Paleontology and Stratigraphy of the 

Rabbit Hill Limestone and 

Lone Mountain Dolomite of 

Central Nevada 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 

Paleontology and Stratigraphy of the 

Rabbit Hill Limestone and 

Lone Mountain Dolomite of 

Central Nevada 

By C. W. MERRIAM 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 

A comparative study of fossils from contrasting 

carbonate facies near the Silurian-Devonian 

boundary, and a review of stratigraphic relations 

J 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1973 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress catalog-card No. 73-60012 5 

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

Washington, D.C. 20402 - Price $1.75 

Stock Number 2401-02379 
CONTENTS 

Page 

Abstract 

Introduction ............................................................................... . 

1 

1 

2 

2 

3 

4 

Purpose and scope of investigation ............................... . 

Acknowledgments ............................................................. . 

History of investigation ................................................... . 

Methods ............................................................................. . 

Silurian and Early Devonian depositional belts of 

the Great Basin ............................................................ .......... 4 

Areal distribution and stratigraphy of the 

Rabbit Hill Limestone .................................................. 5 

Rabbit Hill, northern Monitor Range ....................... .... 6 

Dobbin Summit, Monitor Range .................................... 7 

Northern Toquima Range .............................................. 7 

McClusky Peak area, Simpson Park Range ................. 8 

Coal Canyon, northern Simpson Park Range .............. 8 

Cortez Mountains and Tuscarora Mountains .............. 9 

Beacon Peak Dolomite, Sulphur Spring Range .................. 10 

Age and correlation of the Rabbit Hill Limestone .............. 10 

Lone Mountain Dolomite ........................................................ 12 

Lone Mountain Dolomite, Lone Mountain ................... 12 

Lone Mountain Dolomite, southern Mahogany Hills .. 13 

Lone Mountain Dolomite, southern 

Fish Creek Range........................................................... 15 

Lone Mountain Dolomite, Sulphur Spring Range ........ 15 

Age and correlation of the Lone Mountain Dolomite .......... 15 

Conclusions regarding relation of Rabbit Hill Limestone 

to Lone Mountain Dolomite ................................................ 17 

Great Basin Silurian and Devonian coral zones ................ 18 

Systematic and descriptive paleontology ............................. 18 

Fossils of the Rabbit Hill Limestone and Beacon Peak 

Dolomite Member of the Nevada Formation................... 19 

Order Tabulata Edwards and Haime .................... 19 

Family Favositidae Dana ·-····-----·-···---·····-···---· 19 

Genus Favosites Lamarck ·-··-······-····--····-- 19 

Favosites cf. F. helderbergiae Hall .. 19 

Genus Striatopora Hall ............................ 20 

Striatopora cf. S. gwenensis 

Amsden ............................................. 20 

Genus Pleurodictyum Goldfuss ................. 20 

Pleurodictyum nevadensis n. sp ...... 20 

Pleudorictyum dunbari n. sp ............ 21 

Order Rugosa Edwards and Haime ........................ 21 

Family Laccophyllidae Grabau ...................... 21 

Genus Syringaxon Lindstrom ................ 21 

Syringaxon foerstei n. sp. ................ 22 

Family Streptelasmatidae Nicholson .............. 23 

Genus Siphonophrentis O'Connell .......... 23 

Siphonophrentis sp. B ...................... 23 

Family Endophyllidae Torley ........................ 23 

Genus Australophyllum Stumm ............ 23 

Australophyllum landerensis n. sp .. 24 

Australophyllum stevensi n. sp ........ 24 

Australophyllum sp. v ·----·--·-············ 25 

Family Disphyllidae Hill ................................ 25 

Genus Billingsastraea Grabau ................ 25 

Fossils of the Rabbit Hill Limestone and Beacon Peak 

Dolomite Member of the Nevada Formation-Con. 

Order Rugosa Edwards and Haime-Continued 

Family Disphyllidae Hill-Continued 

Genus Billingsastraea Grabau-Con. 

Page 

Billingsastraea sp. m ........................ 25 

Phylum Brachiopoda ........................................................ 25 

Order Orthida Schuchert and Cooper .................... 25 

Family Rhipidomellidae Schuchert ................ 25 

Genus Rhipidomella Oehlert ................ .... 25 

Rhipidomella rossi n. sp .................. 25 

Family Dalmanellidae Schuchert .................. 26 

Genus Levenea Schuchert and Cooper .... 26 

Levenea subcarinata subsp 

antelopensis n. subsp .................. 26 

Family Orthidae Woodward ............................ 27 

Genus Orthostrophia Hall ........................ 27 

Orthostrophia strophomenoides 

subsp. newberryi n. subsp ............ 27 

Order Strophomenida Opik .................................... 27 

Family Stropheodontidae Caster .................. 27 

Genus Leptostrophia Hall and Clarke .... 27 

Leptostrophia sp. cf. L. becki 

tennesseensis ·Dunbar ................... 27 

Genus Pholidostrophia Hall and Clarke.. 28 

(?) Pholidostrophia sp. R ................. 28 

Genus Strophonella Hall ......................... 28 

Strophonella cf. S. punctulifera 

(Conrad) .......................................... 28 

Family Leptaenidae Hall and Clarke ........... 28 

Genus Leptaena Dalman ........................ 28 

Leptaena fremonti n. sp ................... 28 

Family Schuchertellidae Williams ................ 29 

Genus Schuchertella Girty ...................... 29 

Schuchertella cf. S. haraganensis 

Amsden ............................................ 29 

Order Pentamerida Schuchert and Cooper .......... 29 

Family Parastrophinidae Ulrich and Cooper 29 

Genus Anastrophia Hall .......................... 29 

Anastrophia cf. A. verneuili (Hall) .. 29 

Order Rhynchonellida Kuhn .................................. 29 

Family Uncinulidae Rzhonsnitskaya ............ 29 

Genus Plethorhyncha Hall and Clarke .... 29 

Plethorhyncha andersoni n. sp ........ 29 

Order Spiriferida Waagen ........................................ 30 

Family Meristellidae Waagen ........................ 30 

Genus Meristella Hall .............................. 30 

M eristella martini n. sp ................... 30 

Family Ambocoeliidae George ...................... 30 

Ambocoelia sp. a .. ................. ................... 30 

Family Leptocoeliidae Boucot and Gill ........ 31 

Genus Leptocoelia Hall .......................... 31 

Leptocoelia occidentalis n. sp ......... 31 

Family Retziidae Waagen .............................. 31 

Genus Trematospira Hall ........................ 31 

III 
IV CONTENTS 

Page 

Fossils of the Rabbit Hill Limestone and Beacon Peak 

Dolomite Member of the Nevada Formation-Con. 

