An Unusual Lower from


An Unusual Lower Cambrian Trilobite Fauna from Nevada By ALLISON R. PALMER CONTRIBUTIONS TO


Twelve representing the , , Ogygopsidae, , Zacanthoididae^ and are described andfigured


GEOLOGICAL SURVEY Thomas B. Nolan, Director

The U.S. Geological Survey Library has cataloged this publication as follows: Palmer, Allison Ralph, 1927- An unusual Lower Cambrian trilobite fauna from Nevada. Washington, U.S. Govt. Print. Off., 1964.

iii, 14 p. 3 plates, map, diagr. 30 cm. (U.S. Geological Survey. Professional Paper 483-F) Contributions to' paleontology. Bibliography : p. 12. 1. . 2. Paleontology Nevada. 3. Paleontology Cam­ brian. I. Title. (Series)

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, B.C. 20402 CONTENTS

Page Abstract.______-______-______-__-______-_-___----_----_-----__--- Fl Introduction.______-______-______--___-____---__--_------1 Systematic paleontology______-______-__..___----_---_------2 Olenellidae-- ______2 Dorypygidae.-____-_-___-_-______-__-___-______-_-_--___-_--_----_--_------_--- 5 Ogygopsidae______6 Oryctocephalidae.__--_____-______-______-_____-__--_----_----_-- 7 Zacanthoididae ____-______-______-____-____----__-_------_- 8 Ptychopariidae______11 Position uncertain______11 References.______12 Index_^______13


[Plates follow index]

PLATE 1. Olenellidae, Oryctocephalidae. 2. Ogygopsidae, Dorypygidae. 3. Zacanthoididae, Ptychopariidae, position uncertain. Page FIGURE 1. Map showing the locality of the collection described in this report. Fl 2. Position of described fauna in regional stratigraphic context-______2 ill




117° ABSTRACT A fauna of at least 12 species of trilobites, from lower Cam­ brian rocks in Esmeralda County, Nev., constitutes the largest single assemblage of trilobites yet described from Lower Cambrian beds in . Well-preserved specimens of the Olenellidae, Oryctocephalidae, Ogygopsidae, Dorypygidae, NYE Zacanthoididae, and Ptychopariidae are present. New taxa include Paedeumias granulatm n. sp.; GoWfieldia pacifica n. gen., n. sp.; Bonn/Id caperata n. sp.; Zacanthopsig contractus n. sp.; ZacantJiopsina eperephes n. gen., n. sp.; and Stephenaspist a/vitus n. sp.

