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H. B. whittingtonA New Calymenid from the Maquoketa Shale, I T I A

are separate lines of descent or whether phylogeny ABSTRACT is complicated by parallel serieshas yet to be demon- strated. Dimculties have been encountered in using Parts of the exoskeleton,other than the thorax, of the is flat, trilobite mammillata Hall, 1861, form of the preglabellar field-whether it are redescribed from the orieinal and new material. ridged or rolled in sagittal profrle-in the way Shirley The latter comes from the ciphalopod coquina beds used it, and care must be taken to distinguish the form in the Elgin Shaly Limestone Member, the lowest mem- as seen in intemal molds from that of the external ber the of the Maquoketa Shale; this is probably orig- surface of the exoskeleton. Nevertheless,the criteria inal locality. The Elgin Member is of Richmond, or possibly slightly older, age. The absenceof buttresses Shirley used have been applied to discriminate spe- from fixed cheek to glabellar lobes, the large basal cies and genera in British (Dean, 1962, 1963) and glabellar lobe, papillation of the anterolateral angle North American (Whittington, 1954; Stumm and of the glabella, and long, gently sloping preglabellar Kaufiman, 1958; Ross, 1967) material. fleld with a lateral boss combine to distineuishthe There has been little recent work on caly- cranidium of C. mammillata from thar of any known species.It is regardedas the type-speciesof a new menidsexcept for that of Tillman (1960) and Camp- genuq Thelecalymene, and as most closely related to bell (1967). Until more is known of exoskeletal Grauicalymene, speciesof which have been described charactersof calymenids throughout their stratigraph- recently from contemporaneousand older rocks of the ical lange, it will not be possible to delineate phylo- midcontinent and Niw York Stare. genetic lines. The species from fowa described here exhibits a group of cranidial and pygidial characterswhich set it apart from any other; consequently,it is rnade the type In 1936 Shirley discussedearlier work on calymenid of a nervgenus. The age cannot be given more precisely and distinguished five new genera, basing than rvithin the upper part of the Cincinnatian Series, his distinctions on characters of the glabella and ad- and relationshipsto other genera are uncertain, though jacent fixed cheeks,and the preglabellar freld (anterior species of Grauicalymene may be the most closely border) , He drew attention to the presence,in certain related. species,of papillation of particular glabellar lobes,and The material from Iowa was collected in 1952 on of corresponding buttressesprojecting from the fixed field trip undertaken with the advice of Dr. G. Arthur cheek to meet such papillae, and he pointed out that a indebted- thesepapillae and buttressesproject over the axial fur- Cooper. It is a pleasure to acknowledge my rore to form a bridge. He divided calymenidsinto two ness to him for many hours of companionship in the series,based on presenceor absenceof the papillate- field, for his n'ise guidance during my studies of Or- buttressed structures: however. whether these series dovician rocks and , and for his inspiring ex- ample as a practicing paleontologist.I am indebted also L. Batten, American Museum of Natural H. B, Whitt;ngton, Departme ol Geology, Uniaerity ol to Dr. Roger Cambtid gc, Cambrid ge, England. History (AMNH) for the loan of Hall's t)'Pe mate- r29 130 SMITHSONIAN CONTRIBUTONS TO rial, and to the late ProfessorA. K. Miller for the loan ton, 1954, pp. 147,l4B1-Stumm and Kauffman, 1958) of specimensin the geology department of Univenity have, as Ross (1967, p. 89) remarks, the axial furrorv of Iowa (UI) . The material