Page 

Fossils of the Rabbit Hill Limestone and Beacon Peak 

Dolomite Member of the Nevada Formation-Con. 

Phylum Brachiopoda-Continued 

Order Spiriferida Waagen-Continued 

Family Retziidae W aagen-Continued 

Genus Trematospira Hall-Continued 

Trematospira mcbridei n. sp .......... 31 

Family Delthyrididae Waagen ........... ... ........ 32 

Genus Kozlowskiellina Boucot ................ 32 

Kozlowskiellina nolani n. sp .......... 32 

Genus Howellella Kozlowski .................. 33 

Howellella cycloptera (Hall) 

subsp. monitorensis n. subsp ....... 33 

Genus Acrospirifer Helmbrecht and 

Wedekind ........................................ 33 

Acrospirifer kleinhampli n. sp ...... 34 

Family Costispiriferidae Termier and 

Termier .................................................... 34 

Genus Costispirifer Cooper ........................ 34 

Costispirifer arenosus (Conrad) 

subsp. dobbinensis n. subsp ............ 35 

Tentaculitids and conulariids of the Rabbit 

Hill Limestone .................................. ...................... 35 

Order Conulariida Miller and Gurley .................. 35 

Family Conulariidae Walcott ........................ 35 

Genus Conularia sp. cf. C. 

huntiana Hall .......................................... 35 

Mollusca of the Rabbit Hill Limestone .......................... 35 

Family Platyceratidae Hall ............................ 36 

Genus Platyceras Conrad ........................ 36 

Platyceras sp. a................................... 36 

Platyceras sp. b ................................... 36 

Platyceras (Orthonychia) sp. c ...... 36 

Trilobites of the Rabbit Hill .................................. ........ 36 

Family Odontopleuridae Burmeister ............ 36 

Genus Leonaspis Richter and Richter.... 36 

Leonaspis cf. L. tuberculatus (Hall) 36 

Genus M iraspis Richter and Richter ...... 37 

(?)Miraspis sp .................................. 37 

Family Phacopidae Hawle and Corda .......... 37 

Genus Phacops Emmrich ........................ 37 

Phacops sp. A, cf. P. logani Hall ...... 37 

(?)Phacops sp. B, cf. P. canadensis 

Stumm ................................ .............. 37 

Trilobites of the Rabbit Hill-Continued 

Family Dalmanitidae Vogdes ........................ 37 

Fossils of the Lone Mountain Dolomite ................................. 37 

Order Rugosa Edwards and Haime ......................... 37 

Family Tryplasmatidae Etheridge .................. 37 

Genus Tryplasma Lonsdale .................... 37 

Tryplasma sp. f .................................. 38 

Family Kyphophyllidae Wedekind................ 38 

Genus Entelophyllum Wedekind............ 38 

Entelophyllum engelmanni n. sp .... 38 

Entelophyllum engelmanni subsp. b 39 

Entelophyllum eurekaensis n. sp .... 39 

Phylum Brachiopoda ........................................................ 40 

Order Orthida Schuchert and Cooper ................... 40 

Family Enteletidae Waagen .......................... 40 

Genus Salopina Boucot ............................ 40 

Salopina sp. f .................................... 40 

Order Rhynchonellida Kuhn ................................... 40 

Family Camarotoechiidae Schuchert and 

Levene ...................................................... 40 

Genus Camarotoechia Hall and Clarke.. 40 

Camarotoechia pahranagatensis 

Waite ................................................ 40 

Camarotoechia sp. b .......................... 40 

Camarotoechia sp. f .......................... 40 

Order Spiriferida Waagen ...................................... 40 

Family Meristellidae Waagen ........................ 40 

Genus Hyattidina Schuchert .................. 40 

?Hyattidina sp. f ................................. 40 

Genus Hindella Davidson ........................ 41 

Hindella sp. a .................................... 41 

Family Atrypidae Gill ...................................... 41 

Genus Atrypa Dalman .............................. 41 

Atrypa sp. f ........................................ 41 

Family Delthyrididae Waagen ........................ 41 

Genus Howellella Kozlowski .................. 41 

Howellella pauciplicata Waite ........ 41 

Howellella smithi Waite .................. 41 

Locality register ......................................................................... 42 

Selected bibliography .............................................................. 43 

Index ............................................................................................. 47 

ILLUSTRATIONS 

[Plates follow index] 

PLATE 1. Striatopora, Pleurodictyum, Favosites, and Platyceras. 

2. Syringaxon, (?)Phacops, (?)Miraspis, Leonaspis, and Conularia. 

3. Leptostrophia, Orthostrophia, (?)Pholidostrophia, Stropheodonta, Strophonella, Schuchertella, and Leptaena. 

4. Levenea and Rhipidomella. 

5. LeptocQelia and Anastrophia. 

6. Plethorhyncha, Trematospira, and Kozlowskiellina. 

7. Costispirifer, Acrospirifer, Howellella, M eristella, and Ambocoelia. 

8. Siphonophrentis, Schuchertella, Leptostrophia, Orthostrophia, Howellella, Rhipidomella, and Phacops. 

9. Billingsastraea and Australophyllum. 

10. Entelophyllum. 

11. Atrypa, Camarotoechia, Salopina, Tryplasma, Entelophyllum, pycnostylid coral, and Pycnostylus. 

12. Howellella, ?Hyattidina, and Hindella. 
FIGURE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

CONTENTS v 

Page 

Index map of part of the Great Basin showing location of Rabbit Hill Limestone and Lone Mountain 

