Trilobites of the 

Upper Cambrian 

Dunderberg Shale 

Eureka District, Nevada

By ALLISON R. PALMER

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 334-C

Fifty-three species of trilobites representing 

genera are described and illustrated

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C. - Price 65 cents (paper cover)
CONTENTS

Abstract...___________________________

Introduction __________________________

Acknowledgments. -___-.______--_____-_

Stratigraphy._________________________

Taxonomic procedure__________________

Terminology __________________________

Hypostome morphology and identification.

Systematic paleontology.___-_-_-___-_._

Agnostidea_ _ ____._-_____--___.__

Angostidae___________________

Pseudagnostus_ ___________

Homagnostus ______________

Phalacroma. ______________

Ptychoparioidea_ _ _________________

Elviniidae ___----___-________-

Dunderbergia- _____________

Elburgia- _________________

Elvinia ___________________

Elviniella- ________________

Irvingella ___--_____-__-.__

Housiidae____ ___--_-______ ____

Housia- -___-_-___-_______

Parahousia- _______________

Prehousia- ________________

Olenidae_ _____________________

OlenusC?)-------- -----__--

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Systematic paleontology Continued

Ptychoparioidea Continued Page

Pterocephaliidae.. _ _________________________ 80

Aphelaspidinae_ -_-_--____--____________ 80

Litocephalus--- ______________________ 81

Taenora- _____--.-__--_____-_-__.__ 83

Pterocephaliinae. _______________________ 84

Cernuolimbus-- __-__-__-____-_-_.___ 84

Pterocephalia- ______________________ 86

Sigmocheilus _______________________ 89

Ptychoparioidea unassigned. _____________________ 92

Anechocephalus _________-___------__--______ 92

Bynumiella, ______--__---___-_-_-_-_----_-_. 93

Bynumina--------------------------------- 93

Cheilocephalus------------------------------ 94

Dokimocephalus_ _ _________________________ 95

Iddingsia---------------------------------- 95

Kindbladia.-------------------------------- 97

Minupeltis--------------------------------- 98

Morosa------------------------------------ 98

Oligometopus------------------------------- 100

Pinctus.----------------------------------- 100

Pseudosaratogia----------------------------- 101

Genus and species undetermined l_____--_____- 101

Genus and species undetermined 2_____________ 102

Genus and species undetermined 3_____-------- 102

Locality information, __________-___-__--__-----_--__ 102

References cited____________-_-_--____-_.------_---_ 103

Index,_-___-_-----_---------_-----------------_--- 107

ILLUSTRATIONS

PLATE

9.

10.

11.

FlGTRE 5. 

6.

9.

10.

11.

12.

13.

14.

[Plates 4-11 follow page 110] 

Agnostidae and Elviniidae. 

Elviniidae.

Elviniidae and Olenidae. 

Housiidae and Aphelaspidinae.

Pterocephaliinae, Aphelaspidinae, and Anechocephalus. 

Pteroceph aliinae.

Pterocephaliinae and unassigned genera. 

Unassigned genera and Hypostomes. 

Map showing relations of the Eureka district to other localities in the Great Basin with Dunderberg faunas______

Map showing location of measured section through Dunderberg shale___-_____- ______-______-_____--_--__

Ranges of trilobites in the Dunderberg shale ------------------------------------------------------------

Comparison of the ventral courses of the cephalic sutures in some Late Cambrian trilobites. A, Pterocephalia. 

B, Housia. C. Dunderbergia. D, Prehousia. E, Aphelaspis------------------------------------------

Dunderbergia polybothra n. sp____________________-___________________-__-------------------_---___-----

Elburgia quinnensis (Resser)_____________________-_________________________--__--_-__-___-_-----------

Eli'inin roemeri (Shiunard)________________________________________-_--_---__--------__---------_-----

Housia ovata n. sp_________________________________________________--__---_-___----__-_-_-------------

Parahousia constricta n. sp________________________________________________-_______-___------------_--_

Prehousia alata n. sp_____________________________ ________________________-_---_--_-__---------------

15. Olenus(?) wilsoni Heniiingsmoen__ _______

16. Litocephalus bilobatus (Hall and Whitfield.

17. Taennra expansa n. sp_ ______ ^ __________

18. Cernuolimbus orygmatos n. sp______ ______

19. Pterocephalia sanctisabae Roemer _______

20. Sigmocheilus serratus n. sp _____________

21. Bynumiella? acuminata 11. sp____________

22. Rlorosa longispina n. sp_________________

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99

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEW. DA

By ALLISON R. PALMER

ABSTRACT

The Dunderberg shale in the Eureka district is the northwesternmost expression of a relatively thin nonresistant unit 

(100-300 ft thick) of interbedded shale and fossiliferous limestone of Late Cambrian age lying between generally less fossiliferous and more resistant carbonate units in southeastern 

Nevada and adjacent parts of Utah and California. Five local 

lithic units, designated by letter and beginning at the base 

with a shale unit (A), are recognized within the Dunderberg 

shale. Overlying units alternate in dominance between limestone and shale. All but the upper unit (E) contain thin fossiliferous limestones bearing generally distinctive trilobite assemblages. Ranges of many common species are sufficiently 

restricted so that isolated collections from structurally disrupted areas within the Eureka district can be placed within 

20 to 40 feet of their original stratigraphic position within the 

upper or lower parts of the Dunderberg shale. The fauna of 

units A-C belongs to the upper half of the Dunderbergia zone 

of late Dresbach age. The fauna of unit D correlates with 

the basal part of the Elvinia zone of early Franconia age. The 

presence of Homagnostus obesus (Belt) and Olenusl wilsoni 

Henningsmoen in units A and B indicates a correlation of 

these beds with the Olenus and If. obesus zone in the early 

Late Cambrian section of the Scandinavian region.

Fifty-three species representing 32 genera are described. The 

following new taxa are named: Subfamily Aphelaspidinae (of 

the family Pterocephaliidae); Genera Elburgia, Elviniella, Prehousia, Parahousia, Cernuolimbus, Sigmocheilus, Taenora, Alinupeltis, Morosa, Anechocephalus; and species, Dunderbergia 

bigranulosa, D. polybothra, Elviniella laevis, Prehousia semicircular is, P. alata, Parahousia constricta, Housia ovata, Cernuolimbus semigranulosus, C. orygmatos, C. depressus, Pterocephalia 

concava, P. elongata, Litocephalus verruculapeza, L. granulomarginatus, Taenora. expansa, Sigmocheilus serratus, Minupeltis 

conservator, Morosa longispina, Bynumiellal acuminata, Anechocephalus trigranulatus, Pseudosaratogia leptogranulata, and P. 

abnorrnis. Evidence is shown that primary species characteristics are to be found in the external ornament of the exoskeleton. 

Genera are composed of species sharing nearly common shape 

but differing consistently in characteristics such as external 

ornament. Emphasis in family groupings is placed on structure 

of the glabella, frontal area, and pleural parts of the pygidium. 

Application and elaboration of the principles for grouping trilobites into genera and families are illustrated particularly with 

regard to the families Elviniidae, Housiidae, and Pterocephaliidae.

INTRODUCTION

The Dunderberg shale is a relatively nonresistant 

unit of interbedded shale and fossiliferous limestone; 

its type locality is in the Eureka district, Nevada. In 

this district, the Dunderberg lies conformably on the

more resistant Hamburg dolomite and is overlain, also 

conformably, by the generally cherty Catlin member 

of the Windfall formation (Nolan and others, 1956). 

A similar fossiliferous nonresistant unit of interbedded limestone and shale with approximately the earne 

relation to adjacent carbonate units is present in almost every Upper Cambrian sequence of rocks south 

of the 40th parallel in southern Nevada and adjacent 

parts of Utah and California (Palmer, 1956b). Despite the apparent extensive geographic distribution 

of the Dunderberg shale or correlative lithic units 

(over 250,000 square miles) (fig. 5) and the generally fossiliferous nature of the Dunderberg, less than 

30 species of trilobites in its large fauna have been 

described.

The earliest descriptions of trilobites from the Dunderberg shale are by Hall and Whitfield (1877) and 

Walcott (1884). Since these publications, only occasional references have been made to Dunderberg trilobites principally as nomenclatural changes or brief 

descriptions of new forms in large regional faunal papers (Walcott, 1916, 1924, 1925; Kesser, 1935, 1936, 

1937, 1942; Palmer, 1955). The purpose of this- paper is to describe the trilobites of the Dunderberg 

shale in its type area and to document as precisely as 

possible the stratigraphic distribution of the described 

fossils within the unit.

The bulk of the material examined during this study 

came from collections by C. D. Walcott, and geologists of the 40th parallel survey in the late 1800's; 

collections by the late Josiah Bridge and G. A. Cooper 

in 1939; and collections by the writer in 1951 and

1957.

The collections in 1951 and 1957 were obtained from 

the section in Windfall Canyon chosen by Nolan and 

others (1957, p. 19) as the most complete and unbroken section of the Dunderberg shale in the Eureka 

district (fig. 6). Each collection was obtained from a 

single bed and located with respect to stratigrr.phic 

distance from the base of the formation with a steel 

tape. Descriptions of localities for all the collections 

referred to in the text are given on pages 102, 103.

53
54 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

117 C 116 C 115 C 114 C 113 C

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\

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area

CALI

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orings 

L N^ Pintwatt

\ 

s

\ 

s

Nopah Range ^

FORNIA

Providence Moi

L Eureka 

district

o White Pin* 

district

\DA

Egan Range 

^Quinn Canyo

1

 Cherry Creek 

Range |

^

i i

Snake Range 9

I

 Shell Creek 

t Range

I 

I

n

Highland Range*

*Pa

 Yucca Flat

x Range * Desel

9 Spring Mountains

\

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iranagat Range

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« House

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50 Miles i

40 C

38 C

36 :

35 C

FIGURE 5. Map showing relations of the Eureka district to other localities In the Great Basin with Dunderberg faunas.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 55

Eureka

Measured section

FIGURE 6. Map showing location of measured section through 

Dunderberg shale.

The collections from the measured section were 

studied first so that association of species and stratigraphic ranges of species could be correctly determined. Supplemental material for morphologic study 

was obtained from the collections by Bridge and 

Cooper. Identification of taxa that were not new was 

determined by comparison with the types in the U.S. 

National Museum collections.

Parts of each of the Bridge and Cooper and later 

collections were dissolved in formic acid to obtain insoluble residues. Most of them contain abundant 

phosphatic brachiopods. Occasionally a few silicified 

small trilobites were also recovered. The only silicified 

specimen illustrated is the free cheek of Bymimiella'* 

acum-inata n. sp.

The other specimens illustrated and studied were 

prepared by hand. Most of the matrix surrounding 

each specimen was first ground away with a thin diamond-bearing blade in a dental drill. The remainder 

of the matrix was removed using a Burgess Vibrotool fitted with a chuck for holding a needle. This 

sufficiently improved the efficiency of preparation so 

that only occasionally wT as final cleaning by hand with 

a sharpened needle necessary.

All the specimens were whitened for study with a 

light coating of magnesium oxide obtained by burning 

a short length (% in.) of magnesium ribbon. Generally it is not possible to determine properly the characteristics of a specimen without this coating, especially in groups where surface texture is an important 

taxonomic feature.

Drawings were prepared for all species represented 

by cranidia and free cheeks. Thoracic segments and 

pygidia were included where known. Specimens selected for drawing were properly oriented under a 

binocular microscope fitted with an eyepiece containing an ocular grid. The image was transferred from 

the ocular grid to graph paper. A projector that 

could enlarge or reduce drawings by several diameters proved invaluable for reconstruction of trilobite 

cephala, because it is generally not possible to find a 

cranidium and free cheek of the same instar that are 

sufficiently well preserved for illustration.

All the photographs were prepared using standard 

photographic techniques. Specimens were coated with 

ammonium chloride for photography because depth of 

coat is easier to control for this material than it is 

for the magnesium oxide used for study. Most of 

the original Hall and Whitfield and Walcott typer are 

illustrated here by stereophotographs, as are holot;rpes 

or selected paratypes of all new species.

ACKNOWLEDGMENTS

Assistance in the field, in addition to that given by 

U.S. Geological Survey personnel, was rendered by 

Dr. A. B. Shaw, of the University of Wyoming, in 

the summer of 1951. All photographs of fossils were 

prepared by N. W. Shupe, of the U.S. Geological 

Survey. Dr. Hans Frebold, head of the Division of 

Stratigraphic Paleontology, Geological Survey of 

Canada, loaned for comparison, types of the Upper 

Cambrian trilobites from British Columbia described 

by Kobayashi (1988).

STRATIGRAPHY

The Dunderberg shale in the Eureka district is 

composed of iiiterbedded limestone and shale. It can 

be divided roughly into five lithic units alternating in 

dominance between one or the other of these rock 

types (Nolan and others, 1956, p. 19). The limestone 

is generally thin to medium bedded, and many of the 

thin beds contain abundant remains of trilobites and 

phosphatic brachiopods. No fossils have been found 

in the shale. Lithic units with their thicknesses are 

designated here by letter, beginning with the oldest:
56 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Unit A, about 35 feet, dominantly shale; unit B, about 

 45 feet, dominantly limestone; unit C, about 1-40 feet, 

dominantly shale; unit D, about 35 feet, dominantly 

limestone; and unit E, about 10 feet, dominantly shale.

Trilobites are most abundant in unit B and in limestone beds of units A and C. Unit D is only locally 

fossiliferous, and no fossils are known from unit E.

The fauna of unit A is characterized by relatively 

large numbers of specimens of Dimderberg ia bigranulosa n. sp. Cermiolimbus orygmatos n. sp. is common 

in a limestone bed near the top of the unit but is also 

common in a collection from the basal part of unit B.

Unit B contains over half of the described species 

of the Dimderberg fauna. Its most distinctive constituent is Morosa lo-ngispina n. sp. Relatively numerous specimens of species of Dunderbergia* Litocephalns, and Pterocephalia also characterize the 

fauna of this unit. Homagnostus tinnidosu* (Hall and 

Whitneld) is common, but ranges upward through the 

rest of the Dimderberg and into the overlying Windfall formation.

Few of the thin limestones of unit C are fossiliferous. The limestones of the upper part of the unit are 

characterized by tfigmofheilus serratus n. sp., Housia 

ovata n. sp., and Parahousia co-nxtricta n. sp., in association with the long-ranging species Dunderbergia 

nit id a (Hall and Whit field). Collections from the 

lower part of unit C seem to be transitional to the 

fauna of unit B. The assignment of a collection to 

unit C can be confirmed, however, by preparing an 

insoluble residue. Limestones of unit C generally yield 

shells of the acrotretid brachiopod Linnarsso-nella, 

whereas unit B lacks brachiopods of this genus and 

generally has a large and varied assortment of other 

acrotretid brachiopods.

The fauna of unit D is not so well known as those 

of the older units. Only one small collection was obtained from this unit in the measured section. This 

collection contained Kindbladia crffinix (Walcott). Collections by the early surveys of the Eureka district 

containing A', a-jfini* in association with species of 

Irvingella (Parairvingella), Bynumina globosa (Walcott), and Iddhigxid robuxta (Walcott) probably came 

from this unit because none of these species are known 

from unit C or from the basal beds of the overlying 

Windfall formation.

All the trilobites in units A-C, and the majority of 

the trilobites described in this paper, represent the 

fauna of the recently established Dunderbergia zone 

(Lochman and Wilson, 1058, p. 3oo). This zone was 

denned to include the faunas, formerly assigned to 

the post-ApftchrspJs zone (Palmer, 1954), that occur 

between the well-known and widespread Aphelaspis 

and Elvinia faunas in the Great Basin, central Texas,

and perhaps in Missouri. As with mos^ Upper Cambrian trilobite zones, individual genera, including 

Dunderbergia, may range above or below the zonal 

limits, and precise boundaries between adjacent zones 

cannot always be drawn.

In the Dimderberg shale, the boundary between the 

Dunderbergia zone and the overlying Elvinia zone is 

approximately at the top of unit C. The trilobites 

from unit D represent genera that are k^owii from the 

Elvinia fauna at many localities in the western half 

of the United States. Most of the triloHtes from unit 

C are known only from the Great Basin in beds older 

than those with Elvima.

The lower limit of the Dunderbergia zone is not 

demonstrable in the Eureka district. Correlation of 

the Dimderberg shale with fossiliferous Upper Cambrian units of eastern Nevada and western Utah indicates that the Dimderberg fauna represents perhaps 

only the upper half of the, fauna of the Dunderbergia 

zone. The lower fauna of this zone is still largely 

undescribed but is probably represented in the Lincoln Peak formation in the Snake Range, Nev., and 

the Orr formation in the House Rang0 , Utah.

Ranges of the trilobites in the measured section of 

the Dimderberg shale in the Eureka district are shown 

in figure 7.

Fossiliferous units partly or wholly equivalent in 

age to the Dimderberg shale are known in the Great 

Basin (fig. 5) from the basal parts of the Nopah 

formation in the Quartz Spring area (McAllister, 

1952) and the Nopah Range, Calif.; the basal Cornfield Springs formation in the Providence Mountains, 

Calif., and in the Goodsprings district, Nevada 

(Palmer and Hazzard, 1956); the Dimderberg shale 

on the east side of Yucca Flat, Nev. (Hibbard and 

Johnson, 1957) ; unnamed formations in the Desert 

Range, Spring Mountains, and Pintwater Range, the 

east side of the Highland Range, the Pahranagat, 

Egan, Shell Creek, and Cherry Creek Ranges, and the 

White Pine district, Nevada; the Johns Wash limestone and Corset Spring shale in the Snake Range, 

Nev. (Drewes and Palmer, 1957); the Hicks formation in the Deep Creek Range and the Orr formation 

in the House Range, Utah.

Outside the Great Basin, the upper part of the 

Lion Mountain sandstone member of the Riley formation in central Texas and part of the Davis formation 

in Missouri have some trilobites in common with the 

fauna of the Dimderberg shale.

The occurrence of Homtif/noxtiiN obesus (Belt) and 

an olenicl in the lower part of the Dimderberg shale 

and species of IrvingeUa (Parairvingella) in the upper part of the shale indicate a probrble correlation 

of the formation with zone II (Olenus; H. obesus)
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 57

(Henningsmoen, 1957) of the Upper Cambrian section of the Baltic region, where H. obesus and /. (P.) 

suecica Westergard have the same relative positions.

TAXONOMIC PROCEDURE

Classification of trilobites into species, genera, and 

particularly into higher taxonomic categories requires 

careful attention to two independent categories of 

facts: exoskeleton morphology and geologic occurrence. A lasting classification can be derived only by 

proper interpretation of the relative taxonomic significance of the observed morphologic features, the 

range of the trilobite in time and space, and the environments inhabited by the trilobite.

Species characters. The subtleties of specific differences and the importance of careful examination 

of all possible parts in determining species characteristics are perhaps best exemplified by the species of 

Dunderbergia, Cernuolimbus, and Litocephalu^.

Large collections from 7 thin fossiliferous limestone 

beds in the lower 80 feet of the Dunderberg shale in 

the measured section averaged nearly 40 specimens 

referable to Dunderbergia. Comparison of these specimens shows that shape alone does not provide a satisfactory means for discrimination of the trilobites 

represented in the successive collections. Examination of the external surfaces of all parts shows, however, that for any one collection the nature of the

Species

Agnostidae: 

Pseudagnostus communis (Hall and Whitfleld) 

Homagnostus obesus (Belt) 

Pseudagnostus? aciitus (Kobayashi) 

Homagnostus tumidosus (Hall and Whitfleld) 

Phalacroma? sp. 

Pseudagnostus prolongus (Hall and Whitfleld) 

Elviniidae: 

Dunderbergia biffranulosa n. sp. 

pnlybothra n. sp. 

variagranula Palmer 

Elburgia granulosa (Hall and Whitfleld) 

Elviniella laei'is n. sp. 

Elburgia quinnensis (Resser) 

Dunderbergia nitida (Hall and Whitfleld) 

Ehinia"! sp. 

Elrinia roemeri (Shumard) 

*Irvingella (Parairvingella) angustilimbata 

Kobayashi 

* (Parairvingella,) eurtkensis (Resser) 

*Elvinia granulata Resser 

Housiidae: 

Prehousia semicireularis n. gen., n. sp. 

Parahousia constricta n. gen., n. sp. 

Housia ovata n. sp. 

Olenidae: 

Oleums? u'ilsoni Henningsmoen 

granulatus n. sp. 

Pterocephaliidae : 

Certniolimbus semigramilosus n. gen., n. sp. 

orygmatos n. gen., n. sp. 

Sigtnocheilus utahensis (Resser) 

Cernuolimbus depressus n. gen., n. sp. 

Sigmoche ilus grata (Resser) 

Pterocephalia mncava n. sp. 

Litocephalus btlnhatus (Hall and Whitfield) 

verrneulapeza n. sp. 

granulomarginatus n. sp. 

Pte-roi'ephaba elcmgata n. sp. 

sanctisabae Roemer 

Taenura ejcpansa n. gen., n. sp. 

Sigmocheilus pogonipensis (Resser) 

serratus n. gen., n. sp. 

Family unassigned: 

Afinupeltis conservator n. gen., n. sp. 

Genus and species undet. 1 

Morosa longispina n. gen., n. sp. 

Bynumtflla? acitmmata n. sp. 

Genus and species undet. 2 

Genus and species undet. 3 

Anechocephalus tn granulatus n. gen., n. sp. 

PinL'tus? spp. 

Cheilocephalus sp. 

Pseudosaratogic lepttigranulata n. sp. 

Oligomt'topus brfi'ieeps (Walcott) 

Pseudosaratogia abnortnis n. sp. 

Kindbladia affinis (Walcott) 

*Idtiingsia robusta Walcott 

*Doknnocephalus pernasutus Walcott 

*Bynumma globosa (Waloott)

Dunderberg shale unit and collection number

A |

tf ig

-\

B

I

-

-

-

-

 

 ,

-

t

C

i il I I

 

-

 

H-9 E

u

7. RangfH of trilohites in the Duiiderhcrg shale. Collections located according to distances measured hy steel tape from base of

Dunderlierg shale. Member boundaries approximate.
58 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

surface is virtually constant. Thus, all specimens of 

Dunderbergia in collection 2295-CO that retain their 

exoskeletoii (most of the 99 identified specimens) have 

a granular ornament: cranidia have fine granules on 

the border and glabella and faint coarse scattered 

granules on the brim; free cheeks have fine granules 

on the border and faint coarse scattered granules on 

the ocular platform, and pygidia have fine granules 

on all parts. In collection 2296-CO, only 10 feet 

higher in the same section, all specimens of Dunderbergia retaining their exoskeleton (most of the 58 

identified specimens) have a distinct pitted ornament 

on nearly all surfaces of all parts. If the exoskeleton 

surface in these 2 collections was not known, it would 

be nearly impossible to determine either by inspection 

or by statistical analysis that the trilobites represent 

2 different taxa (cf. pi. 5, figs. 1 and 14; 13 and 19). 

For the reasons given above, the specimens of Dunderbergia in collections 2295-CO and 2296-CO are 

here considered to represent populations of two distinct species. Analagous relationships in Cernuolimbus and Litocephalus are discussed below.

Cernuolimbus is represented by 30 specimens in 

USGS collection 2294-CO and by over 100 specimens 

in USGS collection 2295-CO, 18 feet higher in the 

measured section. Most of the specimens retain some 

or all of their exoskeleton. In collection 2294 CO 

all specimens with exoskeleton preserved bear fine 

granules: on the cranidium they are on the top of 

the glabella and on the palpebral lobes; on the free 

cheek they are on the genal spines; and on the pygidium they are present, though faint, over most of the 

surface. In collection 2295-CO, all parts with exoskeleton preserved are coarsely pitted and, in addition, each axial ring on the pygidium has a pair of 

coarse granules. Although there are slight differences 

in shape also, that is, shape of anterior margin and 

width of the border of the free cheek, the feature that 

emphasizes the specific difference of the two assemblages is the surface ornament of the exoskeleton (cf. 

pi. 8, figs. I and 5; 2 and 6).

A third example showing the primary importance 

of surface ornament as a species character is given by 

Litocephalus. Although specimens are not so numerous as in the preceding 2 genera, 3 successive collections, USGS collections 2297-CO 2299-CO contain 

specimens that are distinguishable primarily by the 

ornament on the border of the cranidium. L. bilobatus (Hall and Whit field) has a smooth cranidial 

border, L. rerruculapesa. n. sp. has a cranidial border 

with scattered coarse granules, and L. granulomargintit'us 11. sp. has a cranidial border covered with fine 

close-spaced granules. Discrimination of the species 

on shape alone is considerably more difficult and less 

reliable (cf. pi. 8, figs. 12 and 13; 14 and IT).

In Dunderbergia^ Cernuolimbus, and Litocephalus, 

therefore, primary definitive species characteristics are 

to be found by examination of the surface of the exoskeleton and not necessarily by comparison of shape. 

Absence of consistent difference in shapo between all 

parts of two assemblages should not be used as a criterion for conspecificity without knowledge of the exoskeleton surface. This does not deny the taxonomic 

significance of shape, however. Consistent differences 

in shape of any part between two assemblages having 

otherwise similar exoskeletoiis probably also indicate 

a real taxonomic difference between the assemblages.

Discrimination of the 51 species here described is 

based on the principles outlined above. Diagnostic 

characteristics of those species that are indicated to 

be moderately common, common or abundant (that is, 

25-50, 50-100, or more than 100 identified specimens) 

will probably not be significantly modified by study 

of new material from other areas. Diagnostic criteria 

of species indicated to be moderately rare, rare or 

very rare (that is, 10-25, 2-10, and single identified 

specimens) may be modified by later work.

Generic groupings. Grouping of specimens together into species can be done on a reasonably objective basis as outlined above. Grouping of these 

species into genera is considerably more subjective. 

The principles used here are best illustrated by examination of the species assigned to Dunderbergia and 

to Litocephalus (pi. 4, 5, 7, 8). In both genera, the 

species share a nearly common shape in all of their 

parts. Very likely, the living trilobites swimming or 

crawling in the sea would not have been noticeably 

different until their surfaces were examined with a 

lens or microscope (excluding, of course, the probability that the soft parts or color would provide additional characters). The fact that trilobites with 

roughly the same shape differ specifically in their surface ornament has been of primary importance in 

establishing genera. Trilobites with similar shapes, 

differing only in details such as ornament, or perhaps 

of shape of only one part, are here considered congeneric. Trilobites having consistent differences particularly in their cranidia and especially in shape or 

outline of the border, frontal area or glabella, are 

here considered to represent different genera. Differences observed on other parts of the trilobite are generally considered to be of secondary importance. As 

with the species, those genera that have a strikingly 

distinct shape, or those that are represented by moderately common to abundant material of more than 

one species, are the least likely to be modified by study 

of new material.

Xup rage n e ric g ro u pin gx. Supra generic groupings 

are necessarily generalizations, outlining, in the considered opinion of a specialist, the presumed relation-
TRILOBITES OF THE TJPPE.R CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 59

ships between genera. As successive generations of 

specialists learn more about the. morphology of fossils 

and their stratigraphic and geographic distribution, 

the generalizations of the preceding generation require refinement. Eventually a reasonable stability 

in the content and characteristics of suprageneric 

groups is attained. Comparisons of the family classifications recently discussed by Hupe (1953, 1955) and 

Lochman (1953, 1956) indicate that, this stage has not 

yet been reached by students of Cambrian trilobites.

In this paper, trilobites are grouped into suprageneric categories of morphologically similar forms on 

the premise that such morphologic similarity between 

unrelated trilobites is unlikely in a single sedimentary 

basin during a period of time when there was little, 

if any, significant change in environmental conditions 

or paleogeography. The stratigraphic and geographic 

continuities of faunas are particularly important in 

such an initial compilation because they are the only 

criteria other than morphology for determining probable relationships between trilobites. Without knowledge of occurrence of two trilobites, it is difficult to 

evaluate properly the taxonomic significance of their 

apparently similar structures.

Once suprageneric categories are defined using the 

criteria just discussed, it is possible to evaluate intelligently the degree of taxonomic relationship between 

apparently similar trilobite genera that are isolated 

stratigraphically by faunal discontinuities or geographically by existence in different basins of sedimentation.

The trilobite genera of the Dunderberg shale developed in an area of nearly continuous sedimentation 

and relatively little environmental change through a 

restricted part of Late Cambrian time. There are no 

striking "faunal breaks." Thus, many of these genera 

are probably related, and the relationships are most 

likely to be expressed by shared structural features 

of the exoskeleton. Examples of the application of 

the principles outlined above to the Dunderberg trilobite fauna are illustrated particularly in the discussions of the Elviniidae (p. 64) and the Pterocephaliidae 

(p. 80).

TERMINOLOGY

The descriptive terminology used in this paper for 

dorsal features of the trilobites is that proposed by 

Howell and others (1947) with the additions and 

modifications given below. Glabella includes the 

occipital furrow and occipital ring. Frontal area 

(Nelson, 1951, p. 771) refers to that part of the cranidium in front of the glabella. Axial lobe is the 

generally raised axial part of the exoskeleton; on the 

pygidium it may be divided into axial rings bounded 

by ring furrows (Whittington and Evitt, 1954, p. 14). 

Pleural ribs refer to generally transverse poorly defined raised ridges that cross the pleural platform 

and, on some trilobites, the border of the pygidium.

Descriptive terminology for the hypostome is that 

proposed by Warburg (1925).

Sagittal, exsagittal, and transverse refer to directions in vertical planes in the axial line, parallel to 

the axial line, or at right angles to the axial line, 

respectively (Whittington and Evitt, 1954, p. 12). 

Measurements in the sagittal plane (along chords) are: 

length of border, from the anterior margin to the middle 

of the marginal furrow; length of brim, from the middle 

of the marginal furrow to the middle of the dorsal 

furrow in front of the glabella; length of glaHIIa, 

excluding occipital ring, from the middle of the dorsal 

furrow in front of the glabela to the middle of the 

occipital furrow. The occipital ring is not included 

in measurements of the length of the glabella unless 

so indicated because it is so commonly broken on 

specimens preserved in limestone. Measurements in 

transverse planes are: width of palpebral lobes, from 

the outer edge of the palpebral lobe to the middle of 

the palpebral furrow at about the midlength of the 

palpebral lobe; width of cheek, from the middle of 

the palpebral furrow to the middle of the dorsal furrow 

on a line through the midlengths of the palpebral 

lobes; and basal glabellar width between the dorsal 

furrows just anterior to the occipital furrow. Length 

of the palpebral lobe is measured along a chord between 

the points of maximum indentation of the sides of the 

cranidium above the eyes by the facial sutures.

Depressed, downsloping, horizontal, upsloping, and 

elevated refer to positions of the border, brim and 

fixed cheeks on the cranidium, and the border and 

pleural platforms of the pygidium with respect to a 

horizontal plane passing through the dorsal furrow, 

as defined by Lochman (1947, p. 60).

Convex, concave, and flat refer to degrees of curvature of various parts of the trilobite as seen in transverse or sagittal cross section. Degree of convexity 

or concavity is indicated as gentle, moderate, or strong 

if the arc of the part described subtends an angle of 

less than 90°, 90° to 180°, or more than 180°, respectively (Whittington and Evitt, 1954, p. 12). Convexity or concavity of the brim, border and occipital 

ring, and longitudinal convexity of the cranidium, 

glabella, pygidium, and hypostome are described as 

seen in saggital cross section. Convexity of the fixed 

cheeks and transverse convexity of the cranidium, 

glabella, hypostome, and pygidium are described as 

seen in transverse cross sections through the midlengths of the palpebral lobes, glabella, and hypostome 

and through the anterior margin of the pygidium, 

respectively.

Ornament of the external parts of the exoskelton may 

be granular, with granules all of one size Elburgia 

granulom (Hall and Whitfield), pi. 6, fig. 19 or
60 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

with two or more sizes (Dunderbergia bigranulosa n. 

sp., pi. 5, fig. 13); smooth or pitted (pi. 5, fig. 14; pi. 8, 

fig. 5). It is generally absent from all furrows. When 

present, it may be evenly distributed over most of the 

surface as in Dunderbergia polybothra n. sp. or restricted 

to the border, brim, or tops of the axial structures. 

Details of external ornament and its distribution are 

consistent between specimens of most species, and this 

is often a characteristic of prime importance for specific 

distinction.

Surfaces of molds may have coarse granules corresponding to those of the external parts of the exoskeleton. Fine-granular ornament is generally lacking. 

Molds of many species with smooth or fine-granular 

external ornament are finely pitted.

Terrace lines are present on the doublures of all 

specimens, on part, or all, of the cephalic and pygidial 

borders, and on the tips of the thoracic segments of 

some species, particularly in the Pterocephaliinae.

HYPOSTOME MORPHOLOGY AND IDENTIFICATION

Hypostomes are rare in the collections from the 

Dunderberg shale. As a result, the few specimens that 

have been obtained cannot generally be assigned to a 

particular species. Nevertheless, hypostomes of at 

least five species are recognizable. All of these share 

the following characteristics: Moderate to strong 

transverse and longitudinal convexity, elongate quadrangular outline with rounded posterior margin, moderately well defined lateral furrows with a distinct 

oval or circular depression adjacent to the posterior 

lobe of the middle body, distinct terrace lines on the 

lateral and posterior margins, and prominent dorsally 

directed posterior wings. Differences are most apparent in presence or absence of a distinct posterior border and in details of the lateral furrow and surface 

ornament.

Hypostome A (pi. 11, fig. 12) is characterized by 

having a distinct posterior border and faint pits on 

the posterior part of the anterior lobe of the middle 

body. The lateral furrow is deep adjacent to the 

middle part of the anterior lobe of the middle body. 

Two hypostomes of this type from USGS collection 

2302-CO are present; the largest is 4 mm long. Sigmocheilm serratm n. sp. and Dunderbergia. nitida 

(Hall and Whitfield) are the. only two common trilobites in that collection that were large enough to have 

borne this hypostome.

Hypostome B (pi. 11, fig. 7) is characterized by a 

distinct but narrow posterior border and a faint 

roughening of the axial part of the anterior lobe of 

the middle body. This type is represented by 1 specimen, 5.5 mm long, from USGS collection 2295-CO. 

Dunderbergia bigrannlo^a n. sp. and Cernuolimhus

or yg mat os n. sp. are the only two common large trilobites in this collection.

Hypostome C (pi. 11, fig. 4) is characterized by 

absence of a distinct posterior border, shallow lateral 

furrows, low scattered granules on the surface posterior to the middle furrow, and a tendency towards a 

subangular outline to the posterolateral and posterior 

margins. Minute pits are on the posterior part of the 

anterior lobe of the middle body. Specimens of this 

type are present in USGS collections 2294-CO and 

2295-CO. The largest specimen is 5 mm long. Dunderbergia bigranulosa n. sp. or species of Cernuolimbus are the only common large trilobites in these 

collections.

Hypostome D (pi. 11, fig. 9) is characterized by 

absence of a distinct posterior border, shallow lateral 

furrows, and an evenly curved posterior margin. The 

only ornament is minute, barely visible pits on the 

posterior part of the anterior lobe of the middle body. 

Specimens of this type come from USGS collections 

2300-CO and 2301-CO. The largest, specimen is 5.5 

mm long. Pteroeephalia elongata n. sp. from collection 2300-CO, Sigmacheilus pogon-ipensis (Resser) 

from collection 2301-CO, and Dunderbergia nitida 

(Hall and Whitfield) which occurs in both collections are the common large trilobites most likely to 

have borne the hypostomes of this type.

Hypostome E (pi. 11, fig. 8) is characterized by 

absence of a distinct posterior border, shallow lateral 

furrows, and distinct pits on the posterior part of the 

anterior lobe of the middle body and or the posterior 

lobe of the middle body. This hypostome, which is 

5 mm long, comes from USGS collection 2296-CO 

where the only common large trilobite is Dunderbergia 

polybothra n. sp.

Each of the hypostome types, except type E, is associated with common species of Pterocephaliidae and 

Elviniidae. Whittington and Evitt (If54, p. 20, 21) 

have indicated that hypostomes show relationships at 

the family level. Hypostome type E is certainly assignable to a species of the Elviniidae. This hypostome shares two common characters with hypostome 

types C and D: absence of a distinct posterior border 

and presence of pits anterior to the middle furrow on 

the anterior lobe of the middle body. Each of these 

hypostome types occurs in a collection with a common 

species of Dunderbergia, and the ornament posterior 

to the middle furrow corresponds to the ornament on 

the glabella of the Dunderbergia species. Thus, it 

seems possible that these are Dunderbergia, hypostomes. 

They differ from hypostome types A and B by lacking a distinct posterior border, and this may be the 

character that distinguishes hypostomes of the Elviniidae from those of the Pterocephaliidae. However, application to types A and B of this hypothesis
TRILOBITES OF THE UPPE,R CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 61

and a corollary, that ornament of posterior to the 

middle furrow corresponds to ornament of the glabella, 

casts some doubt on its correctness. Type A should 

have a granular ornament posterior to the middle 

furrow, and type B should have a distinct pitted ornament but this is not true. There is no guarantee, 

however, that the hypostomes are parts of the common species in the collections. Until more hypostomes 

are known from more collections with only one common species, criteria for correct specific, generic, and 

family assignment of individual specimens must remain uncertain.