INTRODUCTION 37° During reconnaissance geologic mapping of Esmer­ alda County, Nev., J. P. Albers and J. H. Stewart, of the U.S. Geological Survey discovered many localities of fossiliferous Lower Cambrian rocks. Collections from most of these localities were submitted to me for examination. In 1960 a collection from one of these localities (fig. 1) was found to contain an association of nonolenellid trilobites of Middle Cambrian aspect together with undoubted olenellids. In 1961 I was guided to this locality by J. H. Stewart and obtained FIGURE 1. Map showing the locality of the fossil collection de­ a large supplemental collection. That collection is the scribed in this report. principal source of the specimens described here. Lower Cambrian trilobite collections from the West­ beds are about 40 feet above a 45-foot-thick brown ern States rarely contain assemblages of more than half sandstone unit (Stewart, written communication, June a dozen species. Most of the trilobites in any one col­ 1963). The sandy have the characteristics lection are olenellids, although occasionally a simple of a rock type that is found in the lower part of the ptychoparioid or a species of Bonnia or of Zacanthopsis Saline Valley Formation (Nelson, 1962) just above a may be present. Barely are the specimens well pre­ basal sandy or quartzite unit. Nelson subsequently served. Thus, the discovery of an excellently preserved visited this locality and confirmed the identification of Lower Cambrian trilobite assemblage that contains at the fossiliferous beds as the lower part of the Saline least 10 genera representing at least 6 families can be Valley Formation. Nelson also examined stratigra- properly termed unusual. phically important sections in the Last Chance Range, The fossil-bearing beds (USGS Colln.3T48-CO) crop Calif, (fig. 1), in company with J. H. Stewart and me in out in a series of low north-facing hills about 3 miles April 1963. It was determined that the basal quartzites southeast of the junction of Nevada Highways 3 and of the Saline Valley Formation in the northern part of 71 south of Goldfield, Nev., and about 5 miles northeast the range correlate with the Zabriskie Quartzite ex­ of Gold Point in the SWV* sec. 28, T. 6 S., E. 42 E., posed in the southern part of the range. Collections Goldfield (1: 250,000) quadrangle, Nevada. The trilo­ from the upper part of the Saline Valley Formation bites are preserved in dark-gray beds less than have yielded species of the olenellid BristoUa. 6 inches thick that are characterized by well-rounded This is a characteristic and locally abundant genus in the grains of quartz sand "floating" in the limestone matrix Lower Cambrian part of the Carrara Formation, which or concentrated in the lower part of the beds. These is above the Zabriskie Quartzite, in the Death Valley Fl CONTRIBUTIONS TO PALEONTOLOGY region. Thus, the fauna described here from the lower (1948) from the Lower Cambrian of Quebec and re­ part of the Saline Valley Formation seems firmly estab­ ported by him (Easetti, 1951) from the Lower Cambrian lished in the upper part of the Lower Cambrian in a of British Columbia, are absent from this assemblage. position slightly older than that yielding the Sampling of the Lower Cambrian of the West­ fauna (fig. 2). ern States has just begun, however, and an increase in our knowledge of these older trilobite faunas can be anticipated. Last Chance Death Valley Range region SYSTEMATIC PALEONTOLOGY v/vs/vVWvVVvV The descriptive terminology used for the olenellids Vw^VV^tyv/yyv^/ Lower lime­ is the same as that used earlier by me. (See Palmer, Mule stone member 1957.) Descriptive terminology for the other trilobites Spring Limestone is that found in the illustrations or glossary of the _ Bristol/a _ Treatise on Invertebrate Paleontology, Part O, Arthro- poda 1 (Harrington and others, 1959). Familial or Carrara generic assignments that have no comment indicate Saline Formation Valley acceptance of the classification in the treatise. Local­ Formation Fauna described ity data and identifying locality numbers for figured /in this report specimens are recorded in the Cambrian- locality catalog of the U.S. Geological Survey. All figured specimens, unless otherwise indicated, are from Basal Zabriskie U.S. Geological Survey collection 3748-CO. sandy member Quartzite An/UlWVM AnWuVMA Bichter Family OLENELLIDAE Vogdes Genus PAEDETJMIAS Walcott FIGURE 2. Correlation of parts of the Lower Cambrian for- mational sequences between the Last Chance Range and Paedeumias Walcott, 1910, p. 304; Resser, 1928, p. 4; Poulsen, the Death Valley region, California, showing the approxi­ 1932, p. 26; Resser and Howell, 1938, p. 225; Poulsen, 1959, mate stratigraphic position of the fauna described in this report. p. 192. Type species. Paedeumias transitans Walcott, 1910, This trilobite assemblage cannot be compared at pres­ p. 305, pi. 34, fig. 1. ent with any other known assemblage in the Cordil- Diagnosis. Olenellidae having glabella distinctly leran region of North America. Lower Cambrian as­ separated from cephalic 'border by preglabellar field semblages, which include various nonolenellids but but generally connected to border by narrow median fewer total species, have been described by Easetti ridge. Cephalic border wirelike. Palpebral lobes (1948) from boulders in the Levis conglomerates of long; line connecting posterior tips crosses glabella Quebec and by Eesser (1938) from limestones of the posterior to midlength of preoccipital segment. In- Austinville district, ; but the fauna described tergenal spines short and directed nearly straight here is by far the largest and most varied assemblage of posteriorly in mature holaspids; near genal spines. Lower Cambrian trilobites yet described from North Discussion. Walcott originally diagnosed Paedeu­ America. Entirely new forms are Zacanthopsina mias as a genus differing from by having eperephes n. gen., n. sp., and Stephenaspis ? avitus n. sp. thoracic segments posterior to the spine-bearing 15th Typical Lower Cambrian species include Paedewnias segment. Eesser (1928) correctly referred one of granulatus n. sp., cf. W. walcottana (Wan­ Walcott's best paratypes (Walcott, 1910, pi. 33, fig. 1) ner) , Zacanthopsis contractus n. sp., Bonnia caperata n. to Olenellus, thus negating the generic differentiation sp., and Syspacephalus sp. In addition, the fauna in­ proposed by Walcott. However, Resser then presented cludes batis (Walcott), which represents a a new diagnosis based on cephalic features. With some long-ranging genus that until recently (Nelson, 1963) modifications and additions, this is the concept of was not definitely known to occur in Lower Cambrian Paedeumias presently in use. Eesser and Howell beds; the fauna also includes the first Cordilleran rec­ (1938) noted the distinctive narrowness of the cephalic ord of Lower Cambrian representatives of border as a generic feature. The usefulness of this (at least two unnamed species) and of the family Oryc- characteristic was demonstrated statistically by Palmer tocephalidae (Gold- pacifica n. gen., n. sp.). It (1957) on a silicified sample of associated species of is rather surprising that eodiscids, described by Easetti Olenellus and Paedeumias. LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA F3 Several olenellid species share the characteristics of length of lobe; transverse width of this rim about one- long palpebral lobes, narrow cephalic border, and fourth width of ocular lobe. distinct preglabellar field but differ in sagittal length Interocular area narrow and depressed below gla­ of the preglabellar field, length of the palpebral lobe, bella and ocular lobe; has moderately to poorly defined ornamentation, and other features. They constitute a hump in posterior part and, on largest specimens, dis­ supraspecific (Paedeumias} that differs from tinct veination. Greatest width about equal to width another taxon of comparable rank (Olenellus] in which of ocular lobe. the species have a characteristically broader border. Extraocular cheek broad and nearly flat and has The arguments of Bell (1931) and Shaw (1955) for moderately well-defined radial veination; greatest suppression of Paedeumia,s as a synonym of Olenellus width about one-fourth or slightly less than one-fourth are no longer valid. Discussion of subgeneric versus greatest width of cephalon. Cephalic border narrow; generic status for Paedeumias is moot, at least until an width one-fifth or less than one-fifth width of extraocu- acceptable classification is presented for the Olenellidae. lar cheek. Therefore, Paedeumias is considered here as a distinc­ External ornamentation of most specimens consists tive genus of the Olenellidae. of closely spaced fine granules, often apparent only after whitening, on all parts except furrows and cheek Paedeumias granulatus n. sp. area in front of glabella. Some large specimens have Plate 1, figures 1-10 external surface nearly smooth or have irregular short Description. Cephalon subsemicircular in outline, terrace lines on all observed parts. gently to moderately convex transversely and longitu­ has anterior lobe of middle body inflated. dinally. Anterior and lateral margins evenly curved. Anterior margin slightly acuminate on axial line, rim Posterior margin straight and perpendicular to axial narrow, upturned. Middle furrows deep. Posterior line between intergenal spines; directed slightly an- lobe of middle body reduced; six pairs of marginal terolaterally between intergenal and genal spines. spines on specimen 6 mm in length. Genal spine slender, directed straight posteriorly; Discussion. This distinctive species of Paedeumias length slightly more than one-half distance from genal differs from all others so far described by the granular angle to base of occipital segment. Intergenal spine ornamentation of many specimens and by the well- present only as node on posterior margin; separated defined furrow on the lateral parts of the ocular lobes. from genal spine by distance slightly less than three The intergenal spines are farther from the genal spines, times basal width of genal spine. the ocular lobes are longer, and the interocular areas Glabella prominent and has well-defined glabellar are narrower than in many other species of the genus. furrows; separated from border by sagittal distance All known specimens of this species are broken, but equal to slightly less than twice sagittal length of parts of at least 50 cephala are in the collection. These border and connected to border by low, poorly defined cephala range from 2 mm to about 20 mm in sagittal median ridge. Glabellar segments generally defined length. The small meraspid specimens do not have a only at distal ends. Occipital and preoccipital fur­ well-defined furrow on the ocular lobe, but the granular rows deep, narrow at sides of glabella, hardly apparent ornamentation can be seen on the extraocular cheeks. across top. The two remaining furrows represented by The principal variable features of the holaspid speci­ deep narrow slots isolated from sides of glabella by mens are the ornamentation and the definition of the ocular lobe or by posterolaterally directed distal ends furrow outlining the posterior part of the frontal lobe of first leg segment. Posterior pair of slots generally of the glabella. shorter transversely than anterior pair. A moderately Genus WANNERIA Walcott well-defined furrow may connect anterior pair of slots and outline posterior margin of frontal lobe of glabella. Wanneria Walcott, 1910, p. 296; Poulsen, 1932, p. 35; Lake, 1937, p. 245; Resser and Howell, 1938, p. 227; Poulsen, 1958, Larger cephala (pi. 1, fig. 10) consistently bear small p. 16; Poulsen, 1959, p. 197. dimple on axial line just anterior to this furrow on posterior part of frontal lobe. Occipital ring has dis­ Type species. Olenellus (] walcottanus tinct node on axial line at posterior margin. Wanner, 1901, p. 267, pi. 31, figs. 1, 2; pi. 32, figs. 1-4. Ocular lobes long, slender, gently curved; posterior Diagnosis. Olenellidae in which cephalon has genal tips opposite midlength of occipital segment and barely spines at posterolateral corners; intergenal spines not separated from it by narrow posterior extension of apparent. Glabella has expanded frontal lobe reaching infraocular cheek. Each ocular lobe has distinct fur­ to or nearly to inner edge of border. Ocular lobe ar­ row delineating a narrow lateral rim along entire cuate and has well-defined longitudinal furrow. Ex- F4 CONTRIBUTIONS TO PALEONTOLOGY ternal surfaces of all parts generally have characteristic the genal spines at the posterolateral cephalic corners. strong reticulate meshwork of raised ridges. W. buelnaensis is here considered a distinct species rath­ Anterior width of thorax nearly as great as width er than a variety of W. walcottana (Wanner) because of cephalon; third segment not macropleural. of the consistently advanced position of its genal spines. The general shape of the cephalon of the species de­ Wanneria cf. W. walcottana (Wanner) scribed here is most like that of W. nathorsti Poulsen Plate 1, figures 11-13, 15 from Greenland. However, it differs from W. natliorsti Wanneria walcottana Wanner. Walcott, 1910, p. 302, pi. 30, by having deeper anterior glabellar furrows and by hav­ figs. 1-12. ing the reticulate ornamentation less well defined at Description. Cephalon subsemicircular in outline, comparable stages of growth. gently to moderately convex transversely and longitu­ Small specimens that have relatively longer palpebral dinally. Anterior and lateral margins evenly curved. lobes than have associated large specimens of Wanneria Posterior margin nearly straight; curved gently back­ ivalcottana in were considered by Walcott ward distally to base of genal spine. Genal spine mod­ to show that the size of the palpebral lobe relative to erately short, not divergent from lateral margin of cephalic size decreased as individuals became larger cephalon; length on small holaspid (sagittal length of (Walcott, 1910, p. 296, pi. 30, figs. 3, 4). Resser and cephalon 12 mm) slightly less than distance from inner Ho well (1938, p. 229, pi. 8, fig. 10) assigned Walcott's edge of spine to base of occipital segment. Separate small illustrated specimens to macer (Wal­ intergenal spine not apparent. cott) without comment. The holotype of E. macer, Glabella prominent, reaching to or nearly to inner which is from a different locality, is a small, nearly com­ edge of border. Glabellar furrows well defined, deep­ plete specimen having a narrow thorax. The posterior est distally, shallow across axial line. Distal ends of cephalic margin of this specimen is not well preserved, first leg segment directed for short distance postero- and it is not possible to determine whether morphologic laterally outside of anterolateral ends of second leg seg­ features that usually indicate a narrow thorax are pres­ ment. ent. Walcott's small specimens are associated with Ocular lobes strongly curved, moderately close to gla- large specimens of W. walcottana which has a broad bella; line connecting posterior tips passes about over thorax. These small specimens have posterior cephalic occipital furrow. Distinct longitudinal furrow on ocu­ outlines essentially like those of the large specimens lar lobe, delineating narrow lateral rim. and there is no compelling reason for removing them Interocular area depressed; greatest width opposite from the species sample solely because of small size. preoccipital furrow and aUout equal to transverse width The small cephala from Nevada also have long palpe­ of ocular lobe on same line. bral lobes and do not differ in any other observable Extraocular cheek gently to moderately convex; has feature from W. walcottana. Therefore, they may be moderately wide well-defined lateral and posterior bor­ coiispecific with the specimens from Pennsylvania. ders. Border furrows joined at moderately acute genal The ornamentation on large specimens in the Nevada angle. Width of lateral border about one-third greatest collection is unusual. Fragments of the , distance from lateral margin of to border furrow. when viewed from below, show a striking series of External surfaces of smaller specimens covered with perforations arranged in a reticulate pattern exactly coarse ornamentation of poorly formed reticulations paralleling the pattern of reticulate ridges on the ex­ mixed with irregularly raised terrace lines, so that ternal surface (pi. 1, fig. 11). The exoskeleton breaks whitened specimens appear in part to be granular. along the margins of the reticulations, showing that the Large specimens have coarse raised reticulate network perforations continue upward into the exoskeleton as on all parts. tubes that do not reach the dorsal surface. These tubes Discussion. This species, which is less common than outline polygonal plates, which make up the entire exo­ Paedeumias granulatus, is represented by only two in­ skeleton. This exoskeletal structure may well be a char­ complete small cephala, a large hypostome, and many acteristic feature of the genus Wanneria. Similar per­ fragments of large specimens that display well-defined forations from the ventral surface outline polygonal reticulate ornamentation. The species is not well plates on scraps associated with one of the paratypes of enough represented to be separately named. However, W. buelnaensls Lochman, and specimens of W. walcott­ it differs from the Mexican species, Wanneria buelnaen- ana that are slightly crushed show breakage along lines sis Lochman (in Cooper and others, 1952), by having of weakness around the margins of polygons. LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA F5