was prepared and photo- straight or slightly curved convexly outrvard, this curva- graphed in the Museum of Comparative Zoology, Har- ture being related to the evenly graduated size of t}te vard University (MCZ). Dr. V. Jaanusson, State lateral glabellar lobes. None of these lateral lobes is Museum of Natural History, Stockholm (RM), kindly buttressedto the fixed cheek, the pleural region of the loaned type and other material of Papillicalymene thorax is narrorv (transverse) than the axis, and there papillata, on wh\ch Figures 1e-,h are based. is no smooth border on the . Of these char- acters, the lack of buttresseson the fixed cheek, is thc only one that Flexicalymene has in common with Family Burmeister, 1843 Thelecalymene- 0 The type-species of Diacalymene, D. diadem.ata i! T helccalymene, new (Figures lc,d, herein and Whittington, in Moore, 1959, DraoNosts.-Glabella bell-shaped in outline, three p. 0450, figs. 353,2a,b) is from the Silurian, Wenlock, pairs of lateral lobes, anterolateral angle of frontal of Czechoslovakia.Lateral glabellar lobe 2p is opposed glabellar lobe papillate. No genal buttiessesto lateral closelyby a genal buttress,and the preglabellar field is lobes 1-3p. Preglabellar field broad (sagittal and strongly ridged, the posterior-facingslope having a lorv exsagittal), sloping foruard and upward from furrorv, projection where it meets the anterior border opposite low boss at lateral margin projects towards comer of the axial furrow. Rostral suture is situated some dis- frontal glabellar lobe. Eye lobe oppositelateral glabellar tance down the anterior-facing slope of the 6eld. The lobe 2p, broad low eye ridge; anterior, inner comer of inner, anterior corner of the fixed cheek is inflated and cheek slightly buttress€d towards comer of frontal projects slightly, but the anterior angle of the frontal glabellar lobe. without swelling or ridge glabellar lobe is not papillate. The inflated inner comer on anterior lobe of middle body, posterior lobe with of the fixed cheek and the slight distal projection (not median posterior indentation; outline of posterior a buttress) on the preglabellar field.arc asin T helecaly- border bilobed. mene, but the genal buttress opposite lobe 2p and the Pygidium with pleural region displaying deep pleural ridged preglabellar field distinguish Diacalymene from genus. pygidium furrows which die out distally, leaving a border of that The of Diacalymene has vnartow smooth border, but includes only five axial rings and width one-third that of the region; faint interpleural pleural ribs. Thus, while Diacalymene and Thelecaly- furrows. Dxternal surface of exoskeleton granulate, ex- mene have some characters in common, the two are cept in furrows. not closelyrelated if genal buttressesopposed to lateral TyrE-spEcros.-Calymene mammillafa Hall, 1861. glabellar lobes are consideredimportant characters in Drscussrorv.-The diagaosispresented above is in- phylogeny. tended to be read in conjunction with my diagnosis ln Grauicalymene (figure l&,1) the glabella is like (Whittington, in Moore, 1959, pp. 0450, O45l) of that of T helecalymene in baving a relatively large basal the familn lines two to four of which should read lobe, so that the outline of the lateral margin is curved "widest acrossoccipital ring or pre-occipital (i.e., lp) concavely outward. There are no genal buttressesto lateral lobes; may or may not project in front of genae," lateral lobes l-3p in either genus, but Grauicalymene Dean (1962, pp. lll-118; 1963,pp. 216-228) de- does not have the outer angle of the frontal lobe papil- scribed, from the Ordoviciar of Britain, species of late. The preglabellar field is strongly ridged in Grazi- Flexicalymene, Diacalymene, and Graoicalymene and