884, by original designation. holotype cranidium (Rasetti, 1959, pl. 55, figs. 1-3) Diagnosis.-The concept of Bowmania described is 4.6 mm long (sag.) and has evenly spaced scat­ by Rasetti (in Harrington and others, 1959) is fol­ tered coarse granules and interspersed closely spaced lowed here. fine granules on the preglabellar field. Paratype

527-763 0- 74- 4 22 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE cranidia (Rasetti, 1959, pl. 55, figs. 4, 5) are 3.9 1953), and Alberta (Derby and others, 1972). and 2.9 mm long (sag.). Prosopon of the preglabel­ Genera closely similar to M issisquoia are unknown lar fields of the two paratypes is similar to that of in North America. However, Parakoldinioidia Res­ the holotype except for the presence of abundant ser and Endo (Endo and Resser, 1937, p. 329, pl. 71, pits interspersed among the fine granules. The figs. 17-23), based on P. typicalis Resser and Endo cranidium from the Whitehall Formation is 3.5 mm from the Upper Cambrian of Manchuria, has some long (sag.) and intermediate in size between the similarities. Both forms possess a more or less paral­ two paratypes, and prosopon is similar to both para­ lel sided to slightly expanding glabella with short types. Therefore, the Whitehall cranidium is here lateral glabellar furrows and a distinct anterior considered conspecific with the paratypes. However, glabellar notch. The similarity seems to be greatest whether these forms are conspecific with the bolo­ between Missisquoia depressa Stitt (1971, pl. 8, fig. type cannot be proved without additional data. The 5, 6) and Parakoldinioidia typica,lis (see Kobayashi, fact that the nonpitted holotype is larger than the 1956, pl. 2, fig. 10-13). Both have bifid S1 lateral pitted forms suggests that late ontogenetic morpho­ glabellar furrows. Also, the small size of the exo­ logical changes may be a factor in explaining the skeleton and position of the palpebral lobes is similar differences. However, the available sample is too in both species. The principal differences between the small to rule out the alternative possibility that two two forms are the strongly convergent preocular species are present in the type collection. The White­ facial suture across the anterior border in Para­ hall cranidium is only tentatively assigned to Bow­ koldinioidia and the parallel preocular sutures in mania pennsylvanica for this reason. Missisquoia. Whether the similarities represent close Bowmania pennsylvanica was reported by Long­ relationship or homeomorphy is unknown at present. acre (1970) from the Sa.ukiella serotina Subzone in the Wilberns Formation of central Texas. The Texas Missisquoia typicalis Shaw forms differ in possessing glabellae that are slightly Plate 3, figures 1-9 expanded anteriorly. However, presence or absence Missisquoia typicalis Shaw, 1951, p. 108, 109, pl. 23, figs. of pits on the anterior part of the cranidium was not 1-10; Winston and Nicholls, 1967, p. 88, 89, pl. 13, figs. 2?, 5, 6, 10, 12, 15, 181; Stitt, 1971, p·. 26, pl. 8, mentioned by Longacre. figs. 1-4. Stitt (1971) reported B. pennsylvanica from the lower part of the Signal Mountain Formation in Material available.-Thirty cranidia, four libri­ south-central Oklahoma. The taxon ranges through genae, and 52 pygidia from locality 4 70bl ; 45 cra­ the Saukia Zone in that area (Stitt, 1971, p. 22). nidia, six librigenae, and 47 pygidia from locality Stitt also noted that some specimens have "pits scat­ 7098-CO; 59 cranidia, 25 librigenae, and 123 pygidia tered around the granules" but the feature was not from locality 7099-CO; and, two cranidia and one discussed in detail. pygidium all questionably assigned from locality Occurrence.-Saukiella serotina Subzone at locali­ H-2. ty H-1, lower Whitehall Formation, Washington Description of Whitehall material.-Exoskeleton County, N.Y. oval in outline, moderately convex, probably about one-half em long. Cranidium subquadrate, moder­ Family MISSISQUOIIDAE Hupe, 1953 ately convex. Glabella variable, slightly tapered to Genus MISSISQUOIA Shaw, 1951 slightly expanded anteriorly, basal width 0. 7 to 0.8 Missisquoia Shaw, 1951, p. 108; Winston and Nicholls, 1967, length (sag.), anterior lobe with medial notch. Axial p. 88. glabellar furrows well defined, anteriorly confluent Type species.-Missisquoia typicalis Shaw, 1951, with anterior border furrow. Lateral glabellar fur­ by original designation. rows pitlike on sides of glabella. S1 convex, deeply Diagnosis.-The diagnosis provided by Winston impressed, connected to axial glabellar furrow. S2 and Nicholls (1967) is followed here. transverse, straight, deeply impressed, connected to Discussion-Missisquoia is a widespread genus in axial glabellar furrow. S3 transverse, straight, North America. The taxon is known from the Missis­ faintly impressed, not connected to axial glabellar quoia Zone of Vermont (Shaw, 1951), New York furrow. S4 faint or absent, straight, connected to (this report), Oklahoma (Stitt, 1971), Texas (Win­ axial glabellar furrow. Occipital ring simple, round­ ston and Nicholls, 1967), Utah and Nevada (Taylor, ed posteriorly. Occipital furrow deep, straight. 1971), Wyoming (U.S. Geol. Survey, unpub. data, Medial region of occipital ring with node or short SYSTEMATIC PALEONTOLOGY 23 spine in small individuals, node may or may not be distortion seems to have modified the Vermont ma­ present in large individuals. Preglabellar field ab­ terial. Comparison of New York specimens with sent. Anterior border horizontal, flat, length (sag.) undistorted topotypic collections from the Highgate about 0.1 cranidial length. Anterior margin evenly suggests that the forms are conspecific. rounded. Anterior fixigena evenly downsloping an­ Winston and Nicholls (1967) assigned material terolaterally. lnterocular fixigena (including palpe­ from the Wilberns Formation of central Texas to M. bral lobe) convex, raised about one-half glabellar typicalis. The Texas material is similar to the New height, width (tr.) about 0.5 adjacent glabellar York specimens except for the attributed librigena width. Posterior fixigena subtriangular, downslop­ (Winston and Nicholls, 1967, pl. 13, fig. 2). The ing laterally, about equal in width (tr.) to occipital Texas librigena is equidimensional, with a short ring. Posterior border furrow not connected to oc­ ( tr.) posterior margin, and slender incurved genal cipital furrow. Eye ridge faintly developed to absent, spine. Such shape contrasts markedly with libri­ abuts axial glabellar furrow opposite S3 where genae here attributed to M. typicalis from New observable. Palpebral lobe rounded, subhorizontal, York. The New York form is rather long and slender not differentiated from interocular fixigena by pal­ and lacks a posterior border furrow. The otherwise pebral furrow, length (exsag.) 0.3 to 0.4 glabellar strong similarity between cranidia and pygidia from length (sag.), centered opposite S2. Preocular facial Texas and New York suggest that the librigena sutures parallel, straight, downsloping anteriorly at illustrated by Winston and Nicholls may have been about 30° angle from horizontal. Postocular facial attributed in error and should be reevaluated. sutures divergent, convex. Stitt (1971) attributed material from the upper Librigena narrow, evenly rounded laterally. Genal part of the Signal Mountain Limestone of south­ field convex, downsloping laterally to deep border central Oklahoma toM. typicalis. The specimens il­ furrow, genal field continuous with genal spine pos­ lustrated by Stitt seem to fall within the range of terolaterally through genal corner. Ocular incisure variation of the New York material. with raised eye socle and holochroal visual surface Missisquoia typicalis occurs in the upper part of often attached. Eye socle about 0.5 height of visual the Notch Peak Limestone of west-central Utah surface. Lateral border horizontal, flat, differenti­ (Taylor, 1971). The Utah collections contain a ated from genal field by abrupt change in slope. greater proportion of individuals with slightly ex­ Genal spine broken on all observed specimens. panded glabella than do the New York collections. Thorax unknown. However, taxonomic significance of this difference Pygidium variable, strongly convex to moderately is presently unknown as both collections are highly convex, subtriangular in outline, length about 0.8 variable in this feature. width. Axis straight sided, tapered posteriorly, nine axial rings plus terminal piece. Axial rings become Occurrence.-Missisquoia Zone localities 470ht, faintly defined posteriorly. Pleural regions flat, 7098-CO, 7099-CO, and H-2 ( ?) from the upper strongly downsloping to near vertical at margin, Whitehall Formation, Washington County, N.Y. five pairs deeply impressed interpleural furrows, six Family PLETHOPEL TIDAE Raymond, 1925 pairs les.s deeply impressed pleural furrows. Pleurae terminate distally into apparent blunt spines. Genus PLETHOMETOPUS Ulrich, 1931 Prosopon consists of fine closely spaced granules Plethometopus Ulrich in Bridge, 1931, p. 221 on the glabella, fixigena, genal field, and pygidium and occasional scattered larger granules. The bor­ Type species.-Bathyurus armatus Billings, 1860, ders of the cranidium and librigena have longitudi­ by original designation. nal terrace lines. Discussion.-Morphological characteristics of the Discussion.-Samples from the Whitehall Forma­ genus have been summarized in Harrington and oth­ tion are morphologically variable in degree of taper ers (1959, p. 0410). Plethometopus is distinguished of glabella, convexity of pygidium, and relative from other members of the Plethopeltidae by the abundance of large scattered granules on dorsal presence of at least four of the following five fea­ surfaces. tures: a triangular-shaped occipital region, occipital The type material from the Highgate Formation furrow, effaced preglabellar furrow, faint to absent near Highgate Falls, Vt. (Shaw, 1951, 1955, 1958), posterior axial glabellar furrows, and posterior bor­ has similar variability, although some diastrophic der furrows. 24 LATE GAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