Dolomite fossils and approximate limits of Late Silurian-Early Devonian depositional facies belts............ 5 

Photograph showing view northwest across Copenhagen Canyon from Martin Ridge, showing Rabbit Hill 

and overthrust Ordovician Antelope Valley limestone cliffs .................................................................................... 6 

Photograph showing south side of Rabbit Hill, showing minor drag folds in west-dipping Rabbit Hill 

Limestone of the type section ----------------------·-------·------------------------------------------------------------------·--·-···································· 7 

Correlation diagram showing stratigraphic relations of the Rabbit Hill Limestone and inferred equivalence 

of Lone Mountain Dolomite to the Silurian Roberts Mountains Limestone ........................................................ 9 

Diagram illustrating history and present usage of the stratigraphic name Lone Mountain Dolomite ---------------------- 13 

Photograph showing south side of Lone Mountain, showing east-dipping stratigraphic section upward from 

Ordovician Antelope Valley Limestone to Devonian Nevada Formation ···----------------------------------------------------------· 14 

Correlation diagram showing stratigraphic relations of the Lone Mountain Dolomite and its equivalence 

to the Laketown Dolomite of Utah----------------------·-----------------------------------------------------------------------------·····--------------------··--- 14 

Correlation diagram showing stratigraphic relation of Rabbit Hill Limestone to Lone Mountain Dolomite 

as interpreted ---------------------------------------------------------··-----------------------------------------------------·-----------------------···----------------------·---- 17 

TABLES 

Page 

TABLE 1. Characteristic fossils of the Rabbit Hill Limestone and Beacon Peak Dolomite Member of the Nevada Formation 10 

2. Characteristic fossils of the upper Lone Mountain-Laketown biofacies ·----·-···----·····----·--·-·---·············-----·········-············ 16 

PALEONTOLOGY AND STRATIGRAPHY OF THE RABBIT HILL 

LIMESTONE AND LONE MOUNTAIN DOLOMITE 

.OF CENTRAL NEVADA 

By C. W. MERRIAM 

ABSTRACT 

Lateral facies changes from diagenetic dolomite on the east 

to limestone on the west greatly complicate stratigraphy and 

paleontology of the Silurian and Devonian Systems in the central Great Basin. Occupying the Silurian interval on the east, 

the Lone Mountain Dolomite is nearly barren of specifically 

identifiable fossils in its type section, but in the Fish Creek 

Range and other parts of its type area it has recently been 

found to contain well-preserved fossils. In the west-central 

Great Basin, the highly fossiliferous Rabbit Hill Limestone of 

Helderberg (Early Devonian) age overlies Silurian limestone 

and calcareous graptolitic shale of the Monitor-Simpson Park 

belt, in which no Lone Mountain dolomite has been discovered. 

The Rabbit Hill Limestone lithofacies is unknown to the east 

in the Antelope-Roberts Mountains belt, in which Lone Mountain Dolomite occurs; however, Rabbit Hill fossils are present 

locally in dolomite and dolomitic limestone of the Beacon Peak 

Dolomite Member of the Nevada Formation. Southeast of 

Eureka, Nev., in its type area, this member disconformably 

overlies the Lone Mountian Dolomite, being the lowermost 

member in that section of the Devonian Nevada Formation. In 

the Sulphur Spring Range, fossiliferous Beacon Peak underlies Oriskany-age Nevada Formation containing Costispirifer 

arenosus. 

The Rabbit Hill fauna is far more diverse taxonomically 

than the Lone Mountain Dolomite fauna. Its diagnostic fossils 

include the corals Pleurodictyum nevadensis, Pleurodictyum 

dunbari, and Syringaxon foerstei and the brachiopods Levenea 

subcarinata subsp. antelopensis, Leptocoelia occidentalis, Kozlowskiellina nolani, and Howellella cycloptera subsp. monitorensis. Upper beds of the Rabbit Hill Limestone at Dobbin 

Summit, Monitor Range, contain the large spirifers Costispirifer arenosus subsp. dobbinensis and Acrospirifer kleinhampli, forms that foreshadow the Oriskany (Siegenian) age 

faunas in the lower part of the Nevada Formation. 

Species of Pleurodictyum, Levenea, Howellella, and Anastrophia, among others, indicate correlation of the Rabbit Hill 

Limestone and Beacon Peak Dolomite with Helderbergian 

rocks of New York and Tennessee. Whereas the westerly facies 

Rabbit Hill Limestone was initially regarded as a possible 

time-stratigraphic equiv~lent of the easterly Lone Mountain 

Dolomite facies, paleontologic and stratigraphic evidence fails 

to support this view. A remote possibility of a very early Devonian horizon in topmost unfossiliferous beds of the Lone Mountain is not entirely ruled out. 

In areas recently mapped geologically within a few miles of 

Lone Mountain, silicified corals and brachiopods characterize 

dark-gray carbonaceous dolomite lenses in the upper part of 

the Lone Mountain Dolomite. Of these Lone Mountain fossils, 

the most diagnostic are species of the rugose coral Entelophyllum and the brachiopod Howellella. The small spiriferoids 

Howellella pauciplicata and Howellella smithi indicate a correlation with the uppermost part of the Silurian Laketown 

Dolomite in the Confusion Range, Utah. Entelophyllum is 

unknown later than the Silurian. 

INTRODUCTION 

The stratigraphy and paleontology of the Silurian 

and Devonian Systems in the central Great Basin is 

complicated by lateral facies changes from diagenetic 

dolomite on the east to limestone on the west. In the 

Silurian, the principal direction of this change is northwesterly, limestones on the west and northwest occupying stratigraphic positions in which dolomite comes to 

prevail in the opposite directions. For example, at Lone 

Mountain and in the Eureka mining district the Silurian is entirely dolomite, whereas to the northwest in 

the Roberts Mountains and adjacent parts of the Simpson Park Range it is largely limestone. Biofacies 

changes accompanying westerly to northwesterly disappearance of the Silurian diagenetic dolomite are commensurate with enclosing lithofacies differences. Faunal 

disparity explainable by facies appears to be of such 

magnitude as to eliminate or render uncertain a direct 

paleontologic correlation of these two contrasting Silurian carbonate facies. 