calymene, not gently upsloping medially as in Thele- I erected the gerus Onnicalymeze, distinguished from calymene. In certain species of Graoicalymene (G. i Flexicalymene essentially by the relatively posterior hagani, Grauicalymene sp. of Roas, 1967, pl. 3, figs. I, position of the eye lobe. Ross (1967, pp. B7-Bl7) has 19) there is a slight development oI a buttress on the discussed F/e.ticalymene and Graaicalymene and de- outer part of the preglabellar field that resemblesthe scribed speciesof them from the Ordovician of Ken- much stronger bossin this position in Thelecalymene. tucky and . Speciesof Fleicalymene in Britain The deep, trenchlike posterior border furrow in (Figure L',j) and North America (see also Whitting- Graoicalynene hagani Ross, widest medially, is like NUMBER 3 131

Graaicalymenesp. 4 by Ross(1967, pp. 812, 813, pl. 3, "-rJ figs. 14-17), from the same formation, may belong with this pygidium; it has a preglabellar field which is lessstrongly ridged than that of many speciesof Graui- calyrnene,and thus is more lile that of Thelecalymene. Among Ordovician calymenids, Thelecalryene is tlrus most like Graoicalymene, and is approximately contemporaneouswith it in the lower part of the Ma- quoketa Shale (G. afr. quadricapila of Ross, 1967, pl. I 4, figs. 14, 15). An Ordovician speciesthat is like Thelecalymenemammillata in having the anterolateral \ angle of the frontal glabellar lobe buttressedfrom the inner, anterior comer of the fixed cheek is Papillicaly- mene husseyiStumm and Kauffman (1958, pp. 957- 959, pl. 123, fig. 18) from high Richmond strata of . This latter specieshas lateral glabellar lobes 2p and 3p opposedby low genal buttresses,and it shows a low projection at the outer edge of the preglabellar field; it differs from T. matnmillata in having a deep preglabellar furrow and hence a strong flexure in the preglabellar field at the margin of this furrow, and the palpebral lobe may be situated slightly farther back. Stumm and Kauffman referred their speciesto Papillicalymene Shirley ( 1936,p. 396, fig. 1) , of which the t;pe-species,Calyrnene papillata Lindstr'om, 1885, FtcuRE l.-Outlines of cranidia of type speciesof cal),rnenid genera, sagittal profile and dorsal views: z, b, Thelecaly- is from strata of Ludlow age in Gotland. Through the mene mamnillata (Hall, 186l ), based on MCZ 8672/2 (see kindness of Dr. V. JaanussonI have been able to ex- Plate 1: figures 1-4) ; c. d, Diacalynene diademata (Bar- amine the type and other material of this Swedish rande, 1846), based on MCZ 8346, Wenlock age portion of species,and it will be redescribedelsewhere. P- papil- Litei Shale, St. Ivan, Prague district, Czechoslovakiaje, f, Papillicalymcne |atillata (Lindstorn 1885), based on RM lata (Figve 1e-h) has prominent genal buttressesop- Ar 6208, Hemse Beds of Ludlow age (Martinsson, 1967), posedto lateral lobes2p and 3p, the anterolateral mar- Ostergarn, g, Gotland; h, P. lapillata, based on RM Ar gin of the frontal glabellar lobe papillate, and a deep 27199, Hemse Beds of Ludlow age, Hammars, Ostergam, and narrow preglabellar furrow, from the anterior Gotland; i, 1, Flexicalymene cf. caractaci (Salter, 1865), bas€d on original of Whittington (1965, pl. 18, figs. 9, 10), margin of which the preglabellar field curves upward Longvillian Stage, ,North ; k, l, Grzzi- closeto the frontal slope of the glabella before arching calymefle conuolaaShirley, 1936, basedon SedgwickMuseum through 180' to descendveftically to the rostral suture. A5877, Ashgill Series,Birdshill quarry, near Llandeilo, South Wales. The frontal glabellar lobe may be opposed by a but- tresslrom the inner corner bf the fixed check (Figure that in Thelecalytnene rnammillata (Hall). The py- ll), or from the