Pletbometopus obtusus Rasetti Lochman (1946, p. 551, pl. 1, figs. 7-9) described Plate 1, figures 11-14 and illustrated Plethometopus knopfi from weathered Plethometopus obtusus Rasetti, 1945, p. 472, pl. 62, figs. 1, dolomite 1~ miles south of Pine Plains, Dutchess 2; Rasetti, 19·59, p. 383 pl. 53, figs. 11-14; Longacre, County, N.Y. The holotype illustrated by Lochman 1970, p. 19, pl. 6, figs.. 14, 15; S.tittt, 1971, p. 35; pl. 6, fig. 16. (fig. 9) is similar to material from Whitehall except that the cranidium is more quadrate in outline. The Unassigned pygidium no. 7, Rasetti, 1945, p. 477, pl. 62, figs. 29 30. ratio of cranidial width (measured transversely be­ Plethometopus modestus Ulrich. Winston and Nicholls, 1967, tween distal margins of palpebral lobes) to cranidial p. 87, pl. 10, fig. 11. length is approximately 1.0 in P. knopfi and 0.8 in Whitehall material attributed to P. obtusus. Material available.-Eight fragmentary cranidia Longacre (1970) established the presence of P. from locality 473f. obtusus in the Wilberns Formation of central Texas Diagnosis.-A species of Plethometopus with pal­ where she assigned occurrences of the species to the pebral lobes centered anterior to the cranidial mid­ Saukiella serotina and Corbinia apopsis Subzones. line; axial glabellar furrows only present opposite The Wilberns material previously assigned to Ple­ and posterior to the palpebral areas; slightly di­ thometopus modestus Ulrich by Winston and vergent preocular facial sutures ; subtriangular­ Nicholls (1967) was reassigned to P. obtusus by shaped occipital lobe that lacks an occipital spine; Longacre (1970). and a deeply impressed, posteriorly concave occipital Stitt (1971) collected P. obtusus from the Signal furrow. Mountain Formation of south-central Oklahoma Description of Whitehall material.-Cranidium where he assigned its occurrences to the Saukiella subrectangular in outline, width (tr. between palpe­ serotina and Corbinia apopsis Subzones. bral lobes) approximately 0.8 length (sag.), sagit­ Search of the USNM collections yielded a single tally convex. Glabella undifferentiated except oc­ cranidium from New Jersey which can be tentative­ cipital region. Axial glabellar furrows consist of ly assigned to P. obtusus. The locality is listed as shallow depressions extending from posterior border number 11c, which Walcott (1912a, p. 178) described to a position opposite palpebral lobes. Axial furrows as follows: "Upper Cambrian: Hardyston quartzite absent anteriorly. Lateral glabellar furrows absent. ***,O'Donnell and McManniman's quarry, Newton, Occipital ring simple, subtriangular in outline, well Sussex County, N.J." Later, Walcott (1914, p. 389) defined by occipital furrow. Occipital furrow deep, emended the stratigraphic designation to "Kittatin­ slightly concave posteriorly. Frontal area evenly ny limestone." The specimen occurs as an internal downsloping at about 45° angle from horizontal, mold in fine-grained dolomitic sandstone. The crani­ continuous with glabellar region. Anterior border dium is well enough preserved to show the divergent absent. Posterior fixigena short (tr.), width (tr.) preocular facial sutures, subtriangular-shaped oc­ about 0.3 basal glabellar width, triangular shaped, cipital lobe, and incomplete axial glabellar furrows deep border furrow present. Anterior fixigena un­ which are characteristic of the species. differentiated. Palpebral lobes consist of narrow Occurrence.-Saukiella serotina Subzone, locality (tr.) raised ridges, length (exsag.) 0.2 cranidial 473f, Washington County, N.Y. length (excluding occipital lobe), centered slightly anterior to cranidial midpoint. Preocular facial Pletbometopus sp. A sutures slightly divergent, downsloping. Postocular Plate 1, figures 15-17 facial sutures strongly divergent, convex. Material available.-One cranidium from locality Exoskeletal surfaces and internal molds are 473f. smooth. Librigena, thorax, and pygidium are un­ Description.-Cranidium subtrapezoidal in out­ known in Whitehall collections. line, strongly convex sagittally, length 0.9 width. Discussion.-Plethometopus obtusus was original­ Glabella undifferentiated. Axial glabellar furrows ly described by Rasetti (1945) from Boulder 57 at faint, only present on posterior one-fourth of cra­ Levis, Quebec. Later, Rasetti (1959) recorded the nidium. Occipital ring undifferentiated. Frontal area species from the Conococheague Limestone of Wash­ downsloping at about 60° angle from the horizontal. ington County, Md., and attributed pygidia from Anterior fixigena undifferentiated. Posterior fixi­ Levis that had previously (Rasetti, 1945) been illus­ genae triangular, width (tr.) 0.3 basal glabellar trated but unassigned. width. Posterior border furrow shallow, pitlike. SYSTEMATIC. PALEONTOLOGY 25