In the central Great Basin, the Silurian limestones 

and calcareous shales are more abundantly fossiliferous 

than the easterly dolomites. Until recently, in fact, 

identifiable fossils were unknown in the Lone Mountain 

Dolomite in its type area, which includes Lone Mountain and mountain ranges within and adjacent to the 

Eureka mining district. Whereas the Silurian age of 

much of the limestone and shale has now been fixed 

paleontologically with some confidence, dating heretofore of the dolomite facies has remained inferential 

because of the scarcity of determinable fossils. 

1 
2 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

The name Roberts Mountains Formation (Merriam, 

1940, p. 11) was applied to the Silurian limestones and 

calcareous shales of the westerly belt in this part of the 

Great Basin. Limestones originally included as the 

uppermost part of the Roberts Mountains Formation in 

the Monitor Range (Merriam and Anderson, 1942, p. 

1687) were found, in 194 7, to be of probable Helderberg 

(Early Devonian) age. In 1963 (Merriam, 1963, p. 42) 

these lithologically distinctive and fossil-rich upper 

limestones were described as a separate formation, the 

Rabbit Hill Limestone. Rabbit Hill fossils described 

here include those of the original list from the Monitor 

Range type area (Merriam, 1963, p. 43). 

PURPOSE AND SCOPE OF INVESTIGATION 

The main objectives of this paleontologic report are 

to describe and illustrate stratigraphically significant 

megafossils from the Rabbit Hill Limestone in its type 

area in the Monitor Range and the Lone Mountain 

Dolomite in its type area in the vicinity of the Eureka 

.mining district, Nevada. Collections from the Rabbit 

Hill in its type area are supplemented by material from 

outlying areas in the Monitor Range, Toquima Range, 

Simpson Park Range, Cortez Mountains, and the Tuscarora Mountains, where the Rabbit Hill fauna was 

discovered during the course of geologic mapping programs. Especially significant stratigraphically are Rabbit Hill fossils found in the lowermost part of the 

Nevada Formation of the Sulphur Spring Range during 

the Kobeh Valley program. Conclusions regarding relative geologic ages of the Rabbit Hill Limestone and the 

Lone Mountain Dolomite, which as lithologic entities 

do not occur in the same stratigraphic section, are 

based upon paleontologic comparisons made in conjunction with studies of the structure, stratigraphy, and 

areal geology of their outcrop belts. Details of the stratigraphy of both units have been dealt with in other 

contributions (Merriam, 1940, 1963, 1973a, 1973b; 

Nolan and others, 1956). 

This comprehensive study of the previously undescribed Rabbit Hill and Lone Mountain faunas is 

intended to amplify and support stratigraphic-paleontologic conclusions of monographic studies of rugose 

corals in all Silurian and Devonian formations of the 

central Great Basin (Merriam, 1973a, 1973b, 1973c). 

Proposed zonation of Great Basin Silurian and Devonian rocks by means of Rugosa (Merriam, 1973a, 

1973b) takes into consideration the stratigraphic 

occurrences of associated fossil groups, especially the 

brachiopods. Several well-represented phyla remain to 

be studied by specialists. 

Conodont and graptolite investigations bearing upon 

the complex interrelations of the Lone Mountain, Rabbit Hill, and Roberts Mountains Formations have, in 

recent years, led to conflicting age results, conclusions 

seemingly out of phase with those founded upon coral 

and brachiopod research. A first step toward adjustment of this confusion is the systematic collection and 

study of conodont material ~nd graptolites, from beds 

and sequences that also yield diagnostic corals, brachiopods, and other megafossils. Encouragement of such 

unifying field and laboratory procedures is an ancillary 

objective of this investigation. 

Conodonts are abundant in the Rabbit Hill Limestone in its type area and are briefly considered here 

(Huddle, J. W., written communs., 1969, 1970). Monograptid graptolites are reported from the type section 

(W. B. N. Berry, oral commun., 1971), although none 

were obtained during this study. In contrast, the Lone 

Mountain Dolomite in its type area has yielded neither 

conodonts nor graptolites during the course of this 

study. Accordingly, a searching review is called for of 

the somewhat circuitous and inductive stratigraphic 

speculations of conodont researchers whose reasoning 

leads to Devonian rather than Silurian age for the 

greater part of the Lone Mountain Dolomite (Clark 

and Ethington, 1966; Johnson, 1970). 

ACKNOWLEDGMENTS 

Reconnaissance geologic mapping of counties in the 

central Great Basin by geologists of the U.S. Geological 

Survey has extended known areal distribution of the 

Rabbit Hill Limestone and led to discovery of richly 

fossiliferous exposures of this formation. Among contributors to the map areas involved are F. J. Kleinhampl, northern Nye County, Nev.; R. J. Roberts and 

R. E. Lehner, northern Eureka County, Nev.; and E. H. 

McKee and J. H. Stewart, Lander County, Nev. L. D. 

Cress, U.S. Geological Survey, discovered the northernmost known Rabbit Hill exposures at Maggie Creek 

during geologic mapping in the vicinity of the Carlin, 

Nev., gold mine. Geologic mapping by E. H. McKee in 

the Wildcat Peak and Dianas Punch Bowl quadrangles, 

Toquima Range, Nev., led to the finding of Rabbit Hill 

fossils and has aided in clarifying the stratigraphic 

relations of the Rabbit Hill Limestone to Silurian strata 

correlative with the Roberts Mountains Limestone. 

Correlation and age determination of the Lone 

Mountain Dolomite were facilitated by mapping, stratigraphic study, and fossil collecting by R. K. Hose, U.S. 

Geological Survey, in the Silurian Laketown Dolomite 

of the Confusion Range, Utah. 

Glacial cobbles collected by F. K. Miller, U.S. Geological Survey, in Stevens County, northeast Washington, yielded silicified fossils suggestive of the Rabbit 

Hill fauna. 