outer part of the preglabellar field gi.dia"of Grauicalyrnene from (as described (Figure I [). The pygidium is like that of T. mammil- by Ross) appear to have one less pleural rib than in lata, but it has a much lessconspicuous sixth pleural T. mamrnillata, and lack the distinct border; inter- rib and a narrower (transverse) border. Thus, Papilli- pleural furrows are similar in being deeper proximally calymene is quite distinct trom Thelecalymene. and distally. Only the pygidium described as Grauicaly- Stumm and Kauffman's speciesis based on a single, mene?sp.5 by Ross (1967,p. B13, pl. 3, fig. 13) hasa incomplete internal mold of the cranidium, and more distinct border, but it has one lessaxial ring and pleural material is needed to confirm its generic assignment, rib than ?. mammill.tta. The cranidium described as as those authors have recosnized. 372-386 O-71-10 132 CONTRIBUTIONS TO PALEOBIOLOCY

T helccalymene mammillata (Hall, 1861) cation, March 1968) has identified in collectionsfrom the GraJ section this species and also Orthograptus FIcune la, D; Pr.e,rr1: FrcuREs1-7; Pr.etr 2: FrcuREsl-13. truncatus abbreoiatus (Elles and Wood), a form he Calymenemammillata Hall, 1861,pp. 50, 51; Hall, in Hall consideG confined to Richmond and younger strata. and Whitney,1862, p. 432,figs. 1, 2; Walter, 1927,p.239- Glenister (1957) concluded from her study of cono- 241,pl. 19,figs. l-3. donts that the Elgin Member in Iowa was Richmond- Me.renw, cEoLoGrcAL HoRrzoN, AND AcE.-AM ian or possibly slightly older. Professor Walter C. NH 1408a-g, originals of Hall (1861); 1408a, holo- Sweet (personal communication, 28 January 1968) type, incomplete cranidium, original of Hall (1862, statesthat the Elgin of Iowa has felded a number of fig. 1); 1408e, incomplete pygidium, original of Hall specimensof the conodont Phagmodus undatus, which (1862, fig. 2) and a second pygidium on the same slab he considersis probably of Eden age, though it may be (Plate 2: ucunrs 7, 9, 19, 13) that has someof the younger. The "graptolite zone" of Ladd embracesbeds, exoskeleton attached and is not flattened; l408b-d, at scatteredlocalities, containing abundant graptolites; three incomplete cranidia; and 1408f, g, incomplete my investigations showed that different species oc- pygidia; all are from "the shales above the Galena curred at particular localities, and cast doubt on the Limestone, It4aquoketa Creek, 12 miles west of Du- view that the age of these beds at different localities buque, Iowa." UI 9069,9077-8, originals of Walter lay within the same limited span of time. Thus, the (1927) from the samelocality as Hall's specimens,arrd age of the Elgin Member appearsto be Upper Ordovi- approximately from the well-known section,one-quar- cian, possiblyRichmond, possiblyolder. ter mile southwest of Graf, Dubuque County, Iowa Drscmprron.-Occipital ring widest (sagittal) (Ladd, 1929,pp. 341-343). This sectionis in Ladd's medially, distally curying forward to merge, across graptolite zone of the Elgin Shaly Limestone Member, the shallow axial furrow, with the inner, posterior the lowest part of the Maquoketa Shale. When visiting corner of the cheek. Occipital furrow deepensbehind this section in August 1952 I observedsome 20 feet of basal glabellar lobe into transversely elongate apo- dark gray shales,in the upper 6 feet of which were demal pit. Basal (1p) lateral lobe oval in outlineJ calcareousJsandy beds,6J inches thick, with cephalo- inflated, separatedby shallow longitudinal furrow from pods (Miller and Youngquist, 1949). Dissociatedexo- median lobe. The 2p lateral lobe similar in outline skeletal parts of the calymenid (MCZ 8672) occur in and inflation to 1p lobe, length (exsagittal) half that the lower part of the cephalopod