SYSTEMATIC PALEONTOLOGY

Superfamily AGNOSTIDEA Richter 

Family AGNOSTIDAE McCoy

The Agnostidae of the Dunderberg shale have for 

the most part been described in an earlier paper 

(Palmer, 1955). The information given below supplements and modifies the information presented at 

that time.

Subfamily PSEUDAGNOSTINAE Whitehouse 

Genus PSEUDAGNOSTUS Jaekel

Pseudagnostus Jaekel, 1909, p. 400; Kobayashi, 1935, p. 107;

1937, p. 451; 1939, p. 157; Shinier and Shrock, 1944, p. 601;

Shaw, 1951, p. 112; Palmer, 1954, p. 719; 1955, p. 93. 

Rhapatagnostus Whitehouse, 1936, p. 97. 

Plethagnostus Clark, 1923, p. 124; 1924, p. 16.

Type species. Agnostus cydopyge Tullberg, 1880, 

p. 26.

Diagnosis. Cephalon with trilobed glabella and a 

preglabellar median furrow. Basal glabellar lobes 

simple.

Pygidium with anterior third of axial lobe defined 

by subparallel dorsal furrows; pseudolobe moderately 

well to poorly defined by accessory furrows that may 

disappear posterolaterally so that pseudolobe merges 

with pleural lobes. Marginal spines present or absent.

Pseudagnostus communis (Hall and Whitfield) 

Plate 4, figures 3, 4

Agnostus communis Hall and Whitfield, 1877, p. 228, pi. 1,

figs. 28, 29. 

Agnostus neon Hall and Whitfield, 1877, p. 229, pi. 1, figs. 26,

27. 

Pseudngnostits communis (Hall and Whitfield). Palmer, 1954,

p. 720, pi. 76, figs. 1-3; 1955, p. 94, pi. 19, figs. 16, 19-21;

pi. 20, figs. 4-11, 14.

Diagnosis. Specimens of Pseudagnostus with glabella and first glabellar lobe moderately well defined 

on external surface of cephalon. Preglabellar median 

furrow shallow. All furrows deeper on surface of 

mold.

Pygidium with anterior third of axial lobe well defined. Shallow accessory furrows generally only apparent along anterolateral parts of pseudolobe. Single 

short marginal spines present slightly anteror to 

posterior margin.

Discussion. P. co-jmmmis is distinguishable from 

P. prolongus, the most similar species of Pseudagnostus presently recognized within the Dunderberg shale, 

by having all parts of the cephalon and pygidium better defined and by having marginal pygidial spines. 

The stratigraphic ranges of the two species are also 

different. P. commimis is found in most collections 

from the lower half of the Dunderberg shale. P. prolongus is known only from collections in the upper 

part of the Dunderberg shale.

Occurrence: Abundant lower 130 ft of Dunderberg shale; 

units A-C. USGS colln. 789-CO, 795-CO, 809-CO, 873-CO, 

952-CO, 953-CO, 2294-CO, 2296-CO 2300-CO.

Figured specimens: Plesiotypes, cephalon and pygidium, 

USNM 136832a, b, USGS colln. 2299-CO.

Pseudagnostus prolongus (Hall and Whitfield) 

Plate 4, figures 5, 6

Agnostus prolongus Hall and Whitfield, 1877, p. 230, pi. 1, figs.

30, 31. 

Pseudagnostus prolongus (Hall and Whitfield). Palmer, 1955,

p. 98, pi. 19, figs. 17, 22. (Fig. 18 belongs to an unnamed

species, see below.)

Diagnosis. Specimens of Pseudagnostus with distinct cephalic border but with glabella hardly c^fined 

on external surface. Pygidium with anterior part of 

axial lobe poorly defined by dorsal furrow. Pseudolobe not defined. Marginal spines lacking.

Discussion.. Collections from the Dunderberg shale 

made in 1957 have provided new information about 

this species. The type cephala of P. prol-ongus come 

from a block of limestone containing a pygidium of 

tiigmocheilus serratus n. sp., a characteristic trilobite 

in the upper Dunderberg shale. Pygidia of a nearly 

smooth pseudagnostid, also from the upper D mderberg shale, lack marginal spines and are associated 

with cephala indistinguishable from P. prolongus. 

The lower part of the overlying Windfall formation 

has a species of Pseudagnostus with a cephalon that is 

also nearly indistinguishable from P. prolongus but 

with a pygidium that has marginal spines. It now 

seems that this pygidium was mistakenly identified as 

P. prolongus (Palmer, 1955, pi. 19, fig. 18). TH correct association of cephalon and pygidium is here 

figured.

Occurrence: Moderately common, 140-200 ft above base of 

Dunderberg shale; unit C. USGS colln. 864-CO, 2301-CO, 

2302-CO.

Figured specimens: Plesiotypes, cephalon and pygidium, 

USNM 136833a, b, USGS colln. 2301-CO.

507219 0 59 2
62 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Pseudagnostus ? acutus (Kobayashi)

Plate 4, figures 10-12 

Homaonostus acutus Kobayashi, 1938, p. 172, pi. 16, figs. 18-22.

Diagnosis. Specimens of IPseudagnostus with posterior part of axial lobe distinctly inflated, well defined, slightly pointed posteriorly, reaching marginal 

furrow on axial line.

Cephalon without known distinctive characteristics.

Discussion. Three pygidia from two different collections in the Dimderberg shale seem to be conspecific 

with H. acutus. The change in generic assignment is 

made for two reasons: first, the axial lobe of the 

pygidium reaches to the marginal furrow; and second, one specimen has muscle scars that are virtually 

like those of Pseudagnostus (Palmer, 1955, pi. 20, fig. 

14). The convergent pairs of small scars on the posterior portion of the axial lobe have not been observed 

on any specimen of Homagnostux. In addition, the 

furrow between the first and second segments of the 

axial lobe does not curve inward and forward from 

the dorsal furrow as it does on most species of 

Homagnostus. The cephalon figured by Kobayashi, 

however, lacks a preglabellar median furrow; but there 

is no certainty in the small type collection that it is 

correctly assigned to the species. Until a cephalon 

can be certainly established for this species, its generic 

assignment must remain doubtful. If this species is 

properly placed in Pseudagnostus^ it differs from all 

known species of Pseudagnostus by having the pseudolobe fully defined.

Occurrence: Rare, 40-60 ft above base of Dunderberg 

shale ; unit B. USGS colln. 2296-CO, 2297-CO.

Figured specimens: Plesiotypes, pygidia, USNM 136836a, 

b, USGS colln. 2297-CO.

Subfamily GERAGNOSTINAE Howell 

Genus HOMAGNOSTUS Howell

Homagnostus Howell, 1935, p. 15; Kobayashi, 1939, p. 162;

Whitehouse, 1939, p. 261; Shinier and Shrock, 1944, p. 600;

Lochman and Duncan, 1944, p. 139; Shaw, 1951, p. 110. 

Oncagnostus Whitehouse, 1936, p. 84. 

Geragnostus Palmer, 1954, p. 719; 1955, p. 88 (O. tumidosus

only).

Type species. Agnostus pixiformis obesus Belt, 

1867, p. 295, pi. 12,'fig. 4.

Diagnosis. Cephalon with well-defined bilobed glabella and distinct border. Preglabellar median furrow, if present, incomplete; generally deepest near 

glabella and fading out before reaching marginal 

furrow.

Pygidium with prominent well-defined axial lobe 

generally broader than pleural lobes. Posterior portion of axial lobe generally parallel sided or expanded 

slightly, well defined posteriorly, reaching nearly to 

marginal furrow.

Description. Generally small agnostids (about 5 

mm or less in length). Cephalon with well-defined 

border, narrowest at posterolateral corners; widest anterolaterally. Glabella well defined by dorsal furrows. 

Posterior lobe prominent, with poorly defined median 

node. Anterior lobe clearly separated from posterior 

lobe by transverse furrow, generally distinctly lower 

than posterior lobe. Basal lobes simple. Preglabellar median furrow, if present, deepest near glabella, 

generally disappears anteriorly before reaching marginal furrow.

Pygidium with prominent axial lobe that is generally wider than pleural lobes. A prominent median 

node located 011 axial lobe at junction between second 

axial segment and posterior part of axial lobe. Furrows outlining first axial segment generally curved 

forward to cut anterior margin and divide first segment transversely into three parts. Posterior part of 

axial lobe parallel sided or, more commonly, slightly 

expanded posteriorly, well defined, reaching nearly to 

marginal furrow. Border well defined, generally with 

pair of short posterolateral marginal spines.

Surface smooth or coarsely pitted.

Discussion. In two earlier papers (Palmer, 1954, 

1955) H. tumidosus (Hall and Whitfield) has been 

placed in Geragnostus because it lacked a preglabellar 

median furrow and because of similarity in form of 

the axial lobe of the pygidium to that of some species 

of Geragnostus. The appearance of H. obesus (Belt) 

in the lower part of the Dunderberg shale emphasizes 

the close relationship between H. tu?nidosu$ and H. 

obesus, and new material shows that some cephala of 

H. tumidosus have a short remnant of a, preglabellar 

median furrow just in front of the glabella. Furthermore, the group of agnostids typified by H. obesus, 

with the posterior part of the axial lobe on the pygidium slightly expanded, seems to be characteristic of 

older beds than those bearing typical forms of Geragnostus that have the posterior part of the axial lobe 

characteristically tapered posteriorly. There is now 

sufficient evidence both morphologically and stratigraphically for considering Homagnostus and Geragnostus as distinct but related genera.

Westergard (1947) believed that Homagnoshts 

should be no more than subgenerically separated from 

Affnostu*; because of observed overlap in form between 

species of the two taxa. Although a suite of H. 

obesus (Belt) from Scandinavia was not available for 

study, several specimens of coquina of Agn-ostus pisiform is (Linnaeus) from Ringsaker, Norway, and many 

specimens closely related to, if not conspecific with, 

H. obesus from Western United States were examined. 

The relatively slender, somewhat tapered, axial lobe of 

pygidia of A. pisiformis and the general presence of
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 63

a well-defined complete preglabellar median furrow 

are characteristics that show a greater degree of difference from H. obesus than H, obesus does from H. 

tumidosus. Agnostids have so few characters for use 

in discrimination of taxa that apparent overlap of 

morphologic features as cited by Westergard is a constant problem. However, inclusion in one genus of 

populations as distinct as A. pisiform-is and H. obesm 

may oversimplify an extremely complex situation. 

Agnostus, Homagnostus, and Geragnostus are here 

considered to be related taxa of comparable rank, 

worthy of designation as genera.

Homagnostus tumidosus (Hall and Whit field) 

Plate 4, figures 1, 2

Agnostus tumidosus Hall and Whitfield, 1877, p. 231, pi. 1,

fig. 32. 

Geragnostus cf. G. tumidosus (Hall and Whitfield). Palmer,

1954, p. 719, pi. 76, figs. 4, 6. 

Geragnostus tumidosus (Hall and Whitfield). Palmer, 1955,

p. 89, pi. 19, figs. 3, 4; pi. 20, figs. 1-3, 12, 15.

Diagnosis. Specimens of Ho-nmgnostus with preglabellar furrow absent or represented only by short 

anteriorly directed notch in furrow in front of glabella. Pygidium with first segment of axial lobe generally not distinctly trilobate. Combined length of 

first two segments less than length of posterior portion of axial lobe.

Discussion. This species has been discussed in considerable detail (Palmer, 1955). Additional observations have come from study of collections made in 

1957. Some cephala have a short preglabellar median 

furrow that is barely more than an anteriorly directed 

notch in the dorsal furrow in front of the glabella. 

A few well-preserved molds of cephala are finely 

granular.

H. tumidosus is distinguishable from H. obesus 

(Belt) from slightly older beds in the Dunderberg 

shale principally by lacking a distinct development 

of the preglabellar median furrow.

Occurrence: Abundant, 50-220 ft or more above base of 

Dunderberg shale; units B, C. USGS colln. 864-CO, 872-CO, 

S73-CO, 952-CO 955^CO, 2297-CO 2302-CO.

Figured specimens: Plesiotypes, cephalon and pygidiuni, 

USNM 136831a, b, USGS colln. 2299-CO.

Homagnostus obesus (Belt) 

Plate 4, figures 7-9

Agnostus pisiformis obcxux Belt, 1867, p. 295, pi. 12, fig. 4;

Lake, 1906, p. 9, pi. 1, figs. 13, 14; Westergard, 1922, p.

116, 193, pi. 1, fig. 4. 

Homagnostus obesus (Belt). Howell, 1935, p. 17, figs. 11, 12;

Shinier and Shrock, 1944, pi. 251, figs. 9, 10; Wilson, 1954,

pi. 25, fig. 19, pi. 26, figs. 23, 27. 

Agnostus (Homagnostus) obesus (Belt). Westergard, 1947,

p. 3, pi. 1, figs. 10, 11.

Diagnosis. Specimens of Homagnostus with preglabellar median furrow generally apparent for about 

half distance from glabella to marginal furrow. Pygidium with first segment of axial lobe somewhat 

trilobate.

Discuxsio-n. Specimens in two collections in the 

lower part of the Dunderberg shale are indistinguishable from the specimen figured by Westergard (1922, 

pi. 1, fig. 4) as Agnmtus pisiformis obesus. They also 

apparently are conspecific with specimens figured as 

H. obesus, but not described, by Wilson (1954).

Certain identification of H. obesus is probably not 

possible on pygidia alone. Although the pygiclium 

here figured has a distinctly trilobate division of the 

first segment of the axial lobe, some specimens of H. 

tum-idosus approach this condition. The cephala are 

unlike any observed for H. tum-idosus. Some specimens in USGS collection 2296 have a coarsely pitted 

surface. This feature seems to be variable within a 

population.

Occurrence: Rare, 10(?)-10 ft above base of Dunderberg 

,shale; units A, B. USGS colln. (?)2294-CO 2296-CO.

Figured specimens: Plesiotypes cephalon and pygidium, 

USNM 136834a, b, USGS colln. 2296-CO. Cephalon, USNM 

136835, USGS colln. 2295-CO.

Subfamily PHALACROMIHTAE Corda 

Genus FHALACROMA Corda

Pliatoeroma Corda, 1847, p. 159; Kobayashi, 1939, p. 136; 

Westergard, 1946, p. 92.

Type species. Battus bibullatm Barrande, 1846, p. 

14.

Diagnosis. Agnostidae with smooth cephalor, with 

or without border or median tubercule. Pygidium 

with axial lobe not defined; broad well-defined unspined border present.

Phalacroma? sp. 

Plate 4, figure 13

A single cephalon of a Phal'aeroma -like agnostid is 

recorded here primarily to show the presence of agnostids of this type in the Dunderberg fauna. The 

cephalon is completely smooth, with no trace of a 

border. Only the posterior marginal furrow, the occipital ring, and the posteriormost parts of the basal 

lobes of the glabella are apparent. Although the 

specimen does not seem to differ significantly from 

specimens of P. glandiforme (Angelin) except in size, 

correct generic assignment cannot be made without 

knowledge of the associated pygidiuni.

Occurrence: Very rare, about 90 ft above base of Dunderherg shale; unit B. USGS colln. 2300-CO.

Figured specimen: Cephalon, USNM 136837, USGS colln. 

2300-CO.
64 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Superfamily PTYCHOPARIOIDEA Richter 

Family ELVINIIDAE Kobayashi

History. Elviniidae was proposed by Kobayashi 

(1935) as a subfamily of the Ptychoparidae. It was 

raised to family status and enlarged in 1953 by both 

Lochman and Hupe, though the generic groupings of 

these authors include only one common genus besides 

Elvinia. Hupe (1955) presents the same information 

about the Elviniidae as in 1953 but adds diagnoses of 

the genera included in the family. Henningsmoen 

(1957) accepts the grouping of genera proposed by 

Lochman as representative of a subfamily contrasting 

with another subfamily grouping including Taenicephalus and related genera corresponding for the 

most part to the Parabolinoididae of Lochman (1956).

As conceived by Kobayashi, Hupe, and Henningsmoen, the Elviniidae seems to be an artificial grouping of genera in which the probability of close genetic 

relationship for most of the genera is slight. For 

example, Taenicephalus is included in the Elviniidae 

by all three authors, and Conaspis was included by 

Kobayashi and Hupe. Lochman (1956) has shown, 

based on the work of Bell, Feniak, and Kurtz (1952) 

and Berg (1953), that Taenicephalus and Conaspis 

belong to separate families having little, if anything, 

in common with Elvinia.

Lochman (1953) includes Elvinia, Maladioides, 

D pumas pis, and Chariocephalus in the Elviniidae and 

discusses their relationships in considerable detail.

Maladioides is a genus known only from Manchuria 

and Korea whereas the other genera occur only in 

North America. Plaster casts of the types of Maladioides asiaticus Kobayashi, the type species of Maladioides, show that the trilobite had a pygidium with a 

border, axial lobe, and overall shape unlike any of the 

trilobites included here in the Elviniidae. The cranidium is not well-enough preserved for adequate comparison. If Maladioides has any real relationships to 

American Upper Cambrian trilobites, they apparently 

are more with the Housiidae, as here used, than with 

the Elviniidae.

Drumaspis and Chariocephalus may be related 

Elvinia. However, they are found in beds separated 

from those bearing Elvinia by a significant sequence 

of fossiliferous Upper Cambrian beds lacking intermediate forms. Furthermore, one of the major Upper Cambrian faunal breaks occurs between the faunas 

bearing Elvinia and those bearing Drumaspis and 

Chariocephalus. Although Drumaspis and Chariocephahts pygidia have characteristics typical of the 

Elviniidae, the character of the anterior branches of 

the facial suture is unknown. Until more is known 

of these trilobites, their assignment to the Elviniidae 

should be considered only tentative.

Definitive features. The five genera included here 

in the Elviniidae (Elvinia, Elvinwlla, Elburgia, Dunderbergia, and Irvingella) share, in addition to stratigraphic continuity, the following morphologic features: Glabella prominent, generally well-defined at 

sides by deep dorsal furrow; border and doublure on 

cranidium and free cheek narrow, of nearly constant 

width, subcircular in cross section; rostrum present; 

facial suture submarginal, along at least middle-third 

of anterior margin of cranidiuni (fig. 8C) ; border and

FIGURE 8. Comparison of the ventral courses of the cephalic sutures 

in some Late Cambrian trilobites. A, Pterocephalia; B, Housia; 

C, DunderJ)ergia; D, PreJiousia; E, Aphelaspis.

doublure of pygidium narrow, of nearly constant 

width; axial lobe of pygidium prominent, generally 

reaching nearly to border, connected to it by poorly 

defined postaxial ridge.

Discussion. Of the features listed abcve, the character of the border and doublure on the cephalon and 

pygidium and the course of the cephalic sutures seem 

to be most critical family features.

The possible interrelationships of the genera of the 

Elviniidae in the Dunderberg shale leave the problem 

of subfamily groupings unresolved. Unfortunately for 

the present study, species of genera other than Dunderbergia are not common. Using only cranidia, several potential lineages are apparent (cf., pi. 5, 6). 

Elviniella -* Irvingella(Pavairvingella} -» Irvingella 

(Irvingella] might be included in one lineage by assumming reduction in the length of the frontal area 

and gradual decrease in the taper of the glabella for 

these three taxa with long arcuate palpebral lobes. 

This lineage could be contrasted with one from Dunderberg?a^> Elburgia^ Elvinia in which the posterior 

glabellar furrows are first deepened, and then connected across the top of the glabella. These three 

genera have similar pygidia. In addition, Dunderbergia and Elbwrgia, share a bluntly pointed anterior
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 65

margin and marginal furrow; and, Elburgia, on the 

basis of observation of specimens from California, has 

free cheeks indistinguishable from those of Elvinia.

Alternative possibilities might be to derive Elvinia 

from Elvimellct by gradual reduction in length of the 

palpebral lobe or to group the genera with noticeably 

arcuate palpebral lobes and transglabellar posterior 

furrows together in one subfamily (that is, ElvimeUa, 

Elvinia, IrvingeUa) and leave the genera with simple 

palpebral lobes (Dunderbergia*, Elburgia] in a second subfamily.

Obviously, more information about the genera of 

the Elviniidae is needed before an acceptable subfamily classification can be prepared. Perhaps studies of 

the faunas of the Dimclerberg shale elsewhere in the 

Great Basin will provide this information.

Genus DUNDERBERGIA Walcott, 1924 

Text figure 9

Dunderbet-ffia Walcott, 1924, p. 56; 1925, p. 84; Resser, 1935, p. 

23; Raymond, 1937, p. 1112; Kobayashi, 1938, p. 181; 

Shimer and Shrock, 1944, p. 625; Palmer, 1954, p. 760.

Type species. Crepicephalus (Loganelhtx) n-itidus 

Hall and Whitfield, 1877, p. 212, pi. 2, fig. 8.

Diagnosis. Elviniidae with prominent subquadrate 

glabella; glabellar furrows hardly visible. Length of 

palpebral lobe about ^ to 1/4 length of glabella including occipital ring. Line connecting midlengths of 

palpebral lobes crosses glabella just posterior to junction of second glabellar furrows with dorsal furrow. 

Anterior margin and marginal furrow commonly 

come to a blunt point on axial line instead of forming an even curve. Thorax includes either (or both) 

segments with pleural spines short, laterally directed, or 

long, backwardly directed. Pygidium subsemicircular 

in outline, widest at anterolateral corners. Border 

narrow, of nearly constant width. Axial lobe prominent, subparallel sided, bluntly rounded posteriorly. 

Pleural lobes nearly flat.

Modification of this diagnosis from that given earlier (Palmer, 1954) results from a consideration of 

the characters of the genera assigned to the Elviniidae.

Description. Medium-sized trilobites, probably few 

longer than 40 mm. Form of entire exoskeleton unknown. Cephalon subsemicircular in outline, moderately to strongly arched transversely and longitudinally. Cranidium exclusive of posterior limbs subquadrate in outline, anterior margin commonly bluntly 

pointed. Glabella prominent, elevated above brim and 

cheeks, tapered slightly forward, bluntly rounded or 

truncate anteriorly. Width just anterior to occipital 

furrow nearly equal to length exclusive of occipital 

ring. Three pairs of shallow glabellar furrows may 

be present. Posterior pair generally with bigenicuFIGURE 9. Partial reconstruction of Dundwbergia polybothra n. sp., 

about X 8.

late form. Occipital furrow always moderately deep, 

particularly at distal ends. Occipital ring with low 

median node adjacent to occipital furrow. Dorsal 

furrow deep at sides of glabella; shallow across front. 

Border distinct, moderately to strongly convex; length 

one-half or slightly less than that of brim. Marginal 

furrow deep, generally conies to blunt point or axial 

line. Brim gently to moderately convex. Fixed cheeks 

gently to moderately convex, horizontal or slightly 

upsloping; width about one-third basal gl?bellar 

width. Palpebral lobes semicircular in outline, moderately well defined by shallow palpebral furrow; 

width one-third or slightly more that of cheek; length 

about % to i/4 length of glabella including occipital 

ring. Ocular ridges generally visible, anterior margin best defined. Posterior limbs sharply pointed, 

length (transverse) generally slightly greater than 

basal glabellar width. Marginal furrow on posterior 

limb broad, deep; broadens laterally. Anterior course 

of facial suture slightly divergent from palpebral lobe 

to marginal furrow; turns inward across border, cuts 

anterior margin at point slightly less than or°,-half 

distance from anterolateral corners of cranidium to 

axial line. Connective sutures convergent posteriorly, 

not meeting on axial line. Rostral suture beneath 

midlength (sagittal and exsagittal) of border (fig. 8C). 

Posterior course of facial suture divergent-sinuous.
66 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Free cheek with well-defined continuous lateral and 

posterior marginal furrows; posterior marginal furrow generally deepest. Border narrow. Ocular platform gently convex, twice or more width of border. 

Genal spine short, sharply pointed, tip on some species curved slightly inward; length generally less than 

axial length of glabella on associated cranidium.

Hypostome and rostrum not known.

Form of thorax unknown. Thoracic segments of the 

same species with pleural spines either short, sharp, 

and directed laterally; or long, slender, and directed 

posteriorly. Width (transverse) of pleurae, from dorsal furrow to geniculation, between 1 and 2 times 

width of axial ring.

Pygidium short and wide, nearly flat except for 

prominent axial lobe. Axial lobe with 1 or 2 prominent ring furrows and with blunt indistinct posterior 

termination near inner margin of border. A low 

poorly defined median ridge connects axial lobe with 

border. Border well defined along all of margin except directly on axial line; width about half greatest 

width of pleural platform. A slight median indentation of margin may be present.

Surface of exoskeleton variously ornamented. External surface of cranidium and cheeks entirely smooth, 

partly or wholly granular, or coarsely pitted. Surface of mold of cranidium and cheeks ornamented with 

either pits or fine pits interspersed with coarse granules. Fine-granular and coarse-pitted ornament not 

apparent on surface of mold.

Ornamentation of surface of thoracic segments 

comparable to that of cheeks and cranidium.

Pygidium with top surface of axial lobe and border 

always bearing granules. Border generally also with 

prominent terrace lines. Pleurae either smooth, 

coarsely (but weakly) pitted, or granular. Surface 

of mold generally finely pitted.

Discussion. Walcott (1924, p. 56) proposed Dunderbergia to include Crepicephalus (Loganellus) nitidus 

Hall and Whitfield and gave a brief diagnosis of the 

genus. Other brief mentions of some of the characteristics of Dunderbergia were given by Walcott (1925, p. 

83), Raymond (1937, p. 1112) and Kobayashi (1938, 

p. 181). A more detailed description of the genus was 

given by Palmer (1954, p. 760) and is repeated with 

only slight modification here.

Thirteen species, besides the type species, have been 

assigned to Dunderbergia. These were Crepicephalus 

(Loganellus) maculosus Hall and Whitfield, Crepicephalus 

(Loganellus) simulator Hall and Whitfield, Crepicephalus 

(Loganellus) granulosus Hall and Whitfield, Ptychaspis 

pustulosa Hall and Whitfield, Ptychoparia suada Walcott, and Dunderbergia halli Resser assigned by Resser 

(1935, p. 23, 24); Dunderbergia'! declivita (Miller, 1936, 

p. 30); Crepicephalus (Loganellus) anytus Hall and

Whitfield (Resser, 1937, p. 9); Dunderbergia vermontensis 

(Raymond, 1937, p. 1120); Dunderbergia canadensis, 

D. convexa, and D. quadrata assigned by Kobayashi 

(1938, p. 181, 182) who included the latter two species 

along with D. pustulosa Hall and Whitfielc1 , D. maculosa 

(Hall and Whitfield), and D. granulosi, (Hall and 

Whitfield) in a new subgenus, Megadunderbergia; and 

Dunderbergia variagranula (Palmer, 1954, p. 761).

Wilson (1948, p. 33) considered Dunderbergiaf declivita Miller a synonym of Deadwoodia duris (Walcott). 

Wilson, (1951, p. 636) also removed Dunderbergia suada 

(Walcott) from the genus and considered it a senior 

synonym of Dellea wilbernsensis Wilson (1949, p. 35). 

Shaw (1952, p. 475) pointed out that Dunderbergia 

vermontensis Raymond is a young individual of MeteoraspisT minuta (Raymond). A review of the 11 other 

species during this study shows that only D. nitida 

(Hall and Whitfield), D. anyta (Hall and Whitfield), 

D. quadrata Kobayashi, and D. variagranula Palmer are 

recognizable species remaining in Dunderbergia. Of 

the seven other species, D. simulator (Hall and Whitfield) was considered a synonym of D. nitida (Hall and 

Whitfield) by Walcott (1884, p. 57), was later resurrected by Resser (1935, p. 24), and is here, again, considered a synonym of D. nitida. D. granulosa (Hall and 

Whitfield) is removed from Dunderbergia and assigned 

to the new genus Elburgia. D. halli Resser is based on 

a pygidium correctly assignable to Housia (p. 75); and 

D. maculosa (Hall and Whitfield) (pi. 5, fig. 5), D. 

pustulosa (Hall and Whitfield) (pi. 5, fig. 8), D. canadensis Kobayashi and D. convexa Kobayashi are based 

on such poor material that the specimens, though 

probably belonging to Dunderbergia, cannot be assigned 

with confidence to any of the species of the genus here 

recognized and are considered indeterminate. The 

names should be restricted to the type specimens.

Because D. maculosa (Hall and Whitfield), the type 

species of Megadunderbergia Kobayashi, is considered 

an indeterminate species, the subgenus also must be 

considered indeterminate. No subgener,<\ of Dunderbergia are recognized in this paper.

Species presently assigned to Dunderbergia: 

Dundbergeria anyta (Hall and Whitfield) 

bigranulosa n. sp. 

nitida (Hall and Whitfield) 

polybothra n. sp. 

quadrata Kobayashi 

variagranula Palmer 

maculosa (Hall and Whitfield)^

pustulosa (Hall and Whitfield) I ,.,,, , . ^ , . , ,. > Restricted to holotype 

canadensis Kobayasm

convexa Kobayashi J

Dunderbergia bigranulosa n. sp. 

Plate 5, figures 10-13, 15-23

Diagnosis. Members of Dunderbergia with external surface of cephalon bearing low scrttered coarse
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 67

granules on brim, fixed cheeks, posterior limbs, and 

ocular platforms; fine close-spaced granules on border, top of glabella, and outer margins of palpebral 

lobes. Surface of mold shows position of coarse granules; surface beneath fine-granular areas is finely pitted. Pygidium with fine granules on border and top 

of axial lobe; scattered low coarse granules on pleural platforms.

Discussion. Some variation in degree of expression and detailed distribution of the coarse granules 

was observed within collections of D. bigranulosa. On 

some specimens the coarse granules are only apparent 

after the specimen has been lightly whitened and observed with low oblique lighting (pi. 5, fig. 13). On 

specimens from USGS collection 795, associated with 

D. nitida (Hall and Whitfield), the coarse granules 

are exceptionally prominent (pi. 5, figs. 10, 11), and 

in this way resemble the coarse granules of D. variagranida Palmer; however, the border and glabella 

have the fine granules characteristic of D. bigranulosa.

Two types of free cheeks, perhaps indicating dimorphism within the species, have been found in collections of D. bigranulosa and D. variagranula. On 

one type, the border broadens slightly anterior to the 

base of the genal spine and it is distinctly flattened. 

On the other type, the border maintains an even width 

and it is gently convex (cf. pi. 5, figs. 16, 17).

An unusual, apparently pathologic, pygidium is 

present in USGS collection 2295-CO (pi. 5, fig. 23). 

This specimen includes two distorted thoracic segments that have their right pleurae free and their 

left pleurae fused with each other and the remainder 

of the pygidium.

Occurrence: Abundant, lower 40 ft of Dunderberg shale; 

unit A. USGS colln. 795-CO, 2294-CO, 2295-CO.

Figured specimens: Holotype cranidium, USNM 136847, 

USGS colln. 2295. Paratypes: Cranidium, USNM 136848a, 

USGS colln. 2295-CO; cranidia, USNM 136846a, b, USGS colln. 

795-CO; cranidium, USNM 136849b, USGS colln. 2294-CO; 

free cheeks, USNM 136848b, c, USGS colln. 2295-CO; free 

cheek, USNM 136849a, USGS colln. 2294-CO; pygidia, USNM 

136848d-f, USGS colln. 2295-CO; pygidium, USNM 136849c, 

USGS colln. 2294-CO.

Dunderbergia nitida (Hall and Whitfield) 

Plate 4, figures 14-21, 23, 24

Crepicephalus (Loganellus) nitidus Hall and Whitfield, 1877,

p. 212, pi. 2, fig. 8. 

Crepicephalus (Loganellus) simulator Hall and Whitfield, 1877,

p. 218, pi. 2, figs. 16-18. 

Ptuchoparia nitidus (Hall and Whitfield). Walcott, 1884, p.

57. 

Dunderbergia nitida (Hall and Whitfield). Walcott, 1924, p.

56, pi. 11, fig. 2; 1925, p. 84, pi. 16, fig. 4; Shinier and

Shrock, 1944, pi. 264, fig. 29.

Dunderbergia simulator (Hall and Whitfield). Resser, 1935, 

p. 24.

Diagnosis. Members of Dunderbergm with external surface of exoskeletoii smooth except for top of 

axial lobe and border of pygidium which bear fine 

close-spaced granules and border of free cheek which 

has terrace lines. Surfaces of molds of all parts of 

exoskeletoii are finely pitted.

Discussion. This species is the most comnior species of Dunderbergia in the collections studied. Some 

cranidia from USGS collection 2300-CO have rare 

low barely discernible coarse granules on the brim, 

suggesting that D. nitida may have been derived from 

a form like D. bigranulosa through the loss of the 

fine granules on the border and glabella.

The holotype of this species was not designated by 

Hall and Whitfield. Two specimens in the typ-^ collection have handwritten labels bearing the or; gmal 

name pasted on the rock. One, USNM 24572b, a mold, 

(pi. 4, fig. 16) is the specimen cited by Walcott (1925, 

p. 132, fig. 5) as an "original type specimen." The 

illustration given by Walcott is not of this specimen, 

nor is it of the other with the handwritten label. The 

second specimen, USNM 24572, preserves enough of 

the external surface (pi. 4, fig. 15) to show that it was 

for the most part smooth. Inasmuch as Walcott did 

not designate holotypes of the other species in his 

1925 paper, Walcott's cited comment is interpreted 

here to mean only that he was illustrating one of the 

original types. Because the illustration does not conform to either of the labeled specimens, Walcott's comment is not considered a valid citation of a lectotype 

for D. nitida, and the specimen bearing USNM 24572 

and the handwritten label "C. (L.} nitidus'" is here 

designated as lectotype of the species.

The pygidium illustrated for D. nitida by Walcott 

(1925, pL 16, figs. 6, 7) and Shinier and Shrock (1944, 

pi. 264, fig. 30) is a Homia. pygidium (p. 75; pi. 7, 

fig. 8).

Occurrence: Common, from 50-200 ft above the btse of 

the Dunderberg shale; units B, C. USGS colln. 789-CO, 795- 

CO, 864-CO, 872-CO, 873-CO, 953-CO 955-CO, 2295-CO 

2302-CO.

Figured specimens: Lectotype cranidium, USNM 24572. 

Paratype cranidium, USNM 24572b. Plesiotypes: Cranidium, 

holotype of D. simulator (Hall and Whitfield), USNM 24575; 

cranidia, USNM 136838b, c, USGS colln. 2300-CO; free cheeks, 

USNM 136838d, f, USGS colln. 2300-CO; free cheek, USNM 

136839, USGS colln. 873-CO; pygidia, USNM 136838a, e, USGS 

colln. 2300-CO.

Dunderbergia polybothra n. sp. 

Plate 5, figures 1-4, 6, 7, 9, 14

Diagnosis. Members of Dunderbergia with surfaces 

of all parts of exoskeleton except top of axial lob? and 

border of pygidium bearing coarse pits. Pits most 

apparent on border of cephalon, top of glabella, and 

axial parts of thoracic segments; visible on other parts
68 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

of exoskeleton only on exceptionally well-preserved 

specimens. Top of axial lobe and border of pygidium 

bear close-spaced granules. Surfaces of molds of all 

parts of exoskeleton are finely pitted.

Discussion. This distinctive species is known from 

only two collections, where it is the only species of 

Dunderberg ia present. It differs from all other species in the genus by having a pitted surface.

Occurrence: Moderately common, about 40 ft above base 

of Dunderberg shale, unit B. USGS colln. 1297-CO, 2296-CO.

Figured specimens: Holotype cranidium, USNM 136845, 

USGS colln. 2296-CO. Paratypes, cranidium, free cheeks, thoracic segments, and pygidium, USNM 136844a-f, USGS colln. 

2296-CO.

Dunderbergia variagranula Palmer

Plate 4, figures 22, 25, 26, 28, 29

Dimderbergia variagrenula Palmer, 1954, p. 761, pi. 88, fig. 7.

Diagnosis. Members of Dunderbergia, with external surfaces of all parts of exoskeleton bearing scattered coarse granules. Surfaces of molds of all parts 

of exoskeleton also bearing scattered coarse granules.

Discussion. In view of observations made on reasonably abundant material of this species in the Eureka district, the only illustrated specimen from Texas 

now retained in this species is the holotype (Palmer, 

1954, pi. 88, fig. 7). The other three illustrated specimens may represent a species not known in the Eureka 

district.

One difference was noted between the holotype and 

the Nevada specimens. Coarse granules are rare on 

the posterior limbs of the few specimens of D. variagranula from Nevada that have the limbs preserved. 

The posterior limbs of the holotype bear abundant 

coarse granules. Unfortunately, not enough specimens are known from either area to determine if this 

is a consistent difference. Because the distribution of 

coarse granules on other parts of the cranidium is 

somewhat variable among cranidia in a single collection, the Texas and Nevada specimens are here considered to be most likely conspecific.

D. quadrat a Kobayashi (pi. 4, fig. 27) is represented 

by a single cranidium that has coarse granular ornament on both the external surface and the surface of 

the mold. Fine granules are also present on the border. These are characteristic features of D. variagramrta. However, the cranidium of D. quadrata is 

three times larger than any cranidia of D. variagranula known, has a much more prominent glabella, and 

appears to have a relatively shorter frontal area and 

broader border. Although D. rariagranula may be a 

synonym of D. quadrata, more knowledge of D. quadrata is desirable before suppressing D. variagranula.