A fossil collection from the Cortez Mountains, Nev., 

made by A. J. Boucot of Oregon State University has 
INTRODUCTION 3 

aided in establishing the relation of the Rabbit Hill to 

the Wenban Limestone. C. H. Stevens, San Jose State 

College, contributed a well-preserved colonial rugose 

coral from the Sunday Canyon Formation of the Inyo 

Mountains, Calif. 

J. W. Huddle, U.S. Geological Survey, prepared 

reports on Rabbit Hill Limestone conodonts, and Jean 

M. Berdan, of the Survey, identified ostracods from the 

same formation. 

The writer gratefully acknowledges the critical reading of the manuscript by G. Arthur Cooper, of the 

Smithsonian Institution. 

HISTORY OF INVESTIGATION 

The "Lone Mountain Limestone" in its type area, as 

described by Hague (1892, p. 57-62), included beds 

now differentiated as Late Ordovician and Silurian. In 

1892 the Ordovician or "Lower Silurian" had not been 

fully adopted by the U.S. Geological Survey as a system. Hague's (1892, p. 324-325) initial "Upper Silurian" assignment of the higher part of the Lone Mountain was inferential at best and predicated upon the 

position of these dolomites beneath strata of established Devonian age (Walcott, 1884, p. 4, 99-211). 

In redefining the "Lone Mountain Formation" at 

Lone Mountain in 1940, Merriam removed the separately mappable Late Ordovician dolomite as a lateral 

equivalent of the Hanson Creek Limestone. Merriam 

also concluded that an overlying medium-gray dolomite 

of Hague's original "Lone Mountain Limestone" could 

reasonably be interpreted at that time as a southerly 

dolomite equivalent of the Silurian Roberts Mountains 

Limestone exposed 20 miles to the northwest. Still 

undated by fossils, the restricted "Lone Mountain Formation" of Merriam ( 1940, p. 13) was viewed as resting 

conformably upon the Silurian Roberts Mountains 

Limestone in the Roberts Mountains, and upon its 

inferred dolomitic counterpart at Lone Mountain. A 

prominent chert marker unit occurs at the base of the 

Silurian Roberts Mountains Limestone of the type area 

and occupies the same position below the Silurian 

dolomite at Lone Mountain. The chert unit has been 

referred to as the Silurian basal chert, because in 

subsequent years it was discovered at many widely 

scattered localities in the Great Basin, where it lies 

upon Late Ordovician strata of Hanson Creek Richmondian age. In some areas where thick dolomites 

above the chert marker have yielded no fossils, the 

higher part of this dolomite sequence probably includes 

beds of Early or even Middle Devonian age. 

Reconnaissance geologic mapping and stratigraphic 

investigation in the northern Monitor Range during the 

1930's (Merriam and Anderson, 1942, p. 1687) disclosed a Silurian graptolitic sequence comprising cal506-612 0 - 73 - 2 

careous shale and platy limestone resting upon the 

Silurian basal chert; these graptolitic beds are in the 

area overlain by richly fossiliferous limestones later 

mapped separately and designated as Rabbit Hill Limestone. In 1942, all of these beds, including the Rabbit 

Hill, were considered part of the Silurian Roberts 

Mountains Limestone. In accordance with Merriam's 

1940 redefinition, the entire sequence appeared, therefore, to be older than the restricted Lone Mountain 

Formation at Lone Mountain. Absence of dolomites in 

this westerly Monitor Range column could be explained 

by absence in the west of beds representing their timestratigraphic interval; more likely, the interval above 

the Silurian basal chert recorded by dolomite at Lone 

Mountain was occupied in the Monitor Range by limestone and calcareous shale facies of deposition. 

Paleontologic evaluation of the Rabbit Hill Limestone by Merriam in 1947 led to the conclusion that it 

was of Helderbergian (Early Devonian) age rather than 

Silurian, encouraging search elsewhere for equivalent 

Devonian strata at the top of the Roberts Mountains 

Limestone. In the light of this disclosure and the theory 

of lithofacies change from easterly dolomite to limestone in the west, it now appeared not improbable that 

the Lone Mountain Formation as restricted by Merriam in 1940 might also be of Devonian age. 

Progress toward eventual clarification of the Lone 

Mountain-Rabbit Hill age relation was made after 1957 

because of continued geologic mapping and stratigraphic work under the Kobeh Valley project ofT. B. 

Nolan and Merriam. Discovery of Rabbit Hill fossils 

in lowermost beds of the Nevada Formation and the 

finding of Silurian faunas containing Entelophyllum 

and Howellella in the upper 500 feet of the Lone Mountain Dolomite in its type area convincingly suggested 

that the Rabbit Hill Limestone was actually younger 

than the restricted Lone Mountain. Beds containing 

the lowest Nevada Rabbit Hill fossils are assigned to 

the Beacon Peak Dolomite Member of the Nevada Formation which, in the Eureka mining district, rests disconformably upon the Lone Mountain Dolomite as 

mapped in that area (Nolan and others, 1956, p. 42). 

Restudy of the thick dolomite sequence that overlies 

the type section of the Roberts Mountains Limestone 

at Roberts Creek Mountain gave no direct fossil evidence of its age. These dolomites underlie the Nevada 

Formation, and in the absence of fossils were assigned 

in 1940 by Merriam to the Lone Mountain Formation. 

In the present state of knowledge of these rocks, it 

appears not unlikely that the upper part of the dolomite may represent the Beacon Peak Dolomite Member of the Nevada Formation, whereas the lower part is 

conceivably a northwestward-extending tongue of the 

Lone Mountain Dolomite. The underlying highest beds 
4 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

of the Roberts Mountains Limestone contain the fauna 

of Silurian coral zone D. The fauna of Silurian coral 

zone E would be expected in the overlying dolomite, 

conceivably followed upward by an Early Devonian 

fauna of the Rabbit Hill Limestone within the uppermost dolomite. 