Palpebral lobes consist of raised ridges, length (ex­ lection upon which it was based. She provided a sag.) 0.2 cranidial length, centered anterior to cra­ diagnosis and concluded that Plethopeltis can be dis­ nidial midline ( 0.4 cranidial length). Preocular tinguished from other genera of the Plethopeltidae facial sutures strongly convergent, forming bluntly by the presence of complete axial and preglabellar pointed anterior cranidial margin. Postocular facial furrows and lack of an anterior border furrow. sutures strongly divergent, convex. These features distinguish Plethopeltis from the Exoskeletal and internal mold surfaces smooth similar genus Plethometopus Ulrich. except for bertillion prosopon on the posteriormost part of the occipital region. Pletbopeltis sp. indet. Discussion.-The single cranidium is similar to Plate 1, figures 1-3 forms assigned to both Stenopilus and Plethometop­ Discussion.-Locality H-3 from the Whitehall us. The former usually have strongly convergent Formation contains five poorly preserved cranidia preocular facial sutures, narrow palpebral lobes, which conform to the concept of Plethopeltis. The absence of dorsal furrows, and coalescence of the forms have well-defined axial furrows, shallow pre­ occipital region with the basal glabellar lobe. In glabellar furrows, and lack lateral glabellar furrows. contrast, species assigned to Plethometopus usually Axial furrows are straight to slightly concave later­ have slightly divergent to subparallel preocular ally. Occipital lobes are triangular in outline and facial sutures, narrow palpebral lobes, axial glabel­ well defined by a simple, slightly convex occipital lar furrows in varying degrees of completeness, and furrow. Four of the internal cranidial molds retain usually a differentiated occipital region. An excep­ sufficient exoskeletal material to show that prosopon tion is Plethometopus convergens (Raymond) which consists of evenly spaced granules on three cranidia possesses slightly convergent preocular facial su­ and a smooth surface on the fourth specimen. Sur­ tures. However, Plethometopus sp. A differs from faces of well-preserved internal molds are finely pit­ P. convergens in having more strongly convergent ted. No pygidium is known from the sample. preocular facial sutures and palpebral lobes which Granular prosopon has been reported on several are centered anterior, rather than posterior, to the forms assigned to Plethopeltis. They include: Ple­ cranidial midline. (See also Rasetti, 1959, pl. 53, figs. thopeltis granulosa Resser, 1942, from New York; 15, 16; Longacre, 1970, p. 19.) Plethopeltis arbucklensis Stitt, 1971, from south­ Morphologically, the cranidium of Plethometopus central Oklahoma; and, Plethopeltis sp. of Long­ sp. A is intermediate between Plethometopus and acre ( 1970) from central Texas. Plethopeltis granu­ Stenopilus. However, the subtle differences point up losa was based on part of Walcott's hypodigm of the arbitrary and highly subjective distinction be­ Agraulos saratogensis from locality 76 at the Hoyt tween these genera when only their cranidia are quarry, 4 miles west of Saratoga Springs, N.Y. It considered. This situation should serve as a caution­ differs from the Whitehall material in having lateral ing influence in applying too much emphasis on bio­ glabellar furrows, more deeply impressed axial and stratigraphic correlations when only fragmentary anterior glabellar furrows, and more closely spaced smooth trilobites are available. granules. Occurrence.-Plethometopus sp. A by association Plethopeltis arbucklensis Stitt differs from the is assigned to the Saukiella serotina Subzone, at Whitehall specimens in having laterally convex axial locality 473f, Washington County, N.Y. glabellar furrows and a more strongly tapered glabella. Genus PLETHOPEL TIS Raymond, 1913 Plethopeltis sp. of Longacre ( 1970) from the Sau­ Plethopeltis Raymond, 1913, p. 64; Field, 1915, p. 37; Ulrich kiella pyrene Subzone of central Texas seems similar in Bridge, 1931 p. 219; Bridge and Cloud, 1947, p. 556; Longacre, 1970, p. 19. to the Whitehall specimens. An apparent difference is the presence of axial glabellar furrows which are Type species.-Agraulos saratogensis Walcott, slightly convex laterally in the Texas material. The 1890, by original designation. apparent similarity between New York and Texas Discussion.-Plethopeltis was originally based on specimens may be a result of the few features avail­ material from the Hoyt quarry (Walcott's locality able for comparison. Because of this possibility and 76), 4 miles west of Saratoga Springs, N.Y. Long­ the fact that Plethopeltis seems to range throughout acre (1970, p. 19-21) recently discussed the complex the Trempealeauan Stage, caution should probably nomenclatural history of the genus and the type col- be exercised in making biostratigraphic inferences. 26 LATE GAM.BR.IAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE from material assigned to Plethopeltis unless all arcuate, concave abaxially. Preocular facial sutures morphologic parts are present and taxa can be more convergent, convex. Postocular facial sutures weak­ precisely characterized than can be done on cranidial ly divergent, slightly convex. features alone. Librigenae long, narrow, steeply downturned later­ Occurrence.-Saukiella serotina Subzone, locality ally. Genal field downsloping continuously to lateral H-3, lower Whitehall Formation, Washington margin, anteriorly confluent with frontal area, pos­ County, N.Y. teriorly confluent with genal spine. Ocular incisure Family PTYCHASPIDIDAE Raymond, 1924 with raised eye socle and attached ( ?) visual surface. Subfamily PTYCHASPIDINAE Longacre, 1970 Posterior border deeply impressed adaxially from Genus EUPTYCHASPIS Ulrich, 1931 genal spine. Lateral border furrow faintly im­ Euptychapsis Ulrich in Bridge, 1931, p. 217; Winston and pressed. Genal spine long, length about twice cra­ Nicholls, 1967 p. 78; Longacre, 1970, p. 40. nidial length, triangular in cross section, distally Type species.-Euptychaspis typicalis Ulrich in curved slightly downward below level of cranidium. Bridge, 1931, by original designation. Thorax unknown. Discussion.-The generic concept given by Long­ Pygidium subelliptical in outline, length 0. 7 width. acre ( 1970) is followed here. Information on the Axis tapered posteriorly, length about 0.6 pygidial previously undescribed pygidium of E. typicalis is length (sag.), two axial rings plus terminal piece. added under the description of new material below. Pleural regions diminutive, separated from wide Euptychaspis typicalis Ulrich border by ridge. Border downsloping, lower than Pla.te 2, figures 4-11 pleural regions. Euptychaspis typicalis Ulrich in Bridge, 1931, p. 218, pl. Prosopon consists of reticulate pattern of ridges 19, figs. 5-7; Dake and Bridge, 1932, p. 740, pl. 12, fig. on the cranidial dorsum and heavy anastomosing 3; Rasetti, 1959, p. 393, pl. 52, figs. 11-13; Winston terrace lines on the frontal area and lateral parts of and Nicholls, 1967, p. 78, pl. 9, fig. 17; Longacre, 1970, p. 42, pl. 4, fig. 9; Stitt, 1971, p. 42, pl. 6, fig. 19. the librigenae. Internal molds finely pitted. Pygidial surfaces poorly preserved, border region with scat­ Material available.-Nine cranidia, nine libri­ tered pits which may be fortuitous. genae, and three pygidia from locality H-1; 15 cranidia and two librigena from locality H-3; and Discussion.-Longacre (1970, p. 42) noted that one cranidium tentatively assigned from locality cranidia assigned to E. typicalis from central Texas 473f. possess a narrow (sag.) anterior border. A narrow Description of Whitehall material.-Cephalon anterior border is present on some, but not all, speci­ semicircular in outline, strongly convex. Glabella mens from New York and one of Ulrich's syntypes subparallel sided to expanded forward, basal width (USNM 83493) from Missouri. This feature, in 0.85 length. Axial glabellar furrows deep, broad; association with relatively wide fixigenae and an anterior furrow shallow. Lateral glabellar furrows anterior glabellar lobe that does not reach the anteri­ well developed, deep. S1 and S2 continuous across or margin, distinguishes E. typicalis from other glabella forming straplike L1 and L2. S3 faintly im­ nominal species assigned to the genus. pressed rarely on internal molds. Occipital ring The pygidium, described here for the first time, drawnout into broad blunt spine. Occipital spine tri­ has a border markedly depressed below the level of angular in cros·s section, inclined at approximately the axis and pleural regions. This construction prob­ 45o to horizontal. Frontal area downsloping, nearly ably facilitated enrollment by providing a notch for vertical, length (sag.) 0.1 glabellar length. Pregla­ abutment between the ventral doublure-rostral re­ bellar field absent. Anterior border wirelike or gion of the cephalon and the pygidial dorsum. absent. Anterior fixigenae not differentiated, contin­ Euptychaspis typicalis is known from the Saukia uously curved laterally from frontal area. Interocu­ Zone of southern Missouri (Ulrich, 1930) and Mary­ lar fixigenae upsloping, width (tr.) 0.7 adjacent land (Rasetti, 1959) ; the Saukiella junia Subzone of glabellar width. Posterior fixigenae approximately central Texas (Winston and Nicholls, 1967; Long­ equal to occipital ring width (tr.) Eye ridge mod­ acre, 1970) ; and the Saukiella junia and Saukiella erately developed on dorsum, strongly developed on serotina Subzones of Oklahoma (Stitt, 1971) and internal molds, abutts axial glabellar furrow at L3. east-central Nevada (Taylor, 1971). Palpebral lobes poorly preserved, apparently raised Occurrence.-Saukiella serotina Subzone, locali­ above level of fixigenae, length ( exsag.) 0.3 glabellar ties H-1, H-3, and tentatively 473f, lower Whitehall length, centered opposite L2. Palpebral furrow deep, Formation, Washington County, N.Y. SYSTEMATIC PALEONTOLOGY 27