A single small cranidium from USGS collection 

2302 (pi. 4, fig. 26) is tentatively referred to D. variagranula. It conforms to the species in all respects

except that the border bears only close-spaced fine 

granules. Also, it occurs with D. nitida,, about 120 

feet higher than any collection in which granular species of Dunderbergia are common. This certainly indicates that the granular and smooth forms of Dunderbergia have a nearly common range in time. However, the abundance of granular species in the relatively common limestones of the lower Dunderberg, 

where smooth forms of Dunderbergia gre rare, and 

the reverse situation in the relatively rare limestones 

of the middle shaly part of the DunclerSerg may indicate that the granular and smooth forms have different facies preferences.

Occurrence: Moderately common, 50-75 ft above the base 

of the Dunderberg shale; units B, C. USGS colln. 809-CO, 

873-CO, 952-CO, 2297-CO, 2298-CO.

Figured specimens: Plesiotypes cranidium end free cheek, 

USNM 136840a, b, USGS colln. 2297-CO; cranidium, USNM 

136841, USGS colln. 2298-CO; crandium, USNM 136842, USGS 

colln. 2302-CO; pygidium, USNM 136843, USGF colln. 809-CO.

Genus ELBURGIA n. gen. 

Text figure 10

Type species. Ore pice phahis (Loganelhis} granulosus Hall and Whitfield, 1877, p. 214, pi. 2, figs. 2, 3.

Diagnosis. Elviniidae with cranidium having palpebrai lobes about one-third length of glabella including occipital ring, and with posterior pair of glabellar furrows deep, bigeniculate, connected by a shallow furrow across top of glabella. Second glabellar 

furrows also conspicuous, only slightly cnrved. Anterior glabeller furrows only conspicuous on mold. 

Pygidium and free cheeks not distinguishable from 

Elvmia.

FIGURE 10. Partial reconstruction of Elburgia qttinnensis Resser, 

about X 6.

Description. Medium to large trilobites (as much 

as 90 mm in total length). Outline of cranidium, exclusive of posterior limbs, subquadrate; anterior mar-
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 69

gin evenly rounded or bluntly pointed. Glabella 

prominent, elevated above cheeks, tapered forward, 

bluntly rounded or truncate anteriorly; with just anterior to occipital furrow about equal to length exclusive of occipital ring. Three pairs of glabellar 

furrows present. Anterior pair shallowest, short; middle pair moderately deep, reach about three-fourths 

distance to axial line; posterior pair deep, bigeniculate, connected across top of glabella by shallow furrow. All furrows more conspicuous on mold. Occipital furrow broad, deep. Occipital ring with low 

median node adjacent to occipital furrow. Dorsal 

furrow deep at sides and anterolateral corners of 

glabella, shallow across axial line. Border distinct, 

moderately to strongly convex, length one-half or 

slightly less that of brim. Marginal furrow broad, 

deep, with slight tendency to come to a blunt point 

on axial line. Brim gently to moderately convex. 

Fixed cheeks gently to moderately convex, nearly horizontal. Width slightly less than one-half basal glabellar width. Palpebral lobes moderately arcuate in 

outline; width about one-third width of cheek; length 

about one-third length of glabella including occipital 

ring. Palpebral furrow broad, well denned. Ocular 

ridges visible but not prominent; anterior margin best 

defined. Posterior limbs sharply pointed, length 

(transverse) equal to or slightly greater than basal 

glabellar width. Marginal furrow on posterior limb 

broad, deep, broadens laterally. Anterior course of 

facial suture only slightly divergent from palpebral 

lobes to marginal furrow; turns inward across border; 

cuts anterior margin and becomes submarginal at point 

slightly less than one-half distance from anterolateral 

corner of cranidium to axial line. Posterior course 

of facial suture divergent sinuous.

Hypostome rostrum and thoracic segments not 

known.

Free cheek and pygidium same as Elvinia (cf. figs. 

10, 11).

Discussion. This genus includes, at present, two 

species whose cranidial shape and stratigraphic ranges 

are intermediate between those of Dunderbergia and 

Elvinia. The form of the preglabellar area is characteristic of Dunderbergia, and the posterior glabellar 

furrows connected across the glabella are characteristic of Elvinia. These characters combined, plus the 

general prominence of all glabellar furrows, are the 

distinguishing characteristics of the species of Elburg ia.

Species differentiation in Elburgia^ as in Dunderbergia, is primarily based on the nature of the external surface and the surface of the mold of the cranidium.

Two cranidia representing this genus, but identified 

as Elv'mia sp., were figured by Palmer and Hazzard

(1956, pi. 1, figs. 1, 2) from the Cornfield Springs 

and Nopah formations in California.

Elburgia granulosa (Hall and Whitfield) 

Plate 6, figures 16, 17, 19

Crepicephalus (Loganellus) granulosus Hall and Whitfield. 1877, 

p. 214, pi. 2, figs. 2, 3.

Ptychoparia granulosus (Hall and Whitfield). Walcott, 1884, p. 

57.

Dunderbergia granulosa (Hall and Whitfield). Resser, 1935, p. 

24.

Dunderbergia (Megadunderbergia) granulosa (Hall and Whitfield). Kobayashi, 1938, p. 181.

Diagnosis. Members of Elburgia with cranidium 

having external surface and surface of mold, exclusive 

of furrows and palpebral lobes, thickly covered with 

coarse granules.

Discussion. No further comments on the character 

of this species have been published since the original 

description by Hall and Whitfield, though Walcott, 

Resser, and Kobayashi successively transferred it to 

three different genera or subgenera. Kobayashi (1938) 

included granulosa with Dunderbergia pustulosa (Hall 

and Whitfield) in a new subgenus, Megadunderl vrgia. 

The holotype of the type species of Megadunderbergia 

(D. pustulosa] is here considered (p. 66) an indeterminate specimen of Dunderbergia. Thus, Megadunderbergia is also indeterminate, and the identifiable species assigned to it require reassignment. E. 

granulosa* with its conspicuous Elvina-\ik& glabellar 

furrows, does not fit the present concept of Dunderbergia and is here designated as the type species of 

Elburgia (see generic discussion). It is easil;T distinguished from the only other species presently assigned to the genus E. quinnemis (Resser) by the 

coarse granular nature of the external surface and 

the surface of the mold of the cranidium.

Occurrence: Rare, 45-70 ft above base of Dunderberg 

shale; unit B. USGS colln. 795-CO; 2297-CO.

Figured specimens: Holotype cranidium, USNM 24573. 

Plesiotypes : Cranidium, USNM 136857, USGS colln. 2237-CO; 

cranitlium, USNM 136856, USGS colln. 795-CO.

Elburgia quinnensis (Resser)

Plate 6, figures 11-13, 15

Taenicephalus quinnensis Resser, 1942b, p. 105, pi. 21, figs. 18, 

23.

Diagnosis. Members of Elburgia with external surface of cranidium nearly smooth. Lateral parts of 

brim and of posterior limbs with numerous closespaced low granules visible only when specirien is 

whitened and viewed in extreme oblique lighting. 

Brim also bears scattered low coarse granules, also 

barely visible. Surface of mold with numerous fine 

pits most noticeable on brim and cheeks. Positions 

of coarse granules may be indicated by low elevations
70 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

with terminal pits slightly larger than those on other 

parts of cranidium.

Discussion. This species was described by Resser 

(1942, p. 105) as Taenwephalus quinmmis from a 

small collection of unknown stratigraphic position 

collected by J. E. Spurr while on reconnaisance in 

Nevada in 1899. Although the prominent glabellar 

furrows are reminiscent of Taenicephalus, the facial 

sutures do not cut the margin near the axial line as 

they seem to do in that genus, and no true species of 

Tafnicephahis have the posterior pair of glabellar 

furrows connected across the glabella. Furthermore, 

this species is associated with a species of Sigwwcheilus 

n. gen., a genus characteristically found in beds older 

than those bearing Elvinia. Taenicephahis is known 

only from beds younger than those bearing Elvinia.

Free cheeks and pygidia associated with cranidia of 

this species in the lower part of the Nopah formation, 

California, are virtually indistinguishable from those 

of Elvinia. A pygidium and free cheek, probably of 

Elbwgia quirmemiv, were figured by Resser from the 

small type collection from the Quinn Canyon Range, 

Nev.

Occurrence: Moderately rare, 70-100 ft above base of Dunderberg shale; unit B. USGS colln. 2298-CO, 2299-CO, 2300- 

CO. Outside the Eureka district, this species has been recognized in collections from the Nopah formation in California 

and in Dunderberg equivalents in the Las Vegas quadrangle, 

Nevada.

Figured specimens: Holotype exfoliated cranidium, USNM 

108838a, USNM loc 7j ; Dunderberg( ?) shale, Quinn Canyon 

Range, Nev. Paratype, cranidium, on same block as holotype, 

with external surface preserved. Plesiotypes: Cranidium, 

USNM 136855, USGS colln. 2298-CO; cranidium, USNM 136438, 

USGS colln. 2299-CO.

Genus ELVINIA Walcott, 1924 

Text figure 11

EMnia Walcott, 1924, p. 56; 1925, p. 88; Bridge and Girty, 

1937, p. 252; Kobayashi, 1938, p. 179; Shimer and Shrock, 

1944, p. 625.

Moosia Walcott, 1924, p. 59; 1925, p. 106.

Diagnosis. Elviniidae with posterior glabellar furrows connected across glabella forming single arcuate 

furrow of nearly even depth. Other glabellar furrows 

rarely apparent. Palpebral lobes arcuate, length about 

one-third that of glabella including occipital ring. 

Width of fixed cheeks between % and l/o basal glabellar width. Anterior margin of cranidium evenly 

curved. Marginal furrow appears nearly straight in 

dorsal view. Anterior course of facial sutures nearly 

straight forward from palpebral lobes.

Free cheek with short sharp genal spine diverging 

from general curvature of cheek margin. Ocular 

platform broad, separated from moderately to strongly 

convex border by broad deep marginal furrow, connection between lateral and posterior marginal furrows 

shallow.

Pygidium subsemicircular in outline, w; dest at anterior margin. Border narrow, of nearly constant width. 

Axial lobe prominent, subparallel sided, bluntly 

rounded posteriorly. Pleural lobes nearly flat.

FIGURE 11. Partial reconstruction of Elvinia roemeri (Shumard >, 

about X 3.

Discussion. Bridge and Girty (1937, p. 252; pi. 69, 

figs. 1-21) described the genus in detail and illustrated 

specimens from many parts of the United States. The 

inclusion of E. gmnmlaia, (Resser) in the genus requires the following slight modification in the otherwise excellent characterization given by Bridge and 

Girty: Frontal area with length (sagittal) of border 

equal to or less than length (sagittal) of brim. External surface smooth or granular.

Species differentiation in Elvinia is here based primarily on the nature of the surface of the cranidium 

and secondarily on the character of the frontal area. 

The inadequacy of minor variations of cranidial proportion for species differentiation withir Elvinia has 

already been treated by Bridge and Girty (1937) and 

Frederickson (1949).

Elvinia roemeri (Shumard) 

Plate 6, figure 7

Dikelocephalus roemeri Shumard, 1861, p. 220, 221.

Crepicephalus (Loganellus) unisulcatus Hall and Whitfield, 1877, 

p. 216, pi. 2, fig. 22.

Ptychoparia matheri Walcott, 1912, p. 268, pi. 44, figs. 15-17.

Elvinia roemeri (Shumard). Walcott, 1924, p. 56, pi. 11, fig. 3; 

1925, p. 88, pi. 17, figs. 9-13; Bridge, 1933, p. 232, pi. 2, 

figs. 17-19; Miller, 1936, p. 30, pi. 8, fig. 36; Bridge and 

Girty, 1937, p. 251, pi. 69, figs. 1-22; Shimer and Shrock, 

1944, pi. 264, figs. 34-37; Wilson, 1949, p. 38, pi. 10, figs. 

5, 9, 10, 12, 13; Frederickson, 1949, p. 352, pi. 69, figs. 19- 

21; Lochman, 1950, pi. 47, figs. 21-23; Wilson, 1951, p. 

642, pi. 92, figs. 18-22; Nelson, 1951, p. 77f, pi. 107, fig. 8; 

Bell, and others, 1952, p. 183, pi. 30, figs. la-d.

Moosia grandis Walcott, 1924, p. 59, pi. 14, fig. 9; 1925, p. 107, 

pi. 23, figs. 20, 21.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 71

Elvinia tetonensis Resser, 1937, p. 12.

Elvinia texana Resser, 1938, p. 30.

Elvinia shumardi Resser, 1938, p. 30; Shimer and Shrock, 1944,

pi. 264, figs. 41, 42. 

Elvinia bridgei Resser, 1938, p. 31; 1942b, p. 97, pi. 18, figs.

28-31; pi. 19, figs. 1-5. 

Elvinia missouriensis Resser, 1938, p. 31; 1942b, p. 96, pi. 18,

figs. 13-17.

Elvinia dakotensis Resser, 1938, p. 32. 

Elvinia utahensis Resser, 1938, p. 32; 1942b, p. 95, pi. 18, figs.

5, 6.

Elvinia gregalis Resser, 1942b, p. '97, pi. 18, figs. 28-31. 

Elvinia longa Resser, 1942b, p. 97, pi. 18, figs. 24-27. 

Elvinia vagans Resser, 1942b, p. 98, pi. 19, figs. 6-9. 

Elvinia brevifrons Resser, 1942b, p. 98, pi. 19, figs. 10-14. 

Elvinia matheri (Walcott). Shimer and Shrock, 1944, pi. 264,

fig. 40.

Diagnosis. Specimens of Elvinia with smooth external surface of crandium. Brim generally moderately convex; length (sagittal) nearly twice that of 

border.

Discussion. This species has been discussed or illustrated perhaps more than any other Upper Cambrian species. Crepicephalus (Logan-ellus] unisulca,- 

tus, described by Hall and Whitfield (1877) from the 

Eureka district, was shown by Bridge and Girty 

(1937) to be a synonym of E. roemeri. Later, Resser 

(1937, 1938, 1942) described many new species of Elvinia. Except for E. granulata Resser and E. reud<emanni Resser, and E. hamburgensis (Resser), originally described as Parairvingella hatnburgemis (Resser, 1942) and transferred to Elvinia by Kobayashi 

(1954, p. 34), all other species assigned by Resser to 

Elvinia are now considered synonyms of E. roemeri 

(Shumard). Frederickson (1949) discussed much of 

the synonymy, and those species that he did not return 

to E. roemeri are here returned. Elvinia utahensu 

was used by Resser twice, both times cited as a new 

species (1938, p. 32; 1942, p. 95). Both holotypes are 

conspecific with E. roemeri.

Occurrence: Rare, upper Dunderberg shale (units C, D) 

and lower part of overlying Windfall formation. USGS colln. 

789-CO, 864-CO; 955-CO; 2302-CO.

Figured specimen: Cranidium, USNM 136851, USGS colln. 

789-CO.

Elvinia granulata Resser

Plate 6, figure 4

Elvina granulata Resser, 1942b, p. 96, pi. 18, figs. 11, 12. 

Elvina ruedemanni Resser, 1942b, p. 95, pi. 18, figs. 7-10;

Fisher and Hanson, 1951, pi. 1, figs. 1, 2. 

IParairvingella hamburgensis Resser, 1942b, p. 27, pi. 4, figs.

23, 24.

Diagnosis. Members of Elvinia with external surface of cranidium, exclusive of furrows and palpebral 

lobes, covered with low granules. Brim generally flat 

or concave in longitudinal profile, axial length about 

equal to that of border.

Discussion. Two species described by Resser (1942), 

E. granulata and E. ruedemanni are indistinguishable 

from each other and represent a distinct species of 

Elvinia. E. granulata, is chosen as the name for the 

species even though E. ruedemanni has page p^eference (p. 96 vs. p. 95) because its holotype is a much 

more complete specimen. A third species, Elvinia 

hamburgensis (Resser) (pi. 6, fig. 5), may also be conspecific with E. granulata, but the granules on the 

glabella are much broader and have peculiar pologonal outlines. Certain identity cannot be established 

because too few specimens assignable to E. grarulata 

are known to determine the amount of variability of 

surface granulation within the species.

Occurrence: Rare, upper Dunderberg shale (unit D), Eureka, Nev.; Galway limestone of Fisher and Hanson (1951), 

near Saratoga Springs, N.Y.

Figured specimen: Holotype cranidium, USNM 108815, 

USNM loc. 63.

Elvinia? sp. 

Plate 6, figure 6

A single cranidium from a collection intermediate 

in stratigraphic position between the known occurrences of ETburgia granulosa (Hall and Whitfield) 

and Elvinia granulata (Resser) is also intermediate 

in morphology between the two species and canrot be 

assigned clearly to either genus. Perhaps, if more 

material becomes available, it can be shown to represent a new genus intermediate between Elburgia and 

Elvinia. In any event, this specimen emphasizes the 

close morphologic relationship of the two genera.

The glabella has three pairs of conspicuous glabellar furrows, the posterior pair connected acrors the 

top of the glabella by a shallow furrow, a characteristic feature of the species of Elburgia. The frontal 

area, the granular surface, and the overall form of 

the crandium are for the most part like those of 

Elvinia. granulata,.

Occurrence: Rare, about 90 ft above base of Duncferberg 

shale; unit B. USGS colln. 2300-CO.

Figured specimen: Cranidium, USNM 136850.

Genus ELVINIELLA n. gen.

Type species. Elviniella lae.vis Palmer, n. sp.

Diagnosis. Elviniidae with cranidium bearing 

conspicuous posterior glabellar furrows competed 

across glabella, other glabellar furrows hardly visible. 

Border and marginal furrow with tendency to come to 

blunt point on axial line. Fixed cheeks broad. Palpebral lobes long, strongly arcuate; length about onehalf that of glabella including occipital ring. Anterior course of facial sutures nearly straight forward 

from palpebral lobes.

Other parts of exoskeleton not known.
72 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Description. Generally small trilobites probably 

not exceeding 15 mm in total length. Cranidium, 

only known part. Outline, exclusive of posterior 

limbs, subquadrate; anterior margin tending to come 

to a blunt point on axial line. Glabella prominent, 

tapered forward, straight sided, bluntly rounded anteriorly. Width just anterior to occipital furrow 

slightly less than length exclusive of occipital ring. 

Only posterior glabellar furrows well defined; deep 

along flanks of glabella, connected across top of glabella by shallow furrow, not connected to dorsal furrow. Occipital furrow broad, deep; deepest at distal 

ends. Occipital ring with median node adjacent to 

occipital furrow. Dorsal furrow broad, deep slong 

sides of glabella and at anterolateral corners, somewhat shallower across axial line. Border distinct, 

gently convex, separated from brim by a distinct 

change in slope and a broad marginal furrow that 

tends to come to blunt point on the axial line. Brim 

gently convex; length (sagittal) slightly more than 

that of border. Fixed cheeks broad, gently to moderately convex, nearly horizontal; width slightly 

greater than one-half basal glabellar width. Palpebral lobes, long, slender, broadly arcuate, situated 

slightly below general level of cheek; line connecting 

anterior tips crosses glabella nearly at anterior margin. Width of palpebral lobes slightly less than onefourth width of cheek; length about one-half length 

of glabella including occipital ring. Palpebral furrow broad, shallow, well defined. Ocular ridges low, 

barely apparent. Posterior limbs relatively short, 

length (transverse) slightly less than basal glabellar 

width. Marginal furrow of posterior limb broad, 

deep. Anterior course of facial suture straight forward from palpebral lobe to marginal furrow; turns 

inward across border and appears to become almost 

immediately submarginal. Posterior course divergent sinuous.

Discussion. This genus is proposed to include nine 

cranidia from collections in the middle part of the 

Dunderberg shale. Although more than one species 

may be represented, only the type species is described 

because even it is represented by only a few specimens 

and the significance of the variant forms, represented 

by single specimens, cannot be certainly determined.

ElvinieTla- most nearly resembles Elvinia, among described genera, particularly in the shape of the glabella. It is easily distinguished from Elvinia, however, by the long, slender palpebral lobes and the 

bluntly pointed anterior margin. The form of the 

frontal area indicates possible relationships to Du-nderbergia and Elburgia and the long palpebral lobes 

indicate possible affinities with IrvingeUa. The possible significance of these relationships in the family 

classification has already been discussed (p. 64).

Elviniella laevis n. sp. 

Plate 6, figures 8-10, 14

Description. The description presented for the 

genus covers most of the characteristics of this species. The external surface of the cranidium is virtually smooth; however, whitened specimens observed 

in oblique lighting show faint irregular anastamosing 

or reticulate markings on the posterior part of the 

cheek and terrace lines along the anterior margin of 

the border.

Discussion. Two specimens differ from the holotype in features that may be significant. One (pi. 6, 

fig. 8) has a much more definitely pointed anterior 

margin, a suggestion of a low median boss on the 

brim, distinctly roughened cheeks posterior to the 

midlength of the palpebral lobes, and the posterior 

glabellar furrow is deepest on the axial line.

The second variant specimen (pi. 6, fig. 14) differs 

from the holotype by having a distinctly shorter and 

broader frontal area and by having the line connecting the anterior tips of the palpebral lobes passing 

slightly anterior to the glabella, thus alro giving the 

ocular ridges the appearance of being directed outward 

and forward from the anterior end of the glabella.

As both variants occur at about the same stratigraphic level and are each associated with forms virtually like the holotype, they may merely indicate that 

there is more variation in shape of specimens of this 

species than in those of such possibly related genera 

as Diniderbergia and Elvinia.

Occurrence: Rare, 60-150 ft above base of Dunderberg 

shale; units B, C. USGS colln. 952-CO, 954-CO, 2301-CO.

Figured specimens: Holotype cranidium, USNM 136854, 

USNM colln. 952-CO; Elviniella sp., USNM 136852, USGS 

colln. 954-CO; Elviniella sp., USNM 136853, US^S colln. 2301- 

CO.

Genus IRVINGELLA TTlrich and Resser, 1924

IrvingeUa Ulrich and Resser (in Walcott), 1924, p. 58; Walcott 

and Resser, 1924, p. 10; Walcott, 1925, p. 97; Resser, 1938, 

p. 33; 1942b, p. 3, 13; Shinier and Shrock, 1944, p. 627; 

Kobayashi, 1954, p. 34.

IrvingeUa (Parairvingella) Kobayashi, 1938, p. 175.

Parairvingella Resser, 1942b, p. 4, 25.

IrvingeUa (Irvingellina) Kobayashi, 1938, p. 175.

Type species. IrvingeUa major Ulrich and Resser 

(in Walcott), 1924, p. 58, pi. 10, fig. 3.

Diagnosis. Elviniidae with prominent subquadrate 

glabella, broadly rounded anteriorly. Posterior glabellar furrows connected across glabella, forming 

single deep furrow; junctions of lateral parts with 

furrow across top generally slightly angular. Middle pair of glabellar furrows generally visible at sides 

of glabella. Frontal area short, less than one-fourth 

length of glabella including occipital ring. Fixed 

cheeks moderately broad; width between palpebral and
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 73

dorsal furrows slightly more than one-third width of 

glabella just anterior to occipital furrow. Palpebral 

lobes long, slender, depressed below general level of 

cheek; length about two-thirds length of glabella including occipital ring. Posterior limbs short, steeply 

depressed.

Free cheek narrow. Border broader than ocular 

platform except posterolateral to eye. Genal spine 

moderately long, continues curvature of border.

Pygidium subtrapezoidal in outline broadest at or 

near anterior margin, with prominent axial lobe 

crossed by 1 or 2 deep ring furrows; length of axial 

lobe about three-fifths length of pygidium. Distinct 

border generally present. Pleural lobes narrower than 

axial lobe.

Discussion. Historically, IrvingeUa has been considered a member of the Komaspidae (Kobayashi, 

1935, 1954; Hupe, 1953, 1955; Lochman, 1954) ;* however, the determination of critical features of the 

Komaspidae is questioned below, and IrvingeUa is 

here placed in the Elviniidae. Komaspis typa Kobayashi, the type species of Komaspis and the Komaspidae, is represented by a single poorly preserved 

cranidium from beds of Middle Cambrian age in 

Korea. The cranidium is somewhat similar in shape 

to craniclia of IrvingeUa (Pamir c ing ell'a), but nothing is known of the free cheeks or pygidium or of 

the critical anterior course of the facial suture of this 

species. Furthermore, nearly all the other species 

assigned to the Komaspidae are from beds of Late 

Cambrian age in North America. Because of the 

poor quality and inadequate knowledge of the morphology of the holotype and only specimen of K. typa, 

its relationships to the North American genera are at 

best tentative, and the characteristics of the Komaspidae, which must ultimately be based on this specimen are, at least for the present, not determinable.

Ulrich and Resser (in Walcott, 1925) have given 

an adequate description of IrvingeUa. Kobayashi 

(1938) proposed two subgenera, ParairvingeUa and 

Irvingellina, for forms with a distinct brim and border, and with the front of the glabella overhanging 

the frontal area, respectively. Resser (1952) raised 

Parairvingella to generic rank and suppressed Irvingellina as a synonym of IrvingeUa based on distorted 

specimens. Westergard (1947) described a species of 

IrvingeUa from Sweden showing gradation from 

forms characteristic of Parairvingella to forms characteristic of IrvingeUa. Lochman (1953) following 

Westergard's suggestion has considered ParairvingeUa a synonym of IrvingeUa. In the Eureka district, forms of IrvingeUa with brim and border present are found in the uppermost parts of the Dunderberg shale whereas forms without a divided frontal

507219 O 59 3

area are known certainly only from the basal beds of 

the overlying Windfall formation.

ParairvingeUa, as a subgenus of IrvingeUa, is a recognizable taxon apparently occurring in slightly older 

rocks than the much more widesreacl IrvingeUa 

(IrvingeUa} species. It is used here in the sense originally intended by Kobayashi.

Subgenus IRVINGELLA (PARAIRVINGELLA) Kobayashi

Type species. Chariocephalu^l twnufrons Walcott 

(not Hall and Whitfield) 1884, p. 61, pi. 10, fig. 16 

(renamed IrvingeUa (Parairvingella) angu^tilin^^atu-s 

by Kobayashi, 1938, p. 175.

Diagnosis. Species of IrvingeUa with a well-developed border on the adult cranidium.

Discussion. Two species are recognized within this 

subgenus. Neither is represented by abundant material, but the differences shown are considered significant.

IrvingeUa (Parairvingella) angustilimbatus Kobayashi 

Plate 6, figures 2, 3

Chariocephalusl tumifrons Walcott (not Hall and Whitfield)

1884, p. 61, pi. 18, fig. 16. 

IrvingeUa (Parairvingella) angustilimbatus Kobayashi, 1938,

p. 175. 

Parairvingella angustilimbatus (Kobayashi), Resser, 1942b,

p. 26, pi. 4, figs. 18-22. 

Parairvingella intermedia Resser, 1942b, p. 27, pi. 4, figs. 25-31.

Diagnosis. Members of ParairvingeUa with axial 

length of border greater than that of brim; axial 

length of frontal area on small cranidia (length 7 

mm) about one-sixth length of glabella not including 

occipital furrow, axial length of frontal area in larger 

specimens proportionately greater. Ocular ridg<?s directed nearly straight laterally from anterolaterg-1 corners of glabella.

Discussion. This species is represented by seven 

cranidia showing the features given in the diagnosis. 

Ressers statement that brim and border of Parairvingella intermedia are subequal in length is not 

correct. The border is distinctly longer (sagittal) 

than the brim, and the species is not distinguishable 

from /. (P.) angustilimbatus. All the cranidip, now 

assigned to this species come from old collections 

whose stratigraphic position within the Dimderberg 

shale is not exactly known. However, the associated 

trilobites indicate that /. (P.) angustilinibatus conies 

from the upper limestone beds of the Dimderberg 

shale.

Occurrence: Rare, upper part of the Dunderberg shale; 

unit D.

Figured specimen: Holotype cranidium, USNM 24643, 

USNM loc. 63. Plesiotype cranidium, USNM 108672, USNM 

loc. 62.
74 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Irvingella (Parairvingella) eurekensis (Resser)

Plate 6, figure 1 

Parairvingella eurekensis Resser, 1942b, p. 26, pi. 4, figs. 15-17.

Diagnosis. Members of Parairvingella. with subequally divided frontal area; axial length of frontal 

area on small cranidia (about 5 mm) about one-fourth 

axial length of glabella exclusive of occipital ring. 

Ocular ridges directed anterolaterally from anterolateral corners of glabella.

Discussion. This species is represented by only two 

cranidia, both from old collections and thus only approximately located stratigrphically within the Dunderberg shale. Both specimens are small, that is, axial 

length of cranidium less than 5 mm. They might, at 

first glance, merely seem to represent small specimens 

of /. (P.) angustiUtnbatus. However, the axial length 

of the frontal area is proportionately greater than 

that of the smallest specimen of /. (P.) angmtilimbatus (cranidial length 7 mm). Ontogenetic studies 

of most ptychoparioid trilobites show that the axial 

length of the frontal area generally increases with 

increasing size, and this is apparently true for the 

seven cranidia assigned to /. (P.) angustHhnbatu-s. 

It therefore seems improbable that the small specimens of /. (P.) eurekensis with the relatively long 

frontal area could be conspecific with /. (P.) angustilimlatus.

This species shows some similarity to one of the 

variants of Elviniella laevi-s n. sp. (pi. 6, fig. 14) from 

beds slightly lower in the Dunderberg shale. It differs from that specimen, however, principally by lacking the distinctly pointed anterior margin and having 

a subparallel-sided glabella. The series of forms occurring in apparent stratigraphic succession, beginning with Elviniella laevis in the middle Dunderberg 

shale and progressing through the variant just mentioned to Irvingella (Parairvingella} eurekensis and 

/. (P.) angustilimbatus in the upper beds of the Dunderberg shale, and finally to Irvingella (Irvingella} 

major in the basal beds of the overlying Windfall 

formation is suggestive evidence for close genetic relationships between Elviniella and Irvingella (p. 6-4).

Occurrence: Rare, upper Dunderberg shale; unit D. TJSGS 

colln. 789-CO.

Figured specimen: Holotype cranidium, USNM 108668, 

USNM loc. 61.

Family HOTJSIIDAE

History. This family name has been used by Hupe 

(1953, 1955) and Lochman (1956) to include only the 

genus Housia. Two of the genera here proposed, 

Prehowia and Parakmtsia, are added to the family 

and the diagnosis is modified accordingly.

Diagnosis. Cranidium with glabella tapered forward, well to poorly defined at sides by dorsal furrow, less well defined across front. Depressions tend 

to be developed in dorsal furrow at anterolateral corners of glabella. Glabellar furrows weak or absent. 

Palpebral lobes situated anterior to midlength of 

glabella and generally close to glabella, poorly defined on external surface. Facial sutures (fig. 8Z?, D} 

intramarginal three-fourths or more distance from anterolateral corners of cranidium to axial line. Rostral 

suture, if present, nearly marginal. Rostrum apparently present only in older genera; younger genera 

with median suture across doublure.

Pygidium with length generally less than width. 

Border broad, poorly defined, of nearly constant width. 

Axial lobe prominent, tapered posteriorly, generally 

bears two or more ring furrows; width i/3 to 1/4 width 

of pygidium.

Discussion. The anteriorly situated generally 

poorly defined palpebral lobes on the cranidium and 

the border of nearly constant width on the pygidium 

are the most distinctive characters of members of this 

family. The other features in the diagnosis are shared 

to some extent with the Pterocephaliidae, and it is 

probable that the two families are closely related.

In addition to the genera given above, the following genera or species may also belong to the Housiidae: 

Morosa, from the Dunderberg fauna (p. 98) ; "Aphelaspis" tumifro-ns Resser, from pre-Dunderberg rocks 

in eastern Nevada and western Utah and the Maynardville limstone member of the Nolichucky shale 

in Tennessee; and possibly Acrocephalaspis from the 

Upper Cambrian of Kazakhstan, Russia (Ivshin, 

1956), and TJllaspis from the late Middle Cambrian 

of Sweden (Westergard, 1948).

Genus HOUSIA Walcott 

Text figure 12

DolicJiometopus (Housia) Walcott, 1916, p. 374. 

Housia Walcott, 1924, p. 57; 1925, p. 93; Shinier and Shrock, 

1944, p. 625; Wilson, 1951, p. 642; Lochman, 1956, p. 456.

Type species. Dolichometopus (Housia} varro 

Walcott, 1916, p. 374, pi. 65, figs. 1-le,

Diagnosis. Housiidae reaching perhaps 60 mm in 

length, with cranidium having brim and anterior part 

of glabella depressed. Border at a distinct angle to 

brim; length (sagittal) slightly less than that of 

brim. Fixed cheek composed almost completely of 

flaplike palpebral lobe, that is situated adjacent to 

dorsal furrow anterior to midlength of glabella. 

Doublure of cephalon crossed by median suture.

Free cheek with moderately broad slightly convex 

border. Lateral and posterior marginal furrows moderately deep, not connected, disappearing near base 

of genal spine. Genal spine short or long.

Thorax with 10 to 11 thoracic segments. Axial lobe 

prominent. Pleural spines short, posteriorly directed.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 75

Pygidium transversely subovate in outline. Axial 

lobe prominent, well defined, extends to inner edge of 

broad, poorly denned border. Border maintains nearly 

constant width.

FIGURE 12. Partial reconstruction of Hoiisia ovata n. sp., 

about X 3.

Description. The genus has been well described by 

Walcott (1925) and Wilson (1951).

Discussion. Housia is found over most of North 

America in beds of the Elvinia- zone. The depressed 

brim and anterior part of the glabella and the extremely narrow fixed cheeks of the craiiiclium are 

the most distinctive features of the genus. In addition, species of Housia characteristically show unusual 

variation in the character of the anterior part of the 

pygidium. Commonly, the last thoracic segment is 

incompletely separated from the pygidium so that 

some pygidia have anterolateral spines, some have a 

thoracic segment developed on one pleural lobe and 

not on the other (pi. 7, fig. 6, developed left pleuron 

broken off), and some pygidia have no anterolateral 

spines. The retention of the last thoracic segment 

in the pygidium on some specimens causes a superficial resemblance of this genus to Proceratopyge. 

Whitehouse (1939) believed that the genera were 

synonyms. Both Wilson (1951) and Lochman (1956) 

have given good reasons for considering Housia as a 

distinct genus perhaps not even closely related to 

Proceratopyge. An additional and perhaps more important reason than those given by Wilson and Lochman is that the spine-bearing anterior pygidial segment of Proceratopyge is a fundamental part of the 

pygidium whereas that segment in Houxia is primarily a thoracic segment that has not been detached in 

normal fashion into the thorax. There is little evidence for or against the suggested relationship of 

Housia to the asaphidae by Wilson (1951).

Housia halli (Resser) 

Plate 7, ngure 8

Crepicephalus (Loganellus) maculosus Hall and WhitfieM 1877

(part), p. 215, pi. 2, fig. 26. 

Dunderbergia halli Resser, 1935, p. 23.

Discussion. The single pygidium original!"7 assigned to Crepicephalus (Loganelhis] maculosus by 

Hall and Whitfield and later made the type of a new 

species in Dunderbergia by Eesser represents a species of flousia whose pygidium differs from the pygidium of H. ovata n. sp. by being relatively broader and 

by having a proportionately wider border. It ir associated with cranidia of Bynumina globosa (Wtflcott) 

and probably came from limestones near the top of 

the Dunderberg shale.

The pygidium does not differ significantly from 

those assigned to H. vacww (Walcott) and H. canadensis (Walcott). When cranidia and free checks of 

H. hatti are found, it may prove to be a synonym of 

1 of those 2 species.

Occurrence: Rare, uppermost (?) Dunderberg shal^; unit

Figured specimen: Holotype pygidium, USNM 90670.

Housia ovata, n. sp. 

Plate 7, figures 1-7, 9

Diagnosis. Members of Housia with free cheeks 

having gently curved lateral margin and long, slender 

genal spine. Pygidium with length (sagittal) about 

two-thirds width. External surface of brim on cephalon, ocular platform of free cheek, and axial loH and 

pleural furrows of pygidium coarsely pitted.

Discussion. Cranidia alone cannot be used satisfactorily for identification of species of Hou$ia; however, the combined features of the cephalon and pygidium of this species distinguish it from the other species in the same genus. H. cansidensis (Walcott) and 

H. vacuna (Walcott) have pygidia with length (sagittal) only about one-half width. The free cheeks of 

H. vacunn and H. canadensis have short genal spines. 

The pygidia in the type lot of H. varro are distorted, 

but seem to have a shape intermediate between that of 

H. lacuna and H. or>ata. The free cheek of H. varro 

has a strongly curved lateral margin. A short genal 

spine is present on some specimens whereas others 

seem to lack a genal spine. H. haUi (Resser) is represented only by a pygidium that may be conspecific 

with either H. canadensis or H. vacuna.