A forward step in unraveling the Late Silurian-Early 

Devonian stratigraphic relation in the central Great 

Basin was made in 1960 by Winterer and Murphy, who 

found the Early Devonian Rabbit Hill Limestone resting conformably upon the Silurian Roberts Mountains 

Limestone in the northern Simpson Park Range. At 

Coal Canyon, 10 miles northwest of Roberts Creek 

Mountain, the uppermost Roberts Mountains Limestone contains Late Silurian coral zone E. No dolomite 

is present in this Simpson Park section, which represents a westerly limestone and calcareous shale facies 

of the Monitor-Simpson Park belt. 

Description of Silurian brachiopods from the Laketown Dolomite (Waite, 1956; Johnson and Reso, 1964) 

of the eastern Great Basin has facilitated study of the 

Lone Mountain Dolomite faunas, which are much more 

closely related to faunas of the Laketown than to 

faunas of the Silurian limestone facies. Detailed geologic mapping and stratigraphic study of the Laketown 

Dolomite in the Confusion Range of western Utah by 

R. K. Hose (written communs., 1954-1964) provided 

the fossil collections and other data employed here. 

MEmODS 

Fossils described here were for the greater part 

systematically collected in conjunction with geologic 

mapping and structural study in a region of intense 

deformation. Lateral facies change, thrusting, and pervasive normal faulting are features that require cooperative effort of the geologist and the paleontologist in 

the piecing together of composite . reference columns 

ever subject to critical revision. As a case in point, discovery of Rabbit Hill fossils in the basal Nevada Forfation above the Lone Mountain failed to support the 

conclusion drawn from initial mapping of the Rabbit 

Hill Limestone and the Lone Mountain Dolomite, that 

these contrasting carbonate facies occupied separate 

depositional belts and were mutually exclusive and 

possibly correlative laterally in a time-stratigraphic 

sense. Difficulty in continuous section measurement is 

well illustrated in the Rabbit Hill Limestone in its type 

area, where incompetent strata are folded and dragged 

beneath a major overthrust; only a few hundred feet of 

section is measurable at any one exposure. Regarding 

true vertical order of the Silurian faunas, in particular, 

uncertainties remain to be resolved by detailed geologic 

mapping and interpretation of geologic structure and 

lateral facies change. 

These paleontologic studies place emphasis upon the 

rugose corals. Systematic and descriptive research on 

these abundant and commonly well-preserved fossils 

makes possible their meaningful use in age determination, geologic correlation, and problems of depositional 

facies. The Rugosa have been used in conjunction with 

brachiopods as a basis for paleontologic zonation of 

Silurian and Devonian rocks of the Great Basin (Merriam, 1973a, 1973b). Because fossils are more abundant 

and better preserved in the Silurian limestone facies 

than in the dolomites, the rugose corals of these facies 

have been more thoroughly investigated and are better 

understood. Because of the biofacies differences, correlation of Silurian faunal horizons across the inferred 

lithofacies boundaries will doubtless remain quite 

speculative. 

This report deals mainly with silicified fossils prepared by acid treatment. In the Rabbit Hill bioclastic 

limestones, silicification was strangely selective; the 

corals and brachiopods were replaced to a much greater 

extent that associated Mollusca, Echinodermata, and 

other organic groups, which evidently were chemically 

less amenable to silica replacement. All identifiable 

fossils from the Lone Mountain Dolomite are silicified. 

Although the fossils from dolomite are well preserved 

externally, the internal structures were commonly 

destroyed in part by recrystallization. 

Sll..URIAN AND EARLY DEVONIAN 

DEPOSITIONAL BELTS OF THE GREAT BASIN 

Silurian marine rocks in the southwestern part of the 

Cordilleran geosyncline (fig. 1) are distributed in three 

contrasting lithologic belts (Merriam, 1973a): (1) A 

western graywacke belt of the Pacific Border, (2) an 

intermediate limestone belt, and (3) an eastern dolomite belt. The intermediate limestone belt traverses 

the west-central Great Basin in a north to northeasterly 

direction between the graywacke on the west and the 

very extensive dolomite belt on the east. Passing from 

one to another of these belts, faunas of about the same 

age show biofacies differences that seem to be related 

in part to change of depositional environment as well 

as to features of paleogeography and faunal dispersal. 

Similar facies belts are recognizable in the Devonian. 

The Silurian Roberts Mountains Limestone and 

overlying Rabbit Hill Limestone occupy the intermediate limestone belt; the Lone Mountain Dolomite 

lies in the eastern dolomite belt. A diagenetic dolomite, 

the Lone Mountain, occurs at the west border of a very 

extensive dolomite sheet which, as the Laketown Dolomite, includes all known Silurian strata of the eastcentral and eastern Great Basin. The graywacke or 

Pacific Border belt is preponderantly graywacke, volcanic rocks, and conglomerate with subordinate lime-
AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 5 