Subfamily SAUKIINAE Ulrich and Resser, 1933 ly divided pygidial pleural fields, presence of an oc­ Discussion.-Ulrich and Resser (1930, 1933) pub­ cipital spine, and granular prosopon on the cranidi­ lished two monographs on the Upper Mississippi um. These differences are all of doubtful taxonomic Valley representatives of the Dikelocephalidae, significance because species have been included in which included subfamilies Dikelocephalinae and Tellerina that have unequally divided pleural re­ Osceolinae (1930) and Saukiinae (1933). General gions; Prosaukia includes species with occipital impracticability of Ulrich and Resser's treatment of spines, and Calvinella includes forms with bertillion, the dikelocephalid genera and species led Raasch granular, or mixtures of both kinds of prosopon on (1951) to a restudy of the fossil groups and estab- cranidia. Problems relating to the artificiality of lishment of many species synonomies. Raasch (1951, Calvinella and other saukiinids is discussed under p. 139) pointed out that among several difficulties the heading "Subfamily Saukiinae." with the Ulrich and Resser systematics is that the "Calvinella" prethoparia Longacre authors based some taxa on misattributed exoskele­ Plate 2, figures 1-3 tal parts which originated from different localities Calvinella prethoparia Longacre, 1970, p. 45, pl. 6, figs. 7- and in some cases different stratigraphic horizons. 12. Unfortunately, Raasch's study did not include nom.­ enclatural stabilization of the type collections or Mat erial available.-Three cranidia and one libri­ revised diagnoses of the dikelocephalid genera. gena from locality H-1; five cranidia, and one libri­ The taxonomic procedure followed by Ulrich and gena questionably assigned from locality H-3. Resser created a critical problem in that many type Description of Whitehall material.-Cranidium species were based on numerous specimens in "co­ subtrapezoidal in outline, moderately convex. Gla­ type series." This results in difficulty in comparing bella subparallel sided to slightly tapered forward, new material with type collections because at­ length (excluding occipital ring) approximately 0.9 tributed specimens in the type collections are suspect basal glabellar width, anteriorly truncate. Axial at best and biologically meaningless at the worst. glabellar furrows wide, deeply impressed. Anterior Because of the taxonomic procedures used by ffirich glabellar furrow less deeply impressed than axial and Resser (1930, 1933), objectively based concepts furrows. Four pairs lateral glabellar furrows. 81 of the dikelocephalid genera cannot be established deeply impressed laterally, faintly geniculate, be­ at present without a comprehensive reevaluation of coming shallower adaxially, connected to axial fur­ their type species. Pending such a reevaluation I row, connected across midline. S2 straight, oblique have chosen to apply the saukiinid generic names backwards, deeply impressed laterally, becoming reservedly, in recognition of the possibility that they faintly connected across midline, connected to axial may not represent natural groupings of species and furrow. S3 shallow, straight, transverse, not con­ that the type collections may contain nonconspecific nected to axial furrow. S4 shallow, straight, oblique attributions of exoskeletal parts. The genera that forward, connected to axial furrow. Occipital ring are affected in this study are Calvinella Walcott and simple, concave forward, with occipital spine (length Prosaukia Ulrich and Resser. not observed). Occipital furrow concave forward, deeply impressed laterally, moderately impressed Genus CALVINELLA Walcott, 1914 adaxially. Preglabellar field concave, consisting of a Calvinella Walcott, 1914, p. 388; Ulrich and Resser, 1933, broadening of the anterior glabellar furrow. An­ p. 215; Lochman, in Harrington and others, 1959, p. terior border width (sag.) approximately 0.2 cra­ 0323; Longacre, 1970, p. 45. nidial length, convex. Anterior border furrow deep, Type species.-Dikelocephalus spiniger Hall, 1863, well differentiated abaxially, becoming shallower by original designation. adaxially and inosculating with anterior glabellar Discussion.-Longacre (1970) has most recently furrow. Anterior fixigena gently downsloping an­ summarized the morphological features of species terolaterally. Interocular fixigena width (tr.) 0.5 assigned to Calvinella. She characterized the pygidi­ adjacent glabellar width, raised above level of axial um as transversely elliptical. However, Ulrich and glabellar furrow, below level of glabellar crest, sub­ Resser ( 1933, pl. 38, 39) included several forms with horizontal. Postocular fixigena triangular in out­ subcircular pygidia. line, width (tr.) approximately 0.8 occipital lobe Features normally used to distinguish Calvinella width. Posterior border furrow deep, straight, off­ from other genera of the Saukiinae include unequal- set posteriorly from occipital furrow. Eye ridge 28 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE absent. Palpebral lobe lunate, flat, below level of flat, interocular fixigenae rather than narrow, interocular fixigena, length (exsag.) 0.5 glabellar abaxially upsloping fixigenae; triangular posterior length, centered anterior to .glabellar midpoint op­ fixigenae, rather than subparallel sided; and rela­ posite anterior part of L2. Anterior end palpebral tively short ( exsag.) palpebral lobes that are cen­ lobes opposite S4, posterior end opposite Sl. Pre­ tered anterior to the glabellar midpoint opposite L2, ocular facial sutures subparallel to anterior border, rather than long palpebral lobes that center behind converging diagonally across anterior border to mid­ the glabellar midpoint opposite Sl. This combination line. Postocular facial sutures divergent, straight. of differences is sufficient to establish a new genus Librigena narrow, margin evenly rounded. Genal of Saukiinae based on Calvinella prethoparia Long­ field gently convex, well differentiated from raised acre. However, such action is held in abeyance pend­ lateral and posterior borders by deep marginal fur­ ing a comprehensive reevaluation of the existing rows. Lateral border furrow and posterior border saukiinid genera. furrow confluent at corner angle, lateral furrow con­ Occurrence.-Saukiella serotina Subzone at locali­ tinuous, faintly impressed onto genal spine. Genal ties H-1 and H-3, lower Whitehall Formation, spine approximately two-thirds librigenal length Washington County, N.Y. ( exsag.) Inner spine angle approximately 90°. Thorax and pygidi urn unknown. Genus PROSAUKIA Ulrich and Resser, 1933 Prosopon consists of anastomosing ridges on the Prosaukia Ulrich and Res,ser, 1933, p. 137; Lochman, in Harrington and others, 1959, p. 0324; Longacre, 1970, cranidium except in furrows which are smooth. p. 47. Large cranidia (approx 8 mm long) have ridges grading to granules with irregularly shaped bases on Type species.-Dikelocephalus misa Hall, 1863, by the adaxial part of the glabella and occipital ring. original designation. Smaller cranidia (approx 4 mm long) lack granules, Discussion.-The original diagnosis of Prosaukia and the anastomosing ridges cover the entire dorsal given by Ulrich and Resser ( 1933) provided few surface. The only librigena attributed with certainty features that are not also characteristic of the other has faint anastomosing ridges on the genal field and genera of the Saukiinae. Lochman (in Harrington lateral border. Weak development of ridges on the and others, 1959) gave an improved diagnosis, librigena may result from poor preservation. which was later slightly modified by Longacre Discussion.-"Calvinella" prethoparia Longacre ( 1970). In summary, Prosaukia has been distin­ was originally described from the Saukiella serotina guished by the presence of an anteriorly tapering Subzone of the Wilberns Formation of central Texas. glabella, convex preglabellar field, an anterior border Cranidia from the Whitehall Formation attributed furrow that shallows transversely across the midline, to the species differ from the Texas material in and librigenae with lateral and posterior border fur­ possessing granular prosopon which is more adaxial­ rows that are not confluent and extend subparallel ly restricted and absent from the anterior border. distally along the genal spine. Forms have been in­ This difference is not considered of taxonomic cluded in the genus which have prosopon described significance. or illustrated as smooth, granular, or consisting of The holotype of C. prethoparia (see Longacre, anastomosing ridges. 1970, pl. 6, fig. 7) is an internal mold having S2 fur­ Species have been assigned to Prosaukia that show rows that connect across the midline. The depth of exceptions to the characteristics normally used to impression of S2 is greater on the holotype than on differentiate the genus. For example, Prosaukia the New York material. This character-state may curvicostata Ulrich and Resser, 1933, possesses a be related to instar size because smaller cranidia parallel-sided, anteriorly rounded glabella and an tend to have more weakly developed S2 furrows than anterior border furrow that is evenly impressed do larger cranidia. The holotype is more than twice across the midline. In addition, most species as­ as long as the largest cranidium illustrated here. signed to Prosaukia have librigenae with noncon­ "Calvinella" prethoparia differs considerably from fuent border furrows. At least one exception is material attributed to Calvinella spiniger (Hall), Prosaukia delecostata Ulrich and Resser ( 1933, pl. the type species of Calvinella. (See Ulrich and Res­ 26, fig. 15) in which the furrows are confluent. Gen­ ser, 1933, pl. 37, 38.) Major differences in cranidial eral problems related to the artificiality of the sau­ structure in "C." prethoparia include: parallel rath­ kiinid genera are discussed under the heading "Sub­ er than divergent preocular facial sutures; wide, family Saukiinae." SYSTEMATIC PALEONTOLOGY 29