Order Kobayashi section strongly divergent behind palpebral lobes, then Family DORYPYGIDAE Kobayashi curved strongly backward to posterior margin. Genus BONNIA Walcott Free cheek narrow and has gently curved lateral Corynexochus (Bonnia) Walcott, 1916, p. 325. margin and short blunt genal spine; width at eye about Bonnia Walcott. Raymond, 1928, p. 309; Resser, 1936, p. 6; one-eighth length of cheek including genal spine. Resser, 1937, p. 44 ; Lermontova, 1940, p. 142 ; Lochman, 1947, Border poorly defined, convex, wider than ocular plat­ p. 68; Rasetti, 1948, p. 14: Lermontova, 1951, p. 118; form. Posterior sutural margin intersects shallow Pokrovskaya, 1959, p. 135; Poulsen, 1959, p. 217. lateral border furrow. Type species. Bathyur-us parvulus Billings, 1861, p. subsemicircular in outline, slightly flared 953, fig. 361. at anterolateral corners. Axis well defined, slightly Discussion. Because this genus has been defined tapered backward, strongly rounded at end; reaches to many times, there is now little controversy about its inner edge of border. Four ring furrows indicated included species. Kasetti (1948) has pointed out, how­ posterior to articulating furrow; only first and, in ever, that species cannot be accurately defined without some specimens second furrows continuous across axis. knowledge of well-preserved associated parts because Pleural fields crossed by three or four shallow pleural the primary distingushing characteristics of external furrows that do not cross border. Border narrow, ornamentation are often different on the cranidium and convex, and of nearly constant width. One pair of on the pygidium of the same species. Secondary short anterolateral border spines present. characteristics of taxonomic value are shape of glabella, External ornamentation variable. Glabella covered particularly at its anterior end; depth of occipital with concentrically arranged irregular terrace lines ex­ furrow; size and shape of occipital ring; depth of cept over areas of muscle scars. Fixed cheeks may have glabellar furrows; depth of pleural and ring furrows on irregular ornamentation of terrace lines in all places pygidium; number and length of pygidial border spines. less well defined than on glabella; or, if terrace lines are subdued, the cheeks have scattered fine pits. Top Bonnia caperata n. sp. of occiptal ring has moderately prominent irregular Plate 2, figures 11-16 terrace lines. Palpebral lobes, tips of posterior limbs, Description. Glabella well defined, moderately and ocular platform of free cheek smooth or covered arched transversely and longitudinally, expanded with scattered fine pits. Border of cranidium and free slightly and evenly forward nearly to border; antero- cheek has subparallel terrace lines. Pygidium either lateral corners strongly rounded; anterior end blunt. nearly smooth or has scattered fine pits on pleural fields Glabellar furrows apparent only as shallow indenta­ and irregular coarse ridges on top of axis or irregular tions adjacent to axial furrows. Occipital furrow deep anastomosing ridges on all parts. at sides, shallow across axis. Occipital ring of nearly Discussion. Although many species of Bonnia have constant width and nearly flat; distinct axial node or been named, most are represented by material inade­ spine absent. Frontal area consists only of narrow quate for meaningful comparison. The adequately gently convex border. Fixed cheek gently convex, represented Cordilleran species are B. columbensis slightly downsloping; width, exclusive of palpebral Kesser and B. fieldensis (Walcott). Both lack signifi­ lobe, slightly less than one-half basal glabellar width. cant external ornamentation, although specimens of Palpebral lobes well defined by change in slope of B. fieldensis have scattered fine pits. In addition, the cheek surface, somewhat sunken, gently curved; length first pleural furrows on the pygidia of both species slightly more than one-third length of glabella exclusive continue across the border to the pygidial margin in­ of occipital ring. Line connecting midlengths of stead of stopping at the border furrow as in B. caperata. palpebral lobes crosses glabella slightly posterior to Species of Bonnia from other regions that are orna­ glabellar midlength. Ocular ridge low, poorly defined, mented with terrace lines differ from B. caperata by parallel with and close to border; contact with glabella having associated granular ornamentation and, gener­ marked by shallow fossula in axial furrow. Posterior ally, a differently shaped glabella and occipital ring. limb broad; tip bluntly rounded; transverse length Bonnia brennus (Walcott) (Kasetti, 1948, pi. 3, figs. 16-25) is perhaps most typical of these forms. slightly more than basal glabellar width. Posterior border furrow deep near glabella, shallow laterally. Genus OLENOIDES Meek Posterior border has no noticeable geniculation. Olenoides spp. Course of anterior section of facial short, Plate 2, figures 7-10 slightly convergent anteriorly in gentle curve from Discussion. At least two species have pygidia pos­ palpebral lobe to anterior margin. Course of posterior sessing the characteristic border spines and well-defined F6 CONTRIBUTIONS TO PALEONTOLOGY

pleural and interpleural furrows of Olenoides. One arcuate, welt defined by shallow palpebral furrows, gen­ has four pairs of long slender border spines (pi. 2, figs. erally connected to glabella by low ocular ridge; length 9, 10), and the other has four pairs of short slender about one-third length of glabella exclusive of occipital border spines (pi. 2, fig. 8). Both species have granular ring. Line connecting midlengths of palpebral lobes external surfaces. passes over glabella posterior to glabellar midlength. All five fragmentary specimens of the short-spined Posterior limbs tapered laterally to blunt point; trans­ species are from a small collection, USGS collection verse length slightly greater than basal glabellar width. 3655-CO. This was the orignal collection submitted Course of anterior section of facial suture nearly by Stewart. A later collection (3748-CO) from the straight forward from palpebral furrow to border, then locality yielded a large fauna, including six specimens curved gently inward to cut anterior margin near of the long-spined species. Other species in collection anterolateral cranidial corners. Posterior section 3655-CO are the same as those in the later collection. straight or slightly convex from palpebral lobes to At the two times of collection, apparently slightly dif­ posterior margin. ferent beds were collected from, as is reflected by the Lateral border of free cheek moderately defined by different Olenoides species. This was confirmed by shallow border furrow that almost disappears near base Stewart (written communication, June 1963), who re- of genal spine. Border distinctly narrower than ocular evaluated his field notes after our collecting trip. platform. Contact between ocular platform and eye Four-spined species of Olenoides having a granular surface marked by low collar that is separated from surface have been described from beds of Early and ocular platform Dnly by sharp change in slope. Genal Middle Cambrian age. However, all such species are spine moderately short; length about equal to length of represented by so few individuals that variability can­ posterior section of facial suture. not be determined, and minor differences between the Thorax consists of eight segments; tips of each seg­ known small samples cannot 'be evaluated. Cranidia ment have single short laterally directed slender spines. that have a granular surface are associated with the Axial rings do not have well-defined nodes or spines. long-spined specimens discussed here and may belong Width of pleural regions distinctly greater than width to the same species. However, until infraspecific vari­ of axis. ability of the pygidia, which have the principal char­ Pygidium subsemicircular in outline; length slightly acteristics of specific value, can be determined, specific more than one-half greatest width. Axis well defined, identification of the specimens illustrated here will be slender, reaching nearly to posterior margin; has seven meaningless. or more complete ring furrows posterior to articulating