Transitory pygidia of H. avata show that retention 

of partially developed thoracic segments with the 

pygidium is even more marked in the meraspid stage 

than in the adult. Several specimens of transitory 

pygidia in collection 955-CO have 3 to 5 almost completely developed thoracic segments (pi. 7, figs. 4, 9).
76 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

On all of these specimens, the grooves between the 

anterior segments of the transitory pygidium are less 

pronounced than those adjacent to the segment that 

will become the last segment of the thorax. The relatively poor differentiation of the anterior segments on 

the transitory pygidium is an unusual feature, because these segments are imminent thoracic segments 

and should be most nearly ready to be detached from 

the pygidium.

Two features are of importance for indicating the 

meraspid development of H. ovata: the last incipient 

thoracic segment on each transitory pygidium is distinctly macropleural, and the smallest transitory pygidium (pi. 7, fig. 9) has the greatest number (5) of 

incipient thoracic segments. The macropleural segment does not advance forward in the incipent thorax, 

indicating that it is probably truly the last thoracic 

segment. Thus, adults may also have the last thoracic segment macropleural. It is also probable that 

the transitory pygidium of meraspid stage 0 has 10 

to 11 partially developed thoracic segments fused with 

the pygidium and that during development these are 

successively shed forward into the thorax. Similar 

development has been shown for Macropyge gladiator 

Ross from the Lower Ordovician (Ross, 1951) and 

Ceraurinetta typa Cooper from the Middle Ordovician 

(Whittington and Evitt, 1954).

Occurrence: Moderately common, about 200 ft or more 

above base of Dunderberg shale; unit C. TJSGS colln. 789- 

CO, 864-CO, 872-CO, 955-CO.

Figured specimens: Holotype cranidium, USNM 136863, 

USGS colln. 872-CO. Paratypes: Free cheek and pygidia, 

USNM 136864a-c, USGS colln. 872-CO; cranidium, adult pygidium, and transitory pygidia, USNM 136865a-d, USGS colln. 

955-CO.

Genus PARAHOTTSIA n. gen.

Text figure 13

Type specie*. Paraho-usia. canstricta n. sp.

Diagnosis. Housiidae with frontal area short; 

length slightly less than one-half that of glabella. 

Marginal furrow shallow. Length (sagittal) of border almost twice length of brim. Palpebral lobes 

prominent, situated close to glabella and anterior to 

glabellar midlength. Palpebral furrow hardly visible. 

Fixed cheek narrow; width about one-fifth basal glabellar width.

Free cheek with conspicuous lateral and posterior 

marginal furrows that disappear near base of long 

slender genal spine and are not connected.

Pygidium strongly arched in transverse profile. 

Axial lobe prominent, extended to inner edge of poorly 

defined depressed border.

Description. Generally small trilobites (length 

probably less than 20 mm) with cranidium subtrapezoidal in outline, gently arched transversely and longiFIGURH 13. Partial reconstruction of Parahousia cvnstricta n. sp., 

about X 8.

tudinally. Anterior margin bluntly pointed. Glabella well defined by dorsal furrow, tapered strongly 

forward, slightly constricted between palpebral lobes, 

bluntly rounded anteriorly. Glabellar furrows hardly 

visible. Occipital furrow shallow, with sinuous course. 

Occipital ring broadest on axial line, with low median 

node. Frontal area short; length slightly less than 

one-half of glabella. Brim flat. Border slightly convex; length (sagittal) almost twice that of brim. 

Fixed cheeks narrow; width about one-fifth basal glabellar width. Palpebral furrow hardly visible. Posterior limbs tapered to a blunt tip; length (transverse) 

slightly less than basal glabellar width. Posterior 

marginal furrow moderately deep.

Anterior course of facial suture slightly divergent 

forward from palpebral lobe to marginal furrow, 

then turned abruptly inward across border to cut anterior margin at axial line. Submargiral course not 

known.

Free cheek with border, at anterior margin, well 

defined by moderately deep lateral marginal furrow; 

breadth about one-half breadth of ocular platform. 

Lateral marginal furrow disappears posteriorly near 

base of genal spine. Posterior marginal furrow moderately deep at junction with posterior limb, disappears laterally near base of genal spine; not connected with lateral marginal furrow. Genal spine 

moderately long, slender; length slightly less than 

length (exsagittal) of ocular platform.

Pvffidium subsemicircular in outline, moderately to *

strongly arched transversely. Axial lobe prominent; 

three shallow ring furrows generally visible. Pleural 

platforms triangular, gently arched, crossed by 3 or 4 

broad shallow pleural furrows that do not extend onto 

border. Border poorly defined, depressed, broadest at
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 77

anterolateral corners of pygidium, narrowed slightly 

on axial line. Posterior edge smooth.

Except for border of cheek and muscle scar areas, 

external surfaces of most parts of cephalon are covered with coarse pits. External surface of axial lobe 

and pleural platforms on pygidium with hardly visible coarse pits. Border of free cheek, genal spine, and 

anterolateral corners of pygidium with prominent terrace lines.

Discussion. This genus is closely related to Hou-sia 

with which it is associated. It has an almost identical 

glabellar shape, anteriorly placed palpebral lobes, and 

nearly identical free cheek. It differs from Plmt^ia 

by having broader fixed cheeks, a less depressed frontal area with proportionately broader border, and less 

sharply pointed posterior limbs on the cranidium. 

The pygidium has a depressed rather than nearly 

horizontal border.

Parahousia constricta n. sp. 

Plate 7, figures 16-18

Diagnosis. This is the only species presently known 

in Parahousia and its characteristics are described under the genus.

Discussion. This species is unlike any other species in the Dunderberg fauna. Its present known 

range is limited to the upper part of the Dunderberg 

shale.

Occurrence: Moderately common, 190-220 ft above base 

of Dunderberg shale; unit C. USGS colln. 955-CO, 2302-CO.

Figured specimens: Holotype cranidium, USNM 136870. 

Paratypes, free cheek and pygidium, USNM 136871a, b. All 

from USGS colln. 955-CO.

Genus PREHOTJSIA n. gen. 

Text figure 14

Type species. Prehousia tilata n. sp.

Diagnosis. Housiidae with frontal area short; 

length (sagittal) slightly more than one-half that of 

glabella. Border well defined, slightly convex; length 

(sagittal) between i/2 anc^ 3/4 that of brim. Palpebral 

lobes scarcely defined by palpebral furrow, situated 

anterior to glabellar midlength; length (exsagittal) 

between !/4 and ^ that of glabella. Fixed cheeks 

narrow; width one-fifth or less basal glabellar width.

Facial sutures cut anterior margin nearly at axial 

line.

Free cheek with well-defined border. Lateral and 

posterior margin furrows joined, not noticeably extended onto base of genal spine. Genal spine slender, 

tapered to sharp point; length less than greatest 

length of pleural platform.

Pygidium transversely subovate in outline; breadth 

greater than twice length. Axial lobe prominent, 

tapered posteriorly, merged with inner part of border; breadth one-third to slightly less than one-fourth 

greatest breadth of pygidium. Border moderately 

broad, separated from pleural platform only by gradual change in slope; maintains nearly constant vddth. 

External surface smooth, pitted, or finely granular 

in axial region.

FIGURE 14. Partial reconstruction, of PreJiousia alata n. sp., 

about X 5.

Description. Small to medium-sized trilobites 

(length of largest specimens about 50 mm). Cephalon subsemicircular in outline, moderately arched 

transversely and longitudinally. Cranidium subtrapezoidal in outline with slightly pointed anterior margin. Glabella well defined by shallow dorsal furrow 

of nearly constant depth; straight sided, tapered forward, bluntly rounded or truncate anteriorly. Glabellar furrows generally not apparent. Occipital furrow shallow, straight. Frontal area divided into distinct brim and border by shallow to moderately deep 

margin furrow that may develop a slight posterior 

median inbend or become perceptibly shallower on 

axial line. Border gently convex; length (sagittal) 

between i/£ and % that of brim, greatest on axial line. 

Brim gently convex. Fixed cheeks narrow; palpebral 

lobes hardly defined by palpebral furrow; low ocular 

ridges may be present. Width of cheek one-fifth or 

less basal glabellar width. Palpebral lobes situated 

anterior to glabellar midlength; length (exsagittal) 

between 1/4 and i/£ that of glabella; width from onehalf to slightly greater than width of cheek. Posterior limbs elongate triangular in outline; length
78 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

(transverse) about equal to basal glabellar width; tips 

bluntly pointed.

Anterior course of facial suture slightly divergent 

forward from anterior end of palpebral lobe to marginal furrow, then curved sharply onto and across 

border to cut anterior margin nearly at axial line. 

Posterior Course of facial sutures divergent-sinuous.

Free cheek with gently to moderately curved lateral margin. Genal spine slender, tapered to sharp 

point; length less than that of ocular platform. Border well defined, gently convex; width at anterior 

margin of cheek between 1/2 and 3/4 width of ocular 

platform. Lateral and posterior margin furrows of 

about equal depth, joined but not extended noticeably onto base of genal spine.

Pygidium transversely subovate in outline. Width 

greater than twice length. Axial lobe well defined, 

bears 2 or 3 shallow ring furrows; width from onethird to slightly less than one-fourth greatest width 

of pygidium; length about two-thirds that of pygidium; posterior end merges with inner part of border. 

Border differentiated from pleural platforms only by 

gradual change in slope. Width nearly constant. 

Pleural platforms crossed by 2 or 3 shallow pleural 

furrows. Posterior margin smooth.

External surface finely pitted, smooth, or finely 

granular in axial regions.

Discussion. This genus is widespread in rocks of 

latest Dresbach age in the Great Basin. A species of 

this genus was illustrated as n. gen. aff. Aphelaspis 

(Palmer and Hazzard, 1956, pi. 1, fig. 3). The type 

species and another undescribed form occur in the 

upper part of the Lincoln Peak formation in the 

southern Snake Eange, White Pine County, Nev. 

(Drewes and Palmer, 1957). The genus is based on 

the species from the Snake Range rather than on the 

one from the Eureka district because of the availability of more abundant and better quality material 

of the Snake Eange species.

Prehousia, as its name implies, is related to Housm 

and occurs consistently in beds older than those bearing species of Hoitsia. The subtrapezoidal shape to 

the cranidium, palpebral lobes placed anteriorly and 

close to the glabella, and the pygidium with poorly 

defined border of nearly constant width all emphasize relationships to flousia. The downsloping rather 

than depressed frontal area, slightly broader fixed 

cheeks and straight-sided well-defined glabella all 

serve to distinguish the genus from Housia. The 

shape of the glabella, course of the facial sutures, and 

shape of the pygidium indicate affinities to Aphelaspis. 

These relationships are the principal reason for considering the Housiiclae to be closely related to the 

Pterocephaliidae of which Aphelaspis apparently is 

the ancestral genus.

differs from Parahmt-sia by having the 

glabella straight sided rather than constricted between 

the palpebral lobes, the brim longer (sagittal) than 

the border on the cranidium, the pygidium transversely subovate in outline rather than subsemicircular, and the border of the pygidium nearly horizontal 

rather than depressed.

Prehousia alata n. sp. 

Plate 7, figures 10, 12, 13

Diagnosis. Members of Prehmisia with length of 

border (sagittal) only slightly greater than one-half 

length of brim. Palpebral lobes short, narrow; length 

slightly less than one-third length of glabella; width 

about one-half width of fixed cheek. Pygidium with 

tendency for border to develop alae at anterolateral 

margins. Width of axial lobe nearly one-third width 

of pygidium. External surface apparently smooth except for low fine granules on axial par* of glabella.

Discussio-n. Specimens of this species are abundant 

at three localities in the Snake Range, White Pine 

County, Nev. The species differs from P. semicircularis n. sp. by having smaller palpebral lobes, a 

broader brim, a broader axial lobe on the pygidium, 

and slightly alate anterolateral pygiclial margins.

Occurrence: Common, 130-146 ft below top of Lincoln 

Peak formation, southern Snake Range, White Pine County, 

Nev. USGS colln. 1197-CO, 1436-CO, 1441-CO.

Figured specimens: Holotype cranidium, USNM 136866. 

Paratypes, free cheek and pygidium, USNM J36867a, b. All 

from USGS colln. 1441-CO.

Frehousia semi circular is n. sp. 

Plate 7, figures 11, 14, 15, 19

Diagnosis. Members of Prehousia with length of 

border (sagittal) about three-fourths length of brim; 

palpebral lobes relatively large; length slightly less 

than one-half that of glabella; width slightly greater 

than width of fixed cheek. Pygidium with evenly 

rounded anterolateral corners; width of axial lobe 

slightly less than one-fourth that of pygidium. External surface smooth on all parts.

Discussion. The distinctions betweer this species 

and P. alata n. sp. are given in the discussion of P. 

alata.

Occurrence: Moderately rare, lower 20 ft of Dunderberg 

shale; unit A. USGS colln. 2294-CO.

Figured specimens: Holotype cranidium, USNM 136868. 

Paratypes, free cheek and pygiclia, USNM 136869a-c. All from 

USGS colln. 2294-CO.

Family OLENIDAE Burmeister

Heimingsmoeii (1957, p. 94) gives a detailed discussion of the characteristics of trilobites assignable to 

this family and points out that the included trilobites
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 79

are so varied that an objective diagnosis is virtually 

impossible. Most of the features considered essential 

to an olenid by Henningsmoen (1957, p. 95) are present on the trilobites discussed below.

Subfamily OLENINAE

Diagnosis. "Olenids with free cheeks with straight 

spine confluent with course of lateral margin or deviating only very slightly outwards.'' (Henningsmoen, 1957, p. 96.)

Discussion. Two closely related species of olenid 

trilobites, 01enu<s ? L wilsoni Henningsmoen and O.f granulatus n. sp. are present in the Dunderberg fauna. They 

differ from typical olenids by having a distinct juncture of the facial suture with the anterior margin of 

the cranidium and by having only 2 distinct ring furrows and 1 pair of pleural furrows on the pygiclium. 

The cranidial shape, as noted by Henningsmoen (1957, 

p. 112) for O.^ wilsoni, is rather more like Parabolma, 

than Olenus. The free cheek of O.I wilsoni, has characteristics more like Olenus than Parabolma. Pygidia 

of both species have fewer axial and pleural furrows 

and a slightly less rounded posterior margin than 

pygidia characteristic of either Olenus or Parabolma. 

Perhaps the two species here described represent a 

new olenid genus unknown in the extensively developed olenid faunas of western Europe.

Olenus? wilsoni Henningsmoen 

Text figure 15; plate 6, figures 18, 20-22

ParabolineUa incerta (Rasetti). Wilson, 1954, p. 280, pi. 26,

figs. 18-22. 

Olenusl wilsoni Henningsmoen, 1957, p. Ill, text fig. 117.

Diagnosis. Members of Olenus 1* with length (sagittal) of frontal area about one-third or slightly more 

than length of glabella exclusive of occipital ring. 

Length of border one-half or slightly more than 

length of brim. Palpebral lobes small, situated anterior to glabellar midlength. Width of fixed cheek 

slightly less than one-third basal glabellar width. 

Free cheek with obtuse inner spine angle. Facial suture cuts anterior margin at slight angle at point in 

front of anterolateral corner of glabella. Pygidium 

without marginal spines. Length (sagittal) slightly 

less than one-third width. Axial lobe with one ring 

furrow; pleural lobes with one pleural furrow. External surfaces of all parts smooth.

Discussion. This species differs from all known 

Olenus species in the combination of features given 

in the diagnosis. It is most similar to O.? granulatus 

n. sp., differing primarily by having a smooth rather 

than granular surface on the cranidium.

Occurrence: Moderately rare, 30-90 ft above base of Dunderberg shale; units A, B. USGS colln. 2295-CO(?), 2296- 

CO. 2297-CO, 2299-CO, 2300-CO.

FIGURE 15. Partial reconstruction of Olenusl wilsoni 

Henningsmoen, about X 12.

Figured specimens: Plesiotypes cranidia and pypidium, 

USNM 136858a, b, USGS colln. 2300-CO; cranidium ard free 

cheek, USNM 136859a, b, USGS colln. 2297-CO.

Olenus? granulatus n. sp. 

Plate 6, figures 23-27

Diagnosis. Members of Olenusl with length (sagittal) of frontal area about one-third length of glabella 

exclusive of occipital ring. Length (sagittal) of border slightly more than one-half length of brim. 

Palpebral lobes small, situated anterior to glabellar 

midlength. Width of cheek slightly more than onefourth basal glabellar width. External surface of 

most of cranidium covered with fine granules.

Pygidium transversely subovate in outline. Length 

about one-third width. Axial lobe prominent, bearing distinct articulating furrow and one ring furrow; 

subquadrate in outline; length about three-fourths that 

of pygiclium. Pleural lobes nearly flat, crossed by one 

deep furrow diverging backward from anterior margin. Border narrow, poorly defined, not crossed by 

pleural furrow. Lateral margin of pygidium sharply 

rounded. Posterior margin gently curved away from 

pygidium from lateral margin to point behind dorsal 

furrow, then gently curved towards pygidium to axial 

line producing a distinct angulation on margin directly behind dorsal furrows on each side of axial 

lobe. External surface covered with low fine granules.

Discussion. This species differs from all described 

species of Olenus by having a granular external surface. The transverse pygidium with only one ring 

furrow distinguishes it from all species except OA 

w ilson i Henningsmoen.

Occurrence: Moderately rare, 70-90 ft above base of Dunderberg shale; unit B. USGS colln. 795-CO, 2299-CO, 2300- 

CO.

Figured specimens: Holotype cranidium, USNM 136861, 

USGS colln. 2300-CO. Paratypes: Cranidium, USNM 136862,
80 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

USGS colln. 795-CO; pygidiuin, USNM 136860, USGS colln. 

2299-CO.

Family PTEROCEPHALIIDAE

History. Contents of a taxon bearing this name 

have been discussed by only two authors. Kobayashi 

(1935, p. 230) proposed the Pterocephaliinae as a subfamily of the Ptychopariidae. As in the Elviniidae, 

the genera grouped by Kobayashi seem to have little 

real relationship. Lochman (1956, p. 458, 459) presented a new combination of genera under this name 

that includes many of the trilobites grouped here in 

the subfamilies Aphelaspidinae and Pterocephaliinae. 

No statement of the family characteristics of the 

Pterocephaliidae was given by Lochman, however; it 

is not possible, therefore, to determine her grounds for 

the family grouping.

Diagnosis. The Pterocephaliidae as used here includes genera that share, in addition to stratigraphic 

and geographic continuity, the following distinguishing morphologic features: Cranidium with glabella 

tapered forward, generally well denned at sides and 

anterolateral corners by dorsal furrows, anterior end 

less well defined; glabellar furrows generally poorly 

defined when distinct, generally broad, rarely, if 

ever, deep and narrow; dorsal furrows with tendency 

to develop depressions at anterolateral corners of glabella ; border generally moderately broad and with 

breadth distinctly greater than distance from upper 

surface to lower surface of doublure; palpebral lobes 

generally well denned, subcentrally located; posterior 

limbs slender, sharply pointed. Facial sutures intramarginal three-fourths or more distance from anterolateral corners of cranidium to axial line (fig. 8A,E). 

Eostral suture, if present, nearly marginal. Kostrum 

apparently present only in older genera; most younger 

genera with median suture across doublure. Pygidium 

with broad border and doublure; width of axial lobe 

generally one-fourth or less that of pygidium; two or 

more ring furrows generally present; border poorly 

defined, generally noticeably narrower on axial line.

Discussion. Of the features listed above, the shape 

of the cranidium posterior to the front of the glabella and the course of the facial suture have been of 

primary importance in relating the genera of the 

Pterocephaliidae. Few North American genera from 

beds older than the Aphelaspis zone or younger than 

the Elvinia zone and few genera of any age outside 

North America have a glabellar shape of the type 

described above. Pterocephalopx (Easetti, 1944) from 

a boulder in the Levis conglomerate in eastern United 

States, MaladioideUa from the Upper Cambrian of 

Manchuria, and Nericia from the late Middle Cambrian of Sweden genera not known from the Great 

Basin are most likely to be representatives of this

family. Gronwallm from the late Middle Cambrian 

of Sweden may also belong to the Pterocephaliidae.

The Pterocephaliidae of this study are grouped into 

two subfamilies, the Aphelaspidinae and Pterocephaliinae, that are distinguished primarily en characteristics of the border of the cranidium anc1 secondarily 

on characteristics of the pygidium and free cheeks. 

Whether these taxa represent families or subfamilies is an unanswerable question. They are here considered as subfamilies to emphasize their many common features that seem to show real genetic relationships, while still permitting recognition of the distinctive features that separate the generic groupings.

Subfamily APHELASPIDINAE n. subfamily

Diagnosis. Pterocephaliid trilobites with border on 

cephalon well-defined, commonly conver; less commonly flat or slightly concave. Pygidium with border 

subequal in width to greatest width of pleural platform.

Discussioji. This subfamily includes the American 

genera Aphelaspis, Labiostria, Litocephalus, and 

Taenom, and possibly also MaladioideUa from the 

Upper Cambrian of Manchuria. Nericia as represented by its type species, N. quinquede^tata Westergard from the late Middle Cambrian of Sweden, has 

a cranidium strikingly similar to that of Labiostria, 

but differs in having relatively smaller palpebral 

lobes. The pygidium has a much narrower border 

than any of the species of the Aphelaspidinae. Nericia septemdentata Westergard, also from the late Middle Cambrian of Sweden, has a frontal area on the 

cranidium and border on the cheek much like Pterocephnlia, but an entirely different pygidium. Although the species assigned to Nericia seem referable 

to the Pterocephaliidae, they do not seem to belong 

to either of the subfamilies here described.

Labiostria as originally constituted (Palmer, 1954), 

included three species, the type species, L. conveximarginatus, L. platifrons, and L. sigmoidalis. L. 

phitifrons is tentatively assigned here to Taetwra n. 

gen., and L. sigmoidaliy, with its concave cranidial 

border, is removed from both the genus and the subfamily and related to Sigmocheiliis n. gen. in the 

Pterocephaliinae.

Aphelaspis, the oldest genus in the subfamily, represents perhaps the root stock of both the Aphelaspidinae and Pterocephaliinae. Although its cephalic 

border is distinct, it lacks the well-defined marginal 

furrow characteristic of the other genera in the subfamily. The pygidium also is relatively smaller and 

has fewer segments than pygidia in the younger 

genera.

Litocephalus and Taenora, as element? of the Dunderberg fauna, are discussed below.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 81

Trilobites of the Aphelaspidinae are the dominant 

elements of the trilobite faunas of the Aphela-spw 

zone. In the Dunder'bergia and Elvinia zones, they 

are subordinate in numbers of species to trilobites of 

the Pterocephaliinae and Elviniidae.

Genus LITOCEPHALUS Resser, 1937 

Text figure 16

Litocephalus Resser, 1937, p. 17; Palmer, 1956a, p. 608. 

Pterocephalina Resser, 1938, p. 42,

Type species. Dicellocephalus rwhnwndensis Walcott, 1884, p. 41, pi. 10, fig. 7 (=DiMloce phalu* Mobatus Hall and Whitfield, 1877, p. 226, pi. 2, fig. 36).

Daignosis. Aphelaspidinae with cephalon having 

border well defined by deep marginal furrow. Thorax 

with pleural spines of most segments long, slender, 

backwardly directed. Pygidium with border concave; 

posterior margin with deep median notch reaching 

nearly to posterior end of axial lobe.

Figure 16. Reconstruction of Litocephalus bilobatus (Hall and 

Whitfiekl), about X 2.

Description. Medium to large trilobites (up to 

about 85 mm in length) with exoskeleton elongate 

subovate in outline; widest about on line through

occipital ring. Cephalon subsemicircular in outline 

with prominent posteriorly directed genal spines.

Cranidium, exclusive of posterior limbs, elongate 

rectangular in outline, moderately arched transversely 

and longitudinally, moderately to strongly rounded at 

anterior margin. Glabella distinct, well defined, 

straight sided, tapered slightly forward, bluntly 

rounded or truncate anteriorly; commonly featureless, 

though traces of three pairs of slightly arcuate glabellar furrows may be seen on exfoliated specimens. 

Dorsal furrows deepest along side and at anterolateral 

corners of glabella, shallow on midline. Occipital 

ring with small median node. Occipital furrow moderately shallow, straight. Brim and border present, 

separated by a narrow marginal furrow. Brin flat. 

Border in profile arched up sharply from marginal 

furrow, then gently arched or flat to anterior margin; 

length (sagittal) from slightly more than one-half to 

about equal that of brim. Fixed cheeks nearly flat, 

slightly upsloping; width about one-third basal glabellar width. Palpebral lobes arcuate in form, moderately well defined by shallow palpebral furrow. Ocular ridges generally distinct. Posterior limbs narrow, 

sharp pointed; length (transverse) about equal to 

basal glabellar width.

Facial sutures diverge slightly to moderately forward from palpebral lobes until reaching marginal 

furrow, turn sharply inward to cut anterior margin 

near point directly in front of anterolateral corners 

of glabella, and continue submarginal nearly tc axial 

line where they curve sharply backward across 

doublure outlining edge of triangular or suttrapezoidal rostrum. Posterior course divergent-sinuous.

Hypostome elongate subovate in outline, strongly 

arched transversely and longitudinally. Anterolateral 

corners extended into short depressed pointed alae. 

Border narrow, distinct, present only along sides. 

Anterior lobe of central body not clearly differentiated from posterior lobe.

Free cheek with long, slender, sharply pointed anterior projection resulting from partly intramarginal 

anterior course of facial suture. Border separated 

from ocular platform by a narrow marginal furrow; 

profile similar to that on border of cranidium. Lateral and posterior marginal furrows of about equal 

depth; they join at genal angle and extend for a 

short distance onto genal spine as a shallow pointed 

depression. Iiifraocular ring present between eye 

surface and ocular platform.

Thorax probably composed of 13 segments. Axial 

lobe distinct, elevated above nearly flat pleural lobes. 

Pleural furrow of each segment broad, shallow, located at, or slightly anterior to, midlength (ersaggital) of segment, not extended to thoracic tip. Pleu-
82 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

ral spines on all but perhaps last two thoracic segments are long, slender, turned sharply backward 

from proximal portion of pleuron; length about equal 

to width (transverse) of proximal portion.

Pygidium wide, short, much smaller than cephalon. 

Axial lobe prominent, elevated above pleural platforms; 4 or 5 distinct axial rings and a bluntly pointed 

terminal part present; posterior margin of first segment distinctly separated on medial line from fused 

part of articulating half ring of second segment. 

Pleural platforms gently arched, downsloping; broad, 

shallow pleural furrows of 4 or 5 segments present, 

extending nearly across border. Border slightly concave, greatest width about equal to that of pleural 

platform; inner margin marked by narrow shallow 

straight furrow extending from tip of axial lobe to 

anterolateral corner of pygidium; lateral margin a 

broad curve extending from anterolateral corner of 

pygidium to base of prominent posterior medial notch 

near tip of axial lobe.

Discussion. Litocephalus is a distinctive genus 

characterized principally by the combination of a 

well-defined border and deep marginal furrow on the 

cephalon and by a deep median notch in the posterior 

margin of the pygidium. Three species of the genus 

are here recognized, based principally on consistent 

differences in the external surface of the cephalic border. The species have short and apparently mutually 

exclusive stratigraphic ranges within that of the 

genus.

Litocephalus bilobatus (Hall and Whit field)

Plate 7, figures 24-27

Dikellocephalus bilobatus Hall and Whitfield, 1877, p. 226, pi. 2'

fig. 36.

Dicellocephalus richmondensis Walcott, 1884, p. 41, pi. 10, fig. 7. 

Litocephalus richmondensis (Walcott). Resser, 1937, p. 17. 

Pterocephalina bilobata (Hall and Whitfield). Resser, 1942b,

p. 77, pi. 14, figs. 39-43.

Litocephalus bilobatus (Hall and Whitfield). Palmer, 1956a, p. 

608-610, pi. 73, figs. 1-6, 8.

Diagnosis. Members of Litocephalus with cranidium 

and free cheek having external surface of border smooth. 

Length (sagittal) of border about three-fourths that 

of brim. Facial sutures cut anterior margin between 

point directly in front of anterolateral corners of 

glabella and axial line. Pygidium with surface of 

axial rings smooth.

Discussion. The type lot of Litocephalus bilobatus 

comes from an unknown stratigraphic position within 

the Dunderberg shale and contains only pygidia of 

this species. Study of the Dunderberg shale fauna 

shows that 3 species of Litocephalus are present, and, 

for 2 of these, isolated pygidia cannot be certainly 

distinguished. Furthermore, pygidia of these two 

species are not distinguishable from the type of L.

bilobatus. Fortunately, on the same pieces of rock 

with the type pygidium and its counterpart, specimens of Morosa longixpina n. sp. and Dunderbergia 

variagranula Palmer are present. Only 1 of the 2 

species of Litocephalus in the stratigraphically controlled collections is associated with M. longwpina and 

D. variagranula, and that one is here considered as 

L. bilobatus. This indicates that L. bilobatus comes 

from the lower part of the Dunderberg shale in the 

Eureka district rather than from the upper part as 

stated earlier (Palmer, 1956a, p. 610). The conclusion is supported by the association of the specimens 

illustrated in 1956 (op. cit.) with Dunderbergia polybothra n. sp., known from only 1 collection in the 

measured section about 40 feet above the base of the 

Dunderberg shale.

Cranidia of L. bilobatus are distinguished from 

those of L. verruculapeza n. sp. and L. granuloniarginatus n. sp. by having a smooth external surface on 

the border. They are further distinguished from L. 

verruculapeza by having relatively large palpebral 

lobes. Pygidia of L. bilobatus cannot be distinguished 

with certainty from those of L. granulomarginatus, 

but lack the paired granules on each axial ring that 

characterize pygidia of L. verruculapeza.

Occurrence: Common, 50-70 ft above base of Dunderberg 

shale; unit B. USGS colln. 809-CO, 2297-CO, 2298-CO.

Figured specimens: Plesiotypes, cranidiur\ free cheek, 

pygidium, and thoracic segment, USNM 128324a. b, d, e, USGS 

colln. 1297-CO.

Litocephalus granulomarginatus n. sp. 

Plate 8, figures 14, 17, 18, 24

Diagnosis. Members of Litocephalus with cranidium having border moderately arched in longitudinal 

profile and covered with low fine granules. Border of 

cheek also covered with low fine granules. Length 

of border (sagittal) slightly less than three-fourths 

length of brim. Length of palpebral lobes about onehalf length of glabella exclusive of occipital ring. 

Facial suture cuts anterior margin between point directly in front of anterolateral corners of glabella and 

axial line. Pygidium with surface of axial rings 

smooth.

Discussion. Except for the fine-granular border on 

the cephalon, this species is like L. bilobatus (Hall 

and Whitfield). The larger palpebral lobes and the 

absence of scattered coarse granules on the border of 

the cranidium and the absence of paired granules on 

the axial rings of the pygidium distinguish this species from L. verruculapeza. n. sp.

Occurrence: Rare, 80-100 ft above base of Dunderberg 

shale; unit B. USGS colln. 795-CO, 2300-CO.

Figured specimens: Holotype cranidium, USNM 136883, 

USGS colln. 795-CO. Paratypes, pygidium ard free cheek, 

USNM 136884a, b, USGS colln. 2300-CO.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 83

Litocephalus verrucnlapeza n. sp. 

Plate 8, figures 12, 13, 15, 16, 19, 20

Diagnosis. Specimens of Litocephalus with cranidium having border nearly equal in length to brim, 

flattened in profile, and bearing scattered coarse granules. Palpebral lobes small, situated about opposite 

second glabellar furrow; length about one-third or 

less that of glabella exclusive of occipital ring. Facial suture cuts anterior margin almost directly in 

front of anterolateral corners of glabella. Pygidium 

with pair of coarse granules on each of first four 

axial rings.

Discussion. The small palpebral lobes, the scattered coarse granules on the border of the craiiidium, 

and the paired granules on the axial rings of the 

pygidium distinguish this species from the other 

known species of Litocephalus.

Occurrence: Moderately rare, 70-80 ft above base of Dunderberg shale; unit B. USGS colln. 2299-CO.

Figured specimens: Holotype cranidiuni, USNM 136881. 

Paratypes, cranidiuni, pygidia, and free cheeks, USNM 136882 

a-e. All from USGS colln. 2299-CO.

Genus TAENORA n. gen. 

Text figure 17

Type species. Taeno-ra e^pansa 11. sp.

Diagnosis. Aphelaspidinae with craiiidium having 

well-defined flat or slightly concave border of nearly 

constant breadth. Fixed cheeks flat, horizontal, width 

less than one-third basal glabellar width. Anterior 

course of facial suture moderately divergent forward 

from palpebral lobe to marginal furrow, intramarginal along most of anterior margin, cuts anterior 

margin nearly imperceptibly near axial line.

Free cheek with moderately broad flat or slightly 

concave border; lateral and posterior marginal furrows joined at base of genal spine, extended for short 

distance onto spine. Genal spine relatively short; 

length less than that of ocular platform. Pygidium 

transversely subovate in shape with poorly defined 

flat or concave border, with or without slight median indentation. Axial lobe prominent, merged posteriorly with inner part of border. All furrows on 

pygidium shallow.

Description. Medium to large trilobites (up to 

about TO mm in length). Craiiidium gently to moderately arched transversely and longitudinally, broadly 

rounded anteriorly. Glabella well defined at sides 

and anterolateral corners by shallow dorsal furrow, 

poorly defined across front; straight sided, tapered 

forward, bluntly rounded anteriorly. Three pairs of 

shallow glabellar furrows may be visible; posterior 

pair bigeiiiculate and 011 some specimens also bifurcate forming Y-shape with posterior branch of Y most

FIGDEB 17. Partial reconstruction of Taenora easpansa n. sp., 

about X 3.

deeply impressed; anterior pairs of glabellar furrows 

straight. Occipital furrow moderately deep, straight, 

shallowest on axial line. Occipital ring gently rrched 

(sagittally), with small median axial node. Frontal 

area divided into well-defined brim and border by 

shallow evenly curved marginal furrow. Border 

broad, flat, or slightly concave near anterior margin, 

horizontal or slightly downsloping, of nearly constant 

breadth. Brim flat or gently convex; length (sagittal) about equal to or less than that of border. Fixed 

cheeks flat, horizontal; width about % to !/£ basal 

glabellar width. Distinct ocular ridges present. Palpebral lobes well defined by shallow palpebral furrows, situated opposite or slightly posterior to midlength of glabella; length (exsagittal) i/£ to % length 

of glabella. Width about one-half width of fixed 

cheek. Posterior limbs slender, tapered to sharp 

point; length (transverse) about equal to basal glabellar width.

Anterior course of facial suture divergent forward 

from anterior end of palpebral lobe to marginal furrow, then curved slightly inward and crossing border 

nearly to anterior margin; intramargiiial from that 

point nearly to axial line. Junction with arterior 

margin hardly noticeable. Posterior course divergentsinuous.

Free cheek with gently convex lateral margin; 

genal spine short, flattened in cross section, trpered 

rapidly to sharp point; length less than that of ocular platform. Lateral and posterior marginal furrows joined and extended slightly onto base of genal 

spine.

Pygidium transversely subovate in outline with 

prominent axial lobe bearing 2 or 3 shallow ring furrows. Axial lobe tapered posteriorly, merged with
84 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

inner part of border or with poorly defined ridge that 

extends to margin; length slightly more than threefourths length of pygidium. Border flat or slightly 

concave, poorly defined; may have distinct median 

indentation. Pleural platforms with 2 or .3 shallow 

pleural furrows.

External surfaces of all known parts smooth.

Discussion. The most distinctive feature of trilobites of this genus is the form of the border on the 

cranidium. Taenora differs from Ldbwstrla, which 

is here restricted to forms with a convex cranidial 

border like that of L. conve.fimarginatus Palmer, and 

Litocephalus by having a flat or slightly concave 

somewhat downsloping border of nearly constant 

breadth on the cranidium. The fact that trilobites 

with this sort of border differ in relative breadth of 

border, size of palpebral lobes, impression of glabellar furrows, shape of genal part of free cheek and 

of posterior margin of pygidium indicates that the 

flat border may be a subfamily rather than a generic 

character. Until more species of this type are known, 

they are being included in the Aphelaspidinae.

Labiostria plat if ram Palmer from the Upper Cambrian of central Texas is tentatively referred to this 

genus.

Taenora expansa n. sp.

Plate 7, figures 20-23

Diagnosis. Members of Taenora with length (sagittal) of border almost twice that of brim. Palpebral 

lobes relatively short, about one-third length of glabella. Glabella with moderately well defined glabellar furrows, posterior pair on many specimens 

Y-shaped. Free cheek with border moderately broad, 

well defined, distinctly narrowed near base of genal 

spine. Pygidium short, wide; with distinct median 

indentation.

Discussion. This species differs from all other species in the fauna by having a nearly flat cranidial border of almost constant width and approximately horizontal fixed cheeks. The relatively wide border on 

the cranidium, shape of the genal part of the free 

cheek, and median indentation in the pygidium distinguish this species from T'.? pla-tifrom (Palmer). 

Two fragmentary cranidia, one each from USGS collections 795-CO and 2298-CO seem to belong to 

Taenora but cannot certainly be assigned to this 

species.

Occurrence: Rare, 70(?)-150 ft. above base of EHinderberg shale; units B(?), C. USGS colln. 954-CO, 2301-CO, 

7795-CO, 72298-CO.