"Prosaukia" spinula Taylor, n. sp. line. Postocular facial sutures divergent, sinuous. Plate 2, figures 15-20 Librigena moderately convex, evenly rounded lat­ Types.-Holotype cranidium, USNM 186598; erally. Genal field convex, well differentiated from paratype cranidia, USNM 186599 and 186600; para­ lateral border by deep furrow. Lateral border raised, type librigena, USNM 186602; paratype pygidium, convex, continuous with long ( ?) genal spine. Lateral USNM 186603, all from locality H-1. Paratype py­ and posterior border furrows deeply impressed, con­ gidium, USNM 186601 from locality H-3. All type nected at corner angle, lateral furrow continuous specimens are from the lower Whitehall Formation, distally onto genal spine. Inner spine angle about Washington County, N.Y. 135°. Thorax unknown. Material available.-Ten cranidia, 15 librigenae, Pygidium subcircular in outline, length about 0.9 and three pygidia from locality H-1; 10 cranidia, width, strongly convex transversely. Axis tapered, six librigenae, and six pygidia from locality H-3; straight sided, length about 0.7 pygidiallength, four 13 cranidia, seven librigenae, and three pygidia from axial rings plus terminal piece, posteriormost ring locality 470b; and three librigenae and one pygidium poorly differentiated. Pleural fields strongly down­ questionably assigned from locality 473f. sloping laterally, subequally divided by five furrows Diagnosis.-A species of saukiinid trilobite with and ridges, furrows strongly backturned. Pleural a pygidium having a single short posteriorly directed fields change slope distally to form poorly differenti­ median marginal spine, an axis greater than one­ ated gently downsloping border. Posterior margin half of the pygidial length and a glabella with ber­ of pygidium drawn out posteriorly into broadly tillion pattern prosopon. pointed spine, length about 0.1 pygidial length, up­ Description.-Cranidium subrectangular in out­ turned slightly distally. Ventral doublure wide, line, moderately convex. Glabella trapezoidal in out­ reaching posterior end of axis (not observed antero­ line, anteriorly truncate, length approximately equal laterally). to basal width; sides straight, slightly tapered an­ Cranidial prosopon consists of bertillion pattern teriorly from L1; L1 bowed outward slightly. Axial on the occipital ring and posterior part of glabella furrows well defined, deeply impressed. Anterior decreasing in degree of definition anteriorly, and glabellar furrow shallower at midline than at an­ faint bertillion pattern on the anterior fixigena. terolateral corners of glabella. Two pairs lateral Other areas of cranidi urn smooth. Internal molds glabellar furrows. 81 concave, deeply impressed smooth. laterally, becomes faintly impressed adaxially, faint­ Librigena with complex anastomosing ridges on ly connected across midline on small holaspids, not genal field, lateral border, posterior border, and connected on large holaspids, may connect on inter­ genal spine. Anastomosing ridges faint on internal nal molds of large holaspids. 82 straight, faintly molds. impressed laterally, not connected across midline. Pygidium with anastomosing ridges on axis, Occipital ring simple, straight, with medial node. pleural regions, and border oriented more or less Occipital furrow curved forward slightly at midline. parallel to margins. Internal molds of pygidium Frontal area length (sag.) 0.2 cranidiallength, sub­ smooth. horizontal. Anterior border slightly raised, poorly Discussion.-"Prosaukia" spinula n. sp. is placed differentiated by shallow anterior border furrow. in "Prosaukia" because of the presence of a convex Preglabellar field convex, length (sag.) about 0.5 preglabellar field, a slightly forward-tapering gla­ anterior border length (sag.). Anterior fixigena bella, and an anterior border furrow that shallows evenly downsloping. Interocular fixigena gently up­ across the midline. The attributed librigenae are sloping laterally, width (tr.) 0.3 adjacent glabellar similar to forms usually assigned to Calvinella in width. Posterior fixigena relatively short (tr.), sub­ possessing lateral and posterior border furrows that parallel sided. Eye ridge absent. Palpebral lobes merge at the corner angle and continue on to the lunate, length ( exsag.) 0. 7 glabellar length, flat, sub­ genal spine as an extension of the lateral furrow. horizontal, below level of interocular fixigena, cen­ Librigena assigned to "Prosaukia" usually have lat­ tered posterior to glabellar midpoint opposite Sl. eral and posterior border furrows that do not become Preocular facial sutures weakly divergent to anterior confluent at the corner angle. border furrow, becoming strongly convergent and Rasetti (1946, p. 541, pl. 1, figs. 17-19) reviewed coursing diagonally across anterior border to mid- Saukia eboracensis Resser, 1942, on the basis of 30 LATE CAM.BRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE additional material collected from the type locality and deep confluent border furrows that do not extend in the Hoyt Limestone, one mile northwest of Sara­ onto the genal spine. The cranidia illustrated by Win­ toga Springs, N.Y. He reassigned the species to ston and Nicholls (figs. 6, 8) differ from those Prosaukia on the basis of attributed cranidia which illustrated by Longacre in having more forward­ have convex preglabellar fields. The attributed cra­ tapering glabellae and relatively wider preglabellar nidia are similar to those here assigned to uPro­ fields. These observations lead to the question wheth­ saukia" spinula. Differences include adaxially dis­ er the librigena placed in synonomy with S. serotina connected, rather than connected, S2 furrows and is indeed correctly attributed. Because of this uncer­ weaker development of cranidial prosopon in "P." tainty, the relationship between "P." spinula and S. spinula. The greatest differences between the two serotina cannot be satisfactorily resolved at present. species are shown by the attributed pygidia. The The pygidia and librigenae here attributed to holotype pygidium of Prosaukia. eboracensis is wid­ "Prosaukia" spinula are most similar to Calvinella er than long, possesses five axial rings rather than americana Kobayashi, 1935 [ = Calvinella walcotti four, and lacks the strongly backturned pleural fur­ Ulrich and Resser, 1933; not Calvin ella walcotti rows and posterior marginal spine characteristic of (Mansuy, 1915)] from the Upper Cambrian of Wis­ uP." spinula. consin. (See Ulrich and Resser, 1933, pl. 40, figs. Lochman (1946, p. 549, pl. 1, figs. 1-6) described 1-14.) The pygidium attributed to C. americana is and illustrated Prosaukia briarcliffensis from weath­ subcircular in outline with the posteriormost part of ered dolomite outcropping 1~ miles south of Pine the margin upturned as in "P." spinula. In all avail­ Plains, Dutchess County, N.Y. The specimens, al­ able specimens of C. americana, the area occupied though fragmentary, are similar to material as­ by the pygidial spine is broken away, and it cannot signed to "P." spinula in possessing librigenae with be definitely stated that it was originally present. anastomotic ridges on the genal field. The cranidium However, fossil preservation is such in the C. ameri­ of P. briarcliffensis has S1 furrows that do not con­ cana sample, that specimens split out of the matrix nect across the midline. However, the furrows are along partings parallel to the bedding. As the py­ relatively deeply impressed laterally, as in "P." gidial spine would have been upcurved it would tend spinula, so that the faint connection of S1 furrows to be in a higher plane than the main part of the in "P." spinula may not be a significant difference. pygidium, thus potentially becoming easily broken The pygidium attributed to P. briarcliffensis is simi­ when the rock was split. In all specimens observed lar to "P." spinula in having a circular outline, back­ (for example, Ulrich and Resser, 1933, pl. 40, figs. turned pleural furrows, similar axial taper, and 11-14, 20) the region of the base of the pygidial number of axial rings. Unfortunately the posterior spine appears roughened as if part was broken part of the border region and margin is broken so away. Because of these facts, I conclude that the that only the ventral doublure is preserved. The pygidium of C. americana probably possessed a ter­ specimen is oriented in the matrix in such a way minal spine. that presence or absence of a posterior spine cannot be determined. Allowing for uncertainties of preser­ The pygidium assigned to "P." spinula differs vation, the greatest apparent difference between from C. americana in possessing more sharply back­ "P." spinula and P. briarcliffensis is in the presence turned plJural furrows and an axial length to of bertillion prosopon on the glabella of the former pygidial length ratio of less than 0.5. and coarse granular prosopon on the glabella of the Librigenae attributed to C. americana by Ulrich latter. and Resser ( 1933) are similar to forms here at­ Cranidia assigned to "P." spinula are remarkably tributed to "P." spinula. Both have marginal fur­ similar to the type cranidia of Saukiella set·otina rows that become confluent at the corner angle and Longacre (1970, pl. 6, figs. 1-3). However, she did in which the lateral furrow continues undeflected on not illustrate a librigena or pygidium, so that critical to the genal spine. The "cotype" librigena illustrated comparison is not presently possible. Longacre by Ulrich and Resser on their plate 40, figure 9, has (1970, p. 53) placed Saukiella norwalkensis of Win­ prosopon preserved on the genal field which con­ ston and Nicholls (1967, pl. 11, figs. 6-8, 12) in sists of anastomosing ridges, although this feature synonomy with S. serotina. The librigena illustrated is not shown in their illustration. Such prosopon is by Winston and Nicholls (fig. 7) is of the "typical virtually identical with that on the genal fields of Saukiella form" with a slightly advanced genal spine librigenae here attributed to "P." spinula. SYSTEMATIC PALEONTOLOGY 31