Family OGYGOPSIDAE Rasetti furrow; width slightly less than one-fourth greatest width of pygidium. Pleural regions broad, gently con­ Genus OGYGOPSIS Walcott vex, crossed by five or more moderately deep pleural Offyyoipsis Walcott, 1889, p. 466; Walcott, 1916, p. 375; Raymond, furrows that reach to inner edge of narrow, convex 1912, p. 116; Shimer and Shrock, 1944, p. 613; Rasetti, 1951, p. 190 ; Rasetti, 1959, p. 219. border of nearly constant width. Interpleural furrows Taxioura Resser, 1939, p. 62; Shimer and Shrock, 1944, p. 617. also present on some specimens. Margin of pygidium smooth or has one or more pairs of short, sharp spines. Type species. Ogygia klotzi Kominger, 1887, p. 12, Discussion. This genus is easily recognizable by the pl.l,fig.l. combination of a cranidium having a prominent sub- Description. Isopygous opisthoparian trilobites; parallel-sided glabella reaching almost the entire cephalon subsemicircular in outline,' gently to moder­ cranidial length and a large pygidium having a narrow ately convex transversely and longitudinally. Glabella axis and border and well defined ring and pleural fur­ long, large, reaching to or nearly to border, strongly rows. Kasetti (1951, p. 191) concluded that Taxioura rounded at front, moderately convex transversely and (Resser, 1939) was a subjective synonym of Ogygopsis longitudinally; sides subparallel or bowed slightly out­ after comparing the type species, T. typicalis Resser, ward. Glabellar furrows generally not apparent on uncrushed material. Occipital furrow moderately well with 0. klotzi. Resser's second species of Tawioura, T. defined, nearly straight. Occipital ring does not have magna, was founded on an incorrect association of parts obvious nodes or spines. Frontal area short; sagittal and is here removed from Ogygopsis. The pygidium of length less than one-eighth that of glabella. Border this species (Resser, 1939, pi. 14, figs. 1, 2) agrees in all narrow, poorly defined by change in slope. Fixed morphological details with T. typicalis. The holotype cheeks gently convex, slightly downsloping; transverse and paratype cranidia of T. magna, all have coarse gran­ width, exclusive of palpebral lobes, slightly less than ular external ornamentation and a short occipital spine. one-half basal glabellar width. Palpebral lobes gently These cranidia probably belong to Olenoides maladensis LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA F7

Resser, a species from the same fauna whose pygidia terrace lines on other parts of the cranidium and free have a coarse granular surface. cheeks. The terrace lines on the pygidium form a fine Nelson noted (1963, p. 246) that batis meshwork of irregular polygons. On 0. batis the ter­ Walcott, from Lower Cambrian beds in western Nevada, race lines on the cheek regions of the cephalon, as well is actually a species of Ogygopsis. Other species pres­ as those on the pygidium form an irregular meshwork ently assigned to Ogygopsis are 0. spinulosa Rasetti and of tiny polygons; in addition, the surfaces of all parts Taxioura elongata McLaughlin and Enbysk. are covered with numerous fine pits. This ornamenta­ Specimens of all species of Ogygopsis except 0. tion is apparent only after whitening of well-preserved elongata (McLaughlin and Enbysk, 1950) were ex­ specimens. amined for this study. Two features of the pygidium Ogygopsis batis (Walcott) were found to be valid for species discrimination. All Plate 2, figures 1-6 species except 0. klotzi have at least one pair of margin­ al pygidial spines, and the number of pairs of spines Bathyuriscus batis Walcott, 1916, p. 337, pi. 48, figs. 4, 4a. is constant for each species. Also, the number of well- Diagnosis. Species of Ogygopsis in which cranid­ defined pleural furrows is constant for each large col­ ium has moderately well-defined anterior border sepa­ lection studied. If these characters are used in rated from glabella by narrow brim; course of border combination, at least five species of Ogygopsis can be furrow an even curve, uninterrupted and undeflected by recognized. Pygidia of 0, Motzi (Rominger) lack mar­ front of glabella. Pygidium has one pair of short, ginal spines and have seven well-defined pleural fur­ sharp, anterolateral border spines and no more than six rows. Pygidia of 0. typicalis (Resser) have one pair of well-defined pleural furrows. Interpleural furrows anterolateral spines and seven well-defined pleural fur­ shallow or absent. External surfaces of pleural regions rows. Pygidia of 0. spinulosa Rasetti have at least of cephalon, thorax, and pygidium, and tops of axial seven pairs of marginal spines, indications of two addi­ rings and occipital ring have fine polygonal network of tional pairs of marginal spines and seven well-defined terrace lines. Surface of glabella has fine "finger print" pleural furrows. These three species are of Middle ornamentation of terrace lines. All parts finely pitted. Cambrian age. Pygidia of 0. batis (Walcott) from Discussion. The type of Ogygopsis batis is a Lower Cambrian beds have one pair of anterolateral poorly preserved specimen from slightly metamor­ marginal spines and five or six well-defined pleural fur­ phosed Lower Cambrian rocks at Miller Mountain, Nev. rows. Pygidia of a second, undescribed Lower Cam­ Unfigured paratype and topotype specimens show a brian species from Esmeralcla County, Nev., have six single pair of anterolateral pygidial spines and fewer or seven pairs of marginal spines and five or six well- than seven pleural furrows. Because these character­ defined pleural furrows. Thus, the principal character istics seem to be of specific value for the well-preserved of stratigraphic value seems to be the number of pleural specimens described here, these specimens are con­ furrows. No Lower Cambrian specimens have more sidered conspecific with the specimens from Miller than six pleural furrows, whereas all Middle Cambrian Mountain. specimens have seven pleural furrows. Ogygopsis elongata (McLaughlin and Enbysk) may Family ORYCTOCEPHALIDAE Beecher be a synonym of 0. typwalis (Resser). Well-pre­ Genus GOLDFIELDIA n. gen. served specimens from the Metaline Limestone in the Type species. Goldfieldia pacific® n. sp. type region for 0. elongata have all the characteristics Diagnosis. Oryctocephalidae which have glabella of 0. typicalis, and the differences in proportion used poorly defined at front, narrowest at occipital ring; for discrimination of the distorted specimens of 0. frontal lobe has median depression in anterior part. elongata may not be valid. Posterior pair of glabellar furrows connected laterally In addition to the easily recognizable pygidial differ­ to axial furrows. Cranidial border wirelike. ences, each species may have characteristic external or­ D'iscusswn. This is a monotypic genus. Its rela­ namentation. Only Ogygopsis Motzi, 0. typicalis, and tions to other trilobites are discussed after the descrip­ 0. batis are represented by specimens well enough pre­ tion of the type species. served to check this character. The external surfaces of all well-preserved specimens of 0. klotzi are smooth Goldfieldia pacifica n. sp. except for low terrace lines on the margins of the cranicl- Plate 1, figures 14, 16-18 ium, free cheek and pygidium. 0 typicalis has a Description. Oryctocephalidae which have cranid­ finely formed "fingerprint" pattern of terrace lines on ium subtrapezoidal in outline, gently convex trans­ the glabella and an irregular close-spaced pattern of versely and longitudinally; width between anterior sec- F8 CONTRIBUTIONS TO PALEONTOLOGY tions of facial sutures about two-thirds width between row. This character, plus the apparent presence of a tips of posterior limbs. Anterior margin gently curved. broad cranidial border is sufficiently different from G. Glabella well defined at sides; axial furrows sub- pac-ifi&a n. sp. to warrant placing the forms in different parallel between occipital and preoccipital furrows, di­ genera, vergent slightly forward between preoccipital and Family ZACANTHOIDIDAE Swinnerton second glabellar furrows, where divergence increases Genus STEFHENASFIS Basetti width of glabella by about one-fourth, then subparallel Stephenaspis Rasetti, 1951, p. 180; Rasetti, 1959, p. 229. to junction with ocular ridge. Front of glabella ante­ rior to ocular ridges not clearly defined. Four pairs of Type species. Steplienaspis bispinosa Rasetti, 1951, lateral glabellar furrows present but not connected p. 181, pi. 10, figs. 1-6. across top of glabella; posterior and anterior pairs con­ Diagnosis. Cephalon has slender anteriorly ex­ nected laterally to axial furrows; second pair from rear panded glabella that reaches to narrow anterior border. consists of isolated pits. Frontal glabellar lobe has Fixed cheeks narrow; width exclusive of palpebral lobes shallow median depression on anterior part. Occipital one-half or less than one-half basal glabellar width. furrow shallow; occipital ring has small median node. Palpebral lobe long, slender, curved; anterior end Frontal area gently concave; border narrow, wirelike. separated from axial furrow by moderately narrow Fixed cheek broad, gently convex, horizontal; width, part of fixed cheek. Posterior limb slender; posterior exclusive of palpebral lobe, about equal to basal gla­ fixigenal spine absent. bellar width. Palpebral lobe well defined by sharp Pygidium subquadrate in outline; has prominent axis change in slope, slightly curved, at distinct angle to and gently convex pleural region lacking well-defined axial line; length about equal to basal glabellar width; border. Posterolateral margin has pair of slender line connecting posterior tips passes over preoccipital posteriorly directed spines. furrow. Ocular ridge poorly defined, reaching axial Stephenaspis? avitus n. sp. furrow about opposite anterior glabellar furrow. Plate 3, figures 10-14 Posterior limbs moderately long, tips rounded; trans­ verse length nearly twice basal glabellar width. Poste­ Description. Cranidium, exclusive of posterior rior border furrow moderately deep distally, becoming limbs, subquadrate in outline and moderately convex shallower toward glabella and nearly disappearing just transversely and longitudinally; width between palpe­ before reaching axial furrow. bral lobes about equal to sagittal length. Anterior Course of anterior section of facial suture straight margin moderately curved. Frontal area constricted forward from palpebral lobe. Course of posterior sec­ in front of glabella, divided laterally into brim and tion of facial suture moderately to strongly convex; border by sharp change in slope. Glabella low, clearly strongly divergent immediately behind palpebral lobe. defined, reaching onto border; gently and evenly ex­ External surfaces of all parts of cranidium smooth. panded forward, anterolateral corners sharply rounded. Other parts not known. Four pairs of lateral glabellar furrows present; pos­ Discussion. The most distinctive features of this spe­ terior pair deepest, directed backward at acute angle cies are the poorly defined front of the glabella, the me­ to axial furrow; second pair nearly at right angles to dian depression in the anterior part of the frontal axial furrow; anterior two pairs directed slightly glabellar lobe, the wirelike cranidial border, the glab­ anteriorly from axial furrow. Occipital furrow moder­ ellar shape, and the posterior pair of glabellar furrows ately deep at sides of glabella, shallower across axial connected laterally with the axial furrows. No other line. Occipital ring nearly flat, moderately long sagit- oryctocephalid species described possesses this combina­ tally; some specimens have low axial keel and all tion of characteristics. Forms such as Lancmtria specimens have a short median spinule on posterior Toddyi (Walcott) and TonkineM-a valida Chernysheva margin. have a wirelike border on the front of the cranidium in Fixed cheeks gently convex; width, exclusive of pal­ addition to a broader border that is in contact with the pebral lobes, about one-half basal glabellar width. glabella. Nothing on the cranidia of Goldfieldia Palpebral lobes well defined by deep palpebral furrows, pacified indicates the presence of any border other than strongly curved, connected to axial furrows at junction the wirelike one. L. roddyl is the only previously de­ with fourth pair of glabellar furrows by low ocular scribed Lower Cambrian oryctocephalid, and the known ridge that crosses moderately narrow part of fixed specimens are rare and are deformed. The holotype of cheek; length of palpebral lobe slightly less than one- L. roddyi shows the apparent connection of the poste­ half sagittal length of glabella. rior glabellar furrows across the top of the glabella but Posterior limb long and slightly backswept and has no clear indication of their connection to the axial fur­ bluntly rounded tip; transverse length generally LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA F9