Figured specimens: Holotype crandium, USNM 136872, 

USGS colln. 954-CO. Paratypes: Pygidium, USNM 136874, 

USGS colln. 954-CO; cranidium and free cheek, USNM 136873 

a, b, USGS colln. 2301-CO.

Subfamily PTEROCEPHALIINAE

Diagnosis. Pterocephaliid trilobites with border of 

cranidium generally broad, concave, and longer (sagittal) than brim. Border of free cheek generally 

broad, concave. Pygidium with broad, poorly defined border on most species.

Discussion. This subfamily includes at present only 

the North American genera Pterovephalia, Cenwolimbm, and ftigmocheilus. Similar foreign trilobites that 

may have some affinities with this subfamily are 

Nericia sept em-dent at a Westergard (p. 80) from the 

late Middle Cambrian of Sweden, and possibly Dikelocephalites flab ell if arm-is Sun, from the Upper Cambrian of China. The latter species is too poorly 

known, however, for adequate deterioration of its 

systematic position. Anechocephalm n. gen. (p. 92) 

may also belong to this subfamily.

Pterocephalinid trilobites are distinctive elements of 

the Dunderberg fauna and its correlatives over most 

of the Great Basin. They are not known from beds 

older than the post-Apfalaspis zone nor younger than 

the Elvinia zone.

Genus CERNUOLIMBUS n. gen. 

Text figure 18

Type species. Cernuolimbux orygmatos Palmer n. 

sp.

Diagnosis. Pterocephaliinae with cranidium having 

distinct brim and border; axial length of border equal 

to or slightly greater than axial length of brim; border 

generally downsloping. Anterior branches of facial 

suture cut anterior margin at distinct angle at a point 

slightly more than three-fourths distance from anterolateral corner of cranidium to axial line.

Free cheek with long genal spine and well-defined 

generally concave border. Lateral marginal furrow 

continuous with posterior marginal furrow. Breadth 

of border varies from one-fourth to slightly less than 

greatest breadth of ocular platform.

Pygidium subovate to subsemicircular in outline; 

axial lobe reaching more than three-fourths total axial 

length of pygidium, bearing 2 to 5 distinct ring furrows. Pleurae with 2 to -i low pleural r; bs extending 

nearly to margin. Border not clearly differentiated 

from pleural platform, concave, widest at anterolateral corners, tapers gradually posteriorly, narrowest 

on axial line.

Description. Medium-sized trilobiter (probably 

averaging -iO mm or less in total length) with cephalon subsemicircular in outline, moderately arched 

transversely and longitudinally, bearing long genal 

spines extending nearly straight back from posterolateral corners. Border well defined by shallow margi-
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 85

FIGURE 18. Partial reconstruction of Cernuolimbua orygmatos n. 

sp., about X 4.

nal furrow. Eyes prominent, at or slightly below 

level of top of glabella.

Cranidium with somewhat pointed anterior margin 

resulting from facial sutures cutting margin at a distinct angle near the axial line. Glabella well defined, 

straight sided, tapered slightly forward, bluntly 

rounded or truncate anteriorly. Glabellar furrows 

hardly visible. Occipital furrow straight, moderately deep. Occipital ring with low median node. 

Dorsal furrows deep at sides and anterolateral corners of glabella, shallow across front. Frontal area 

subequally divided into brim and border, or with border slightly longer (sagittal) than brim. Border 

downsloping, with anterior margin slightly flexed upward; flexure distinctly anterior to midlength (sagittal) of border. Brim gently arched in longitudinal 

profile. Fixed cheeks upsloping from dorsal furrow; 

width between palpebral and dorsal furrows slightly 

less than one-half basal glabellar width. Ocular 

ridges moderately well defined, directed obliquely 

backward from slightly behind anterolateral corners 

of glabella. Palpebral lobes prominent, well defined 

by shallow arcuate palpebral furrow; width about 

one-half width of cheek between dorsal and palpebral 

furrows; length about one-half length of glabella exclusive of occipital ring. Posterior limbs slender, 

sharply pointed; length (transverse) about equal to 

basal glabellar width. Anterior course of facial suture slightly divergent from anterior end of palpebral 

lobe to marginal furrow, then turned diagonally inward and forward across border to cut anterior margin slightly more than three-fourths distance from

anterolateral corner of cranidium to axial line. Posterior course divergent-sinuous.

Free cheek with long, slender genal spine continuing curvature of margin. Border well defined, generally concave. Lateral and posterior marginal furrows connected but not continuous posterolaterally 

onto genal spine.

Pygidium with axial lobe prominent, narrow, tapered posteriorly, bearing 2 to 5 distinct ring furrows. 

Length about three-fourths axial length of pygidium. 

Pleurae with 1 to -i low pleural ridges extending 

nearly to margin. Border not clearly defined, concave, widest at anterolateral corner, tapered backward 

to axial line.

Hypostome, rostrum, and thoracic segments not 

known.

Discussion. This genus seems to be ancestral to 

Pferocephah'a and ftigmo<eheilus. Cranidia can be 

most easily recognized by their pointed anterior margin and flat or slightly arched downsloping border 

that is only slightly longer (sagittal) than the brim. 

The free cheeks have the lateral and posterior marginal furrows characteristically connected and not extending onto the genal spine. Pygidia are most easily recognized by the combined features of an evenly 

rounded posterior margin and a border that is relatively narrower than that of other genera in the subfamily.

Cernuolimbus depressus n. sp.

Plate 8, figures 9, 10

Diagnosis. Members of Cernuolimbua with external surface of cranidium coarsely pitted; border 

downsloping, continuing slope of brim, tapered to a 

point laterally. Facial sutures nearly meeting on 

axial line giving pointed anterior margin to cranidium. Marginal furrow on mold bears single row of 

granules.

Discussion. This species is represented by four 

cranidia. No other parts are known. The character 

of the border is the most striking feature that distinguishes it from C. orygmatos n. sp. and C. semigranuloxus n. sp.

Occurrence: Rare, 50-60 ft above base of Dunderberg 

shale; unit B. USGS colln. 2297-CO.

Figured specimens: Holotype cranidium, USNM 136879. 

Paratype cranidium, USNM 136880. Both from USGS colln. 

2297-CO.

Cernuolimbus orygmatos n. sp.

Plate 8, figures 1, 3, 5, 8, 11

Diagnosis. Members of Cernuolimbus with external surfaces of all parts coarsely pitted. Border of 

cranidium slightly downsloping from marginal furrow, nearly flat or slightly turned up at anterior margin. Pygidium with subsemicircular outline; 4 well507219 O 59-
86 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

defined ring furrows; anterior 4 or 5 axial rings each 

bear a pair of coarse granules.

Discussion,. The distinctive coarse pitted surface 

serves to distinguish this species from G. semigranulos'iis n. sp. It differs from C. depresses n. sp. by having a relatively longer frontal area and less-pronounced lateral taper to the border of the cranidium.

Occurrence: Common, 30-50 ft above base of Dunderberg 

shale; units A, B. USGS colln. 2295-CO, 2296-CO.

Figured- specimens: Holotype cranidium, TJSNM 136875. 

Paratypes, free cheek and pygidia, USNM 136876a-c. All from 

USGS colln. 2295-CO.

Cernuolimbus semigranulosus n. sp. 

Plate 8, figures 2, 4, 6, 7

Diagnosis. Members of Gernuolinibus with border 

nearly flat or slightly turned up at anterior margin; 

generally downsloping from marginal furrow. External surface of cranidium smooth except for tops of 

palpebral lobes and glabella which are thickly covered with small granules. Free cheek with closespaced fine granules on genal spine; breadth of border 

equal to or only slightly less than greatest breadth of 

ocular platform. Pygidium transverse in outline with 

scattered barely visible fine granules over most of 

surface. Axial lobe with two moderately well defined 

ring furrows.

Discussion. This species differs from both Cernuolimbus depressus n. sp. and G. orygmatos n. sp. by 

having a fine-granular rather than coarse-pitted surface ornament. It differs further from G. depressus 

by having a much less laterally tapered and downsloping border on the cranidium, and from G. orygmatos by having a relatively wide border 011 the free 

cheek. The pygidium of G. semigran-ulosits lacks the 

distinct granules on the axial rings characteristic of 

G. orygmatos, and also has only 2 rather than 4 or 5 

distinct ring furrows. Its outline is proportionately 

shorter and wider than that of G. orygtnatos.

Occurrence: Moderately common, lower 20 ft of Dunderherg shale; unit A. USGS colln. 2294-CO.

Figured specimens: Holotype cranidium, USNM 136877. 

Paratypes, pygidium and free cheek, USNM 136878a, b. All 

from USGS colln. 2294-CO.

Genus PTEROCEPHAIIA Roemer, 1849

Text figure 19

Pterocpehalia Roemer, 1849, p. 421; 1852, p. 92; Bridge in 

Bridge and Girty, 1937, p. 247; Shinier and Shrock, 1944, 

p. 631; Palmer, 1954, p. 751.

Type species. PterocephaUa sanctisabae Roemer, 

1849, p. 421.

Diagnosis. Pterocephaliinae with cranidium having 

border broad, concave, scarcely differentiated from 

brim. Length of border (sagittal) greater than three

times length of brim. Junction of facial sutures with 

anterior margin generally imperceptible. Facial sutures stibmarginal beneath part of anterior margin to 

axial line, then turn abruptly backward to form median suture across doublure.

Free cheek with broad concave border, slightly 

raised above level of ocular platform Ft marginal 

furrow. A low ridge parallels entire lateral margin 

nearly to tip of genal spine at distance about onefourth width of border from lateral margin. Genal 

spine moderately long, broad and flat at base, tapered 

to sharp slender point.

Some thoracic segments with long broac1 backswept 

pleural tips.

Pygidium subquadrate to subovate in outline with 

well-defined axial lobe bearing 4 to 8 visible ring 

furrows. Border not differentiated from pleural platform gently arched, crossed by 3 to 5 pleural ridges 

that extend onto but not across border. Border broad, 

concave, with slight to moderate median indentation. 

Edge smooth.

External surface of exoskeleton generally with 

close-spaced fine granules in axial region. Borders of 

cranidium, free cheek and pygidium, and tips of pleurae of thorax generally with prominent terrace lines.

FIGURE 19. Partial reconstruction of Pterocephalit, sanctisabae 

Koemer, about X 2.

Description. Medium to large trilobites (length 

up to about TO mm) with large cephalon and pygidium. Cephalon with broad slightly concave border 

scarcely differentiated from brim on cranidium, with 

inner margin slightly raised above ocular platform
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 87

on free cheek. Length of border (sagittal) on cranidium is greater than 3 and up to 9 times that of brim. 

Low ridge present on border of nearly all free cheeks 

and many cranidia parallel to and about one-fourth 

breadth of border from margin. Genal spines broad, 

flattened, tapered to a sharp point. Glabella straight 

sided, tapered forward, truncate to bluntly rounded 

anteriorly, generally less than one-half length (sagittal) of cranidium. Dorsal furrows deep at sides and 

anterolateral corners of glabella, shallow across front. 

Three pairs of moderately deep glabellar furrows 

present on some species. Occipital furrow straight, 

deep adjacent to dorsal furrow, shallow across axial 

line. Occipital ring with low median node. Fixed 

cheeks broad, upsloping from dorsal furrows; width 

about one-half basal glabellar width. Ocular ridges 

generally well developed. Palpebral lobes moderately 

long, curved, midlength situated slightly posterior to 

midlength of glabella; length (exsagittal) about onehalf length (sagittal) of glabella; breadth (transverse) nearly one-half breadth of fixed cheek. Palpebral furrow moderately deep, arcuate. Posterior 

limbs slender; length (transverse) slightly greater 

than basal glabellar width.

Anterior course of facial suture slightly to moderately divergent forward from palpebral lobe until 

onto border, then curved broadly across border to cut 

anterior margin - nearly imperceptibly and continue 

submarginally to axial line where it turns abruptly 

backward as median suture across doublure. Posterior course of facial suture divergent, sinuous.

Entire thorax not known. Some thoracic segments 

with long broad pleural spines directed posteriorly.

Pygidium with elongate subquadrate to transversely 

subovate outline. Axial lobe well defined, tapered 

posteriorly to a blunt point at inner edge of broad 

border, generally continued across border as a narrow 

ridge. Four to eight ring furrows visible. Pleurae 

not clearly divided into border and pleural platform. 

Pleural platform generally slightly arched, crossed by 

3 to 5 well-defined pleural ridges. Border broad, 

slightly concave; broadest posterior and posterolateral to tip of axial lobe. Margin with slight to moderate median indentation. Edge smooth.

External surfaces of border of cephalon, distal parts 

of thoracic pleurae, and border of pygidium generally 

with well-developed terrace lines. Axial region of 

exoskeleton generally with close-spaced fine granules. 

Scattered large granules on the border may be present or absent within a suite of cranidia of a single 

species.

Hypostome not known.

Discussion. Bridge (1937, p. 246-250) discussed 

Pterocephalia and the species included in the genus to 

that time. He recognized three species, P. sanctisabae

Roemer, P. asiatica (Walcott), and P. occi-dens Walcott. Kobayashi (1936), unknown to Bridge, had 

placed P. asiatica in Paraco<osia. The types of this 

species are incomplete. The cranidium shows prominent bumps on the fixed cheeks adjacent to the dorsal 

furrow and just anterior to its junction with the occipital furrow. The pygidium has short broad spines 

along the margin. These features are here considered 

sufficient to exclude asiatica from Pterocephalm.

Resser (1938) placed specimens of P. sanctisabae 

illustrated by Bridge from various localities in the 

United States in 9 species of which 7 were new. On 

the basis of material from Oklahoma, Frederickson 

(1949) placed three of Resser's species in synonymy 

with P. sanctisabae. Lochman (1950) grouped three 

more of Resser's species together under the npme P. 

bridgei and considered this species distinguishable 

from P. sanctisabae by having a proportionately 

shorter frontal area on the cranidium. Wilson (1951), 

though not mentioning Resser's 1938 paper, included 

all the specimens illustrated by Bridge (1937) in the 

synonymy of P. sanctisabae, thus implying that all 

the species recognized by Resser in 1938 are syronyms 

of P. sanctisabae.

Part of the confusion in the taxonomy of specimens assigned to Pterocephalia results from th°, fact 

that specimens well-enough preserved to study are 

relatively rare, and few collections have sufficient individuals to permit adequate determination of infraspecific variation in the cranidial proportions that 

have been used for specific differentiation. Thus, 

Lochman's recognition of two species of Pterocephalia 

based solely on differing proportions between the 

length (sagittal) of the frontal area and the length 

of the glabella has an inadequate statistical basis. 

All the types and topotypes of the species of Pterocephalia recognized by Resser (1938) and regrouped 

by Lochman have been examined in the course of this 

study. For all the cranidia under 15 mm in length, 

no significant differences are observable in the length 

of the frontal area compared to the length of the 

glabella. Only 6 cranidia longer than 15 mm are 

present. These are distributed among four of the 

species recognized by Resser and include a cranidiuin 

of P. bridge!. Although there is variation in the 

relative lengths of the frontal areas compared to glabella lengths from slightly less than 1.5:1 to 2:1, and 

specimens representing P. bridgei and P. sanctisabae 

are nearly at opposite extremes, no sample has more 

than 2 of the large cranidia and determination of 

the significance of the variation in the proportion 

cited is not possible. Comparison of the variation of 

cranidial characters with size in Cambrian trilobites 

indicates that there is more apparent variation among 

larger specimens than among smaller specimens
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

(Palmer, 1958). Until more is known of the variation of craniclial proportions within a single population of P. xaiwtisabae) the characterization of P. 

bridgei by Lochman is considered inadequate for its 

separation from P. sauwtisabae and all species of 

Pterocephalia listed by Kesser (1938) are here considered synonyms of P. sanctisabae.

P. occidens Walcott is represented by a single small 

exfoliated craniclium (pi. 9, fig. 21) from an unknown 

level within the Dunderberg shale. It could represent either P. concava. n. sp. or P. elongata n. sp. 

Because of this, the species is here considered to be 

indeterminate and the name should be restricted to 

the holotype.

Pterocephalia cf. P. occidens from Texas (Palmer, 

1954) is more like P. concava n. sp. than any of the 

other species of Pterocephalia here recognized and 

should now be designated Pterocephalia cf. P. concava Palmer.

Pterocephalia concava n. sp.

Plate 9, figures 1-6, 9-12

IPterocephalia cf. P. occidens Walcott, Palmer, 1954, p. 752, 

pi. 86, figs. 9, 10; pi. 87, figs. 1, 2.

Diagnosis. Specimens of Pterocephalia with shallow glabellar furrows. Border of cranidium and free 

cheek generally with low scattered coarse granules. 

Length (sagittal) of border increases from 3 to 

greater than 5 times that of brim from small (4-5 mm 

long) to large (14 mm long) mature cranidia.

Some thoracic segments, perhaps all, with long 

broad flattened backwardly directed pleural tips. 

Breadth (transverse) of pleural tips greater than 

breadth (exsagittal) of proximal part of pleuron.

Pygidium transversely subovate in outline, with 

slight median inbend in posterior margin. Axial lobe 

with 4 to 5 distinct ring furrows. Pleural lobes 

crossed by 2 or 3 distinct pleural ridges. Breadth of 

border increases relative to breadth of pleural platform, and border becomes more concave with increasing size.

Discussion. This species, which occurs in preElvinia. zone beds, is most similar to P. sanctisaba«e 

from the Elvinia zone. It differs principally by having less conspicuous glabellar furrows, fewer distinct 

ring furrows and pleural ridges on the pygidium, and 

a strikingly different development of the mature specimens. Small mature specimens of P. concana (cranidial length 4-5 mm) are similar to forms of compparable size in Cemuolimbux and Sigmocheilus^ 

differing principally in the absence of clear distinction 

between the brim and border. Large specimens resemble P. sanctixaboe. Small mature specimens of P. 

sanctisabae, however, look virtually like the large 

specimens of P. sanctisabae (cf. pi. 9, figs. 1, 3, 4, 7). 

The change in form of mature specimens of P. concava, with increasing size emphasizes the relationships 

of Pterocephalia. to Cer-nuolitnbu-s and Sigmoch&ilus. 

The comparative mature development of P. concava 

and P. sanctisabae may be strong evidence indicating 

that P. concava is one of the earliest species of Pterocephalia.

P. concava. differs from P. elongata- n. sp. primarily by having a transverse rather than elongate subquadrate form to the pygidium and by having a less 

well-marked median indentation of tho posterior 

margin.

Occurrence: Moderately common, 50-60 ft above base of 

Dunderberg shale; unit B. USGS colln. 809-CO, 2297-CO. 

Specimens are questionably assigned to this species from USGS 

colln. 795-CO.

Figured specimens: Holotype cranidium, L'SNM 136887. 

USGS colln. 2297-CO. Paratypes : Cranidia, USNM 136888a-c ; 

free cheek, USNM 136888e; pygidia, USNM 1368S8d, f-h; thoracic segment, USNB 1368881. All from USGS c«»lln. 2297-CO.

Pterocephalia elongata n. sp. 

Plate 9, figures 14-20

Diagnosis. Members of Pterocephalia with shallow glabellar furrows. Length (sagittal) of border 

between 3 and 5 times length of brim.

Pygidium with elongate subquadrate outline. Greatest breadth near posterior margin. Sides straight, 

nearly parallel or slightly diverging posteriorly. Posterior margin nearly straight, with slight, median indentation.

Axial lobe with 4 or 5 distinct ring furrows. Junction of lateral and posterior margins strongly rounded. 

Two or three distinct pleural ridges parallel lateral 

margin of pygidium. A narrow ridge continues posteriorly from tip of axial lobe across border to posterior margin.

Hypostome and thoracic segments not known.

Discmsion. The shape of the pygidium of this 

species is its most distinctive feature. Isolated 

cranidia and free cheeks cannot be distinguished with 

certainty from those of P. concava. ThQ cranidium 

of P. elo-ngata differs from that of P. sanctisabae by 

having less conspicuous glabellar furrows, a somewhat more concave border, and a straighter posterior margin.

Occurrence: Moderately common, 80-100 ft above base of 

Dunderberg shale; unit B. USGS colln. 873-CO, 2300-CO.

Fifiitred specimens: Holotype cranidium, USNM 136891, 

USGS colln. 873-CO. Paratypes: Pygidium, USNM 136892, 

USGS colln. 873-CO; cranidium, free cheeks, and pygidia, 

USNM 136893a-c, USGS colln. 2300-CO.

Pterocephalia sanctisabae RoemePlate 9, figures 7, 8, 13

Pterocephalia sanctisabae Roemer, 1849,-p. 421; 1852, p. 92, pi. 

11, figs. 1 a-d; Bridge, 1933, p. 232, pi. 2, figs. 26, 27;
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 89

Kobayasni, 1936, p. 172, pi. 21, figs. 10-12; Bridge, in 

Bridge and Girty, 1937, p. 246, pi. 67, figs. 1 a-d; pi. 68, figs. 

7-43; Shinier and Shrock, 1944, pi. 266, figs. 35-37; Wilson, 

1949, p. 42, pi. 10, figs. 1-3; Frederickson, 1949, p. 355, 

pi. 69, figs. 1-4; (?) Wilson, 1951, p. 647, pi. 91, fig. 24.

Conocephalites (Pterocephalus) laticeps Hall and Whitfield, 1877, 

p. 221, pi. 2, figs. 4-7.

Dikellocephalus multicinctus Hall and Whitfield, 1877, p. 226, pi. 

2, fig. 37.

Pterocephalia dakotensis Resser, 1938, p. 39.

Pterocephalia bridgei Resser, 1938, p. 40; Lochman, 1950, p. 

334, pi. 47, figs. 14-18.

Pterocephalia oriens Resser, 1938, p. 40.

Pterocephalia potosiensis Resser, 1938, p. 40.

Pterocephalia ulrichi Resser, 1938, p. 41.

Pterocephalia silvestris Resser, 1938, p. 41.

Pterocephalia deckeri Resser, 1938, p. 41.

Diagnosis. Members of Pterocephalia with moderately deep glabellar furrows. Length (sagittal) of 

border on cranidium between 5 and 9 times length of 

brim on mature specimens.

Free cheek with breadth of border four or more 

times breadth of ocular platform at anterior margin.

Pygidium transversely subovate in outline, with at 

least 6 distinct ring furrows on axial lobe and with 

4 or 5 distinct pleiiral ridges on pleural lobes: Posterior'margin with slight median indentation.

Discussion. This species is a distinctive element of 

the Elvinia fauna over most of the United States. Its 

complicated nomenclatural history has been reviewed 

in the discussion of the genus. The extremely broad 

border on the cephalon, conspicuous glabellar furrows, 

and the many conspicuous ring furrows and pleural 

ridges on the pygidium are the distinctive specific 

features.

Occurrence: Rare, 140 ft or more above base of Dunderberg shale; unit C. USGS colln. 2301-CO, 2302-CO.

Figured specimens: Plesiotypes cranidium and free cheek, 

USNM 136889a, b, USGS colln. 2302-CO; pygidium, USNM 

136890, USGS colln. 2301-CO.

Genus SIGMOCHEILUS n. gen. 

Text figure 20

Type species. Sicpnocheflus serratus n. sp. 

DicK/nosi*. Pterocephaliinae with generally welldefined border on cranidium. Length of border (sag-

~ > ~

ittal) between 1.5 and 3 times greater than that of 

brim. Border generally concave in profile with greatest depth near its midlength (sagittal). Facial sutures cut anterior margin at slight angle between 

point opposite anterolateral corners of glabella and 

axial line.

Free cheeks with long genal spine and well-defined 

concave border. Lateral and posterior marginal furrows barely connected. Lateral marginal furrow 

shallowest; posterior marginal furrow continues onto 

genal spine. Breadth of border less than greatest 

breadth of ocular platform.

Pygidium sirbquadrate to transversely subovate in 

outline, greatest width about opposite posterior end 

of axial lobe. Axial lobe prominent, bears -i or 5 

ring furrows; tapered to a blunt point at inner edge 

of border. Border and pleural platform not clearly 

differentiated; 3 to 5 pleural ridges generally apparent, geniculated at boundary between pleural platform and border. Lines connecting geniculations 

roughly outline triangular pleural platforms. Pleural 

ridg-es ~ continued onto but not across border. Border

concave, posterior margin evenly rounded, nearly 

straight, or with slight median indentation. Edge 

smooth or with short broad spines.

FIGURE 20. Partial reconstruction of Sigmocheilus serratus, n. sp., 

about X 3.

Description. Medium-sized trilobites (probably 

averaging 40 mm or less in length) with cephalon 

subsemicircular in outline, ; moderately arched' transversely and longitudinally, bearing long genal spines 

extending nearly straight back from posterolateral 

corners. Border well-defined to poorly defined oh 

cranidium and on free cheek by shallow marginal 

furrow. Lateral marginal furrow barely connected 

to posterior marginal furrow. Eyes prominent, at or 

slightly below level of top of glabella.

Cranidium with anterior margin evenly rounded. 

Glabella well-defined, dorsal furrow deep at sides and
90 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

anterolateral corners, shallow across bluntly rounded 

front. Glabellar furrows shallow, posterior pair bigeniculate to slightly Y-shaped with posterior arm of 

Y most strongly developed. Occipital furrow straight, 

deepest adjacent to dorsal furrow. Occipital ring with 

low median node centrally located. Border concave 

in longitudinal profile, deepest part of concavity near 

midlength (sagittal). Length (sagittal) of border 

1.5 to 3 times that of brim. Marginal furrow shallow; 

junction between brim and border generally marked 

by contrast between strong veination or granulation 

of brim and nearly smooth surface of border. Inner 

margin of border sometimes slightly raised above adjacent brim surface. Fixed cheeks horizontal or upsloping. Ocular ridges low, extending backward to 

palpebral lobe from a point slightly posterior to 

anterolateral corners of fflabella. ~ Width of fixed

cheek slightly more than one-third basal glabellar 

width. Palpebral lobes well defined by arcuate palpebral furrow; width about two-fifths width of fixed 

cheek; length between % and 1/2 length of glabella. 

Posterior limb slender, sharply pointed; length 

(transverse) slightly less than basal glabellar width. 

Anterior course of facial suture slightly divergent 

forward from palpebral lobe onto border, then curved 

sharply inward across border to cut anterior margin 

between a point directly anterior to anterolateral corner of glabella and axial line; suture then submarginal to axial line and turned backward across 

doublure as median suture. Rostrum apparently absent. Posterior course of facial suture divergentsinuous.

Free cheek with long tapered genal spine. Border 

concave, well-defined to poorly defined along lateral 

margin by marginal furrow; breadth slightly less than 

greatest breadth of ocular platform. Shallow lateral 

marginal furrow not clearly connected to deep posterior marginal furrow.

Pygidium with axial lobe prominent, narrow, 

tapered posteriorly to inner edge of border; 4 or 5 

ring furrows generally visible; length (sagittal) between y2 and 3/4 length of pygidium. Pleurae with 

3 to 5 low pleural ridges extending laterally across 

poorly defined pleural platform and then turning 

backward onto, but not across, border at an angle of 

between 30° to 45° with axial line. Border concave. 

Posterior margin broadly rounded, nearly straight, or 

with slight median indentation. Edges smooth or 

with short broad spines.

Hypostome and thoracic segments not known.

External surface of cranidium generally partly covered with low small granules. External surfaces of 

other parts smooth or granular. Surface of molds of 

all parts smooth.

Discusxio-n. Species of this genus are most likely 

to be confused with those of CernuoUmbm or early 

forms of Pterwepkalia. Cranidia can be most easily 

recognized by a distinct concave border that is up to 

3 times longer (sagittal) than the brim. Free cheeks 

are characterized principally by having the border 

concave and narrower than the ocular platform. 

Pygidia of 8. grata and /?. utakensis resemble those 

of early species of Pterocephalia and can only be 

certainly assigned to ftigmockeihis when they are 

associated with the characteristic cranidium. Later 

pygidia with scalloped or spinose margins are distinctive of tiigmockeilus.

Resser (1942, p. 76-79) included in a genus PterocepJmlina four new species, P. texana, P. notka, P. 

pogonipenxis^ and P. grata besides the type species, 

P. bilobata (Hall and Whitfield). Pterocepkalma has 

since been shown to be a synonym of Litocepkalus* 

and P. bilobata to be properly Litoeepkalus bilobatus 

( Palmer, 1956a). Of the remaining species, all but 

P. te.vana belong to Sigmocheihis.

P. texana was stated to come from the Wilberns 

formation (Resser, 1942, p. 77) in Texas. An insoluble residue of a part of the limestone piece bearing 

the holotype pygidium contained AtiguJotreta triangularis Palmer, and fragmentary specimens of Apkelaspis are present adjacent to the pygidium. These 

associated fossils show that the holotype came from 

the Apk<ela*pi# zone of the Riley formation. The 

pygidium is probably that of a species of Labiostria.

Wilson (1954, p. 271) figured two fragmentary 

cranidia and referred them to Pterocepkalina cf. P. 

grata Resser. These cranidia represent an indeterminate species of fiigmockeilus.

Iddingsia* quinnemis Resser (1942, p. 88, pi. 16, 

figs. 39 41) is known only from cranidia. It definitely represents a species of Rignwckeihis, but its 

relationships to the species here described will not be 

known until its pygidium is described.

Sigmocheilus grata (Resser) 

Plate 9, figures 22, 23, 26, 27 

Pterocpphalina grata Resser, 1942b, p. 78, pi. 15, figs. 3-6.

Diagnosis. Specimens of Sigmockeilux with length 

of border (sagittal) between 2 and 3 times length of 

brim. Brim nearly flat. Fixed cheeks up^loping from 

dorsal furrow. External surface of border smooth or 

with few scattered low coarse granules. Remainder of 

surface of cranidium, exclusive of furrows, covered 

with low fine granules.

Free cheek with moderately well defined lateral 

marginal furrow. External surface smooth except 

for low veination.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 91

Pygidium with poorly defined border moderately 

expanded posterolaterally, posterior margin broadly 

rounded or straight, with slight median indentation 

on some specimens. Edge smooth. Two or three low 

pleural ridges visible.

Discussion. This species may require redefinition 

and subdivision when more is known of the associated cranidia, pygidia, and cheeks of early species of 

/Sigmocheilus. The present collections contain slightly 

differing forms, but there are not enough specimens 

to establish certainly limits of variation of the differing features within a population. In this paper, 

8. grata- includes forms with a smooth cranidial border, forms with a few low scattered granules on the 

border, and forms with slightly to moderately flared 

pygidial borders.

Occurrence: Moderately common, 50-80 ft above base of 

Dunderberg shale; units B and C. USGS colln. 952-CO, 2297- 

CO 2299-CO.

Figured -specimens: Plesiotypes cranidium, pygidium, and 

free cheek, USNM 136895a-c, USGS colln. 2299-CO; pygidium, 

USNM 136894, USGS colln. 952-CO.

Sigmocheilus pogonipensis (Resser) 

Plate 10, figures 4-7

Pterocephalina pogonipensis Resser, 1942b, p. 78, pi. 15, figs. 

1, 2.

Diagnosis. Specimens of 8igmochfilus with cranidium having brim strongly convex and border strongly 

concave. Length of border (sagittal) about 1.5 times 

length of brim. Front of glabella well defined because of arching of brim. Fixed cheeks upsloping 

from dorsal furrow. External surface of cranidium, 

exclusive of furrows and border, covered with low 

coarse granules.

Free cheek with poorly defined strongly concave 

border. Lateral marginal furrow hardly visible; 

posterior marginal furrow deep.

Pygidium with transverse subovate outline. Axial 

lobe about three-fourths length (sagittal) of pygidium. 

Border not clearly defined. Pleurae crossed by 4 or 5 

prominent pleural ribs; lateral parts bear prominent 

terrace lines. Margin bears six pairs of short asymmetrical spines.

Discussion. The strongly arched brim on the 

cranidium and short asymmetrical marginal spines on 

the pygidium are the most distinctive characteristics 

of this species. The holotype is from an unknown 

position within the Dunderberg shale in the White 

Pine district, Nevada.

Occurrence: Moderately common, 140-150 ft above base of 

Dunderberg shale; unit C. USGS colln. 954-CO, 2301-CO.

Figured specimens: Paratypes cranidium, free cheek, and 

pygidium, USNM 136900a-c, USGS colln. 2301-CO; cranidium, 

USNM 136901, USGS colln. 954-CO.

Sigmocheilus serratus n. sp. 

Plate 10, figures 1-3

Diagnosis. Members of Signwcheilux with cranidium having length of border (sagittal) about 1.5 times 

length of brim. Brim gently to moderately convex, 

border moderately concave. Fixed cheeks upsloping. 

External surface of top of glabella with close-spaced 

fine granules.

Free cheek with poorly defined moderately concave 

border. Surface of ocular platform with moderately 

prominent veination; border with moderately prominent terrace lines.

Pygidium transversely subovate in outline. Axial 

lobe about three-fourths length (sagittal) of pygidium. 

Border not defined. Pleurae crossed by 3 or -4 low 

pleural ridges. Posterior margin bears 5 or 6 pairs 

of broad rapidly tapered sharp marginal spine?; the 

pair nearest axial line generally shorter than the remaining pairs. Pleurae with numerous terrace lines.

Discussion. The relatively subdued convexity and 

concavity of the brim and border on the cranidium 

and the more prominent marginal spines on the pygidium distinguish this species from 8. pogonipensis. 

Isolated cranidia resemble those of 8. grata but have 

a relatively broader brim.

Occurrence: Moderately common, 190-220 ft above base of 

Dunderberg shale; unit C. USGS colln. 789-CO, 864-CO, 878- 

CO, 955-CO, 2302-CO.

Figured specimens: Holotype cranidium, USNM 136898a, 

USGS colln. 955-CO. Paratypes: Pygidium, on same block as 

cranidium, USNM 136898b, USGS colln. 955-CO; free cheek, 

USNM 136899, USGS colln. 864-CO.

Sigmocheilus utahensis (Resser)

Plate 9, figures 24, 25, 28 

Pterocephalina utahensis Resser, 1942b, p. 79, pi. 15, figs' 7-11.

Diagnosis. Specimens of 8igniO'cheilus with cranidium having border poorly defined by shallow marginal 

furrow. Length of border (sagittal) about 1.5 times 

that of brim. Brim gently convex and border gently 

concave. Glabella with moderately deep glabellar 

furrows. Fixed cheeks nearly horizontal. External 

surface of all but border of cranidium and furrows 

covered with close-spaced moderately coarse granules. 

Border with well-defined terrace lines.

Free cheek with poorly defined concave border. 

Pleural platform bears scattered coarse granules on 

external surface.

Pygidium with poorly defined border expanded posterolaterally and with moderately deep median indentation in margin. Two or three low pleural ridges 

generally visible. Surface of axial lobe and pleural 

platform seems to be roughened on larger specimens.

Hypostome and thoracic segments not known.
92 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Discussion. This species is the oldest of the four 

species here assigned to Sigmocheilus. The poorly defined border and coarse-granular surface on the cephalon and the deep indentation in the posterior margin 

of the pygidium are its most distinctive features. The 

holotype is from the Orr formation, Fish Springs 

Range, Utah.

Occurrence: Rare, 30-50 ft above base of Dunderberg 

shale; unit B. USGS colln. 795-CO, 2296-CO.

Figured specimens: Plesiotypes small cranidium, USNM 

136897, USGS colln. 795-CO; free cheek and pygidium, USNM 

136896a, b, USGS colln. 2296-CO.

PTYCHOPARIODEA UNASSIGNED

Species and genera are not assigned to families in 

this paper if they are either well represented, but unlike any other trilobites in the collection; represented 

by small numbers of specimens, generally only cranidia; or are nearly featureless. If a stable family 

classification of Cambrian trilobites is to be developed, 

it must be built from groupings of two or more genera 

in which at least some of the species are well represented by cranidia, pygidia, and free cheeks. Monotypic families, families of superficially similar trilobites from rocks having no paleogeographic or 

stratigraphic continuity, or families for trilobites that 

are inadequately known do not contribute to stability.

Genus ANECHOCEPHALUS n. gen.

Diagnosis. Pterocephaliidae ? with cephalon having 

short frontal area. Brim nearly vertical; border 

slightly arched, subequal in length (sagittal) to brim, 

nearly horizontal. Fixed cheeks elevated; width about 

one-third basal glabellar width. Palpebral lobes raised 

above level on top of glabella; length (exsagittal) 

about two-thirds length of glabella; width about twothirds that of fixed cheeks; midlength situated posterior to glabellar midlength.

Pygidium subquadrate in outline with short posteriorly tapered axial lobe; border downsloping, poorly 

defined, broad, flat, with broad deep median notch in 

posterior margin.

Description. Small pterocephaliid? trilobites (total 

length probably about 15 mm). Cranidium with glabella well defined at sides and anterolateral corners, 

poorly defined on axial line; glabellar furrows shallow; occipital furrow deep, of nearly constant depth. 

Occipital ring gently arched along axial line, with low 

median node near anterior margin. Frontal area short; 

length (sagittal) about one-third length of glabella; 

subequally divided into well-defined brim and border. 