beds, and there also of 1p lobe; 3p lobe inflated, anterior angle of frontal occur gastropods,bivalves, and rarer linguloid brachi- glabellar lobe weakly to strongly papillate, the tip opods.Hall's specimensare in similar calcareoussand- directed slightly upu'ard and outward at some 45o stonesand contain cephalopodsand gastropods.These to the sagittal line; anterior margin of frontal lobe beds must be approximately Beds 1l-16 of Thomas's curved convexly forward, t1ie curvature varying ac- section,quoted by Ladd (1929, pp. 342-343). The cording to the strength of the papillation of the lobe only other trilobite that I have seen from the Graf (compare figures 4 and 5 of Plate 1). Axial furrow section is the cranidium oI Primaspis cf. crosotus a narrow, deep trench curving around the basal gla- (Locke, 1843), a speciesfrom the Eden of the Cincin- bellar lobe, broadening progressivelyanteriorly, deep nati district; the specimenswere collected by Mr. H. anterior pit opposite frontal lobe, Slope of frontal lobe W. Tichenor. USNM 10263, from Maquoketa Creek, of glabella is vertical adjacent to broad, shallow pre- Iowa, presumably is from the same beds. Ladd (1929, pp. 384,395) Iists "C". mammillata only from his de- Ptlrn l,-Thelecalymcne mammilldta (Hall). 1-4, Crani- pauperate zone at the baseof the Elgin Member, but dium: ante or, left lateral,oblique, and dorsalviews (X 3) ; evidently the speciesranges higher, into Ladd's grapto- MCZ 8672/2, Elgin Shaly Limestone Member, Maquoketa 0.25 mile Dubuque Iowa. lite zone. Shale, southwestof Graf, County, 7, Dorsal view ( X 6) of anterior portion of samespecimen, show- The Maquoketa Shale is regarded (Twenhofel, et ing detailsol extemal surface,glabellar lobes,and preglabellar al., 1954) as being of Richmond age; the characteristic field. 5, 6, Holotype, cranidium: dorsal and oblique views ( AMNH above the form in Ladd's graptolite zone of the Elgin Member X 3) ; 1408a, shales Galena Limestone, Maquoketa Creek, 12 miles west of Dubuque, Iowa (prob- being apparently Orthograptus truncatus peosta ably same locality and horizon as original of figures 1-4, 7). (Hall). ProfessorW. B. N. Berry (personal communi- Orisinal oI Hall ( 1B62,rtg. 1). IJJ

I 'a: 134 SMITIISONIAN CONTRIBUTIONS TO PALEOBIOLOGY glabellar furrow, on anterior side of which a broad define six prominent ribs. The pleural furrows die out (sagittal and exsagittal) preglabellar field slopesgently on the outer portion to leave a border of width one- upward to margin, where it is abruptly flexed to slope third that of the pleural region. Five interpleural fur- downward and inward for a short distance to the ros- rows traverse the first five ribs, situated closer to the tral suture (Plate 2: figure 12) . In dorsal view margin posterior t}tan the anterior margin of the rib, and are of preglabellar field is curved so that field projects as deepestadjacent to the axial Iurrow, shallow medialln a lip; a broad, low boss at the inner, lateral margin and deeper distally, where the first three extend on to of this field. Cheek subquadrant in outline, moderately the border. The sixth rib is unfurrowed. convex, the portion in front of the eye lobe inflated External surface, except in furrows, bearing scat- so that it projects slightly over the shallow border fur- tered granules varying in diameter; no regular ar- row; lateral border rounded, widening toward genal rangement of larger granules. angle; posterior border widens progressivelyoutward, Drscussrox.