In contrast to the librigena and pygidium, cra­ Lateral glabellar furrows expressed as oval-shaped nidia attributed to "P." spinula and C. americana regions without prosopon in position of S1 and S2. are distinctly different. "Cotype" cranidia of C. Occipital ring simple, straight, well defined by deep americana all show a lack of a preglabellar field, occipital furrow. Medial region of occipital ring presence of an evenly impressed anterior border lacking node or spine. Frontal area length 0.2 cra­ furrow, and an occipital spine. Ulrich and Resser nidial length (sag.). Preglabellar field sagittally ( 1933, p. 236) described C. americana as "usually convex, downsloping. Anterior border convex, even­ quite smooth, only rarely showing evidence of mi­ ly rounded in lateral profile, length (sag.) about 0.5 nute tuberculation." Examination of the type ma­ preglabellar field length (sag.). Anterior margin terial shows that the specimens have been worn so evenly rounded in dorsal view. Anterior fixigena much, probably since Ulrich and Resers' study, that strongly downsloping anterolaterally. Interocular original prosopon cannot be verified with certainty. fixigena convex, below level of glabellar surface at The cranidium illustrated by Ulrich and Resser on midline, width 0.45 adjacent glabellar width. Pos­ their plate 40, figure 1, seems to show a granular terior fixigena subtriangular, width (tr.) 0.75 width prosopon. In contrast, cranidia assigned to "P." (tr.) occipital ring. Eye ridge weakly developed. spinula have convex preglabellar fields, adaxially Palpebral lobe lunate, subhorizontal, raised above shallowing anterior border furrows, and absence of level of interocular librigena, length (exsag.) 0.45 occipital spines. glabellar length, centered opposite L2. Facial sutures An argument could be made for assigning "P." opisthoparian. Preocular sutures divergent, straight, spinula to Calvinella on the basis of morphological directed downward anterolaterally. Postocular su­ similarity to C. americana. However, I have chosen ture strongly divergent, nearly straight. to place more taxonomic weight on features of the Librigena known from fragments, ellipsoidal in cranidium, the structure of which is most consistent outline, strongly convex. Genal field evenly convex, with the tentative operational concept of Prosaukia. strongly downsloping. Eye socle raised above level Occurrence.-Saukiella serotina Subzone at locali­ of genal field. Lateral border strongly convex, ties H-1, H-3, 470b, and questionably 473f, from strongly differentiated by deep lateral furrow. Genal Washington County, N.Y. spine not observed. Thorax unknown. Family SOLENOPLEURIDAE Angelin, 1854 Pygidium subelliptical in outline, strongly convex, Genus HYSTRICURUS Raymond, 1913 length (sag.) 0.5 width. Axis convex, strongly ta­ Hystricurus Raymond, 1913, p. 60; Ross, 1951, p. 39; Hintze, pering posteriorly to border. Four axial rings and 1953, p. 164; Sando, 1957. p. 136. terminal piece, fourth ring weakly differentiated. Type species.-Bathyurus conicus Billings, 1859, Pleural regions strongly downsloping, three pairs by original designation. moderately deep interpleural furrows, two pairs Discussion.-The generic concept of Hystricurus moderately shallow pleural furrows. Border defined given by Ross (1951) is followed here. by change in slope from pleural regions, not crossed Hystricurus millardensis Hintze by pleural furrows. Plate 3, figures 10-16 Cranidial prosopon consists of large closely spaced perforate granules, except in furrows and on the Hystricurus millardensis Hintze, 1953, p. 168, pl. 6, figs. 17- border. Fine closely spaced granules are interspersed 21; Winston and Nicholls, 1967, p. 76, pl. 12, figs. 14, 18; Stitt, 1971, p. 46, pl. 8, figs. 17, 18. between large granules and occupy furrows. The anterior border has well-developed terrace lines on cranidia, two in­ Material available.-Fourteen the distal side and a few scattered granules on the complete librigena, and one pygidium from locality proximal side. H-2. The single librigena has large closely spaced per­ Description of Whitehall material.-Cranidium forate granules on the genal field and fine closely subrectangular in outline, strongly convex. Glabella spaced granules in the border furrow. The border conical, tapered forward, anterior end bluntly possesses a few granules on the proximal side and rounded, length 0.6 cranidiallength, length 0.9 basal terrace lines on the distal side. Genal caeca are faint­ glabellar width. Axial glabellar furrows deeply im­ ly visible radiating from the base of the eye socle pressed laterally, less deeply impressed anteriorly, into the border furrow. Caeca are under, rather fossulae present at anterolateral corners of glabella. than between, large perforate granules. 32 LATE CAMBRIAN AND EARLY ORDOVICIAN TRILOBITES, EASTERN NEW YORK STATE