Brim nearly vertical, continuing forward curvature of 

glabella. Border gently convex, nearly horizontal, 

tapered slightly laterally. Fixed cheeks elevated; 

width about one-third basal glabellar width. Palpebral lobes large, situated slightly above level of top

of glabella; length (exsagittal) about two-thirds 

length of glabella; width about two-thirds that of 

fixed cheek; midlength situated posterior to glabellar 

midlength; line connecting posterior ends passes just 

in front of occipital furrow. Posterior limbs slender, 

shape not known. Anterior course of facial sutures 

directed nearly straight forward from palpebral lobes 

to marginal furrow, then turned abruptly inward 

across border to cut anterior margin in front of glabella. Ventral course not known. Posterior course 

not known.

Free cheek, thoracic segments, and hypostome not 

known.

Pygidium subquadrate in outline. Axial lobe well 

defined, tapered posteriorly to inner edg3 of border; 

bears 2 or 3 shallow ring furrows; length about onehalf and width about one-third that of pygidium. 

Pleural platforms nearly flat, horizontal, crossed by 

2 or 3 shallow pleural furrows that extend slightly 

onto border. Border broad, flat, dowT nsloping, differentiated from brim only by change in slope. Posterior 

margin with broad deep median notch not reaching 

to end of axial lobe.

External surface of border of cranidium covered 

with distinct terrace lines. Remainder of cranidium, 

except for glabellar and occipital furrows, bears low 

coarse imperfect reticulate ornament. External surface of pygidium smooth except for transverse row of 

three low coarse evenly spaced granules n°,ar posterior 

margin on each side of median notch.

Discussion. This genus is represented by 3 cranidia 

and 3 pygidia of a single species from 1 collection. 

It is not referable to any described genus, and has distinctive enough features to warrant description even 

though represented by a small sample. The association of cranidium and pygidium is not certain, but it 

seems probable because these are the only unassigned 

parts of a pterocephaliid? trilobite in the collection 

from the type locality. Except for the frontal area, 

this genus has several characters of the Pterocephaliinae prominent posteriorly placed palpebral lobes 

on raised fixed cheeks, poorly defined border, and 

curved pleural furrows extending onto the border of 

the pygidium. The subequally divided frontal area 

with a nearly vertical brim and a narrow border that 

is convex instead of concave upward is unlike that of 

any pterocephalinid.

Anechocephalus trigranulatus n. sj\

Plate 8, figures 21-23

Description. In the absence of other species of 

Anechocephalus, the generic description is also a description of this species. The characteristics that will 

probably be most important in differentiating this 

species from any subsequently described are the reticu-
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 93

late surface ornament of the cranidium and the distinctive rows of coarse granules near the posterior 

margin of the pygidium.

Occurrence: Rare, 70-80 ft above base of Dunderberg 

shale; unit B. USGS collu. 952-CO.

Figured specimens: Holotype crauidium, USNM 136885. 

Paratypes, cranidium and pygidium, USNM 136886a, b. All 

from USGS colln. 952-CO.

Genus BY3TUMIELLA Resser

Type species. BynumieUa typicalis. Resser, 1942b, 

p. 57, pi. 10, figs. 1, 2.

Diagnosis. "Small trilobites with a tapering glabella without furrows. Dorsal and occipital furrows 

are well defined. The simple brim varies in width, 

but tends to extend forward in the middle causing the 

anterior outline of the cranidium to project." (Resser, 

1942, p. 57.)

Discussion. A single species from the lower part of 

the Dunderberg shale is tentatively assigned to this 

genus. BynumieUa is based 011 two species represented by only a few imperfectly preserved cranidia 

from beds of Franconia or Trempeleau age in the 

Canadian Rockies. Although the Dunderberg species 

seems to conform reasonably well to the generic diagnosis, the differences between this species and the 

Canadian species in both morphology and stratigraphic 

position indicate that another generic assignment may 

eventually result for the Dunderberg species when 

more is known about the relationships of the small 

smooth trilobites.

BynumieUa? acuminata n. sp. 

Text figure 21; plate 10, figures 9, 10

Description. Small trilobites (length of cranidium 

about 3 mm) with cranidium subtriangular in outline, 

moderately arched transversely, gently arched longitudinally, sharply pointed at anterior margin. Glabella poorly defined by shallow dorsal furrow, straight 

sided, tapered forward, bluntly rounded anteriorly. 

Glabellar furrows not apparent. Occipital furrow 

deep adjacent to dorsal furrow, shallow on axial line. 

Occipital ring widest on axial line, with low median 

node near anterior edge. Frontal area short, with 

straight shallow marginal furrow separating downsloping brim and border; length slightly less than 

one-third length of glabella. Border flat, sharply 

pointed on axial line, tapered rapidly to point before 

reaching anterolateral corners of cranidium; length 

(sagittal) almost twice length of brim. Fixed cheeks 

moderately narrow, flat, downsloping; width slightly 

less than one-third basal glabellar width. Palpebral 

lobes hardly differentiated from cheek; situated 

slightly anterior to glabellar midleiigth; lateral margin gently curved outward, only slightly interrupting

gentle inward curve of facial suture. Posterior limbs 

subtriangular; length (transverse) about three-fourths 

basal glabellar width. Posterior marginal furrow 

broad, shallow, straight. Anterior course of facial 

suture nearly straightforward from palpebral lobes, 

sharply curved inward before reaching margin?,! furrow, and continuing in straight line across border to 

cut anterior margin at distinct angle nearly at axial 

line. Posterior course divergent outward from palpebral lobe, nearly straight until across posterior marginal furrow, then curved backward to posterior margin.

External surface of occipital ring and posterior part 

of posterior limbs with many low coarse granules on 

some specimens, smooth or only faintly granular on 

others. External surface of remainder of cranidium 

smooth.

Free cheek with narrow poorly defined border. 

Ocular platform broad, smooth. Genal spine si ort.

FIGURE 21. Partial reconstruction of Bynumiellaf acuminata n. 

sp., about X 20.

Discussion. This species differs from B. typicalis 

Resser and B. briscoensis Resser by having a smooth 

rather than coarsely pitted external surface of the 

brim and cheeks and scattered coarse granule? near 

the posterior margin of the cranidium, a somewhat 

more truncate anterior end to the glabella, a more 

sharply pointed anterior margin on the cranidium, 

and an occipital furrow that is deeper near the dorsal 

furrow and shallower on the axial line. No other 

known species in the Dunderberg fauna is likely to be 

confused with this one.

Occurrence: Moderately common, about 40 ft above base 

of Dunderberg shale; unit B. USGS collu. 795-CO, 2296-CO.

Figured specimen.*: Holotype cranidium, USNM 136903, 

USGS collu. 2296-CO. Paratype free cheek, USNM 136904, 

USGS colln. 2296-CO.

Genus BYNUMINA Resser

Bunumina Resser, 1942, p. 58.

Type specie*. Bynuminn cueliita Resser, 19-i2b, p. 

58, pi. 10, figs. 18-22.

Diagnosis. Cranidium without distinct furrows on 

external surface. Anterior margin broadly rounded. 

No apparent border. Palpebral lobes small, situated
94 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

anterior to midlength of cranidium. Posterior course 

of facial suture diverges at nearly right angle to axial 

line just behind palpebral lobe, then curves broadly 

to posterior margin.

Free cheek subtriangular in outline, with rounded 

genal angles.

Pygidium simple, without distinctive generic features.

Description. Small nearly featureless trilobites 

(probably not much more than 10 mm in total length) 

with cranidium subtrapezoidal in outline, moderately 

arched transversely and longitudinally, without distinct external furrows. Exfoliated specimens have 

well-defined anteriorly tapered glabella, slightly 

rounded at front. Last two pairs of glabellar furTOAVS, when present, strongly curved posteriorly. Occipital furrow deep, straight. Occipital ring narrow, 

tapered laterally. Frontal area length slightly greater 

than one-third that of remainder of cranidium; shallow marginal furrow when present, separates brim 

and border of nearly equal length. Posterior limbs 

broad (exsagittal), shorter (transverse) than basal 

glabellar width, bluntly rounded or pointed at tips; 

marginal furrow only apparent near dorsal furrow. 

Anterior course of facial suture straight forward or 

slightly convergent from palpebral lobes to anterolateral corners of cranidium, then curved gently inward 

to cut anterior margin imperceptibly about in front 

of anterolateral corners of glabella. Posterior course 

nearly straight laterally directly behind palpebral 

lobe, then curved broadly ot posterior margin.

Free cheek subtriangular in outline, without welldefined border. Eye small. Genal spines absent, genal 

angles strongly rounded.

Pygidium subsemicircular in outline; axial lobe not 

distinctly differentiated on external surface; border 

not apparent. On exfoliated specimens, axial lobe 

tapers backward nearly to posterior margin, not well 

defined by dorsal furrow, bears up to five shallow ring 

furrows. First two axial segments more distinctly 

developed than more posterior segments in some 

species.

External surfaces of all parts smooth.

Discussion. Neither Resser (1942) when he proposed this genus for B. caelata Eesser and B. missourienxis Resser from the Davis formation of Missouri, 

nor Wilson (1951) when he added B. terrenda Wilson 

from the Ore Hill limestone member of the Gatesburg 

formation in Pennsylvania and compared it with the 

type species seems to have recognized that the types 

of the Missouri species are exfoliated cranidia. Reexamination of the type lots of B. caelata and B. misso-urienxix has turned up one cranidium in each lot that 

retains its exoskeleton. The appearance of these cranidia is much like that of B. terrenda (Wilson, 1951, 

pi. 89, fig. 10) and quite unlike the exfoliated specimens.

The gently rounded anterior margin, absence of a 

distinct cranidial border, and strongly divergent posterior course of the facial sutures on the cranidium 

distinguish species of this genus from other nearly 

featureless trilobites. A single distinct species, B. globosa (Walcott), represents this genus in the Dunderberg fauna.

The descriptions of the free cheek and pygidium are 

based on material from the Davis formation in Missouri.

Bynumina globosa (Walcott)

Plate 10, figure 8

Agraulosl globostis Walcott, 1884, p. 61, pi. 9, fig. 23. 

Kingstonia globosa (Walcott). Resser, 1936, p. 24.

Diagnosis. Specimens of Bynumina with cranidium 

having glabella nearly parallel sided, subquadrate in 

outline; anterior part somewhat elevated above adjacent cheeks. Thoracic segments, free cheeks, and pygidium not known.

Discussion. The distinct, although not clearly defined subquadrate glabella, is the principal feature 

distinguishing this species from others in Bynumina,. 

Its relations to the older genus Kingstonia cannot be 

determined until more is known of the?e nearly featureless trilobites.

Occurrence: Moderately common, upper Dunderberg shale; 

unit D. USNM loc. 61.

Fiyured specimen: Cranidium, USNM 136702, USNM loc. 

61.

Genus CHEILOCEPHALTJS Berkey

CheiJocephalus Berkey, 1898, p. 290; Palmer, 19>4, p. 757. 

Pseudolixania Kobayashi, 1935, p. 162; Shinier and Shrock, 

1944, p. 621.

The fragmentary material from the Dunderberg 

shale does not add any new information to the description of this genus already presented (Palmer, 1954).

Cheilocephalus spp. 

Plate 10, figures 13, 14

Discussion. Two cranidia and a pygidium from 

three different collections represent this rare but distinctive genus in the Dunderberg shale. None of the 

specimens are completely preserved. The two cranidia 

have a distinctive coarse granular extern?! surface and 

are perhaps referable to Cheiloceplialux l>uttsi Resser 

(Resser, 1942, p. 36, pi. 11, fig. 6; Wilson, 1951, p. 631, 

pi. 91, fig. 13). This species is known f-om only two 

cranidia in the Ore Hill limestone member of the 

Gatesburg formation in central Pennsylvania.

The pygidium is exfoliated so that, although it has 

a shape characteristic of pygidia of several species of
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 95

Cheilocephalus^ its external surface and thus its affinities are not known.

Reference of the Dunderberg material to new or 

described species must await more complete information about the morphology of associated cranidia and 

pygidia.

Occurrence: Rare, Dunderberg shale; units B, C. TJSGS 

colln. 864-CO, 872-CO, 2299-CO.

Figured specimens: Cranidium, USNM 136907, USGS 

colln. 864-CO; pygidium, USNM 136908, USGS colln. 2299-CO.

Genus DOKIMOCEPHALUS Walcott

Dokimocephalus Walcott, 1924, p. 55; 1925, p. 83; Shinier and 

Shrock, 1944, p. 623; Frederickson, 1948, p. 800; Wilson, 

1949, p. 36.

Type species. Ptychoparia? pernasutus Walcott, 

1884, p. 49, pi. 10, figs. 8, 8a-b.

Discussion. On the basis of relatively abundant 

material in Oklahoma and Texas, Frederickson (1948) 

and Wilson (1949) gave detailed descriptions of this 

genus. Only 2 imperfect cranidia and 1 free cheek 

represent the genus in the Dunderberg faunas.

Dokimocephalus resembles Iddingsia in having a 

prominent glabella with deep posteriorly directed glabellar furrows. It differs from Iddingsia primarily in 

having the border greatly extended anteriorly.

Dokimocephalus pernasutus (Walcott) 

Plate 11, figures 18, 20

Ptychoparial pernasutus Walcott, 1884, p. 49, pi. 10, figs. 8, 8a-b. 

Dokimocephalus pernasutus (Walcott). Walcott, 1924, p. 55, pi.

11, fig. 1; 1925, p. 84, pi. 16, figs. 29-31. 

'!'Dokimocephalus gregori Walcott, 1925, p. 84, pi. 16, figs. 32-33;

Shinier and Shrock, 1944, pi. 264, figs. 38, 39.

Diagnosis. Members of Dokimocephalus with border 

forming a pointed snout with concave sides and with 

tip curved down at end.

Discussion, This species is represented by 2 fragmentary cranidia and 1 free cheek that are inadequate 

for the preparation of a description of the species 

characteristics. Neither cranidiimi has its fixed cheeks, 

lateral margins, or external surface preserved. The 

free cheek is also exfoliated. Only one cranidium, the 

holotype, retains the distinctive pointed snout.

D. gregori Walcott, from Missouri, may be conspecific with D. pern<(*utus. It has a nearly identical 

shape to the border and differs only slightly in observable proportions of other cranidial features. Until 

better material of D. pernasuta is obtained, such a 

synonymy cannot be definitely established.

Occurrence: Rare, upper beds of Dunderberg shale; unit 

D. USNM loc. 61.

Figured specimens: Holotype cranidium, USNM 24608a. 

Paratype free cheek, USNM 24608b.

Genus IDDINGSIA Walcott

Iddingsia Walcott, 1924, p. 58; 1925, p. 97; Shimer and Shrock, 

1944, p. 627. Bell, and others, 1952, p. 184.

Type species. Ptychopario simiUs Walcott, 1884, 

p. 52, pi. 10, fig. 10.

Diagnosis. Cranidium with prominent glabella 

bearing 1 or 2 pairs of deep glabellar furrows. Frontal 

area expanded anteriorly, length between !/£> and % 

that of glabella; subequally divided into briri and 

border. Fixed cheeks generally upsloping, narrow; 

eye ridges prominent; palpebral lobes well defined, 

strongly bowed. Posterior limbs narrow (exsagittal) 

tapered to sharp pointFree cheek with deep lateral and posterior marginal 

furrows and long posterolaterally directed cylirdrical 

genal spine.

Pygidium transverse subtriangular in outline. Axial 

lobe prominent, slightly tapered, reaching to inner 

edge of poorly defined narrow border that is nearly 

absent on axial line.

Description. Medium to large trilobites (up to 

about 90 mm in length) with cranidium bearing prominent glabella well defined by dorsal furrow that is 

deep at sides, slightly bowed outward, and deep or 

shallow across front of glabella. One or two pairs 

of short deep posteriorly directed glabellar furrows 

always present. Occipital furrow broad, deep, deepest adjacent to dorsal furrow. Occipital ring generally with median node, rarely with median spine. 

Frontal area long (sagittal) ; length about two-thirds 

that of glabella; subequally divided into downsloping 

to depressed brim and gently downsloping to horizontal, concave, flat, or slightly arched border by shallow 

marginal furrow or sharp change in slope. Marginal 

furrow generally comes to blunt point on axis,! line. 

Fixed cheeks upsloping to elevated, bearing distinct 

posterolaterally directed eye ridges; width between i/s 

and V2 that of glabella. Palpebral lobes strongly 

bowed, well defined by deep palpebral furrow; length 

between % and V2 that of glabella; width i/£ to 14 

that of fixed cheeks. Posterior limbs narrow (exsagittal), dominated by broad deep posterior marginal 

furrow; tapered to sharp point; length (transverse) 

slightly less than basal glabellar width.

Anterior course of facial suture divergent from 

palpebral lobe to inner edge of border, then angled 

inward across border to cut anterior margin ir front 

of fixed cheek. Posterior course strongly dive.rgeiitsinuous.

Free cheek subtriangular in outline with bro^d flat 

or slightly arched border well defined by deep lateral 

marginal furrow. Lateral marginal furrow may or 

may not be connected to deep posterior marginal furrow. Genal spine long, large, cylindrical, straight, or
96 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

slightly curved, directed posterolaterally at slight angle to margin of cheek.

Pygidium transversely subtriangular in outline; 

axial lobe prominent, gently tapered posteriorly, 

bluntly rounded, extended to inner edge of border. 

Three or four distinct ring furrows present. Pleural 

platforms flat or slightly arched, bearing 1 or 2 shallow pleural furrows. Border narrow, poorly denned, 

tapered towards axial line, nearly absent behind axial 

lobs.

Thoracic segments and hypostome not known.

Discussion. Iddingsia was proposed by Walcott 

(1924, 1925) to include Ptychoparia similis Walcott 

and Ptychoparia similis robusta Walcott known only 

from cranidia in collections from the Eureka district, 

Nevada. A brief statement of the generic characteristics was given at that time. No subsequent description of the genus has been presented until now. Meanwhile, Kobayashi (1938) added 7. concava and Resser 

(1942a) added nine new species, 7. alpersensis^ I. anatina, I. bicincta, 7. crassimarginata, I. missouriensis* 

I. nevadensis, I. simplicitas* 7. iitahensis^ and 7. ? quinnensis. Wilson (1949) proposed a new genus, Plataspella, typified by 7. anafina, to include five of Resser's 

species that differed from 7. similis (Walcott) by possessing an occipital spine, shallow glabellar furrows, 

and "a much more flattened and laterally expanded 

border and brim which lack the convexity of those 

Iddingsia" Later, Wilson (1951) reported intergradation of features formerly thought to be distinctive 

of Iddingsia or Plataspella but continued to recognize 

Plataspella^ as a distinct genus. Bell, Feniak, and 

Kurtz (1952, p. 184) concluded that "the characters 

used by Wilson to separate Plataspella from Iddingsia 

are not generically significant * * *" and made Plataspella, a subjective junior synonym of Iddingsia. 

Lochman (1953) concurred with this conclusion. Since 

then, one additional species, 7. occidentals Delaiid and 

Shaw (1956), has been added to the genus.

To prepare a description of Iddingsia and determine 

its characteristics, type material for all the species 

assigned to Iddingsia except 7. occidentalis Deland 

and Shaw has been reexamined. In this complex of 

trilobites, the texture of the external surface of the 

cranidium, as in the Elviniidae, is the most reliable 

primary feature for differentiation of species. Within 

any one collection, all cranidia have the same external 

surface texture. None of the collections are large 

enough to provide adequate statistical basis for many 

of the slight differences in shape cited as distinctive 

for various species of the genus. Although some of 

the characters given by Wilson for Plataspella do not 

seem important as generic characters, there is a group 

of trilobites, including P. anatina (Resser), that lack 

conspicuous glabella furrows and differ among themselves in surface texture. They also generally have an 

occipital spine and nearly horizontal fixed cheeks. In 

the light of what has been learned during this study 

about the taxonomic importance of shape and surface 

texture in the better represented trilobite groups in the 

Dunderberg shale, the trilobites resembling P. anatina 

(Resser) and bearing the characters cited above are 

here considered to represent a separate genus from 

those resembling 7. similis. Only Iddingsia is represented in the Dunderberg faunas.

As now constituted, Iddingsm includes four described species with the following primary distinguishing external textural characters on their cranidia: 

7. similis (Walcott), top of glabella and occipital ring 

covered with close-spaced moderately coarse granules, 

fixed cheeks and frontal area smooth; 7. robusta (Walcott) (syn. 7. nevadensis Resser), entire cranidium 

covered with close-spaced generally small granules of 

several sizes; 7. utahensis Resser, surface of entire 

cranidium smooth though top of glabella f pintly roughened; 7. missouriensis Resser (syn. 7. crassimarginata 

Resser), glabella and occipital ring covered with low 

coarse granules, frontal area covered with close-spaced 

fine pits, fixed cheeks with both fine pits and low 

coarse granules.

Precise stratigraphic placement of 7. utahensis and 

7. missouriensis within the Elvinia fauna is not yet 

known. 7. similis occurs with other trilobites known 

only in association with Irvingella (IrvingeUa} major 

Ulrich and Resser in the basal beds of the Windfall 

formation which overlies the Dunderberg shale. Iddings id robusta is associated with trilobites known only 

in association with Kindbladia and Irvingella (Parair- 

 vingefla) in the upper beds of the Dunderberg shale.

The specimen identified by Bell, Fenial", and Kurtz 

as 7. similis (1952, pi. 30, fig. 4b) may represent a 

fifth species of Iddingsia characterized by an occipital 

spine. The other specimen identified as 7. similis by 

Bell, Feniak, and Kurtz (1952, pi. 31, fg. 2) represents a species of Plataspella. Species relationships 

of the remaining specimens of Iddingsia illustrated by 

Bell, Feniak, and Kurtz (1952), 7. nevadensis illustrated by Wilson (1949), and 7. occidentalis Deland 

and Shaw (1956) cannot be made without knowledge 

of their external surface textures. Iddingsia concava 

Kobayashi is represented by a single specifically indeterminate cranidium. 7.? quinnensis Resser belongs 

to fiigmocheilu-s n. gen. (p. 90).

Iddingsia robusta (Walcott) 

Plate 11, figures 13-16

Ptyclwparia similia robust us Walcott, 1884, p. 53, pi. 1, figs. 9,

9a. 

Iddinf/sia robusta (Walcott). Walcott, 1924, p. 97, pi. 16, figs.

10-11. 

Iddingsia nevadensis Resser, 1942b, p. 85, pi. 1C figs. 15-17.
TRILOBITES' OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 97

Diagnosis. Members of Iddingsia with dorsal furrow generally shallow across front of glabella. Length 

of frontal area slightly greater than one-half length 

of glabella. Brim and border separated by abrupt 

change in slope. Border nearly flat, slightly downsloping. Fixed cheeks upslopiiig; width about onethird basal glabellar width. Occipital ring with low 

median node. External surface covered with closespaced generally small granules of several sizes. Some 

of the granules along brim arranged in rows paralleling veinatioii.

Discussion. This species is represented only by cranidia. It differs from 7. similis (Walcott) from the 

overlying Windfall formation by having a granular 

rather than smooth surface on the brim and border. 

Exfoliated specimens of the two species cannot be 

identified or differentiated with certainty.

Iddingsia nevadensis Eesser is represented by one 

nearly completely exfoliated specimen that retains a 

small piece of the granular external surface of its 

border, and is not significantly different in any respect 

from 7. robusta.

Occurrence: The holotype is associated with Bynumina 

f/lobosa (Walcott), a species known only from the upper beds 

(unit D) of the Dunderherg shale.

Figured specimens: Holotype cranidiuni USNM 24609, 

USNM loc. 61; plesiotype cranidiuni, USNM 136924, USNM 

loc. 62; /. nevaden-sis holotype, USNM 108796, USNM loc. 61.

Genus KINDBLADIA Frederckson, 1948

ia Fredericks !, 194X, p. SXI2.

Type species. Berkeia wichitaensis Resser, 1942b, 

p. 93, pi. 15, figs. 31, 33.

Discussion. A good description of this genus was 

given by Frederickson (19-18) 011 the basis of abundant 

material from the Honey Creek formation in Oklahoma. The genus is represented in the Dunderberg 

shale by a single species, K. affinis (Walcott), known 

only from craniclia.

Resser (1942a, p. 7) included K. affinis in Berkeia 

without stating reasons why he had changed his earlier 

assignment of the species (Resser, 1937, p. 14) to 

Iddingsia. This species and most of the other species 

assigned to Berkeia by Resser (1942b) differ from the 

type species of Berkeia^ B. typica Resser, by having 

more strongly arched and upslopiiig fixed cheeks and 

by having three shallow depressions in the marginal 

furrow. Frederickson (1948) included species with 

these characters in his new genus Kindbladia. This 

genus can be distinguished from all others in the Dunderberg fauna by its prominent anteriorly tapered 

glabella, strongly rounded in front and bearing two 

deep pairs of glabellar furrows; deep dorsal furrow; 

narrow upslopiiig convex fixed cheeks; and short subequally divided frontal area with three shallow depressions in the marginal furrow.

Kindbladia affinis (Walcott) 

Plate 11, figures 17, 19, 20

Ptychoparia (Eulomal) affinis Walcott, 1884, p. 54, pi. 10, fig. 12- 

Iddingsia affinis (Walcott). Resser, 1937, p. 14. 

Berkeia. affinis (Walcott). Resser, 1942a, p. 7. 

Berkeia comes Resser, 1942b, p. 90, pi. 15, figs. 18-21. 

Berkeia nevadensis Resser, 1942b, p. 91, pi. 15, figs. 26, 27.

Diagnosis. Members of Kindbladia with occipital 

ring bearing median node rather than median spine.

Description. Small to medium-sized trilobites 

(probably about 20 mm in total length) with cranidiuni having prominent anteriorly tapered glabella, 

strongly rounded in front, with slight keel on axial 

line. Two pairs of short deep glabellar furrows generally present; posterior pair strongly curved backward. Dorsal furrow deep around entire glabella. 

Occipital ring well defined by deep occipital furrow; 

bears prominent median node. Frontal area short; 

length about two-fifths that of glabella; subequally 

divided by deep marginal furrow into brim and border both moderately to strongly convex and slightly 

downsloping 011 axial line. Marginal furrow broadly 

curved in dorsal view; depressions in marginal furrow 

shallow, most apparent 011 exfoliated specimens. Fixed 

cheeks moderately to strongly arched, upslopiiig from 

dorsal furrow, narrow; width slightly less than onefourth basal glabellar width. Palpebral lober well 

defined by palpebral furrow; width slightly mor?, than 

one-half that of cheek; length about two-fifths that of 

glabella. Posterior limbs tapered to a point laterally, 

downsloping; length (transverse) slightly less than 

basal glabellar width. Posterior marginal furrow 

deep, nearly straight. Anterior course of facial suture slightly divergent forward from palpebral lobes 

to marginal furrow, then curved strongly acrors border and apparently submargiiial to axial line. Posterior course divergent, sinuous. External surface covered with fine close-spaced granules.

Thoracic segments, free cheeks, pygidium, and hypostome not known.

Discussion. Nearly all the craiiidia of Kindbladia 

affinis and those in the type lots of the other species 

of Kindbladia are exfoliated. This tends to emphasize 

the depth of all the furrows and limits comparison 

of the described species. One of the rare specimens 

of K. affinis retaining its external surface is illustrated 

(pi. 11, fig. 17). No consistent distinction can be 

made between the specimens, mostly exfoliated, in the 

type lots of K. affinis, Berkeia nevadensis Resser, and 

B. comes Resser. They are here considered conspecific, 

and represent a species differing from K. wichitaensis 

(Resser) and A', retusa (Resser) by lacking an occipital 

spine.

Occurrence: Moderately rare, 230 ft or more above base 

of Dunderberg shale; unit D. USGS colln. 2303-CO.
98 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

Figured specimens: Holotype cranidium, USNM 24642, 

USNM loc. 65. Plesiotype, USNM 136925, USNM loc. 61. Holotype of K. nevadensis (Resser), USNM 108788a, USNM loc. 61.

Genus MINUPELTIS n. gen.

Type species. Minupeltis conservator n. sp.

Diagnosis. Small trilobites with subquadrate cranidium having glabella well defined only at sides; not 

denned across front. No distinct glabellar furrows. 

Occipital furrow straight, deepest on axial line. Frontal area with moderately well defined strongly arched 

(sagittal) border; inner part nearly horizontal, outer 

part nearly vertical. Fixed cheeks gently arched, downsloping; palpebral lobes small about opposite glabellar midlength. Posterior limbs short; length about 

two-thirds basal glabellar width. Anterior course of 

facial sutures straight forward from palpebral lobes 

to marginal furrow, curved inward across border to 

cut anterior margin in front of glabella.

Description. Small trilobites (total length probably less than 10 mm). Cranidium subquadrate in 

outline, gently arched transversely and longitudinally. 

Glabella prominent, well defined at sides by shallow 

dorsal furrow, not defined across front. Sides slightly 

bowed. Glabellar furrows not apparent. Occipital 

furrow straight, narrow, deepest on axial line. Frontal area downsloping; length (sagittal) slightly less 

than one-half length of glabella, subequally divided 

into brim and border. Border well defined by broad 

shallow marginal furrow; strongly arched in profile, 

inner part nearly horizontal, outer part nearly vertical. Brim not differentiated from front of glabella. 

Fixed cheeks gently arched, downsloping; width about 

one-third basal glabellar width. Palpebral lobes 

hardly differentiated from cheek, situated about opposite glabellar midlength; length about one-third that 

of glabella. Posterior limbs short, bluntly pointed; 

length (transverse) about two-thirds basal glabellar 

width. Posterior median furrow straight, shallow. 

Anterior course of facial suture nearly straightforward from palpebral lobes to marginal furrow, then 

curved abruptly inward across border to cut anterior 

margin between axial line and point opposite anterolateral corner of glabella. Posterior course of facial 

suture divergent from palpebral lobe, slightly bowed 

outward.

Free cheek, hypostome, thoracic segments, and 

pygidium not known.

External surface of all parts smooth, shiny on wellpreserved specimens.

Discussion. This distinctive trilobite is moderately 

common in the lowest collection from the Dimderberg 

shale. It does not resemble closely any described Upper Cambrian trilobite from western North America, 

or any other trilobite from the Aphelaspis, Dunderbergia, or Elvinia faunas. The overall form of the 

cranidium, except for the anterior course of the facial 

sutures, is similar to that of simple Lower Cambrian 

ptychoparioicls like Cmssifimbra (Palmer, 1958) ; hence 

the species name, conservator. The subequally divided 

frontal area, slightly bowed sides to the glabella, and 

small poorly defined centrally located palpebral lobes 

indicate possible affinities to solenopleurid trilobites, 

such as species of Parasolenopleura (Westergard, 

1953). Minupeltis differs from similar Lower Cambrian trilobites primarily by having the facial sutures 

cutting the anterior margin nearer the axial line; it 

differs from similar solenopleurid forms by having 

the front of the glabella not defined and by having 

the border strongly arched in longitudinal profile.

Minupeltis conservator n. sp. 

Plate 10, figures 11, 12

Description. This is the only species presently 

known in Minupeltis, and the description of the genus 

also gives the characters of the species.

Discussion. One cranidium in the type lot (pi. 10, 

fig. 12) is an unusual pathologic specimen on which 

the right side is not so well developed as the left. 

This is particularly noticeable on the posterior limb 

and at the right anterolateral corner of tl e cranidium.

Occurrence: Moderately common, lower 2C ft of Dunderberg shale; unit A. USGS colln. 2294-CO.

Figured, specimens: Holotype cranidium, USNM 136905, 

USGS colln. 2294-CO. Paratype pathologic cranidium, USNM 

136906, USGS colln. 2294-CO.

Genus MOROSA n. gen. 

Text figure 22

Type species. Morosa lon-gispina n. sp.

Diagnosis. Housiidae? with axial length of frontal 

area slightly less than one-third glabellar length. 

Frontal area subequally divided into well-defined brim 

and border. Border tapered laterally to a point just 

before reaching anterolateral corner of cranidium. 

Anterior margin in front view nearly horizontal; 

course of marginal furrow in front view strongly 

bowed upward. Glabella well defined. Glabellar furrows hardly visible. Fixed cheeks narrow, gently 

arched upward, nearly horizontal; width slightly less 

than one-fourth basal glabellar width. Palpebral 

lobes prominent, situated anterior to midlength of glabella. Occipital ring with prominent median node.

Free cheek with narrow border. Marginal furrow 

distinct at anterior margin, disappears posteriorly. 

Genal spine broad at base, flat, tapered to sharp point. 

Inner and outer margins straight.

Pygidium with prominent axial lobe extending to 

inner edge of moderately wide, slightly concave, poorly
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 99

defined border that maintains nearly constant width 

along entire pygidial margin.

External surface of exoskeleton except areas of 

muscle attachment covered with distinct pits. Surfaces of pleural lobes and axial lobe of pygidium also 

bear low fine granules. Surface of mold smooth or 

pitted.

Marginal parts of cephalon and pygidium with 

prominent terrace lines.

FIGURE 22. Partial reconstruction of Morosa lonr/ispinn n. sp., 

about X 15.

Description. Generally small trilobites (length 

probably less than 20 mm) with cranidium having 

well-defined straight-sided anteriorly tapered glabella, 

truncate anteriorly. Dorsal furrow deepest at sides 

and anterolateral corners of glabella, somewhat shallower across front. Occipital furrow straight, deepest at side of glabella, shallow on axial line. Occipital 

ring with prominent median node, Glabellar furrows 

generally not apparent. Frontal area short, depressed; 

length (sagittal) slightly less than one-third glabellar 

length. Border well defined, downsloping, tapered 

laterally to a point just before reaching the anterolateral corners of the cranidium. Course of marginal furrow when viewed from the front, strongly 

bowed upward. Length (sagittal) of border slightlv 

greater than length of brim. Fixed cheeks narrow, 

gently arched upward, nearly horizontal. Width 

slightly less than one-fourth basal glabellar width. 

Short poorly defined eye lines present. Palpebral 

lobes well defined by nearly straight shallow palpebral 

furrow; width slightly more than one-half width of 

fixed cheek; length slightly less than one-half length

of glabella. Posterior limbs slightly backswept; 

slightly shorter (transverse) than basal glabellar 

width. Posterior marginal furrow deep. Facial sutures divergent anteriorly from palpebral lobe almost 

to marginal furrow, then curved sharply inward 

across marginal furrow and border to cut anterior 

margin near, but not at, axial line. Submarginal 

course not known.

Thoracic segments and hypostome unknown.

Free cheek with ocular platform well defined along 

anterolateral and posterior margins, merges posterolaterally with genal spine. Border narrow; width 

at anterior margin between 1/3 and y± width of ocular 

platform. Lateral marginal furrow distinct but shallow at anterior margin, disappears posteriorly. Posterior marginal furrow deep at junction with posterior 

limb, disappears laterally. Genal spine broad s,t base, 

flat, tapered to a sharp point. Outer and inner margins straight. Length about two-thirds length of ocular platform.

Pygidium with prominent posteriorly tapered axial 

lobe bearing three conspicuous ring furrows and extending to inner edge of poorly defined border. Pleural platform triangular, crossed by 1 or 2 pleural furrows that do not extend onto border. Border slightly 

concave, maintains nearly constant width along pygidial margin. Posterior margin smooth.

Surfaces of all known parts of exoskeleton except 

muscle-scar areas on cranidium are covered with numerous distinct pits of variable size. Prominent terrace lines on margins of cephalon and pygidium. 

Pleural platform and axial lobe of pygidium with low 

poorly defined granules.

Discussion. This distinctive genus is represented 

by only a single rather common species that has no 

apparent ancestors or descendants in the Dunderberg 

shale fauna. It may belong to the Housiidae because 

of the anteriorly placed palpebral lobes on the cranidium and the even width of the pygidial border. However, the character of the frontal area and the distinct palpebral furrows are not typical of the family, 

and the genus is not here assigned to any family or 

subfamily.

Morosa longispina n. sp.

Plate 10, figures 15-17

Dia<nuwK. As this is presently the only described 

species of Morosa, the diagnosis is the same as that 

for the genus.

DiKciiMion. The range of this abundant species is 

sufficiently restricted to mark a distinctive faunal subzone within the Dunderberg shale. A second species 

of this genus is known, but not yet described, from 

the basal beds of the Nopah formation in California. 

It differs from J/. longispina principally in having
100 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

much shorter genal spines and a relatively broader 

free cheek.

Occurrence: Abundant, 40-100 ft above base of Dunderberg shale; unit B. USGS colln. 795-CO, 873-CO, 2296-CO, 

229S-CO 2300-CO.

Figured specimens: Holotype cranidium, USNM 136909, 

USGS colln. 2299-CO. Paratypes, pygidium and free cheek 

USNM 136910a, b, USGS colln. 2299-CO.

Genus OLIGOMETOPUS Resser 

Oligotnetopus Resser, 1936, p. 28.

Type species. Ptychoparia (Soleno pleura 1*} breviceps Walcott, 1884, p. 49, pi. 10, fig. 9.

Diagnosis. Small trilobites with cranidium having 

well-defined anteriorly tapered glabella reaching to 

marginal furrow. Border straight, thickened, nearly 

vertical. Fixed cheeks moderately arched, slightly 

downsloping; width about one-half basal glabellar 

width. Palpebral lobes small, narrow, situated below 

level of cheek about on line through glabellar midlength. Posterior limbs short; length (transverse) 

less than basal glabellar width. External surface of 

cranidium covered with low coarse granules.