-The relations between Thelecaly- posterior border furrow a steep-sided,flat-bottomed nene mammillata and speciesof other genera are dis- trench which is widest (exsagittal) medially. Eye lobe cussedabove, and it is considered that Thelecalymene situated midway across cheek, the transverse line may be most closelyrelated to Grauicalymene,though through midpoint runs through anterior portion of 2p it has somecharacters in common with Diacalymene.A, lobe. Palpebral lobe with low, broad rim, continued speciesof Gruaicalymene is present in the lower part acrossfixed cheek by broad, low, eye ridge, which runs of the Maquoketa Shale (Ross, 1967, Plate 4: figures down into adal furrow opposite lateral glabellar lobe 14, 15\ , as is Flexicalymenefayettensis (Slocum, 1913; 3p (Plate 1 : figures 5, 7). Anterior branch of suture Ladd, 1929, p. 395; Whittington, 1954, p. 148), runs forward and slightly inward to reach margin well which appears to be a typical member of the genus. outside projected line of axial furrow; course of pos- "F." gracilis (Slocum, 1913), from the highest mem- terior branch angulate (Plate 1: figures 3, 4), the ber of the Maquoketa Shale (Ladd, 1929, p. 395), oblique angle situated a short distance out and back appears from Slocum's description to have the anter- from the eye lobe, from whence the branch runs olateral margin of the frontal glabellar lobe closely straight outward and backward to the rounded genal approachedby a buttressfrom the inner, anterior angle angle. Hypostome with median body gently convex, of the cheek. Such a structure is similar to that in the middle furrow deep at border furrow, extending in- ward and backward as a fa.int furrow; the two median furrows curve to meet and outline a faintly more con- Pu'rx, 2.-Thclecalymcnc mammillata (Hall). 1, 5, Cranid- vex, crescenticposterior lobe of the middle body; medi- ium; dorsal and oblique views ( X 2) ; AMNH l408c, shales an depression in posterior margin of posterior lobe, above the Galena Limestone, Maquoketa Creek, 12 rniles west of Dubuque, Iowa (probably same locality and horizon Anterior border continuous with anterior wing, narrow as originals of figures 3 and 4 of this plate), 2, Glabella and and flexed to slope downward and forward, sutural part of left fixed cheek: donal view (X 2); AMNH 1408d, margin cuwed convexly forward. Lateral border nar- same locality as figures l, 5 (above). 3, Incomplete hypo- row, convex; posterior border broader, horizontal and stome:extenor vi€w (X 3);MCZ8672/1, Elgin ShalyLime- bilobed in outline, a sagittal furrow bisecting the stone Member, Maquoketa Shale, 0.25 mile southwest of border. Graf, Dubuque County, Iowa. 4, Free cheek: exterior view (X 3); MCZ 8672/3, samelocality as figure 3 (above).6, Thorax unknown. Axis of pygidium composed of Pygidium: dorsalview (X 2 ) ; AMNH 1408e,same locality as seven rings (Plate 2: figures 6,9), this portion taper- figures1,5 (above).Original of Hall (1862,fig. 2). 7, 9, 10, ing evenly, and a prominent, parallel-sided, posterior Pygidium: right lateral, dorsal, and posterior views (X 2); portion which is bluntly rounded posteriorly. Fint on same slab as AMNH 1408e. 8, Pygidium: first axial ring and adjacent parts of pleural regions broken ofi, dorsal six ring furrows complete, deepest distally, seventh view (x 4.5); AMNH 14089, same locality as figurcs 1, 5 furrow not so deepened and not reaching axial furrow, (above). 11, Holotype cranidium: anterior view (X 2); shallower and narrower (transvene) eighth furrow AMNH 1408a (seealso Plate 1 : figures 5, 6). 12, Incomplete on posterior portion. Pleural regions cuwed down so cranidium: anterior view, showing ventrally-facingportion of that the outer part slopessteeply, but not vertically. Six preglabellarfield (X 2) ; AMNH 1408b, samelocality as fig- ures1,5 (above).13, Obliqueview (X 6) of samespecimen deep pleural furrows (Plate 2: figure l3), which, to- as in figures 7, 9, l0 (above), showing dctails of extemal sur- gether with the axial furrow along the margin of the face; first pleural furrow at exteme left, anterior band of first seventh axial ring and posterior portion of the axis, pleura broken orff. 135