The pygidium has large perforate granules more H-1.-Lower Whitehall Formation. Sample com­ widely spaced than on the cranidia and librigena. posed of light- to medium-gray (N 5-7) ooid­ Interspaces contain fine closely spaced granules. skeletal grainstone collected at the east end of Axial rings possess an additional pair of relatively Crossman quarry (inactive), near the road en­ large granules symmetrical about the sagittal plane. trance to the quarry, in place 11 feet above quarry Terrace lines are present on the border. floor. Crossman quarry is on the north side of Internal molds of cranidia have scattered fine pits. Washington County Route 10 (Sciota Road) and Discussion.-Hystricurus milla1·densis was origin­ the south side of a low hill immediately south of ally described from the lower part of Symphysurina Finch Marsh. Map coordinates, x = 396, y = 323. B Zone in the House Limestone of the Southern Collected by R. B. Halley, July 7, 1970. Filed in the House Range, west-central Utah (Hintze, 1952). U.S. Geological Survey collections in Washington, The Whitehall specimens differ from the House D.C., under number 7602-CO. material in possessing granular prosopon on H-2. Upper Whitehall Formation. Sample composed librigenae. of medium-gray (N 5) lime mudstone collected in Winston and Nicholls (1967) attributed material place from the southwest corner of Warner Hill, to H. millardensis from the Symphysurina Zone of at about 400 feet elevation, north of Finch Marsh. the Wilberns Formation, central Texas. The only Map coordinates, x = 398, y = 378. Collected by R. observed difference between Whitehall and Wilberns B. Halley, June 16, 1970. Filed in the U.S. Geo­ specimens is the apparent absence of granule-free logical Survey collections in Washington, D.C., glabellar furrow areas in the Texas material. under number 7603-CO. Stitt ( 1971) attributed specimens from the Sym­ H-3.-Lower Whitehall Formation. Sample com­ physurina Zone at the base of the McKenzie Hill posed of light- to medium-gray (N 5-7) ooid­ Limestone of south-central Oklahoma to H. millard­ skeletal grainstone collected in place from the ensis. The Oklahoma material differs from Whitehall northwest side of Warner Hill, about 800 feet specimens in lacking granule-free glabellar furrow southeast from cluster of buildings immediately areas and in possessing granules rather than pits on east of School House Marsh, between 200 and surfaces of internal molds (Stitt, 1971, p. 46). 300 feet elevation. Map coordinates, x = 404, These differences are not considered taxonomically significant. y=413. Collected by R. B. Halley, June 16, 1970. Filed in the U.S. Geological Survey collections in Flower (1969, p. 33, pl. 7, fig. 4) described and Washington, D.C., under number 7604-CO. illustrated a cranidium from the Fort Ann Lime­ stone, east of Smith Basin, N.Y., which he assigned 418e (old series) .-Sample composed of light- to to Hystricurus cf. conicus (Billings). The cranidium medium-gray skeletal packstone collected "two differs from material known from the Whitehall miles north-northeast of Whitehall, New York," Formation in having a less tapered glabella, less by C. D. Walcott, date unknown. Locality data are deeply impressed fossulae, and coarse-textured insufficient for determining the precise collecting granular prosopon. locality. The sample may have come from either Occurrence.-Missisquoia Zone, locality H-2, up­ the Crossman quarry area along Washington per Whitehall Formation, Washington County, N.Y. County Route 10, or Warner Hill. (See fig. 1 for general location.) DESCRIPTION OF FOSSIL LOCALITIES U.S. Geological Survey files contain a copy of the Whitehall, New York-Vermont, 15-minute All fossil localities studied are described below quadrangle, 1902 edition, used by Josiah Bridge with reference to the southwest quarter of the to record the location of fossil collections 470b, Whitehall 71;2-minute quadrangle, New York-Ver­ 470bl and 473f. These localities were replotted on mont, 1950 edition, Washington County, N.Y. Co­ the southwest quarter of the Whitehall 71/2- ordinates are given following a system often used minute quadrangle, 1950 edition, and coordinates by Franco Rasetti, where the abscissa(x) and ordi­ were determined which are given below. nate (y) are given in millimeters from the origin 470b (old series) .-Sample composed of medium­ at the lower left, southwest corner of the map. Color gray (N 5-6) ooid-sk:!letal grainstone and pack­ designations are based on the "Rock-Color Chart" stone. "Hall farm, one mile northeast of White­ of the National Research Council (Goddard, 1948). hall, N.Y. All material except 'crytozoans' from REFERENCES CITED 33

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[Italic paee numbers indicate major references and descriptions]

Paee: A Dirachopea sp Matherella Distribution of biofacies sp ------5 Acheilops ------7, 17, 19 Matthevia ------4, 6 dilatus ------19 E sp ------5 masonensis ------4, 5, 7, 16, 19; pl. 1 Methods and problems ------4 norwalkensis ------19, 20 eboracensis, Prosaukia ------30 Methods of analysis ------18 Acknowledgments ------I Saukia ------29 millardensis, Hystricurus __ 4, 5, 7, 8, 81; pl. 3 Age and correlations ------4 Eminence Do:omite of Missouri ------6, 15 misa, Dikelocephalus ___ ------28 Agraulos saratogensis ------25 Environmental setting ___ ------9 Missisquoia ------2, 5, 7, 8, 22 americana, Arethusina ------21 Environments, inferred ___ ------10 depressa ------li!2 Calvinella ------30, 31 Euptychaspis ------7, 17, S6 typicalis ------4, 5, 6, 7, 8, 22; pl. 3 Analysis methods ------18 typicalis ------4, 5, 7, 26; pl. 2 Zone ------6, 22, 32 Apoplanias ------8 sp ------4, 5 Missisquoiid!ae ------22 apopsis, Corbinia ------6, 7 Models ------11 arbucklensis, Plethopeltis ------25 F modestus, Plethometopus ------24 Arethusina americana ------21 Morphological terminology ------18 armatus, Bathyurus ------23 Fort Sill Formation 6 Murchisonia sp ------6 Assemblages dissimilar to Whitehall Fossil collections ------I N fauna ------16 Fossil localities, description ------IS Asemblages similar to Whitehall Fossils, other, from Whitehall fauna__ 4 norwalkensis, Acheilops ------19, 20 fauna 18 G Saukiella ------30 Notch Peak Limestone ------8, 13, 23 B nuculiti!ormis, Ribeiria ------2, 4, 5 Garden City Formation ------8 Bathyurus conicus ------31 Gastropods ------4 0 Bibliography ------33 Geologic setting ------1 granulosa, Plethopeltis ------25 Biofacies distribution ------11 Objectives ___ ------Biostratigraphie studies ------4 obtusus, Plethometopus ------4, 5, 7, ~4; pl. 1 H Biostratigraphy ------4 Osceolinae ------27 Bowmania ------7,17, U Other fossils from Whitehall fauna ___ 4 pennsylvanica ------4, 5, 7, 16, S1; pl. 2 Hedinaspis fauna ------18 Heterocaryonidae ______------Briarcliff Do~omite ------6 21 p briarcliffensis, Prosaukia ------6, 3•0 Highgate Formation ------6, 23 Highgatella ___ ------7, 8 Parabolinella 7 H omagnostus 7, 8 0 Parakoldinioidia 2,22 House Limestone ------­ 8, 32 typicalis ______------______22 Hoyt Limestone ------­ 6, 30 Calvinella ------6, 7, 17, ~7. 29 Pelagiella ______------6 Hoyt Member of Whitehall Formation __ 2 americana ------30,31 pennsylvanica, Bowmania _ 4, 5, 7, 16, 21; pl. 2 Hungaia magnifica fauna ------6, 16, 18 prethoparia ------4, 5, 6, !7; pl. 2 Petrology ------9 Hyolithoids ------4, 5 spiniger ------28 Plethometopus ------7, 16, 17, 28,25 Hystricurus ------4, 7, 8, 81 walcotti ------30 convergens ------25 conic?ts ------32 Cambrian-Ordovician boundary ------8 knopfi ------6, 24 millardensis ------4, 5, 7, 8, 81; pl. 3 Catillicephalidae ------18 modestus ------24 Clelandia ------7 sp. D ------8 obtusus ------4, 5, 7, 24; pl. 1 Composition of Whitehall fauna ----- 4 I sp. A ------4, 5, 7, 24; pl. 1 conicus, Bathyurus ------31 Plethopeltidae ------23,25 Hystricurus ------32 lllaenttrus Zone ------17 Plethope/tis ------4, 7, 8, 16, 17,25 Conococheague Limestone of Index of faunal resemblance 13 arbucklensis ------25 Maryland ------6, 15, 21 granulosa ------25 convergens, Plethometopus ------25 J sp ------4, 5, 25; pl. 1 Corbinia apopsis ------6, 7 Pleurotomariacean gen. indet ------5 Subzone ------7,8,9,20,24 .Jujuyaspis ------7 Potsdam Formation ------2 juma, Saukiella ------5, 7, 26 Correlations and age ------4 Potsdam limestone ------6 Crossman quarry ------2, 4, 6, 9, 33 K prethoparia, Calvinella ---- 4, 5, 6, 7, 27; pl. 2 curvicostata, Prosaukia ------28 Previous work ------I Kittatinny Limestone ------15 Problems and methods ------4 D knopfi, Plethometopus ------6, 24 Prosaukia ------7, 16, 17, 27,28 briarcliffensis ------6, 30 delecostata, Prosaukia ------28 L curvicostata ------2S. depressa, Missisquoia ------22 Lytospira sp 6 delecostata ------28 Description of fossil localities ------8~ eboracensis ------30 Dikelocephalidae ------27 M spinula ------4, 5, 7, 29; pl. 2 Dikelocephalus misa ------28 Ptychaspididae ------26 spiniger ------27 magnifica, Hungaia 6, 16, 18 Ptychaspidinae ------26 dilatus, Acheilops ------19 masonensis, Acheilops ___ 4, 5, 7, 16,19; pl. 1 pyrene, Saukiella ------5, 7 37 38 INDEX