o L4~e:e~ R-E ~ :__ 

I 

Manhattan 0 Eastern 

Do lomite 

~~~~~~~~---+----~T~o~no~p~~~+- -- lt __ -n~~7-

0 8akersfield 

120" 116" 

25 50 75 100 MILES 

Ibex 

Hills 

EXPLANATION 

• 

Rabbit Hill fossils (Helderbergian age) 

!:> 

Coral-bearing limestone of possible Rabbit Hill 

(Helderbergian ) age 

• 

Lone Mountain Dolomite with fossils of Silurian age, 

and the upper Lone Mountain-Laketown biofacies 

I. Type section of Rabbit Hill Limestone, northern 

Monitor Range. 

2. Rabbit Hill Limestone, Dobbin Summit, medial Monitor 

Range. 

3. Rabbit Hill Limestone, Petes Canyon area, northern 

Toquima Range. 

3a. Rabbit Hill Limestone, Ikes Canyon, Toquima Range. 

4. Rabbit Hill Limestone, Walti Ranch, Simpson Park 

Range. 

5. Rabbit Hill Limestone, Coal Canyon, Simpson Park 

Range. 

6. Rabbit Hill Limestone, Cortez Mountains. 

6a. Rabbit Hill Limestone, Maggie Creek, Tuscarora 

Mountains. 

7. Beacon Peak Dolomite Member, Bailey Pass area, 

Sulphur Spring Range. 

8. Beacon Peak Dolomite Member, South Mulligan 

Gulch area, Sulphur Spring Range. 

8a. Beacon Peak Dolomite Member, type section in 

Oxyoke Canyon. 

9. Lone Mountain Dolomite, type area at Lone Mountain. 

10. Lon~ Mountain Dolomite, Mahogany Hills, southern part. 

11. Lone Mountain Dolomite, Fish Creek Range, southern part. 

12. Lone Mountain Dolomite, Sulphur Spring R.ange. 

13. Laketown Dolomite, Ibex Hills, Confusion Range, Utah. 

14. Laketown Dolomite, Pahranagat Range. 

15 . Silurian dolomite, Ruby Mountains. 

16. Vaughn Gulch Limestone (upper part), lnyo Mountains, Calif. 

17. Sunday Canyon Formation (upper part), lnyo Mountains, Calif. 

FIGURE I.-Index map of part of the Great Basin showing fossil localities of Rabbit Hill Limestone and Lone Mountain Dolomite 

and approximate limits of Late Silurian-Early Devonian depositional facies belts. 

stone; it contains no diagenetic dolomite. These westernmost Silurian rocks occur at Taylorsville, Calif., just 

north of the Sierra Nevada, but are best exposed in the 

Klamath Mountains and southeastern Alaska. 

AREAL DISTRIBUTION AND STRATIGRAPHY 

OF THE RABBIT HILL LIMESTONE 

Within the major intermediate limestone belt (fig. 1) 

of the southwestern part of the Cordilleran geosyncline, 

the Rabbit Hill Limestone rests upon Silurian limestones and calcareous shale; its exposures are confined 

to the more localized Monitor-Simpson Park facies belt 

in the west-central Great Basin. Scattered outcrops of 

this formation are known from Dobbin Summit in the 

Monitor Range northward 140 miles to the Tuscarora 

Mountains. On the east, in the subparallel north-south 

Antelope-Roberts Mountains facies belt, distinctive 

elements of the Rabbit Hill fauna, but not the Rabbit 

Hill Limestone itself, occur in dolomitic limestones 

assigned to the Beacon Peak Dolomite Member at the 

bottom of the Devonian Nevada Formation. 

At Dobbin Summit in the medial part of the Monitor 

Range, the Rabbit Hill Limestone overlies Silurian 

limestone containing calcareous shale and is in turn 

overlain by limestone of uncertain age yielding conodonts reported as Mississippian ( J. W. Huddle, written 

commun., 1966). Twenty miles north at the Rabbit 

Hill type section, this formation rests upon Silurian 

graptolite-bearing calcareous shale facies of the Roberts Mountains Formation (Merriam, 1963, p. 42). 

Because of faulting and erosion, no younger Paleozoic 

strata are found here. 

A key section with respect to stratigraphic relations 

of the Rabbit Hill Limestone is that in the northern 

Simpson Park Range, where this formation is conformably underlain by the highest Roberts Mountains Lime-
6 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

stone carrying the Late Silurian faunas of coral zone E. 

The Devonian Nevada Formation is here in fault contact with the Rabbit Hill Limestone. Limestones containing a Rabbit Hill fauna occur in the Toquima 

Range (McKee and others, 1972), where they rest 

conformably on the Roberts Mountains. Outlying areas 

where this fauna has been collected from limestones 

are Mount Tenabo in the Cortez Mountains and Maggie 

Creek northwest of Carlin. 

In terms of the major Silurian lithologic belts of the 

Cordilleran geosyncline referred to above, the Beacon 

Peak Dolomite containing Rabbit Hill fossils lies 

areally within the eastern dolomite belt. Here strata of 

Rabbit Hill Early Devonian age, but differing lithology, 

underlie Nevada Formation unit 1, which contains 

fossils of Oriskany (Siegenian) Early Devonian age. 

RABBIT HILL, NORTHERN MONITOR RANGE 

About 250 feet of Rabbit Hill Limestone is well 

exposed at Rabbit Hill in Copenhagen Canyon, Horse 

Heaven Mountain quadrangle (fig. 1). Here, in the 

type section at the south end of this small isolated hill, 

platy limestones and calcareous shales or siltstones 

separate thick lenses and beds of bioclastic limestone 

(pl. 8, fig. 15) containing abundant silicified fossils. 

Throughout the Rabbit Hill type area (figs. 2 and 3) 

these incompetent beds reveal evidence of drag folding 

(Merriam, 1963, p. 10). Deformation of these strata is 

sympathetic to the overthrust beneath which they lie 

and as a result the Pogonip Group on the west overrode 

the Roberts Mountains Formation and the Rabbit Hill. 

Because of the nature of this lower plate dislocation, it 

has not been determined whether the Rabbit Hill fossils 

range through a thickness much greater than 250 feet 

stratigraphically, as these beds are probably repeated 

across the broad exposure by drag folding and sympathetic slicing beneath the overthrust sole. 

All fossils collected from the 250 feet of type section 

of the Rabbit Hill Limestone are regarded as a single 

fauna. Other collections of fossils within these deformed 

strata of the type area north and west of Rabbit Hill 

itself appear to represent about the same assemblage. 

The largest fossil collections from the Rabbit Hill 

Limestone, those listed in connection with the original 

description of this formation (Merriam, 1963, p. 43) 

and described here, came from the southeast side of 

Rabbit Hill. Conodonts from the type section are listed 