slightly more than basal glabellar width. Posterior Description. Small corynexochid trilobites; total border furrow broad, deep. length of largest known specimen estimated as 25 mm. Course of anterior section of facial suture slightly Cranidium subquadrate in outline, gently to moderately divergent forward from palpebral lobe to border, then convex transversely and longitudinally. Glabella long, sharply turned inward across border to merge imper­ slender, expanded slightly at anterior end, bluntly ceptibly with anterior margin. Course of posterior rounded in front. Glabellar furrows poorly defined. section of facial suture moderately convex from pal­ Occipital furrow deep, straight. Occipital ring has pebral lobe to posterior margin. slender posteriorly directed axial spine extending from Free cheek has moderately curved lateral margin posterior margin. Frontal area moderately short; continuing backward into short genal spine. Border sagittal length between one-third and one-fourth of narrow, well denned; width distinctly less than width sagittal length of glabella exclusive of occipital ring. of ocular platform. Lateral and posterior border fur­ Border moderately to poorly defined; where apparent, rows of even depth, joined in sharp curve at genal separated from glabella by narrow concave brim. angle. Fixed cheeks broad, horizontal or gently upsloping, External surfaces of most parts covered with fine flat or gently convex; width, exclusive of palpebral closely spaced granules generally apparent only after lobes, about three-fourths basal glabellar width. Pal­ whitening. pebral lobes long, strongly bowed, transversely convex, Discussion. The general cranidial characteristics of well-defined by palpebral furrows, generally slightly this species, including the long anteriorly expanded elevated above surface of fixed cheek; lateral margins glabella, the long palpebral lobes that have the anterior vertical; anterior ends distinctly separated from axial ends moderately separated from the axial furrows, and furrows by moderately narrow part of cheek that is the posterior limbs that have no posterior fixigenal crossed by distinct ocular ridges. Transverse line spines, are those of Stephenaspis. On 8.1 avitiis the through midpoints of palpebral lobes passes over facial sutures are less divergent forward and the cheek posterior half of glabella. Posterior limbs short and width between the anterior end of the palpebral lobe have rounded tips barely extending laterally beyond and the axial furrow is greater than on the genotype, S. palpebral lobes. bispinosa Rasetti. The genal spine on the free cheek Course of anterior section of facial suture divergent is also somewhat shorter. However, without knowl­ forward from palpebral lobe to border, then curved edge of the structure of the pygidium, which is of inward across border to merge imperceptibly with an­ critical importance for generic identification in this terior margin. Posterior section of facial suture di­ group, the species described here cannot be definitely vergent almost straight laterally behind palpebral lobe, assigned to Stephenaspis. If the pygidia described on then curved strongly backward to posterior margin. page F12 belong in S.? avitus, the trilobite resembles Free cheek known only for type species. Border Poliellci denticulate*. (Rasetti, 1951, pi. 12, figs. 6-9). broad, gently convex, extending laterally into broad- However, P. denticulata has distinctly narrower fixed based genal spine that is distinctly anterior to genal cheeks adjacent to the anterior ends of the palpebral angles of cephalon. Lateral border furrow shallow. lobes. Posterior border furrow narrow, moderately deep, con­ Ptarmigania and Ptarmiganoides are two somewhat nected to lateral furrow at base of genal spine. Eye similar genera in which cranidia have long palpebral surface joined to ocular platform without intervening lobes and have a moderate distance between the anterior infraocular ring. Ocular platform gently convex, end of the palpebral lobe and the axial furrow. In about as wide as border. Anterior sutural margin about both these genera, however, the genal spines are ad­ parallel to posterior border furrow. vanced, and the posterior limbs of the cranidia bear Pygidium small, subovate in outline; known only for prominent posterior fixigenal spines. These character­ type species. Axis prominent, tapered backward, istics are so much like those of that both bluntly rounded at rear; width about equal to width of Ptarmigania and Ptamn iganoid&s probably should be re­ pleural region, length slightly less than that of pygid­ moved from the Dolichometopidae, in which they were ium. Two ring furrows present posterior to articu­ placed by Rasetti (1951) and by Poulsen (1959), and lating furrow. Pleural fields crossed by one or two placed in the Zacanthoididae. shallow pleural furrows. Border poorly defined and narrow and has three or four pairs of short marginal Genus ZACANTHOPSIS Resser spines. Type species. Olenoides lev is Walcott, 1886, p. 187, External surfaces of known species partly or wholly pi. 25, figs. 3,3a. covered with fine closely spaced granules.