Paae: Paae. Paae R Signal Mountain Limestone 8, 23 Ticonderoga Formation ------2 Sinuopea sp ------5 Trempealeauan fossils ------2, 16 Ribeiria nuculitifarmis ------2, 4, 5 Skene Member of Whitehall Formation 2 Trempealeauan Stage ------15, 25 sp ------4, 5 Skene Mountain ------3, 4, 6, 9 Triaf'thropsis ------20 Solenopleuridae ------31 Triblidium ------6. s spinifera, Stenochilina ------20, 21 Trilobita ------18 spiniger, CalvineUa ------28 Tri!obites ------' saratogensis, Agraulos ------25 Dikelocephalus ------27 Tub Mountain ------9 Saukia ------5, 7 spinula, Prosaukia ------4, 5, 7, !9; pl. 2 typicalis, Euptychaspis ------4, 5, 7, 26; pl. 2 ebaracensis ------29 Stenochilina ------4, 6, 7, 17,10 Missisqucna ------4, 5, 6, 7, 8, u; pl. 3 Zone ------5, 6, 9, 13, 21, 26 spinifera ------20, 21 Parakoldinioidia ------22 Saukiella junia ------5, 7, 26 sp. A ------4, 5, 7, tO; pl. 1 Subzone ------6, 20, 26 Stenopilus ------25 w norwalkensis ------30 Stratigraphy of the Whitehall area --- 2 pyrene ------5, 7 Summary ------I Subzone ------25 Survey Peak Formation ------8 Whitehall tauna, assemblages similar to 18 serotina ------5, 7, 30 Symphysurina ------7, 8 Whitehall fauna, composition ------' Subzone __ 6, 9, 20, 22, 24, 25, 26, 28, 31 B ------7 Whitehall Formation ------1, 6, 8, 9, 22, 32 Saukiinae ------!7, 28 Zone ------7, 8, II Wilberns Formation of Texas ---- 5, 7, 13,22 Schizopea sp. A ------5 Systematic paleontology ------18 walcotti, CalvineUa ------30 sp B ------15 Warner Hill ------2, 6, 8, 9, 32 sp ------4 T Whipple Cave Formation ------13 serotina, SaukieUa ------5, 7, 30 Whitehall fauna, assemblages Signal Mountain Formation ------5,13 Tellerina 27 dissimilar ------11

U.S. GOVERNMENT PRINTING OFFICE: 1974 0-527-763 PLATES 1-4

Contact photographs of the plates in this report are available, at cost, from U.S.

Geological Survey Library, Federal Center, Denver, Colorado 80225. PLATE 1

FIGURES 1-3. Plethopeltis sp. indet. (p. 25). 1. Internal mold of cranidium, USNM 186578, X 2.8, loc. H-3. 2, 3. C!anidium, USNM 186579, X 6.5, loc. H-3, latex external cast and peripheral part of same cranidium. 4, 5. Acheilops masonensis Winston and Nicholls (p. 19). 4. Librigena, USNM 186580, X 8.7, loc. 470b. 5. Granidium, USNM 186581, X 6.2, loc. H-3. 6-10. Stenochilina sp. A (p. 20). 6, 7, 9. Cranidium, USNM 186582, X 6.3, loc. 418e, lateral, an­ terior, and dorsal views. 8. Granidium, USNM 186583, X 6.7, loc. 418e. 10. Cranidium, USNM 186584, X 5.5, loc. 418e. 11-14. Plethometopus obtusus Rasetti (p. 24). 11-13. Granidium, USNM 186585, X 4.5, loc. 473f, lateral, an­ terior, and dorsal views. 14. Cranidium USNM 186586, X 5.2, loc. 473f. 15-17. Plethometopus sp. A (p. 24). Cranidium, USNM 186587, X 6.3, dorsal, anterior, and lateral views, loc. 473f. GEOLOGICAL SURVEY PROFESSIONAL PAPER 834 PLATE 1

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PLETHOPELTIS, ACHE/LOPS, STENOCHILINA, AND PLETHOMETOPUS PLATE 2 FIGURES 1-3. "Calvinella" prethoparia Longacre (p. 27). 1. Librigena, USNM 186588, X 6.0, loc. H-1. 2. Small cranidium, USNM 186589, X 7.7, loc. H-1. 3. Large cranidium, USNM 186590, X 4.3, loc. H-3, specimen silicified on right side. 4-11. Euptyckaspis typicalis Ulrich (p. 26). Figures 4-7, 10 from loc. H-3; figures 8, 9, 11 from loc. H-1. 4. Cranidium, USNM 186591, X 5.8. 5. Cranidium, USNM 186592, X 6.9. 6, 7. Cranidium, USNM 186593, X 6.9, dorsal and anterior views. 8, 9. Librigena, USNM 186594, X 6.1, lateral and dorsal views. 10. Cranidium, USNM 186595, X 6.7. 11. Pygidium, USNM 186596, X 7.4. 12-14. Bowmania cf. B. pennsylvanica Rasetti (p. 21). Cranidium, USNM 186597, X 8.2, dorsal, anterior and lateral views, loc. H-1. 15-20. "Prosaukia" spinula Taylor, n. sp. (p. 29). Figure 18 from loc. H-3; figures 15-17, 19,20 from loc. H-1. 15. Holotype cranidium, USNM, 186598, X 6.2. 16. Small paratype cranidium, USNM 186599, X 6.9. 17. Paratype cranidium, USNM 186600, X 9.2. 18. Latex cast of paratype pygidium, USNM 186601, X 4.2. 19. Paratype librigena, USNM 186602, X 6.3. 20. Paratype pygidium, USNM 186603, X 6.5. GEOLOGICAL SURVEY PROFESSIONAL PAPER 834 PLATE 2

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"CAL V/NELLA ," EUPTYCHASPIS, BOWMAN/A, AND "PROSA UK/A" PLATE 3 FIGURES 1-9. Missisquoia typicalis Shaw (p. 22). Figures 1, 3 from loc. 7098.-CO; figures 2, 4, 8 from loc. 7099- CO; figures 5-7, 9 from loc. 470bl. 1. Cranidium, USNM 186604, X 12.0. 2. Granidium, USNM 186605, X 12.0. 3. Cranidium, USNM 186606, X 12.0. 4. Cranidium, USNM 186607, X 13.0. 5. Libtigena, USNM 186608, X 14.0. 6. Librigena, USNM 186609, X 9.3. 7. Cranidium, USNM 186610, X 12.5. 8. Pygidium, USNM 186611, X 11.3. 9. Cranidium, USNM 186612, X 11.1. 10-16. Hystricurus millardensis Hintze (p. 31). Figu"es 10-16 from loc. H-2. 10. Pygidium, USNM 186613, X 7.0. 11-13. Cranidium, USNM 1866>14, X 4.2, anterior, lateral, and dorsal views. 14. Librigena USNM 186615, X 5.8. 15, 16. Cranidium, USNM 186616, X 4.5, anterior and dorsal views. GEOLOGICAL SURVEY PROFESSIONAL PAPER 834 PLATE 3

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MISSISQUOIA AND HYSTR!CUR US PLATE 4 [Bar is 0.5 mm long, except ilg. 3 in which bar is 0.13 mm long. All photomicrographs taken in plane-polarized light unless indicated otherwise] FIGURES 1-6. Lower Whitehall Formation, Crossman quarry. 1. Oolitic grainstone composed of ooids, oolitically coated pel­ lets, and skeletal fragments. 2. Pelletal and lithoclastic grainstone containing minor amounts of quartz sand. 3. Length-slow chalcedony from along the fenestral wall of a thrombolite, crossed polarizers. 4. Thrombolite fenestra partly filled with internal pelleted sedi­ ment. 5. Border between light and dark clots of thrombolite having a clastic internal texture. Spar-rich area (left) does not appear grain supported, and is dark gray in hand specimen. Area of closely packed pellets (right) appears light gray in hand specimen. 6. Stromatolite laminations produced by variations in grain size. 7. Echinoderm fragments characterized by serrate edges, single-cry­ stal extinction, and syntaxial cement, Hoyt Limestone, Lester Park, Saratoga County, N.Y. 8. Oblique section through fragment of dasycladacean alga, USNM 186617, Hoyt Limestone, Lester Park, Saratoga County, N.Y. Dasyclads from ·the Hoyt were identified by John L. Wray (written commun. to Halley, 1970). GEOLOGICAL SURVEY PROFESSIONAL PAPER 834 PLATE 4

PHOTOMICROGRAPHS OF PETROGRAPHIC THIN SECTIONS