PLATE 2 136 SMITIISONIAN CONTRIBUTIONSTO PALEOBIOLOGY

species Papillicalymene husseyi St.urrLr::.and Kauffman, Fiireningens i Stockholm Fi;thand.l;ngar, 89 i35O- 1958 (see above), However, Stumm and Kauffman 386, 3 figures. Miller, A. K., and W. Youngquist (1958, p. 955), in discussing "F." gracilis, do not men- 1949. The Maquoketa Coquina of Cephalopods.Journal tion any buttress; evidendy both gracilis and husseyi ol ,23:.199-204,plates 40 42. need f urther investigation. Moore, R. C. (editor) 7959. Treat;se on Inuertebtate Paleontology, Part O, Arthtotoda, l. 560 pages, 415 figures. Literature Cited City and Lawrence, Kansas: Geological Society of Barrande,J. America and University of Kansas Press. 1846. Notice fr'dlirninaire sur le SystAmeSilur;en. et les Ross,R. J., Jr. I Ttilob;tes de Bohime. vi + 19 pages.L€ipzig. 1967. Calymenid and Other Ordovician Trilobites from Campbell, K. S. W. Kentucky and Ohio. United Stater Geological Sxt- 1967. Trilobites of the Henryhouse Formation (Silurian) aey ProlessionalPaPet, 583-Bt l-19, 5 plates. I in Oklahoma. Oklahoma GeologicalSuroey BuLletin, Shirley,J. 115:1-68, 7 figures,19 plates. 1936. SomeBritish Trilobites of the Family Calymenidae. Dean, W. T, Quarterly lournal of the Geolag;cal Society ol 1962. The Trilobites of the Caradoc Series in the Cross London, 92:384422, plates 29-31, Fell Inlier of Northern Engla .. Bullettn ol the Slocum,A. W. Brit*h Museum (Natunl History) Geology,7:65- 1913. New Trilobites from the Maquoketa Bedsof Fayette 134,plates 6-18. County, Iowa. Field Museum ol Natnal Histot:,) 1963. The Ordovician Trilobite Faunas of South Shrop- GeologicalSeries, 4(3) :43-a3, plates13-18. Bulleti of the Btitish Muse ln (Natutal shire,IlI. Stumm, E. C., and E. G. Kauffman :213-254, plates 37-46. History) Geology,l 1958. Calymenid Trilobites from the Ordovician Rocks of Glenister,A. T. Michigan. outnal of Pa'leontolo gy, 32 : 943-960, of the Ordovician Maquoketa For- ! 1957. The Conodontr plates 123, 124. mation in lowa. Journal of Paleontology, 3l :715- Tillman, C.G. 736, plates85-BB. 1960. Spathacalrmere,an unusual New Silurian Trilobite Hall, J. Gelus, ol Paleontology,34: B9l-895, plate 1861- Relott of the Superintendent ol the Geological Journal 116. Suraey, l|/isconsin. 52 pages. Madison, Wisconsin. Twenhofel, W. H., et al. Hall. J., and J. D. Whitney 1862. Relofi of the Geological Suroey ol the State ol 1954. Correlation of the Ordovician Formations of North l(isc onrin, | : 1455, mapg Ameica. Geological Soeiety ol Ametican Bulletin, Ladd, H. S. 65:247-298. 1929. The Stmtigraphy and Paleontology of the Ma- Walter, O. T. quoketa Shale of Iowa, Part l. Ioua Ceological 1927. Trilobites of Iowa and Some Related Paleozoic Swaey,34t30544B, plates 4-17, figures 64-76. Forms. Iowa GeologtcalSuraey, 3l t 167400, platet Lindstriim, G. 10-27. 1885. Fiirteckning pe Cotlands siluriska Crustac6er. Whittington, H. B. Oloerst Konglig V etenskals-Akad.miensF6rhand- 1954. Ordovician Trilobites from Silliman's Mount, lingar AngdnE,42a(6):37-100, plates12-16. in A. K. Miller, W. Youngquist, and C. Collinson, Locke, J. Ordovician Cephalopod Fauna of Bafin Island, 1843. Notice of a New Tilobite, Ceraurut crosoru!.Anet- Ceological Society of America Memoir, 62:119- ican J ournal of Science,4*346. 149, plates 59-63, Martinsson,A. 1965. The Ordovician Trilobites of the Bala Area, 1967. The Succession and Correlation of Ostracode Merioneth, P^rt 2. Palaeontogralhical Society Faunas in the Silurian of Gotland. Ceologisha (Monogaph), pages 33-62, plates 9-lB. London. I I I