Discussion. The description is based on the study of Zacanthopsina eperephes n. sp. all the specimens of Zacanthopsis in the collections at Plate 3, figures 7-9 the U.S. National Museum or in the U.S. Geological Description. Small corynexochid trilobites; total Survey. The slender anteriorly expanded glabella and length of largest individual probably less than 2 cm. the wide fixed cheeks having long arcuate palpebral Cranidium subquadrate in outline; sagittal length about lobes whose anterior ends are distinctly separated from two-thirds greatest width. Glabella long, slender, and the axial furrows, combined with the presence of a mod­ well defined in posterior part, expanded forward and erately well-defined frontal area and short posterior poorly defined anteriorly, reaching nearly to border. limbs distinguish species of this genus from other Three pairs of shallow lateral glabellar furrows appar­ corynexochid trilobites. All known specimens of ent. Occipital furrow deep, straight. Posterior mar­ Zacanthopsis are from Lower Cambrian rocks. Be­ gin of occipital ring produced posteriorly into short, cause the associated parts of Z. lev is (Walcott), the slightly upsloping median spine. Frontal area short; type species, have never been adequately illustrated, sagittal length between one-third and one-fourth sagit­ they are presented here (pi. 3 figs. 1-3) for comparison tal length of glabella; anterolateral corners depressed. Brim in front of glabella strongly concave, differen­ with Z. contracts n. sp. and for future reference. tiated only by change in slope from strongly convex, Zacanthopsis contractus n. sp. elevated border. Fixed cheeks broad, flat, nearly hor­ izontal; width, exclusive of palpebral lobes, slightly Plate 3, figures 4-6 greater than basal glabellar width. Palpebral lobes Diagnosis. Species of Zacanthopsis in which the prominent, long, strongly arcuate, continuous with cranidium has anterior border convex, moderately well prominent ocular ridge that extends to and merges with defined; width between anterior sections of facial anterior part of frontal lobe of glabella; line connecting sutures considerably less than width between lateral posterior tips of palpebral lobes crosses glabella just margins of palpebral lobes; occipital ring has short anterior to occipital furrow. Lateral parts of palpe­ slender occipital spine. Axial part of glabella has fine bral lobes strongly curved downward and inward, so closely spaced granules. Granules also apparent on that sutural margin is slightly underneath dorsal part fixed cheeks of some specimens; not observed on frontal of palpebral lobe. Posterior limbs short, bhmt; trans­ area. verse width of cranidium between tips of posterior limbs slightly less than cranidial width between lateral mar­ Discussion. This species is distinguished from gins of palpebral lobes. Posterior border furrow deep, ZacantJiopsis levis (Walcott) and from Z. virginica straight. Resser by having a better defined anterior border and Course of anterior section of facial suture slightly by being distinctly narrower between the anterior sec­ convergent forward from palpebral lobe to inner edge tions of the facial sutures than between the palpebral of border, then more strongly curved across border to lobes. Although the species is known from only five merge imperceptibly with anterior margin of cranidium. cranidia, these characteristics seem constant. The Course of posterior section strongly convex from palpe­ small occipital spine, unfortunately, was broken from bral lobe to posterior margin. the holotype during preparation. External surfaces of all parts of cranidium smooth. Other parts of exoskeleton unknown. Genus ZACANTHOPSINA n. gen. Discussion. The inner end of the ocular ridge of Type species. Zacanthopsina eperephes n. sp. Zacanthopsina eperephes is slightly expanded at its con­ Diagnosis. Small Corynexochida that have promi­ tact with the glabella, somewhat like that shown by nent ocular ridges undifferentiated from arcuate pal­ Hupe (1953, p. 264, fig. 63A) for Kingaspis campbelli pebral lobes; ridges expanded slightly adjacent to (King). Also, each palpebral lobe has its lateral mar­ gin turned down and slightly inward, so that the sutural glabella and merged with frontal glabellar lobe. margin is actually beneath the dorsal surface of the Discussion. The genus most similar to Zacanthop- palpebral lobe, similar to the structure of the palpebral sina is Zacanthopsis, which also has broad fixed cheeks, lobe of Pertomella yorkemis Resser (Rasetti, 1955, pi. 5, short posterior limbs, and a short frontal area that has fig. 2). However, in Z. eperephes, the ocular ridge a strongly concave brim and strongly convex, elevated forms a continuous band, diverging only slightly pos- border. In Zacanthopsis, however, the ocular ridge terolaterally from the anterior part of the frontal lobe reaches the glabella at the posterior part of the frontal of the glabella to the palpebral lobe. This structure lobe and does not merge with the frontal lobe. is unique among members of the order Corynexochida. LOWER CAMBRIAN TRILOBITE FAUNA FROM NEVADA Fll

This is a relatively rare species in the fauna and is surfaces of all parts covered with moderately coarse represented by fewer than 10 specimens. granules. Discussion. This species, known from 10 pygidia Order PTYCHOPABIIDA Swinnerton ranging in sagittal length from 2 mm to 9 mm, is Family PTYCHOPABIIDAE Matthew characterized particularly by well defined pleural and Genus SYSPACEPHALTTS Kesser interpleural furrows and by two pairs of anterolateral Syspacephalus? sp. border spines. Plate 3, figures 15, 20 The species is most like Olenoides hybridus Resser Discussion. Several fragmentary cranidia and a (1938, p. 91) from the Lower Cambrian of Virginia in pygidium may represent a species of /Syspacephalus. possessing twro pairs of short anterolateral spines. It The cranidia are characterized by gently convex down- differs from the eastern species by having the ridges ad­ sloping fixed cheeks, small palpebral lobes situated jacent to each interpleural furrow on the pleural field opposite the anterior half of the glabella, and facial of the pygidium of nearly constant and equal width. sutures that converge slightly forward. These have In this respect, the pleural fields are more like those of been cited by Rasetti (1955) as distinctive character­ Bonniopsis virginica Resser, which also has two border istics of Syspacephalus. However, the species illus­ spines. In B. virginica, however, the border behind the trated here has much longer distal parts of the posterior spines is a flat flange. More must be learned about the limbs than does the type species, S. charops (Walcott). other parts of the trilobite described here before it can In S. charops the transverse length of the distal part be adequately understood and formally named. of the posterior limb is less than half the transverse Genus and species undetermined 2 length of the proximal part. On the specimen illus­ Plate 3, figure 17 trated here the transverse length of the distal part of Description. Small pygidia, subovate in outline; the posterior limb is nearly equal to that of the sagittal length about five-eights maximum width. Axis proximal part. The form of the posterior limb is gen­ prominent, broad, strongly rounded at rear, nearly erally not so variable in younger ptychoparioid genera; reaching to posterior margin; width slightly less than for this reason, the generic assignment of the illus­ one-half maximum pygidial width. Two ring furrows trated specimen is questioned. An associated pygid­ posterior to articulating furrow; first furrow unusually ium having fine granular ornamentation similar to that deep, overshadowed by strongly convex ring of first seg­ of the illustrated cranidium may belong to the species. ment. Pleural regions narrow, subtriangular; border It is characterized by being nearly twice as wide as not well defined. Two shallow pleural furrows, not it is long, by having a low axis that tapers backward reaching to margin. Margin has four pairs of short and merges with the posterior part of the pygidium, spines decreasing in size posteriorly. External surface and by having four or five ring furrows and two or covered with fine closely spaced granules. three pleural furrows. No clearly defined border is Discussion. This pygidium is most like the pygidium present. Without a larger sample, these specimens of Zacanthopsls levis (Walcott) and may be the pygid­ cannot be adequately identified. ium of Z. contractus n. sp. However, the possibility POSITION UNCERTAIN that it may be the pygidium of either Zacanthopsina Pygidia of at least four species of trilobites cannot eperephes n. sp. or Stephenaspisl avitm n. sp. cannot be assigned with certainty to the cranidia described be excluded, and therefore, the generic assignment is in herein. Their description and possible affinities are doubt. discussed below. Genus and species undetermined 3 Plate 3, figure 18 Genus and species undetermined 1 Description. Small pygidia, subsemicircular in out­ Plate 3, figure 16 line, length slightly less than one-half maximum width. Description. Pygidium subsemicircular in outline. Axis prominent, tapered backward, strongly rounded at Axis long; sides subparallel; posterior end strongly end; length from articulating furrow about eight-tenths rounded, prominent, reaching to inner edge of border. length of pygidium; width slightly less than one-third Four or five complete ring furrows posterior to articu­ maximum pygidial width. Two complete ring furrows lating furrow. Pleural fields crossed by five broad, posterior to articulating furrow. Pleural regions have deep pleural furrows and four narrower interpleural poorly defined narrow border and three shallow furrows furrows that terminate at inner edge of border. Border and two even shallower interpleural furrows, not cross­ narrow, of nearly constant width; has two pairs of ing border. Pygidial margin does not have spines. short prominent anterolateral border spines. External External surface smooth or slightly roughened. F12 CONTRIBUTIONS TO PALEONTOLOGY