Free cheek, hypostome, thorax, and pygidium not 

known.

Description. Small trilobites (length of cranidium 

about 4 mm) with cranidium subquadrate in outline, 

anterior margin nearly straight. Glabella prominent, 

well defined by broad dorsal furrow, straight sided, 

tapered forward, bluntly rounded anteriorly, extended 

to marginal furrow. Three pairs of broad shallow 

glabellar furrows visible. Occipital furrow deep, 

deepest adjacent to dorsal furrow. Occipital ring 

broken on known specimens, shape not known. Frontal area made up entirely of narrow border that is 

thickened and nearly vertical along entire anterior 

margin. Fixed cheeks broad, moderately arched upward, slightly downsloping; width about one-half 

basal glabellar width. Low ocular ridges extend 

obliquely outward and backward from junction of 

glabella with marginal furrow. Palpebral lobes well 

defined, small, situated below general level of cheek 

about on line through glabellar midlength; length 

about one-third that of glabella; width about one-fifth 

that of cheek. Posterior limbs short, bluntly terminated; length (transverse) less than basal glabellar 

width. Posterior marginal furrow broad, deep, 

straight. External surface of all parts except border and furrows covered with low coarse granules. 

Border bears conspicuous terrace lines.

Anterior course of facial suture slightly convergent forward from palpebral lobe to marginal furrow, then turned abruptly inward and nearly straight 

across border to cut anterior margin near anterolateral 

corners of cranidium. Posterior course directed laterally in a broad curve to posterior margin.

No other parts of exoskeleton known.

Discussion. This rare genus seems to have affinities 

to asiatic genera, such as Chuanc/ia and Pagodia, which 

also have broad fixed cheeks and a glabella that 

reaches to, or nearly to, the marginal furrow. OHgometopus differs from the asiatic genera either in 

the shape of the glabella or of the frontal area. No 

American or other foreign genera can be easily confused with Oligojnetopus. The placement of this 

genus in a family and adequate comparison with 

known genera must await knowledge of other parts 

of the exoskeleton.

Oligometopus breviceps (Walcott) 

Plate 10, figures 19, 20

Ptychoparia (Soletwpleura-l) breviceps Walcott, 1884, p. 49,

pi. 10, fig. 9.

Oliyometoptts breviceps (Walcott). Resser, 19?'3, p. 29. 

Stenelymus breviceps (Walcott). Raymond, 1937, p. 1101.

Discussion. Raymond's reference of this species to 

Stenelymus seems to have been based on inadequate 

knowledge of the holotype. The shapes of the fixed 

cheeks, glabella, and frontal area are urlike those in 

Stenelymus. Recently, Lochman (1953, p. 888) considered fSteneh/tm/s a synonym of Gen-evievella, a genus 

that is entirely unlike Oligometopus in its critical 

diagnostic features.

Besides the holotype, only one other cranidium of 

Oligometopus is known. This specimen shows that 

the species had a granular external cranidial surface 

rather than a smooth surface as stated by Walcott. 

The holotype, which has most of its external surface 

damaged, shows the granules on the posterior limbs.

Occurrence: Rare, 140 ft or more above base of Dunderberg shale; units C, D. USGS colln. 954-GO.

Figured specimens: Holotype, USNM 24577, USNM loc. 

62. Plesiotype cranidium, USNM 136913, USGS1 colln. 954-CO.

Genus PINCTTIS Wilson

Type specie*. Pinctus kitus Wilson, 1951, p. 646, 

pi. 93, figs. 1-4, 15.

Description. This genus was described by Wilson 

(1951, p. 646).

franidiuni small and bluntly triangular in shape, moderately 

convex with well-developed furrows. Glabella very long, prominent, convex, and quadrate with three pairs of well-impressed 

oblique furrows; occipital ring posteriorly extended at axis. 

Brim reduced and depressed; border prominent, widely arcuate, and considerably tapered; brim: border ratio about 1 or 

less. Fixed cheeks downsloping, moderately wide (ratio 2 or 

less) ; palpebral lobes small and thin, slightly anterior; posterior limbs broad and extended.

Facial .suture intramargiual almost to axis, I eginning to diverge already just behind anterolateral corner, indenting but 

slightly at each end of palpebral lobe, and sweeping outward 

behind it enough to give cranidium a wide base.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 101

Pinctus? spp. 

Plate 10, figures 18, 21

Three small cranidia represent two species of a 

trilobite possibly related to Pincutus latus Wilson. 

The cranidia are characterized by a prominent glabella; small anteriorly placed palpebral lobes; broad 

arched horizontal or slightly downsloping fixed cheeks; 

and a well-defined border about equal in length (sagittal) to the brim. Two of the cranidia, from USGS 

collection 952-CO, have the palpebral lobes distinctly 

defined, distinct glabellar furrows, and a border that 

is of nearly constant width across much of the front 

of the cranidiuni. The third cranidium, from USGS 

collection 953-CO, has undefined palpebral lobes, shallow, hardly apparent glabellar furrows, and a border 

that tapers rapidly laterally from the axial line, much 

like that of Morosti lon,gispina n. sp.

Both species differ from Pinctus latus in having 

smooth rather than fine-granular external surfaces and 

in having broader and shorter glabellas. Certain 

generic and specific identification of these trilobites 

must await more knowledge of the small trilobites in 

the Dunderberg and related faunas.

Occurrence: Rare, 60-120 ft above base of Dunderberg 

shale; units, B, C. USGS colln. 952-CO, 953-CO.

Figured specimens: Cranidiuni, USNM 136911, USGS 

colln. 952-CO; cranidiuni, USNM 136912, USGS colln. 953-CO.

Genus PSEUDOSARATOGIA Wilson 1951

Pseudosaratogia Wilson, 1951, p. 647.

Type species. Ps,eudosaratogiu magna Wilson, 1951, 

p. 648, pi. 94, figs. 9-16.

Diagnosis. Elviniidae? with flaring frontal area on 

cranidiuni; axial length of border about one-half or 

less axial length of brim.

Discussion. A complete description of this genus 

was given by Wilson (1951). Specimens of Pseudosaratogia are rare in the Dunderberg shale and do 

not provide any new information concerning the morphology of the genus. The two species here described 

have a rounded glabellar front and nearly horizontal 

cheeks, similar to Pseudosaratogia lata Wilson from 

the Ore Hill limestone member of the Gatesburg formation in central Pennsylvania. This species was 

considered a somewhat aberrant form by Wilson 

(1951). The palpebral lobes are also somewhat smaller 

than those of the Pennsylvania species. Nevertheless, 

the overall characteristics of the cranidia are more 

suggestive of Pseudosaratogia than other genus.

Pseudosaratogia leptogranulata n. sp. 

Plate 11, figure 10

Diagnosis. Specimens of Pseudosaratogia. with 

cranidiuni bearing prominent glabella that is bluntly

rounded anteriorly. Marginal furrow deep, narrow. 

Axial length of border slightly more than one-half 

that of brim. External surface exclusive of furrows 

and palpebral lobes covered with fine granules. Surface of mold pitted.

Discussion. This species is represented by six 

cranidia in USGS collection 954-CO. It is most similar to Pseudosaratogia- I at a Wilson (1951) but differs 

by having a more prominent glabella, a deep marginal furrow, and finer granular ornament present only 

on the external surface of the cranidiuni. Two cranidia in USGS collection 953-CO have the same shape 

as P. leptogramilata, but one is nearly smooth and 

the other has distinct and abundant coarse and fine 

granules on its external surface. The specimens are 

questionably assigned to this species.

Occurrence: Rare, 120-150 ft above base of Dunderberg 

shale; unit C. USGS colln. 953-CO(?), 954-CO.

Figured specimen: Holotype cranidium, USNM 136922, 

USGS colln. 954-CO.

Pseudosaratogia abnormis Palmer n. sp. 

Plate 11, figure 11

Diagnosis. Specimens of Pseudoxarato-gia with axial length of border about one-third that of brim; 

border separated from brim by abrupt change in slope; 

length (exsagittal) of palpebral lobes about one-third 

length of glabella exclusive of occipital ring; surface 

of cranidium covered with moderately coarse granules.

Discussion. A single cranidium from a collection 

about 60 feet above that bearing P. leptogranulata 

n. sp. has the characteristic flared frontal area, narrow upturned border separated from the brim more 

by a change in slope than by a marginal furrov^, narrow fixed cheeks, posteriorly placed palpebral lobes 

and granular external surface characteristic of species 

of Pseudosaratogia. It lacks conspicuous glabellar 

furrows, it has a shorter palebral lobe, and the glabella is more strongly arched longitudinally thpn any 

of the Pennsylvania species described by Wilson 

(1951).

This species differs from P. leptogranulata by having shorter (sagittal) border, less well-incised marginal furrow, and stronger surface granulation.

Occurrence: Very rare, about 220 ft above base of Dunderberg shale; unit C. USGS colln. 955-CO.

Figured specimen: Holotype cranidiuni, USNM If6923.

Genus and species undetermined 1 

Plate 11, figures 2, 5, 6

Two cranidia from USGS collection 2297-CO represent a trilobite unlike any other described from the 

Dunderberg or related faunas. It is characterized by 

low cranidial relief; a nearly parallel-sided squarely
102 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY

truncate glabella bearing three pairs of broad short 

deep slotlike glabellar furrows that are isolated from 

the dorsal furrows; an anteriorly flared frontal area 

with a narrow border of nearly constant width; and 

wide fixed cheeks bearing large well-defined arcuate 

palpebral 4obes.

A third cranidium (pi. 11, fig. 5) in this collection 

probably is congeneric and perhaps conspecific with 

the forms described above. It differs from them principally by having the glabellar furrows marked by 

broad and shallow rather than deep depressions.

Proposal of new names is deferred until more material can be obtained to determine more clearly the 

relationships of these cranidia.

Occurrence: Rare, 50-60 ft above base of Dunderberg 

shale; unit B. USGS colln. 2297-CO.

Figured specimen: Cranidia, USNM 13G915a-c.

Genus and species undetermined 2 

Plate 11, figure 1

A cranidium from USGS collection 2295-CO represents a species that is most similar to genus and 

species undetermined 1. This species is characterized 

by low relief on the cranidium, an expanded frontal 

area with a narrow raised border, a straight-sided 

slightly tapered truncate glabella, and broad fixed 

cheeks bearing large well-defined arcuate palpebral 

lobes. It differs from genus and species undetermined 

1 by having a raised rather than flattened border, an 

anteriorly tapered glabella, and somewhat more posteriorly placed palpebral lobes.

Occurrence: Rare, 40-50 ft above base of Dunderberg 

shale; unit A. USGS colln. 2295-CO.

Figured specimen: Cranidium, USNM 136914.

Genus and species undetermined 3 

Plate 11, figure 3

An incomplete but distinctive elongate pygidium 

from USGS collection 2297-CO cannot be assigned to 

any described trilobite from the Dunderberg fauna. 

It has a long slender well-defined axial lobe bearing 

S ring furrows becoming shallower posteriorly; elongate downsloping pleural lobes bearing 6 shallow 

pleura 1 furrows; and a narrow concave poorly defined border. The posterior margin is curved sharply 

upward and inward to the axial line forming an inverted V when viewed from the rear.

This pygidium shows most similarity to that of 

Cliffia latagenae (Wilson) from the Ore Hill limestone member of the Gatesburg formation in central 

Pennsylvania. It differs by possessing a narrow border and by lacking median nodes on each segment of 

the axial lobe.

Occurrence: Very rare, 50-60 ft above base of Dunderberg shale; unit B. USGS colln. 2297-CO.

Figured specimen: Pygidium, USNM 136916.

LOCALITY INFORMATION

The collections referred to in this pap°r are catalogued under 1 of 2 sets of numbers except for the 

collections studied by Hall and Whitf-ld (1877). 

These were listed only as coming from the Eureka 

district without more precise locality data. They 

have never been given locality numbers.

Many of the collections obtained from the Eureka 

district before 1900 are listed in the U.S. National 

Museum locality catalogue. Specimens from these 

collections bear green paper circles with handwritten 

locality numbers.

Collections since 1939 by the U.S. Geological Survey are listed by collection number in the USGS 

Cambrian-Ordoviciaii locality catalogue. Specimens 

from these collections bear orange paper circles or 

rectangles with machine-printed collection numbers. 

USGS collection numbers referred to in the text bear 

the suffix U-CO" to differentiate them from a parallel 

series of numbers in the Silurian-Devonian (suffix 

"-SI)") locality catalogue.

Unless otherwise indicated in the list below, the 

collections are from the Eureka mining district, Eureka County, Nev. Most of the geographic features 

that are referred to in the locality descriptions are 

shown on the Eureka and Pinto Summit (15-minute) 

quadrangles. Exact location of the measured section 

is shown in figure 6.

USGS collection

795-CO.

Locality description and collector

From limestone in the Dunderberg shale, 

about 200 ft above the Hamburg dolomite. 

In place. 2,050 ft S. 18 E. of the Hamburg 

shaft. Elev 8,025. Josiah Bridge, 1939.

Near base of Dunderberg shale on road to 

Catlin shaft, about 250 ft from New York 

Canyon road. In place. 760 ft S. 29 E. 

of the Catlin shaft. Elev 7,480 ft. 

Josiah Bridge, 1939.

USGS collection

809-CCL

864-CO.

Locality description and collector

Southwest slope of Hoosac Mountain, east 

of the high pinnacle of Hamburg dolomite. 

East of spring in tributary of Secret 

Canyon. In place. 4,980 ft S. 5 E. of the 

Windfall shaft. Elev 8,075 ft. Josiah 

Bridge, 1939.

North side of Widewest Canyon. 900 ft N. 

55 E. of Cyanide shaft. Elev 6,470 ft. 

Josiah Bridge, 1939.
TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 103

USGS collection

872-CCL

873-CO952-CO953-CC),

954-CO955-CO.

1197-CO_

1297-CO.

1436-CO.

1441-CO__.

Locality description and collector

Dump of prospect 1,350 ft N. 64 W. of

USMM 1 10, near Bullwhacker mine.

(Northern 1 of 2 prospects close together.)

Elev 6,327 ft. Josiah Bridge, 1939. 

Dump of prospect 1,300 ft S. 74 W. of

USMM 1 10 (near Bullwhacker mine).

Elev 6,365 ft. Josiah Bridge, 1939. 

Dunderberg shale section, extending east of

prospect pits, 500 ft north of Windfall

shaft, Windfall Canyon, 67 ft above base

of Dunderberg shale. A. R. Palmer and

A. B. Shaw, 1951. 

Same locality as 952

Dunderberg shale.

A. B. Shaw, 1951. 

Same locality as 952

Dunderberg shale.

A. B. Shaw, 1951. 

Same locality as 952

Dunderberg shale.

121 

A.

ft above base of 

R. Palmer and

144 ft above base of 

A. R. Palmer and

215 ft above base of 

A. R. Palmer and 

A. B. Shaw, 1951.

Nevada, White Pine County, Wheeler Peak 

quadrangle. Cambrian section on south 

side of the south fork of Lincoln Canyon, 

at junction with north end of Johns Wash, 

irregular to nodular limestone with shale 

partings; 150 ft below top of Lincoln Peak 

formation. A. R. Palmer 1952.

East side of Sierra Canyon, first baked shale 

outcrop seen after entering from the south. 

Josiah Bridge, 1939.

Nevada, White Pine County, Wheeler Peak 

quadrangle. North trending canyon just 

below Johns Wash limestone, sec. 23, T. 

12 N., R. 69 E. on south line of section at 

elev 7,080 ft. A. R. Palmer-, 1953.

Nevada, White Pine County, Wheeler Peak 

quadrangle. Cambrian section on south 

side of south fork of Lincoln Canyon at 

junction with the north end of Johns 

Wash; 150 ft below top of Lincoln Peak 

formation. A. R. Palmer, 1953.

Windfall Canyon section, north side of spur 

due east of New Windfall shaft, about 12 

ft above Hamburg dolomite; 2-in. limestone bed. A. R. Palmer and R. J. Ross, 

1957.

USGS collection

2295-CCL

2296-CO,

2297-CO.

2298-CO.

2299-CCL

2300-CO.

2301-CO,

2302-CO.

2303-CO_

USNM locality

61.

62

63 _ 

65-

Locality description and collector

Windfall Canyon section, about 30 ft above 

Hamburg dolomite; 8-in. limestone bed. 

A. R, Palmer and R. J. Ross, 1957.

Windfall Canyon section, about 40 ft above 

Hamburg dolomite; 6-in. limestone bed. 

A. R. Palmer and R. J. Ross, 1957.

Windfall Canyon section, about 55 ft above 

Hamburg dolomite; 2 ft below top of 10-ft 

limestone unit. A. R. Palmer and R. J. 

Ross, 1957.

Windfall Canyon section, about 70 ft above 

Hamburg dolomite; 1-ft limestone bed. 

A. R. Palmer and R. J. Ross, 1957.

Windfall Canyon section, about 77 ft above 

Hamburg dolomite; 2 ft above base of unit 

of 1- to 3-in. fine-grained limestone beds 

that crop out sporadically for about 20-25 

ft. A. R. Palmer and R. J. Ross, 1957.

Windfall Canyon section, about 90 ft above 

Hamburg dolomite; 10 ft below top of 

highest limestone in middle of Dunderberg shale. A. R. Palmer and R. J. Ross, 

1957.

Windfall Canyon section, about 195 ft above 

Hamburg dolomite; 3-in. limestone bed. 

A. R. Palmer and R. J. Ross, 1957.

Windfall Canyon section, about 75 ft below 

top of Dunderberg shale. A. R. Palmer 

and R. J. Ross, 1957.

Windfall Canyon section, about 40 ft below 

top of Dunderberg shale. A. R. Palmer 

and R. J. Ross, 1957.

Limestones at the north end of the Quinn 

Canyon Range, 1 mile (1.6 km) northwest 

of the Italian Ranch foothills, Nye County, 

Nev. J. E. Spurr, 1899.

A little south of the Hamburg mine, Eureka 

County, Nev. C. D. Walcott, 1882.

In canyon just north of Adams Hill. C. D. 

Walcott. 1880.

At the base of the Pogonip limestore northeast of Adams Hill. C. D. Walcott, 1880.

Limestone on the east side of Sierra Canyon, 

opposite Pinnacle Peak. Arnold Hague 

and J. P. Iddings, 1880.

1 U.S. mineral marker.

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Lower Cambrian trilobite genera: Jour. Paleontology, v. 

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______ 1950, Upper Cambrian faunas of the Little Rocky 

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p. 322-349.

_____ 1953, Analysis and discussion of nine Cambrian trilobite families: Jour. Paleontology, v. 27, no. 6, p. 889-896.

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101.

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258.

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29 p.

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TRILOBITES OF THE UPPER CAMBRIAN DUNDERBERG SHALE, EUREKA DISTRICT, NEV. 105

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483.

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_____ 1947, Supplementary notes on the Upper Cambrian

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___ 1948, Non-agnostidean trilobites of the Middle Cambrian of Sweden. I.: Sveriges Geol. Undersokning, ser. C, 

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 Part 3, The polymerid trilobites: Queensland Mus Mem.,

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_____ 1949, The trilobite fauna of the Elvinia zone in the

basal Wilberns limestone of Texas: Jour. Paleor Oology,

v. 23, no. 1, p. 25-44. 

______ 1951, Franconian trilobites of the central Appalachians: Jour, Paleontology, v. 25, no. 5, p. 617-654. 

___ 1954, Late Cambrian and Early Ordovician tr'lobites

from the Marathon Uplift, Texas: Jour. Paleontology, v. 

28, no. 3, p. 249-285.

INDEX

[Italic numbers Indicate descriptions 

Page

abnormis, Pseudosaralogia- __________________________ __________ _ ________ 101; pi. 11

Acknowledgments..-_____.____.-__--____ _____ _______ _-__-__.__._ _______ 55

Acrocephalaspis.--- __-__ _-__----_-__.___-_-__ ___-- ____ __ - 74

acuminala, Bynumiella-- --------------- ___________ __ ___..__ 65,95; pi, 10

acutus, Homagnostus... __-,__. __ -_ -._-_---__. ..-_ _-_-._-.__ __- 62

Pseudagnostus...-- -------- ---------------- ___________ _______ 62; pi. 4

affinis, Kindbladia.--- -------------------- _ _ ___,___ --_____ 56, 97-98; pi. 11

Agnostus--.-- ________- ___ . _ _________________-__-_.--_-.______ 62,63

cydopyge...------------------------- ... -_--__________ -__- _ 61

pisiformis------------ .-.. ----- -------- __________ _... ___-__-_.--_- __ 62-63

obesus. ------- ----------------------- ------------ --------- 6#, 63

alata, Prehousia.-.------- -..-...--...._.-_._..-.-..._........_ ____-._ 77, 78; pi. 7

alpersensis, Iddingsia..-- ............... ......_---........._..... ......... 96

anatina, Iddingsia.-- _______ ______________________________________ ___ _ _ 96

Plataspella.... ... ...._....-.......... _______ __-_ ______ ___-_ 96

Aneehocephalus. _______-____---______________--_-__-__.__-_____-_-___-______ 84,9#

frigranulatus----- _ __ --_--__--_._-_________________ -________ 92-93; pi. 8

Angulotretatriangularis----------- ______ __ __--_-__---___-_________-._--_-_ 90

angustilimbatus, Irvingella (PaTairFingetta)..-......._._-..._....__......- 73, 74; pi. 6

anyt a, Dunderbergia... .-_____ _ . _ -_.__..__.. _______.. _.. . -_ 66

Crepicephalus (LogancUus) .----___--__--__-__-___-___-______-___-_______-- 66

Aphelaspidinae.-------------------------- -------------- ___-____-_. SO-SJ,82-84

Aphelaspis..- ----------- ..............._..- ... _____ _ ________ 56,64,78,80,90

tumifrons- ____------__.____--_____-______- _____ _____ _____________ __ 74

Aphelaspis zone.....-- - .. ----.---. --------- ___..__ __- _-_- 80. 81. 90

asiatica, Pterocephalia _ 

Maladindes-----.-

Battus bibvllatus---- 

Bell, W. C., quoted. 

Berkeia.............

nepadensis-- ____ _. _ -_ _ - --_--_---_----__--_----_-_--_----- 

tyriica.-- ___________ _._ ___ - -_-- ---_ -_ .

wichitaengiS---------.----..--------- _ ----- --- ------ ---------------

bibullatus, Ba*tus------ ______.--__---.______ ._ ________ ___.____- _-.-_ 63

bicincta, Iddingsia__------__-----------.----------- .. .___- _._. _ _-___ __.._ 96

bigranulosa, Dunderbergia..---------- ----------- --------- _ 56, 60, 66-67; pi. 5

btlobata, Pterocephalina__ __-_-_______-.-___._-___-._-__ -. _______ _________ 90

bilobatus, Dikellocephalus__________ __ _ _____ _.__ ____ ________ -__.__.__ 81

Litocephalus.-..__..-__._-_.-__.--___- ._ ___._.________._.._ 58, 81, 82, 90; pi. 7

Brachiopods-____ ___-_.___---___-----.- _ _ ___________ ___ -.___ - 55,56

brericeps, Oligometopus- __________ ._ ______ _______ __________ ________ 100; pi. 10

Ptychoparia (Solenopleura)._ ___ __-__.-_.___ _____________________ 100

bridgei, Pterocephalia.------ _____ ____ _ -_-__-__-___ _ .__.___ __- _.87,88

briscoensis, Bynumiella... __ .-__._ ___ ___ _ ___ _ - ---___ __ __ 93

buttsi, Cheilocephalus. _________ ________ _-.____ .___---_-._._....._____-_--- 94

Bynumeilla_.. __ __ _____-__.- ____. _-__- ______ ____________ _____-.__ _ 93

acuminata _. - - _ __ -..-__-...--.._-__ __ _-_ _.-_ _______- ... 55, 93; pi. 10

briscoensiS-------------------------- _____ __________ .__ _______ -_.. _ 93

typicalis... ---......... . ...-.. ...- __-.__. __________-__.-- 93

Bynumina.---- _________ __-________._-. ,. _._._--.._-_____________.__ _ 93-94

caelata. - . ________________________ -_-__.___-.-._ ___ _..___-_______.- 93,94

_7o6osa__________---_.-__.-- .__- _____________ _._ 56, 75, 9,; pi. 10

missouriensis-------------------- .____- ________________ ______________ _ 94

terrenda... .-_________. _. _-__-___.__.___ _ _________________ ___ _____ 94

C 

caelata, Bynumina----- _______ _-.__.---.._.. ____.-_._____-___ _____-_.__ 93,94

canadensis, Dunderbergia- -____ __ ._ ____________________________________ _ 66

Housia- _.-_ _______ __ _________ ________ _______ ___ _ _ ___ _-_ 75

Catlin member of the Windfall formation___________ - _____. __ _______--_ _ 53

Ceraurinella typo, .... ___________ _____-_- ---------- _ ____ ___. ___ _ _ 76

Cerniiolimbus------.- ___ _____ ___ _._ _.__ __.__.-__. _______ 57, 58,60, 84-55, 88,90

depresms-.--- ._ _____ ______ _ ______ ________.___._- _-______-_.__ 55,86; pi. 8

orygmatos--. __ _ .._-_.__-__ ______ __-__-_.___ 56, 60,84, 85-86; pi. 8

semigranulosus- ________ ___-__- _______ _.._ __ ___ _-._--._-____ 85, 86; pi. 8

Chariocephalus-- ________ ____ ____________________ ________ _______--_--___.- 64

tumifrons------------ .. __ ___ ________ __.___.____ __.. __. ___ _ 73

Cheilocephalus _ _ _-_______-__._-. _ _ _-.__-. _____________________ 94,95

biittxi-.---- .----_-_ -_ ______ _____________ ___. ____________________ 94

spp___ ___ -__.__._ _.________.._ ____._ _.__ _ __----___ -__ _ 94-95: pi. 10

Chuangia.-------- .__ ____________ ________ ______ ____________ ____________ 100

Page 

Cliffa latagenae-. ..........---..-........ ...................... _-,_____-__ 102

Collecting: localities, description- --_ - -_-___ __ ____.__-- .. 102-103

Collectors, names.-.------ ---------------------------- - _ -- _ 53,102-103

comes, Berkeia-----..------- -----------------------------------... -___-_-__ 97

communis, Pseudagnostus.----------------------------------------------... 61; pi. 4

Conagpig....---.. ......_........... .-.-....-......_--. .... ------------ 64

concava, Iddingsia-.... _-_---__---_----__---___------____-_-_--..___________. 96

Pterocephalia..---------- ------------ _____________-_______--__---__ 88; pi. 9

conservator, Minupeltis- ___________________________________________.-_, PS; pi. 10

constricta, Parahousia.-.... _---___--_---_ ---_--_---__--___--_.----__- 56, 7), 77, pi. 7

conveza, Dunderbergia- ___________---- _ ____-_ ________________ 66

conveiimarginatus, Labioitria-........... ..........--_. ....-.-_.......... _ 80,84

Crassiftmbra.--.---------------.-- ---.--. ________________________________ 98

crassimarginata, Iddingsia............... _____--_--___-___-____--___-_____.___ 96

Crepicephalus (Loganellus) anytus... ___ __-______-_----_ __--_----__----__- 66

granulosus-.---------------------------------- _____-______-_-__-___ 66

maculosus-- .- ._--_-__---_- _ _____ _. ____- .__ ____ ________ 66, 75

nitidus-- -------------- -.-.---------------- _ _. _______ 65,66,67

simulator------.------.---------.--- ---------------------- _______ 66

unisculcatus- _______--___-_-_______-___-_ __-..---.-----.----.__-___ 71

cyclopyge, Agnostus_ -._-.-_..- ........ ________-_._.-.___ __--___--___-_____- 61

D 

Davis formation, Missouri-------- ____ - _- __ - _--__- -_ 56,94

Deodwoodia duris.-- --------------------- ----_--__--._-_-__-_-_--___-- __- 66

dedii'ita, Dunderbergia------- ._ - -_ _ _-_- ____ __..- 66

Dellea w?76ernsf7zs!s__---____---_---_--__-----_---_-_--._-- ___-____-__-_---_- 66

depressus, Cernuolimbus...-----.................. ___-,_______-___--___- S.5,86; pi. 8

Dicellocephalus richmondensis.---------------------------------------------- 81

Dikellocephalus bilobatus---------- ............ -- .......... ___._____- __ 81

DikelocephalitesflabellifoTmiS--------------------.._----------- --------- --_ 84

Dokimocephalus_-__----__ --__,-__---_------_____ -._---.--_-___-_.----.___ 95

gregori. ---------- _.---_-___-._--------_-___ _____._..-.---_........ 95

pernasutus--........................................................... 95; pi. 11

Dolichometopus (Housia) rarro..--............................................ 74

Dunderberg shale, description.._-___.-_- - ______-._- __._____.-__ _-._ 55-56

lithic units-..--.-_-_-_---_--------.---_-----.-------_-__._-.-.--_-__.- 55-56, 57

measured section, ........................................................ 55

Dunderbergia-------......................... 56, 57, 58, 60, 64, 65-66, 67, 68 69, 72,75

anyta,.................................................................... 66

bigranulosa------............................................. 56, 60, fifi-67; pi. 5

canadensis................................................................ 66

convexa-.- -.-.- -.----- _---------_----___--- ---_ -_- ,- ___-__ 66

dtclh'ita------.-.-------------...----.--.--.-.-....--------____.__-_ 66

granulosa-------..--. .------............................................ 66

ham...................................................................... 66

maculoso-..---------..---------------------------.-------------.--...----- 66

nitida . . .- .- . . . - 56, 60, 66, P7, 68; pi. 4 

polybothra--.....----------------.--...-------.------- 60, 65, 66, f!7-C>8, 82; pi. 5

pustulosa-----------..- ---------------.........--------------.... .-.. 66, 69

quadrata..--............................... __-------__-._..__ 66, 68; pi. 4

simulator................................__.______.____--_.--_- 66, 67

suada.-.---------------- --------_--_,_---_-----.------_--_-_.------------- 66

mriagranula------------------.---- __.-._____.____._ 66, 67, ft8, 82; pi. 4

vermontensis-------------------------------------------------------------- 66

Dunderbergia zone--.--------------------------------------------------------- 56, 81

Drumaspis_---------_..-......-._- -_.---....-...-...---- --.-.-.-..-. 64

duris, Deadmoodia----------------------------------------------- -----------. 66

E 

Elburgia.. . ......................................... 64, 65, 66, 68-69, 71, 72

granulata................................................................. 59

granulosa-----------................................................ 69, 71;pi. 6

quinnensis-...------.--.,....................................... 68, (,9-70; pi. 6

elongata, Pterocephalia.-----..-------- ---....---------------.---------- 60, 88; pi.9

Eh'inia-...-------.................................... 56, 64,65, 68, 69, 70, 71, 72, 89

granulata------... .......... ................................ 70, 71; pi. 6

haniburgensis---.--- ------------------------------------------------- 71; pi. 6

reudemanni.-.-.--------.-........-----..---.-..........--..--..-.------.. 71

roemeri - -.-..--. - -. -.----- ----- .----. 70-71; p.. 6

utahensis.---.................................................... -_.___-_-_-__,71

sp_ _------__.-______.-__.-_-__-_.-...----.-.---._-_---_-_-_______ 69

sp......... ......................-....... ..-..... ...... 71; pi. 6

107
108 INDEX

Page 

EMnia zone._ . -. - _ _ 56, 75, 80, 81, 84

Elri7iiella--------------.------------------.---.---.--.-.,.-....... 64, 65, 71-72, 74

7a«>.s__ - ------ ----_-- -- __ __ 71, 72, 74; pi. 6

Elviniidae.___.-.--_-._.....__.- .. .... 59, 60, 6.-65, 66-74, 80, 81, 96

eurekensis, Irvingella (Parairringella)-.--.-.... ............................. 74; pi. 6

eipansa, Taenora.. _ _ ________-___ . ___ _ __________________ 83, 84; pi. 7

F

Feniak, O. W., quoted ______

flabellifor m is, Dikelocephalites. 84

G

Generic groupings. - - - - .... 58

GenevieveUa - __________ -__ _____ _______-___ _ _ __,._ 100

Genus and species undetermined 1__._.______. _______________________ 101-102; pi. 11

2 .- --------___----_-- __-_-__-______-_____-----__-._---__ .OT; pi. 11

3______ _ ._-- __-_ - _--_-_-_. __--_ --- 102: pi. 11

Geographic distribution, Dunderberg shale. ________________________________ 53, 56

Geragnostinae.. _______ _ ____________________________________________________ 62-63

Geragnostus------------.-- --------------------------------.---....--- ________ 62, 63

gladiator, Macropyge. _________________________________________________________ 76

glandiforme, PhaJacroma ______________________________________________________ 63

globosa, Bynumina.-- _____________________________________________ 56, 75, 94; pi. 10

gra 7i M/af a , £76 w rgia ___________________________________________________________ 59

Elvinia. ____________________ ______________________________________ 70, 7/;. pi. 6

granulatus, Olen «/«_____________________________________________ 79-60.- pi . 6

granulomarginatus, Lifocephalus----. __--___ -___--__-----___--______---_ 58, 8£; pi. 8

(jran u/oso, Dunderbergia _______________________________________________________ 66

£.7&Mrff.a--------------------------------__-_------------_ 69, 71; pi. 6

granulosus, Crepicephalus (io(?an_'?/us)---____________________. ________________ 66

grata , Pterocephalina-. ________________________________________________________ 90

Sigmocheflus--------------.-------. ..---.------------- _________ ____ 90-9/; pi. 9

gregori, TJofcimocfpfiaZus...... _-.-___---_-_..__--_.__-__-._...._ ______________ 95

_-_____- _________________________________________________________ 80

H 

----_----_----------------_-----------------_----__- ____ 66

Homia.-------- _ ____________________________________________________ 75; pi. 7

Hamb urg dolomite _ ------______--__---_____________--________________________ 53

hamburgensis, £"7.:inia___________________________________________ __________ 71; pi. 6

Parair_.J ..(7_'?7a-------_-__--_______ _________________________________________ 71

Henningsmoen, Gunnar, quoted___. __________________________________________ 79

Homagnost us- ---------_____-_________________________--__________________.___ 6^-63

aftt. us.- ---------- ______-----__--___--__--._-.--_---_-______--_____-____ 62

obesus--------. __ -__--__.---_-______--______-_---.-_________ 56-57, 62, 63; pi. 4

/Hmia'osu*--. _-_ __ _ _ __ - _ _-- - _ 56, 62, 63; pk 4 

Housia----------------------.. ------------------------- _______ 64, 67, 7^-75, 77, 78

canadensis __________________________________________________________ 75

fto?.i____-____________. _________________________________________________ 75; pi. 7

o«_.a---_-----------_______--_----__________________-________ ____ 56, 75-76; pi. 7

rac«na_-_- ________ _ _____________________________________________________ 75

t'arro _____ _________________________________________________________________ 75

(Ilousia) varro, Dolichometopus.- ... ___________________________________________ 74

Housiidae______________ ________ _ _____________________________ 64, 74, 75-78, 98, 99

Hypostomes, characteristics_ _________________________________________________ 60

unidentified- _- - - -_ __-__-__--_-___ - __ 60-61; pi. 11

I

anatina.

fo/? cwa _________

crassimarginata7iet'adejisis - _ 

occidentalisrobusta----. _____________________________ ______________________ 56, 96-97;

similis__ _________________ ____________ ___________________________________

96 

96 

96 

96 

96 

96

96,97 

96

9fl, 96

pi. 11

96,97

96

intermedia, Parairringella.

Irvingella (Irringella) _ 

moy'o.'---_- ___

____________ 73

60,6^,6.5,75-73,74 

____________ 64, 73

____________ 74, 96

____________ 72

(Iningellal, /n'i«(7f??a______________________________________ __________________ 64,73

major, Irringella__. ______________________________________________________ 74,96

Irringella ( Parairringella) ________ ______________________________________ 56,64,73,96

anffi/.iWjmftaf«s__--_-_-----__-. -_-.--.-._._..-.._.-...--__---.--- 73,74; pi. 6

£U/-f/>-f..s.s____-__ __________________________________________________ 7.J; pi. 6

swec.ca___ _____________________________________________________________ 57

IrriitffeUina--- _____________ ____________ _____________________________________ 73

Page

96,97 

a./?.?..* ------ -- - ---- - - ----------- 56,97-98; pi. 11

97 

97

Komaspi." typa.. __--_. 