Discussion. This pygidium is most like the pygid- Nelson, C. A., 1962, Lower Cambrian- succession, ium of Wenchemnia (Kasetti, 1951, pi. 11) in general White-Inyo Mountains, California : Geol. Soc. America Bull., v. 73, no. 1, p. 139-144. morphology, but it has one less axial segment and one 1963, Stratigraphic range of Ogygopsis: Jour Paleontol­ less pleural segment. Without good evidence for a cor­ ogy, v. 37, no. 1, p. 244-248. rect association of a cranidium, a generic assignment is Palmer, A. R., 1957, Ontogenetic development of two olenellid not possible. trilobites: Jour. Paleontology, v. 31, no. 1, p. 105-128. Pokrovskaya, N. V., 1959, Trilobitovaya fauna i stratigrafiya Genus and species undetermined 4 kembriyskikh otlozheniy Tuvy: Akad. Nauk SSSR, Geol. Plate 3, figure 19 Inst. Trudy, no. 27, 199 p. Poulsen, Christian, 1932, Lower Cambrian faunas of east Green­ Description. Small pygidia, subsemicircular in out­ land : Medd. om Gronland, v. 87, no. 6, 66 p. line ; sagittal length about one-half width. Axis promi­ 1958, Contribution to the paleontology of the Lower nent, broad, strongly rounded at end; length about Cambrian Wulff River formation: Medd. om Gronland, v. three-fourths length of pygidium; width slightly more 162, no. 2, 24 p. 1959, in Harrington, H. J., and others, 1959. than one-third greatest pygidial width. Two ring fur­ Rasetti, Franco, 1948, Lower Cambrian trilobites from the rows posterior to articulating furrow. Pleural regions conglomerates of Quebec (exclusive of the Ptychopariidea) : do not have well denned border. Three pleural fur­ Jour. Paleontology, v. 22, no. 1, p. 1-24. rows, terminated laterally just before reaching pygidial 1951, Middle Cambrian and faunas of the margin. Three pairs of short, nubby marginal spines. Canadian Rocky Mountains: Smithsonian Misc. Colln., v. 116, no. 5, p. 1-277. External surface covered with fine closely spaced gran­ 1955, Lower Cambrian ptychopariid trilobites from the ules barely visible even after whitening. conglomerates of Quebec: Smithsonian Misc. Colln., v. 128, Discussion. This pygidium cannot be assigned with no. 7, p. 1-35. certainty to any of the described species in the fauna. 1959, in Harrington, H. J. and others, 1959. Raymond, P. E., 1912, Notes on parallelism among the : If classified by relative abundance, size, and external Royal Soc. Canada Trans., 3d ser. v. 5, sec. 4, p. 111-120. ornamentation, it would seem to be the pygidium of 1928, Two new Cambrian trilobites: Am. Jour. Sci., 5th Stephenaspisi. avitus n. sp. Its structure, however, is ser., v. 15, p. 309-313. completely unlike that of the type species of Stephen- Resser, C. E., 1928, Cambrian from the Mohave Desert: aspis. If the association is correct, 8. ? avitus may be Smithsonian Misc. Colln., v. 81, no. 2,14 p. more closely related to the early Middle Cambrian 1936, Second contribution to nomenclature of Cambrian trilobites : Smithsonian Misc. Colln., v. 95, no. 4, 29 p. species, PolieUa denticulata. ( See p. F9). 1937, Elkanah Billings' Lower Cambrian trilobites and REFERENCES associated species: Jour. Paleontology, v. 11, no. 1, p. 43-54. 1938, Cambrian system (restricted) of the southern Ap­ Bell, G. K., Jr., 1931, The disputed structures of the Mesonaeidae palachians : Geol. Soc. America Spec. Paper 15, 140 p. and their significance: Ain. Mus. Novitates, no. 475, 23 p. 1939, The Ptarmigania strata of the northern Wasatch Billings, Elkanah, 1861, On some new or little known species of Mountains: Smithsonian Misc. Colln., v. 98, no. 24, 72 p. Lower fossils from the Potsdam group (Primordial Resser, C. E., and Howell, B. P., 1938, Lower Cambrian Olenellus zone), in Hitchcock, Edward, and others, 1861, Report on zone of the Appalachians: Geol. Soc. America Bull., v. 49, tlie geology of Vermont, v. 2: Claremont, N.H., p. 942-960. no. 2, p. 195-248. Cooper, G. A., and others, 1952, Cambrian stratigraphy and Rominger, C. L., 1887, Description of primordial fossils from paleontology near Caborca, northwestern Sonora, Mexico: Mt. Stephens, NW Territory of Canada: Acad. Nat. Sci. Smithsonian Misc. Colln., v. 119, no. 1,184 p. Philadelphia Proc. for 1887, p. 12-19. Harrington, H. J., and others, 1959, Arthropoda 1, in Treatise on Shaw, A. B., 1955, Paleontology of northwestern Vermont, pt. invertebrate paleonthology, Part O : Lawrence, Kans., Geol. V, The Lower Cambrian fauna: Jour. Paleontology, v. 29, Soc. America and Univ. Kansas Press. 560 p. no. 5, p. 775-805. Hupe, Pierre, 1953, Contribution a 1'etude du Cambrian in- Shinier, H. W., and Shrock, R. R., 1944, Index Fossils of North ferieur et du Precambrien III de L'anti Atlas Morocain: America: Massachusetts Institute of Technology, The Tech­ Serv. Geol. Moroe. Notes and Mem. 103, 402 p. nology Press, 837 p. Lake, Philip, 1937, A Monograph of the British Cambrian trilo- Walcott, C. D., 1886, Second contribution to the studies on the bites, pt. X: Paleontographical Soc., v. 90, p. 225-248. Cambrian fauna of North America: U.S. Geological Survey Lermontova, E. B., 1940, in Vologdin, A. G., Atlas of the leading Bull. 30, 368 p. forms of the fossil faunas of the U.S.S.R., v. 1, Cambrian: 1889, Description of new genera and species of fossils Moscow, VSEGEI, 193 p. from the Middle Cambrian: U.S. Natl. Mus. Proc., v. 11, 1951, Nizhuekenibriiskie trilobity i brakhiopody vostochnoy p. 441-446. Sibiri: Moscow, VSEGEI, 218 p. 1910, Olenellus and other genera of the Mesonaeidae: Lochman, Christina, 1947, Analysis and revision of eleven Smithsonian Misc. Colln. v. 57, no. 6, p. 233-422. Lower Cambrian trilobite genera : Jour. Paleontology, v. 21, 1916, Cambrian trilobites: Smithsonian Misc. Colln. v. no. 1, p. 59-71. 64, no. 5, p. 303-456. McLaughlin, K. P., and Enbysk, B. B., 1950, Middle Cambrian Wanner, Atreus, 1901, A new species of Olenellus from the Lower trilobites from Pend Oreille County, Washington: Jour. Cambrian of York County, Pennsylvania : Washington Acad. Paleontology, v. 24, no. 4, p. 466-471. Sci. Proc., v. 3, p. 267-272. INDEX

[Italic page numbers indicate descriptions] Page Page avitus, Stephenaspis. . Fl, 2,8,11,12; pi. 3 Oleaellidae- Fl,2 Olenettus...... 2,3 Bathyuriscus batis ______7 (Holmia) walcottanus . 3 Bathyurus parvulus ______5 Olenoides...... 2,5,6 batis, Bathyuriscus ______7 hybridus ...... 11 Ogygopsis...... 2,7; pi. 2 levis...... 9 Bibliography ______12 maladensis...... 6 bispinosa, Stephenaspis ______8, 9 spp.- -- B; pi. 2 Bonnia...... ___ .. ______1,5 Oryctocephalidae,. 1,2,7 brennus ...... ______5 caperata ...... 1,2,5; pi. 2 padfica, Goldfieldia...... 1,2,7, columbensis 5 Paedeumias...... ____ .______5 granulatus.-....--.....-...... _ 1, 2, 3, (Bonnia), Corynexochus . 5 transitans...... _._ 2 Bonniopsis virginica ..... 11 parvulus, Bathyurus__---_ 5 brennus, Bonnia...... - . 5 Periometta yorkenm..... ______--- __-__ .-. 10 Bristolia. ______1,2 Poliella denticulata______-_.__-_____-__ - 9,12 buelnaensis, Wanneria...... ______4 Ptarmigania...... -- -- Ptarmiganoides.------...... -. ------... campbelli, Kingaspis...... 10 - 11 caperata, Bonnia______.______1,2,5; pi. 2 Ptychopariidae.-._...--_____- - 1,11 Carrara Formation______1 charops, Syspacephalus...... ^...... 11 columbensis, Bonnia...... 5 Redlichiida . contractus, Zacanthopsis...... 1,2,10,11; pi. 3 rnddyi, Lancastria. Corynexochida..______5 Corynexochus (Bonnia)...... 5 Saline Valley Formation_ 1,2 spinulosa, Ogygopsis.------...... -_ 7 denticulata, Poliella. ______9,12 Stephenaspis ...... 8,9,12 Dolichometopidae:______9 asitv* . ------1,2,8,11,12; pi.3 Dorypygidae . .___..___....______...... __ 1,5 bispinosa______-- - - 8,9 Syspacephalus ------11 elongata, Ogygopsis...... 7 charops------...... _ -- --- 11 Taxioura...... 7 sp...... -- .------_--- 2, 11; pi. 3 eperephes, Zacanthopsina...... 1,2,10,11; pi. 3 Esmeraldina macer...... 4 Taxioura...... - fieldensis, Bonnia. elongata...... magna...... Genera and species undetermined____.______11,12; pi. 3 typicalis...... Goldfieldia...... 7 Tonkinella valida... __ padfica--...... 1.2,7,8; pi. 1 transUans, Paedeumias. granulatus, Paedeumias...... ______.... 1,2,3,4; pi. 1 typicalis, Ogygopsis..... Taxioura...... -... (Holmia) walcottanus, Olenettus. hybridus, Olenoides...... valida, Tonkinella .... ___ ------8 Kingaspis campbelli. virginica, Bonniopsis...... - 11 klotzi, Ogygia...... Zacanthopsis...... ------10 Ogygopsis...... walcottana, Wanneria.-.. . - 2, 4; pi. 1 Lancastria roddyi...... 8 walcottanus, Olenettus (Holmia').- - 3 Levis conglomerates______.______2 Wanneria .... . - - - ^>* levis, Olenoides...... g buelnaensis... - -- - 4 Zacanthopsis...... 10,11; pi. 3 nathorsti.--.------* macer, Esmeraldina... walcottana...... ------2, k P1- 1 magna, Taxioura...... Wenchemnia.-. - 12 maladensis, Olenoides. Metaline Limestone.. yorkensis, Periometta . nathorsti, Wanneria. Zabriskie Quartzite_ ------i Zacanthoides.-...... - - -- 9 Ogygia klotzi...... 6 Zacanthoididae -~--- - 1,8 Ogygopsidae______1,6 10 Ogygopsis...... 6,7 Zacanthopsina... ;pl. 3 batis...... 2,7; pi. 2 eperephes..------1, 2, , U elongata... Zacanthopsis- - - - 1,0,10 klotzi..... contractus... ------1,2, 10, 11;pl.3 spinulosa. levis.....-----.-...----...---.------.-.-.--...... -...-----. 10,11; pi. 3 typicalis... virginica..-...... -.--.-. - - -- 10 F13

PLATES 1-3 Plate 1 FIGURES 1-10. Paedeumias granulatus n. sp. (p. F3). 1. Left side of cephalon, X 4, USNM 144250. 2. Latex cast of central part of cephalon, X 5, USNM 144251. 3. Holotype cephalon, X 3, USNM 144252. 4. Anterior part of cephalon showing granular ornamentation of frontal lobe, X 10, USNM 144253. 5. 7. Meraspid cephala, X 10, USNM 144254, 144255. 6. Central part of cephalon showing granular ornamentatior, X 8, USNM 144256. 8. 10. Fragments of large cephala showing pit in posterior part of frontal lobe and variation in ornamentation, X 3, X 6, USNM 144257, 144258. 9. Hypostome, X 4, USNM 144259. 11-13, 15. Wanneria cf. W. walcottana (Wanner) (p. F4). 11. Detail of ventral surface of a thoracic segment showing perforations outlining margins of polygons, X 15, USNM 144260. 32. Small cephalon showing ornamentation, X 3, USNM 144261. 13. Small cephalon, X 2, USNM 144262. 15. Hypostome showing typical ornamentation of Wanneria, X 2, USNM 144263. 14, 16-18. Goldfieldia pacifica n. gen., n. sp. (p. F7). 14. Stereogram of holotype cranidium, X 8, USNM 144264. 16. Cranidium, X 10, USNM 144265, USGS colln. 3659-CO. 17. Cranidium, X 8, USNM 144266. 18. Cranidium, X 10, USNM 144267. GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-F PLATE 1



FIGURES 1-6. Ogygopsis batis (Walcott) (p. F7). 1. Free cheek, X 3, USNM 144268. 2. Stereogram of typical cranidium, X 3, USNM 144269. 3. Pygidium, X 2, USNM 144270. 4. 5. Pygidia showing variation in ornamentation, and of anterolateral spine, X 5, USNM 144271, 144272. 6. Cranidium showing typical ornamentation, X 5, USNM 144273. 7-10. Olen&ides spp. (p. F5). 7. Cracidium, X 4, USNM 144274. 8. Short-spined pygidium, X 3, USNM 144275, USGS colln. 3655-CO. 9. 10. Long-spined pygidia, X 4, and X 2 respectively, USNM 144276, 144277. 11-16. Bonnia caperata K. sp. (p. F5). 11. Stereogram of cranidium, X 3, USNM 144278. 12. Free cheek, X 3, USNM 144279. 13. Cranidium showing subdued ornamentation on fixed cheeks, X 3, USNM 144280. 14. 15. Pygidia showing variation in degree of development of ornamentation and of veins on pleural segments. X 3, USNM 144281, 144282. 16. Stereogram of holotype pygidium, X 3, USNM 144283. GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-F PLATE 2

15 16


FIGURES 1-3. Zacanthopsis levis (Walcott) (p. FlO). 1. Stereogram of cephalon, X 8, USNM 144284. 2. Free cheek, X 8, USNM 144285. 3. Pygidium, X 8, USNM 144286. All from USGS colln. 1392-CO, Pioche, Nev. 4-6. Zacanthopsis contractus n. sp. (p. FlO). 4. Stereogram of holotype cranidium, X 8, USNM 144287. 5. 6. Cranidia, X 5, USNM 144288, 144289. 7-9. Zacanthopsina eperephes n. gen., n. sp. (p. FlO). 7. Stereogram of holotype cranidium, X 5, USNM 144290. 8. Holotype cranidium, right side view showing course of facial suture, X 5. 9. Latex cast of cranidium, X 5, USNM 144291. 10-14. Stephanaspist avitus n. sp. (p. F8). 10. Stereogram of incomplete cephalon, X 5, USNM 144292. 11. 12. Cranidia, X 4, USNM 144293, 144294. 13. Free cheek, X 5, USNM 144295. 14. Stereogram of holotype cranidium, X 4, USNM 144296. 15, 20. Syspacephalusf sp. (p. Fll). 15. Cranidium, X 10, USNM 144297. 20. Pygidium, X 10, USNM 144298. 16. Genus and species undetermined 1 (p. Fll). Pygidium, X 3, USNM 144299. 17. Genus and species undetermined 2 (p. Fll). Pygidium, X 10, USNM 144300. 18. Genus and species undetermined 3 (p. Fll). Pygidium, X 6, USNM 144301. 19. Genus and species undetermined 4 (p. F12). Pygidium, X 5, USNM 144302.


17 18