Kurtz, V. E., quoted_

-----. - - - - - - 80,84,90

ar9.na?Ms_--__- --_--_-----.-------_-----------------------------__ 80,84

s------------------------------------ - ---------------- 80,84

si(? m oidalis -__ - -- -- - -- - - -- -- - 80

/afrts, S7.'.mW?a_-. ----. -----..-------------------------- ---- 71,72,74; pi. 6

Za?a , Pseudosaratogia ________ ._. ----- -- ._ -_ -._ 101

latagenae, CJiffa-. ----.--.-.----------..--.---------.-.-.------------..-.-.-.- 102

7o^Wc», Pinctus-. _--__-_--__-_--_--------------------------------_------------ 100,101

leptogranulata, Pseiidosaratogia... ___--_____________--_______-__-_-__---._ /O/; pi. 11

Lincoln Peak formation. Snake Range, Nev--____--__-_-_____. -____-_-___ 56,78,103

i i /! narsson ell a --__- - - - - -- - --- - 56

List of collections-------- --.----------------- ------------.---------- 102-103

ii.o«pfia7!/8--.-_-------------- ---. ------------------- 56, 57, 58, 80, 8J-82, 90

fti7o6af«« ------------------- --.---.-------- ---- ------ 58, 81, Si?, 90; pi. 7

granulomarginatus-- _ __._-_--______._._________---_______-_____._-_ 58,8.?,' pi. 8

wrrMCU/ap-'.ra----- -- - - - --- 58,82,83; pi. 8

(Loganellus) anytus, Crepicephalus-- __________..-__.---_______-__---________._ 66

<?ra« ulosus, Crepicephalus. ________________--__-----___--__------_--_______ 66

maculos us, Crepicephalus ____-__--________.---------_--_----_--_------__-_ 66, 75

nitidus, Crepicephalus _._________-__._____--__----__._-_-___-_---_.-___ 65 66,67

si m ulator, Crepicephalus _-__ _ - _ - - - - - 66

« « isciilcatus, Crepicephalus ---__ - _ - --_-- -- 71

longispina, Aforosa_____________------___. ________----___ 56,82.98,99-^00,101; pi. 10

M

Matropyge gladiator.- - __ _ - 

maculosa, Dun derbergia _____________--

maculosus, Crepicephalus (Z/o<?a.?rf7ws) - 

magna, Pseudosaratogia. ________ _- -_

major, Irringella _ ____-___---_ _----___

(Irringella) _______ -_- _--

Maladioides....- _______-_-_----__-._-__--------------------------_--_-_----

asiatictis ______ ________________________-__----__---------__----_--.----_

Megadunderbergia.. _______________________,------_---------------___ -_-__-_-_

Meteoraspis win uta _____________------_----------------------_----------------

Minupeltis. ...-.-- ---_-__------.-------_-------------___---------__--- ----

conservator..... _ ________.-__-..-_--.--___------_----- ___---------__ 98;

min w/a, Mefeoraspis. ......... .^.... ....-.........----------------------

missouriensis, Bynumina. ...._.. ________ __________-----_-----------_----___--_

Iddmgsia.... ..................................................

A/orosa______ _________ _____..______________-------_---_--__--_------__-- 74,

longispina. _.. _________ ________________--_-__----___ 56, 82, 98, 99- WO, 101;

guinguidentata.

76 

66

66.75

101

72

71,96 

80 

64 

64

66, 69 

66 

98

pi. 10 

66 

94 

96

98-99

pi. 10

80 

80

80,84 

97

96,97 

; pi. 4

66,67 

99 

90

neradensis, Berkeia..------------- - .__ __ - __ _- __- ______

Iddingsia---.---- ---------- __- _ __- _- _ -__-_--_

nitida, Dunderbergia-__-_.-------- ----------------------------- 56,60, 66. 67, 68

nitidus, Crepicephalus (Loganellus) --- __ _ ____ -_- _ _ ________ 65

Nopah formation_--_____--__- _ __ _ - ---,-------_-------_-------

notha, Pterocephalina. ________________----------____-------------

O 

obesus, Agnostus pisiformis ---------------------------------------- --------- fi?,03

Homagnostus- _-_______----._--_--_--_---- ------------------ 56-57,62, 63; pi. 4

occidens, Pterocephaha------ __ ---------____ - - ___ -- _- _ 87,88

occidentalis, Iddmgsia.------------- -------------------------------------- ___ 96

Olenidae____ _ __-__- -_ ___ -_--____--- -- -_--__--__- 7S-79

Q\eninsie -------------------------------------------------------------

O1C71US------ - --------- ------------------------------------------------

granulatus _______ _._.___.____--_______-- ___ _-___ ------ _----__ 79-80; pi. 6

ii'ilsoni-- __----___--_ ___-_-_---____ ______---- ______________________ 79; pi. 6

Oligometopus- _______ ____________ ____________ __----.__----_-___--_-__----__ 100

brericeps---------- _____________-___ _- __- ._- _-___--____ 700; pi. 10

Ontogeny, discussion...____-----------_ _____ __----__.. _ _________ ___ 75.76,88

Ore Hill limestone member of Gatesburg formation ______ ____ ___ __ 94,102

Ornamentation, kinds______.__------ _--_-_ ___----__---___ _----___--._ ____ 59,60

Orr formation.- ___- -_ - _- -. -- ---------------- --_____ 56,92

orygmafos, Cernuolimbus-.-----....--.... -...--...... 56,60,81,85-86; pi. 8

omta, Housia-.---- .. ______ ___-_-_____-__ _---_----__--__--_---__- 56,75-76; pi. 7
INDEX 109

p Page 

Pagodia ____ _ ._ _ . ___ _ ________ ____________________________ 100

Parabolina ___ ____

Paraboihioididae 

Paracoosia,---. ----

74,76-

consfr.c.'a. __________ ___.__-_-----__-_-_____ _______________ 56,76,77

Purain'ingella.- ___________________ ___________________ __________________ ____

ha mburgensis- ---------------- -_-----_----------_--__-_____-_____________

intermedia-...---- --------- ------------------------------_----.------.----

(Parairvingdla") angustilimbatus, Iningella... .--.-. ..- ---....-...-....- 73,74

eurekensis, Irringella_- _______-_-----_----____________________ ___ 74

/rdnaeZ^a- ---------------------------------------------------------- 56,64,

suecica, IrvingeUa. ______ _____ ------_--_--_______________________._______

Parasolenoplev ra ___ _ ________ _ - ____ _______ _ __. _ _

pern<isu.tus, Dokimoccphalu.S- ----------------- _______ ___________________ S5;

Ptychoparia...--- ________________________________________________________

Phalacroma. -.---------------------------------------.--------_. ____________

glandiforme.-. _____________ ___-----____---________________._____________

77,78 

pi. 7 

73,74 

71 

73

; pi. 6 

; pi. 6 

73,96 

57 

98

pi. 11 

95 

63 

63 

5.S;pl. 4

Phalacrominae _ --_------__-_----- -- -_ -__ . _ _ 63

------------------------------------------------------- 100

latus..-. _- -__-___ -_-_ __- -- ___ - _-__ - 100,101 

spp______ _.._________.-_____-_ _____________________________________ /0;;pl.lO

pisiformis, Agnostus ---------- ----------------------------------------------- 62-63

obesus, Agnostus- ------------------------------------------- _____________ 62, 63

Plataspella _______ ._ ___ __. _ .___ ____________________ 96

anatina --,---- ---------------------------- ___________________ __ ___ 96

platifrons, Labiostria. ---------- __________________________ ___________________ 80,81

Taenora. _______________________________________ _______________________ 84

pogoninpensis, Pte rocephali no,- _ ______________________________________________ 90

Sigmochei) us _ _________---__-_-__-_-_-__--__-._________________ ____ 60, 91; pi. 10

polybothra, Dunderbergia---- _______________________________ 60,65,66,57-58,82: pi. 5

Post--4 phelaspis zone ___-_-__---------_-__---_________________________. 56, 84

Prehousia...----- ---------------------- ______________________________ 64,74,77-78

alattt------.. -- _________ __-______.__._.__. ___ ___ 77,78; pi. 7

semicircularus----.- ___________________________________________________ 78; pi. 7

Preparation of specimens for study _ ____-_----_---__-_________________ 55

Principles of classiflcatiotl _____________ ______ _____ _____________________ 57-59,92

Proceratopyge, _____________________________________ __________________________ 75

prolongus, PseudagnostuS---------------------- _____----_______-_._.______ _ 61; pi. 4

Pseudagnostus.__- _______________________ _ _____ ___________________________ 61, 62

aciitiis.- ------ _____ ___________________________________________________ 62; pi. 4

communis.--- ----------- ___----_____----_____ _________ ___________ 61; pi. 4

prolongus__-------------------- _____________________________________ _ 61; pi. 4

Pseudosarafogia. ______ ___________________ ___________________________ _____ _ 101

abnormis. ------- __-_.__--___ ____ _ _______________ ________________ J0J;pl.ll

Inta. ______________ _ _ ________ ________________ _______________________ _ 101

leptogranula,ta____-_. ---___--_ ___________________ _________________ 101; pi. 11

magna---_---_--_-_-_ _____ _________________ __________ ________________ 101

Pterocephalia-. -------------- _____ _______ _________ ___ 56,64,80,81,85,65-88,89,90

axiatica. ------ _____________ _____________ _ _____________ ______________ 87

--- _________ ______ __________________________________ 87,88

concaea.-- ___________________ _________ ___________________ _____ _____ 88; pi. 9

elongata.- __________________________________________ 60,88; pi. 9

oecidens--. __________ _________ ______ __________________ _______________ 87,88

sancfisabae ______ __.._ _________ _________ ______________ 86, 87, 88-89; pi. 9

Pterocephaliidae. _________ .___ _____ _______ __________________ 59.60,74,78,80,81-92

Pterocephaliinae______ ___ _____ _____ ___________________ ___ _ _ 60,80,81,84.85-92

Pterocephalina- __________ ________________ _______________ ___________________ 90

b iloba to_______ _______ _______________ ___._ _____ ___________ _ _ _ _____ 90

grata-,----.-.--- _____________ _ ________________ _ ______________________ _ __ 90

notha. --------

pogoninpensiste.rana--------

----------------------------_--_--_- ---__- -- 90

____________________________________________________ 90

______________________________________________________________ 90

Pterocephalops. -------_-----__ --_- ____--_---__-____-________ _-______---- 80

Ptychaspis pustulosa _-_--____.____-_ _______-_-_______ _______ _________ _ _ 66

Ptychoparia pernastus. ___--_-__-_----_--_-__-_-_--____________________________ 95

similis--------.---.--------.----.--.------.----_-_.---_-_-_-------_-__---- 95,9R

robusta ----------------------------------------.--..-------.--.---- 96

(So}enop]enra ) brericeps ___________________________ _ ______________________ 100

suada.-----------.--------.-------.--------.-----_---. ____-_.-...-__-_-- 66

Ptychoparioidea_____________________________________________________________ fVJ-102

pustulosa, Dunderbergia- __________________________________________________ _ __ 66, 69

P_ .Vf/i n,?p_,s_ _-_----_-__--___.____----____._--__________________________-___ fifi

Q 

guadrata, Dimderbergia------------------------.-----.------------------- 66,fi8; pi. 4

gi. innensis, Elburgia __________________________________________________ (i8, fJ9-7f); pi. 6

Wd. n^sw ____-_-..-___--__._-__--_-______--________________________________ 90, 9(1

Tae.?. ce ph al (/«________-__________.____________.__________________._________ 70

quinquedentafa, Nericia---. --__-_--_-------_-----..________________________.___ 80

R

Page

Ranges of trilobites in Dunderberg shale...-.-.................._..-............ 56, 57

Resser, C. E., quoted._...........___....___.__........__...__ 93

retusa, Kindbladiti.-.--..----.--..- ..--.-.-............._...................... 97

reudemanni, Eleinia __............... .................................... 71

richmondensis, Dicellocephalus................................................. 81

robusta, Iddingsia.------- __-._._.._____.______._......__._ 56, 96-S7; pi. 11

Ptychoparia simUis-----.------............................................ 96

roemeri, Elvinia-........................... ------------..-----------. 70-71; pi. 6

sanctisabae, Pterocephalia _____________________.__.. 86,87,88-89; pi. 9

semicircularis, Prehousia.------ ... . -_ ---- - --_---_ 78; pi. 7

semigranulosus, Cernuolimbus---........................................ 85,85; pi. 8

septemdentata, Nericia ___-_-_-_-_----------.-- -----.--__-----.__---.--__-- 80,84

serratus, Sigmocheilus-.-...--- _---------__._____-. .__ 56,60,61,89,9}; pi. 10

Sigmocheilus. ......................................... 70,80,84,85,88,89-90,91,92,96

grata--.-..---------.--- ___----_____.--.__-__-__-_ 90-91; pi. 9

pogonipensis------------------------------------------------------- 60, SI; pi. 10

serratus-..--------------------.-------------------------- 56, 60, 61, 89, 91; pi. 10

«.afte»z...s.------------------------------------------------------- 90.9/-92; pi. 9

sigmoidalis, Labiostria--------------------------------------------------------- 80

similis, Iddingsia-------------------------------------------------------------- 96, 97

PtyeAoparia.--------------------------------------------------------- 95,96

robusta, Ptychoparia_ -- - _--- - -- - -- - 96

simpUcitas, Iddingsia..--------------- _._._._..__ ...-_-_.._..-----.._...- 96

simulator, Crepicephalus (Loganellus}--------------........................... 66

Dunderbergia.------------------------------------------------------------ 66, 67

(Solenopleaura) brei'iceps, Ptychoparia----.---.--------- ------..-.---------- 100

Species characters.------------------ -- - .__ - . --- - 57-58

Stenelymus..---------------------------------------------------------------- 100

Stratigraphy, Dunderberg shale--- - ------------- - - -------------- -------- 55-57

suada, Dunderbergia..........................^......................--..-..-.. 66

Ptychoparia.----- ..--..-----.---.--.--.------.-----.--------- ---. -- 66

suecica, IrvingeUa (Parairvingella)-------------------------------------------- 57

Suprageneric groupings------------------------------------------------------- 58-59

Sutures, ventral cephalic.------------------------------------------------- 64,74,80

T

Taenicephalus- ---------------------------------------------------------

quinnensis-. ------------------------------------------------------ ------

Taeyiora. ------------------------------------------------------------------ 80,

eipansa __ -------------- ---- ------ --------- 83, 8^

platifrons -----------------------------------------------------------------

Terms, morpho logic. ---------------------------------------------------------

terrenda, Bynumina.-- ---------------------- - _- -- -- --- ---

texana, Pterocephalina.. -------------------------------------------------------

triangularis, Angulotreta- ------------ -------------------------------------

trigranitlatus, Anechocephalus-----.------------------------- ------------- 92-93,

tumidosus, Homagnostus.. ------------------------------------------- 56, 62, R3

tu mifrons, Aphelaspis. --------------------------------------------------------

Chariocephalus- ----------------------- ------------------------------------

typa, Ceraurinella.-- ---------------------------------------------- ------------

Komaspis--- --------------- -----------------------------------------------

typica, Berkeia.------- --------------------------------------------------------

t ypicalis, Byn u m iella ---------------------------------------------------------

64,70

70

V Pi. 7 

84

59,60 

94 

90 

90

' pi. 8

 pi. 4 

74 

73 

76 

73 

97 

93

U

Ullaspis- ------------------ -------------

unisculcatiis, Crepicephalus (Loganellus)- 

utahensis, Elrinia. ----------------------

Kigmockeilus--- - --- -- ------------ 90, 91-92; pi. 9

- - ----- ------------------------------------------------------ 75

variagranula, Dunderbergia--------------------------------------- 66, 67, <58, 82; pi. 4

varro, Dolichometopus (Housla)... -......-..---.-.-.--------------------------- "4

Housia ---------------------------------------------------------------- 75

fermontensis, Dunderberffia---------- ------------------------------------------ fifi

rerruculape:a, Litocephalus.----. -.-.---------.---------------------- 58. 82, 83; pi. 8

W

/i iiaensis, Berkeia

wilbernsensis, Dellea --------------------------------------------------------- 66

Wilson, J. L., quoted--.--.-- -- - -------------------- - - -- - - 90- 10°

u'ilsoni, Oienus-------------------- - - --------- - - -- - --------------- --- 79- P1 - 6

Windfall formation. ___________-_.----------------_--------------- 53,56,61,73,74,97

PLATES 4-11
PLATE 4

FIGURES 1, 2. Homagnostus tumidosus (Hall and Whitfield) (p. 63), X 10.

1. Cephalon, USNM 136831a, USGS coUn. 2299-CO.

2. Pygidium, USNM 136831b, USGS colln. 2299-CO. 

3, 4. Pseudagnostus com munis (Hall and Whitfield) (p. 61), X 10.

3. Cephalon, USNM 136832a, USGS colln. 2299-CO.

4. Pygidium, USNM 136832b, USGS colln. 2299-CO. 

5, 6. Pseudagnostus prolongus (Hall and Whitfield) (p. 61).

5. Cephalon, X 10, USNM 136833a, USGS colln. 2301-CO.

6. Pygidium, X 8, USNM 136833b, USGS colln. 2301-CO. 

7-9. Homagnostus obesus (Belt) (p. 63), X 10.

7. Cephalon, USNM 136834a, USGS colln. 2296-CO showing finely pitted outer surface.

8. Pygidium, USNM 136834b, USGS colln. 2296-CO.

9. Cephalon, USNM 136835, USGS colln. 2295-CO. 

10-12. Pseudagnostust acutus (Kobayashi) (p. 62), X 10.

10. Lectotype pygidium, NMC 11996, from so-called Parabolinella limestone, east of Harrogate, British 

Columbia, Canada. Specimen figured by Kobayashi (1938, pi. 16, fig. 18).

11. Pygidium, USNM 136836a, USGS colln. 2297-CO, showing muscle scars.

12. Pygidium, USNM 136836b, USGS colln. 2297-CO. 

13. Phalacromal sp. (p. 63), X 10.

Cephalon, USNM 136837, USGS colln. 2300-CO. 

14-21, 23, 24. Dunderbergia nitida (Hall and Whitfield) (p. 67).

14. Pygidium, X 4, USNM 136838a, USGS colln. 2300-CO.

15. Lectotype cranidium, X 3, USNM 24572, Dunderberg shale, Eureka, Nev.

16. Paratype cranidium, X 3, USNM 24572b, Dunderberg shale, Eureka, Nev.

17. Cranidium, holotype of D. simulator (Hall and Whitfield), X 1, USNM 24575, Dunderberg shale, 

Eureka, Nev.

18. Latex cast of exfoliated cranidium, X 3, USNM 136838b, USGS colln. 2300-CO.

19. Stereogram of cranidium, X 4, USNM 136838c, USGS colln. 2300-CO.

20. Latex cast of underside of right free cheek showing form of doublure, X 3, USNM 136839, USGS 

colln. 873-CO.

21. Latex cast of right free cheek, X 3, USNM 136838d, USGS colln. 2300-CO.

23. Pygidium, X 3, USNM 136838e, USGS colln. 2300-CO.

24. Exfoliated right free cheek showing fine-pitted surface, X 4, USNM 136838f, USGS colln. 2300-CO. 

22, 25, 28, 29. Dunderbergia variagranula Palmer (p. 68).

22, Stereogram of cranidium, X 4, USNM 136840a, USGS colln. 2297-CO.

25. Cranidium, X 4, showing coarse granules on surface of internal mold of glabella, USNM 136841, 

USGS colln. 2298-CO.

28. Pygidium, X 4, USNM 136843, USGS colln. 809-CO.

29. Free cheek, X 4, USNM 136840b, USGS colln. 2297-CO.

26. Dunderbergia variagranulal Palmer (p. 68), X 8.

Cranidium, questionably assigned to this species, USNM 136842, USGS colln. 2302-CO.

27. Dunderbergia quadrata Kobayashi (p. 68), X 2.

Cranidium, NMC 11962, west of Harrogate, British Columbia, Canada.
GEOLOGICAL SUKVEY PROFESSIONAL PAPER 334 PLATE 4 

~

AGNOSTIDAE AND ELVINIIDAE
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 5

20

ELVINIIDAE
PLATE 5

FIGURES 1-4, 6, 7, 9, 14. Dunderbergia polybothra n. sp. (p. 67).

1. Cranidium, X 3, USNM 136844a.

2. 3. Free cheeks, X 4, USNM 136844b, c.

4, 7. Thoracic segments, X 3, USNM 136844d, e.

6. Pygidium, X 3, USNM 136844f.

9. Stereogram of holotype cranidium, X 4, USNM 136845.

14. Detail of top surface of glabella and occipital ring, of cranidium in fig. 1, X 10. All specimens from

USGS colln. 2296-CO. 

5. Dunderbergia maculosa (Hall and Whitfield) (p. 66), X 1.

Holotype cranidium, USNM 24617 Dunderberg shale, Eureka district, Nevada.

8. Dunderbergia pustulosa (Hall and Whitfield) (p. 66), X 1.

Holotype cranidium, USNM 24579 Dunderberg (?) shale, White Pine district, Nev.

10-13, 15-23. Dunderbergia bigranulosa n. sp. (p. 66).

10. Cranidium, X 4, USNM 136846a, USGS colln. 795-CO.

11. Exfoliated cranidium, X 3, USNM 136846b, USGS colln. 795-CO.

12. Stereogram of holotype cranidium, X 3, USNM 136847, USGS colln. 2295-CO.

13. Detail of surface of brim and border of cranidium in fig. 19, X 10.

15. Free cheek, X 4, USNM 136848b, USGS colln. 2295-CO.

16. Free cheek, X 4, USNM 136849a, USGS colln. 2294-CO.

17. Free cheek, X 5, compare border with fig. 16, USNM 136848c, USGS colln. 2295-CO.

18. Cranidium, X 4, USNM 136848a, USGS colln. 2295-CO.

19. Cranidium, X 4, USNM 136849b, USGS colln. 2294-CO.

20. Pygidium, X 4, USNM 136849c, USGS colln. 2294-CO.

21. 22. Pygidia, X 4, USNM 136848d, e, USGS colln. 2295-CO.

23. Pathologic pygidium with partly attached, distorted thoracic segments, X 3, USNM 136848f, 

USGS colln. 2295-CO.
PLATE 6

FIGURE 1. Irvingella (Parairvingella) eurekensis (Resser) (p. 74), X 3.

Stereogram of holotype cranidium, USNM 108668, USNM loc. 61. 

2, 3. Irvingella (Parairvingella) angustilimbatus Kobayashi (p. 73), X 2.

2. Stereogram of small plesiotype cranidium for comparison with /. (P.) eurekensis, USNM 108672, USNM loc. 62.

3. Large cotype cranidium, USNM 24643, USNM loc. 63.

4. Elvinia granulata Resser (p. 71), X 2.

Stereogram of holotype cranidium, USNM 108815, USNM loc. 63.

5. Elvinia hamburgensis (Resser) (p. 71), X 2.

Holotype cranidium, USNM 108669, USNM loc. 61.

6. Elvinia? sp. (p. 71), X 3.

Cranidium, USNM 136850, USGS colln. 2300-CO.

7. Elvinia roemeri (Shumard) (p. 70), X 2.

Cranidium, USNM 136851, USGS colln. 789-CO.

8. 14. Elviniella sp. (p. 72), X 4.

8. Stereogram of cranidium, USNM 136852, USGS colln. 954-CO. 

14. Cranidium, USNM 136853, USGS colln. 2301-CO.

9. 10. Elviniella laevis n. gen., n. sp. (p. 72), X 4.

9. Stereogram of holotype cranidium, USNM 136854a, USGS colln. 952-CO.

10. Latex cast of posterior part of holotype cranidium USNM 136854b. 

11-13, 15. Elburgia quinnensis (Resser) (p. 69).

11. Stereogram of exfoliated holotype cranidium, X 3, USNM 108838a, USNM loc. 7j.

12. Cranidium on same block as holotype, X 3.

13. Granidium, X 4, USNM 136855a, USGS colln. 2298-CO.

15. Exfoliated cranidium, X 3, USNM 136855b, USGS colln. 2298-CO. 

16, 17, 19. Elburgia granulosa (Hall and Whitfield) (p. 69), X 3.

16. Cranidium, USNM 136856, USGS colln. 795-CO.

17. Cranidium, USNM 136857, USGS colln. 2297-CO.

19. Stereogram of holotype cranidium, USNM 24573, Dunderberg shale, Eureka district, Nevada. 

18, 20-22. Olenusf wilsoni Henningsmoen (p. 79), X 5.

18. Cranidium, USNM 136858a, USGS colln. 2300-CO.

20. Cranidium, USNM 136859a, USGS colln. 2297-CO.

21. Free cheek, USNM 136859b, USGS colln. 2297-CO.

22. Pygidium, USNM 136858b, USGS colln. 2300-CO. 

23-27. Olenus? granulatus n. sp. (p. 79).

23. Pygidium, X 5, USNM 136860, USGS colln. 2299-CO.

24. Stereogram of holotype cranidium, X 5, USNM 136861, USGS colln. 2300-CO.

25. Detail of surface, holotype cranidium, X 15.

26. Cranidium, USNM 136862, USGS colln. 795-CO.

27. Detail of surface of pygidium, X 15.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 6

Tii W

24

ELVINIIDAE AND OLENIDAE
GEOLOGICAL SURVEY PROFESSIONAL PAPER 884 PLATE 7

27'

HOUSIIDAE AND APHELASPIDINAE
PLATE 7

FIGURES 1-7, 9. Housia ovata n. sp. (p. 75).

1. Stereogram of holotype cranidium, X 2, USNM 136863, USGS colln. 872-CO.

2. Free cheek, X 1, USNM I36864a, USNM loc. 60.

3. Cranidium, X 4, for comparison with cranidium of comparable size for Parahousia constriuta n. sp. 

(fig. 16), USNM 136865a, USGS colln. 955-CO.

4. 9. Transitory pygidia, X 15, USNM 136865b,c, USGS colln. 955-CO.

5. Exfoliated pygidium, X 2, USNM 136864b, USGS colln. 872-CO.

6. Pygidium showing uneven development of left and right pleural lobes, X 3, USNM 136864c, USGS 

colln. 872-CO.

7. Pygidium, X 4, USNM 136865d, USGS colln. 955-CO. 

8. Housia halli (Resser) (p. 75), X 2.

Holotype pygidium, USNM 90670, Dunderberg shale, Eureka district, Nevada. 

10, 12, 13. Prehousia alata n. gen., n. sp. (p. 78).

10. Stereogram of holotype cranidium, X 3, USNM 136866.

12. Free cheek, X 2, USNM 136867a.

13. Pygidium, X 2, USNM 136867b.

All specimens from USGS colln. 1441-CO, Lincoln Peak formation, Snake Range, Nev. 

11, 14, 15, 19. Prehousia semicircularis n. gen., n. sp. (p. 78).

11. Holotype, small cranidium, X 8, USNM 136868.

14. Pygidium showing posterior margin, X 3, USNM 136869a.

15. Free cheek, X 4, USNM 136869b.

19. Fragmentary pygidium showing anterolateral margin, X 3, USNM 136869c.

All specimens from USGS colln. 2294-CO. 

16-18. Parahousia constricta n. gen., n. sp. (p. 77), X 4.

16. Stereogram of holotype cranidium, USNM 136870.

17. Free cheek, USNM 136871a.

18. Pygidium, USNM 136871b.

All specimens from USGS colln. 955-CO. 

20-23. Taenora expansa n. gen., n. sp. (p. 84).

20. Stereogram of holotype cranidium, USNM 136872, USGS colln. 954-CO.

21. Free cheek, X 2, USNM 136873a, USGS colln. 2301-CO.

22. Pygidium, X 2, USNM 136874, USGS colln. 954-CO.

23. Small cranidium, X 5, USNM 136873b, USGS colln. 2301-CO. 

24-27. Litocephalus bilobatus (Hall and Whitfield) (p. 82), X 2.

24. Stereogram of cranidium, USNM 128324a.

25. Free cheek, USNM 128324b.

26. Pygidium, USNM 128324d.

27. Thoracic segment, USNM 128324e. 

All specimens from USGS colln. 1297-CO.
PLATE 8

FIGURES 1, 3, 5, 8, 11. Cernuolimbus orygmatos n. gen., n. sp. (p. 85).

I. Stereogram of holotype cranidium, X 2, USNM 136875.

3. Pygidium X 2, USNM 136876a.

5. Detail of external surface of right posterior limb of holotype, X 10.

8. Free cheek, X 2, USNM 136876b.

II. Pygidium, X 3, USNM 136876c.

All from USGS colln. 2295-CO. 

2, 4, 6, 7. Cernuolimbus semigranulosus n. gen., n. sp. (p. 86).

2. Stereogram of holotype cranidium, X 3, USNM 136877. 

4. Pygidium, X 3, USNM 136878a.

6. Detail of external surface of back of glabella of holotype, X 10.

7. Free cheek, USNM 136878b.

All from USGS colln. 2294-CO. 

9, 10. Cernuolimbus depressus n. gen., n. sp. (p. 85), X 3.

9. Stereogram of holotype cranidium, USNM 136879.

10. Cranidium, USNM 136880.

Both from USGS colln. 2297-CO. 

12, 13, 15, 16, 19, 20. Litocephalus verruculapeza n. sp. (p. 83).

12. Stereogram of holotype cranidium, X 3, USNM 136881.

13. Detail of cranidial border X 3, USNM 136882a.

15. Free cheek showing shape of anterior part of doublure, X 2, USNM 136882b.

16. Free cheek, X 3, USNM 136882c. 

19, 20. Pygidia, X 3, USNM 136882d, e.

All from USGS colln. 2299-CO.

14, 17, 18, 24. Litocephalus granulomarginatus n. sp. (p. 82). 

14. Detail of border of holotype, X 5.

17. Stereogram of holotype cranidium, X 2, USNM 136883, USGS colln. 795-CO.

18. Pygidium, X 2, USNM 136884a, USGS colln. 2300-CO. 

24. Free cheek, X 2, USNM 136884b, USGS colln. 2300-CO. 

21-23. Anechocephalus trigranulatus n. gen., n. sp. (p. 92), X 5.

21. Pygidium, USNM 136886a.

22. Stereogram of holotype cranidium, USNM 136885.

23. Cranidium, USNM 136886b. 

All from USGS colln. 952-CO.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 8

p/ T 24

21 22

PTEROCEPH ALIIN AE, APHEL ASPIDIN AE, AND ANECHOCEPHALUS
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 9

26

PTEROCEPHALIINAE
PLATE 9

FIGURES 1-6, 9-12. Pterocephalia concava n. sp. (p. 88).

1. Stereogram of holotype cranidium, X 2, USNM 136887.

2. Large incomplete cranidium, X 1, USNM 136888a.

3. Medium-sized cranidium, X 3, USNM 136888b.

4. Small cranidium, X 4, USNM 136888c.

5. Small pygidium, X 3, USNM 136888d.

6. Free cheek, X 1, USNM 136888e.

9. Latex cast of large pygidium, X 1, USNM 136888f.

10. 11. Medium-sized pygidia, X 2, USNM 136888g, h. 

12. Left pleuron of thoracic segment, X 2, USNM 136888i. 

All from USGS colln. 2297-CO.

7, 8, 13. Pterocephalia sanctisabae Roemer (p. 88).

7. Cranidium, X 3, for comparison with comparable-sized cranidium of P. concava n. sp. (fig. 3), USNM 

136889a, USGS colln. 2302-CO.

8. Pygidium, X 3, USNM 136890, USGS colln. 2301-CO.

13. Free cheek, X 2, USNM 136889b, USGS colln. 2302-CO. 

14-20. Pterocephalia elongata n. sp. (p. 88) X 3.

14. Stereogram of holotype cranidium, USNM 136891, USGS colln. 873-CO.

15. Free cheek, USNM 136893a, USGS colln. 2300-CO.

16. Cramdium, USNM 136893b, USGS colln. 2300-CO.

17. Pygidium, USNM 136892, USGS colln. 873-CO.

18. 19. Pygidia, USNM 136893c, d, USGS colln. 2300-CO.

20. Free cheek showing shape of anterior part of doublure, USNM 136893e, USGS colln. 2300-CO. 

21. Pterocephalia occidens (Walcott) (p. 88), X 4.

Holotype cranidium, USNM 24613, USNM loc. 61. 

22, 23, 26, 27. Sigmocheilus grata (Resser) (p. 90).

22. Pygidium, X 3, USNM 136894, USGS colln. 952-CO.

23. Pygidium, X 3, USNM 136895a, USGS colln. 2299-CO.

26. Free cheek, X 3, USNM 136895b, USGS colln. 2299-CO.

27. Stereogram of cranidium, X 3, USNM 136895c, USGS colln. 2299-CO. 

24, 25, 28. Sigmocheilus utahensis (Resser) (p. 91).

24. Pygidium, X 5, USNM 136896a, USGS colln. 2296-CO.

25. Free cheek, X 3, USNM 136896b, USGS colln. 2296-CO.

28. Stereogram of small cranidium, X 4, USNM 136897, USGS colln. 795-CO.
PLATE 10

FIGURES 1-3. Sigmocheilus serratus n. gen., n. sp. (p. 91), X 3.

1. Stereogram of holotype cranidium USNM 136898a, USGS colln. 955-CO.

2. Free cheek, USNM 136899, USGS colln. 864-CO.

3. Pygidium, on same block as holotype, USNM 136898b, USGS colln. 955-CO. 

4-7. Sigmocheilus pogonipensis (Resser) (p. 91), X 3.

4. Stereogram of characteristic cranidium, USNM 136900a, USGS colln. 2301-CO.

5. Latex cast of pygidium, USNM 136900b, USGS colln. 2301-CO.

6. Cranidium showing shape of anterior margin, USNM 136901, USGS colln. 954-CO.

7. Free cheek, USNM 136900c, USGS colln. 2301-CO. 

8. Bynumina globosa (Walcott) (p. 94), X 10.

Stereogram of nearly perfect cranidium, USNM 136902, USNM loc. 61. 

9, 10. Bynumiellaf acuminata n. sp. (p. 93), X 8.

9. Stereogram of holotype cranidium, USNM 136903.

10. Silicified free cheek, USNM 136904.

Both from USGS colln. 2296-CO. 

11, 12. Minupeltis conservator n. gen., n. sp. (p. 98), X 8.

11. Stereogram of holotype cranidium, USNM 136905.

12. Assymetrical cranidium with poorly developed right side, USNM 136906. 

Both from USGS colln. 2294-CO.

13, 14. Cheilocephalus spp. (p. 94), X 3.

13. Cranidium, USNM 136907, USGS colln. 864-CO.

14. Pygidium, USNM 136908, USGS colln. 2299-CO. 

15-17. Morosa longispina n. gen., n. sp. (p. 99), X 6.

15. Stereogram of holotype cranidium, USNM 136909.

16. Pygidium, USNM 136910a.

17. Free cheek, USNM 136910b. 

All from USGS colln. 2299-CO.

18. 21. Pinctus"? spp. (p. 101), X 10.

18. Latex cast of cranidium, USNM 136911, USGS colln. 952-CO. 

21. Latex cast of cranidium, USNM 136912, USGS colln. 953-CO.

19. 20. Oligometopus breviceps (Walcott) (p. 100), X 8.

19. Stereogram of holotype cranidium, USNM 24577, USNM loc. 62.

20. Cranidium, USNM 136913, USGS colln. 954-CO.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 10

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PTEROCEPHALIINAE AND UNASSIGNED GENERA
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334 PLATE 11

18

UNASSIGNED GENERA AND HYPOSTOMES
PLATE 11

FIGURES 1. Genus and species undetermined 2 (p. 102), X 5.

Cranidium, USNM 136914, USGS colln. 2295-CO. 

2, 5, 6. Genus and species undetermined 1 (p. 101), X 5. 

2. Cranidium, USNM 136915a.

5. Cranidium questionably assigned to this species, USNM 136915b.

6. Cranidium, USNM 136915c.

All from USGS colln. 2297-CO. 

3. Genus and species undetermined 3 (p. 102), X 5.

Pygidium, USNM 136916, USGS colln. 2297-CO. 

4, 7-9, 12. Hypostomes (p. 60), X 5.

4. Hypostome, type C, USNM 136917, USGS colln. 2294-CO.

7. Hypostome, type B, USNM 136918, USGS colln. 2295-CO.

8. Hypostome, type E, USNM 136919, USGS colln. 2296-CO.

9. Hypostome, type D, USNM 136920, USGS colln. 2301-CO.

12. Hypostome, type A, USNM 136921, USGS colln. 2302-CO.

10. Pseudosaraiogia leptogranulata n. sp. (p. 101), X 2.

Stereogram of holotype cranidium, USNM 136922, USGS colln. 954-CO.

11. Pseudosaratogia abnormis n. sp. (p. 101), X 3.

Stereogram of holotype cranidium, USNM 136923, USGS colln. 955-CO. 

13-16. Iddingsia robusta (Walcott) (p. 96).

13. Stereogram of holotype cranidium, X 2, USNM 24609, USNM loc. 61.

14. Detail of right anterolateral corner of cranidium in fig. 16, X 5.

15. Cranidium, holotype of /. neradensis Resser, X 2, USNM 108796, USNM loc. 61.

16. Cranidium preserving part of external surface, X 2, USNM 136924, USNM loc. 62.

17, 19, 20. Kindbladia affinis (Walcott) (p. 97).

17. Stereogram of cranidium with external surface preserved, X 5, USNM 136925, USNM loc. 62.

19. Cranidium, holotype of K. nevadensis Resser, X 4, USNM 108788a, USNM loc. 61.

20. Holotype, cranidium, X 4, USNM 24642, USNM loc. 65. 

18, 21. Dokimocephalus pernasutus (Walcott) (p. 95), X 1. 

18. Holotype cranidium, USNM 24608a. 

21. Paratype free cheek, USNM 24608b. 

Both from USNM loc. 61.

U.S. GOVERNMENT PRINTING OFFICE: 1960 O -507Z19