below under age and correlation. Monograptus has 

been reported from the Rabbit Hill in its type area, 

and according toW. B. N. Berry (oral commun., 1971), 

graptolites have been found at Rabbit Hill. In connection with this study, no instance of interlayering of 

Monograptus beds with established Rabbit Hill Limestone was observed within the type area. Moreover, it 

is not unlikely that the thrust slicing within the outcrop 

belt might bring up slivers of graptolitic rock from 

Silurian strata of the subjacent Roberts Mountains. 

Most of the study fossil material from the Rabbit 

Hill Limestone in its type area was silicified and was 

prepared by the acid technique. 

The fauna of the Rabbit Hill Limestone at its type 

section is listed below: 

Favosites cf. F. helderbergiae Hall 

Striatopora cf. S. gwenensis Amsden 

FIGURE 2.-View northwest across Copenhagen Canyon from Martin Ridge, showing Rabbit Hill (RH) right of center, and 

overthrust Ordovician Antelope Valley limestone cliffs (Oa) in distance. Dr-Rabbit Hill Limestone; S---Silurian graptolitic beds of Roberts Mountains; WC-Whiterock Canyon; CC-Copenhagen Canyon. 
AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 7 

FIGURE 3.-South side of Rabbit Hill, showing minor drag folds 

in west-dipping Rabbit Hill Limestone of the type section. 

Pleurodictyum nevadensis n. sp. 

Pleurodictyum dunbari n. sp. 

Syringaxon foerstei n. sp. 

Rhipidomella rossi n. sp. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Orthostrophia strophomenoides subsp. newberryi n. 

subsp. 

Leptostrophia sp. cf. L. becki tennesseensis Dunbar 

(?)Pholidostrophia sp. R 

Stropheodonta sp. 

Leptaena fremonti n. sp. 

Schuchertella cf. S. haraganensis Amsden 

Plethorhyncha andersoni n. sp. 

Meristella martini n. sp. 

Ambocoelia sp. a 

Leptocoelia occidentalis n. sp. 

Trematospira mcbridei n. sp. 

Kozlowskiellina nolani n. sp. 

Howellella cycloptera subsp. monitorensis n. subsp. 

Platyceras sp. a 

Platyceras sp. b 

Platyceras sp. c 

Orthoceras sp. 

Leonaspis cf. L. tuberculatus (Hall) 

(?)Miraspis sp. 

Phacops sp. (large) 

hexactinellid sponge spicules 

crinoidal debris (abundant) 

fucoids (pl. 8, fig. 14) 

DOBBIN SUMMIT, MONITOR RANGE 

Excellent exposures of Rabbit Hill Limestone were 

discovered by F. J. Kleinhampl at Dobbin Summit 

(fig. 1) in the middle part of the Monitor Range during 

geologic mapping of northern Nye County, Nev. The 

Rabbit Hill at this locality resembles that of the type 

section 20 miles north but is less disturbed and occupies a definable stratigraphic interval within a continuous column. Silurian limestone and calcareous shale 

conformably underlying the Rabbit Hill contain brachiopod and graptolite faunas. The overlying limestones, 

which appear to be conformable, have yielded only 

conodonts reported to be Mississippian ( J. W. Huddle, 

written commun., 1966). 

Within the approximately 400 feet of Rabbit Hill at 

Dobbin Summit the faunas change in character somewhat passing upward in the column with introduction 

of the large spirifers Costispirifer and Acrospirifer, not 

found in the Rabbit Hill Limestone in its type area. 

The lower fauna is essentially that of the 250-foot 

interval at the type section. Following is a partial list 

of Rabbit Hill fossils from the lower 300 feet of the 

Dobbin Summit exposures: 

Favosites cf. F. helderbergiae Hall 

Pleurodictyum nevadensis n. sp. 

Syringaxon foerstei n. sp. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Rhipidomella rossi n. sp. 

Leptaena fremonti n. sp. 

Plethorhyncha andersoni n. sp. 

Meristella martini n. sp. 

Leptocoelia occidentalis n. sp. 

Kozlowskiellina nolani n. sp. 

Howellella cycloptera subsp. monitorensis n. subsp. 

Leonaspis cf. L. tuberculatus (Hall) 

In the upper 100 feet of the Dobbin Summit section, 

the two large spirifers Costispirifer arenosus subsp. dobbinensis and Acrospirifer kleinhampli appear; these 

forms are precursors of the later Early Devonian fauna 

of Nevada unit 1 and Great Basin Devonian coral zone 

B. Most of the species in the lower fauna continue into 

the upper interval. 

NORTHERN TOQUIMA RANGE 

Ikes Canyon.-Limestones on the south side of this 

canyon near its mouth contain a fauna of Rabbit Hill 

age as follows: 

Leptaena cf. L. fremonti n. sp. 

Orthostrophia cf. 0. strophomenoides Hall 

Levenea subcarinata subsp. antelopensis n. subsp. 

Kolowskiellina nolani n. sp. 

Meristella cf. M. martini n. sp. 

Limestones underlying those of Rabbit Hill Early 

Devonian age at Ikes Canyon contain a coral assemblage pertaining to Late Silurian coral zone E, below 

which are beds containing Monograptus (McKee and 

others, 1972). In this area, about 400 feet of limestone 

section including these fossils represents a part of the 

Roberts Mountains Formation overlain by the Rabbit 

Hill Limestone equivalent given the local name "McMonnigal Limestone" by Kay and Crawford ( 1964). 

Fossils listed from the "McMonnigal" by Kay and 

Crawford (1964, p. 440) suggest that Lower Devonian 

beds younger than Rabbit Hill may also be represented. 
8 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Petes Canyon area.-A small structurally disturbed 

exposure of Rabbit Hill Limestone was discovered by 

E. H. McKee in the Petes Canyon area during reconnaissance geologic mapping of Lander County, Nev. 

(fig. 1). At this locality (McKee and Ross, 1969, p. 

428), a few feet of deformed Rabbit Hill limestone lies 

in contact with Silurian graptolitic shales. The fossil 

assemblage comprises species characterizing the Rabbit Hill type section in the Monitor Range 20 miles east, 

differing only by the presence of a colonial rugose coral 

Australophyllum landerensis n. sp. This is one of two 

occurrences of colonial Rugosa discovered in the Rabbit Hill. Following is a partial list of the Petes Canyon 

fossil assemblage (Locality M1150): 

Favosites cf. F. helderbergiae Hall 

Striatopora cf. S. gwenensis Amsden 

Pleurodictyum sp. cf. P. nevadensis n. sp. 

Syringaxon foerstei n. sp. 

Australophyllum landerensis n. sp. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Leptocoelia sp. 

Kozlowskiellina nolani n. sp. 

McCLUSKY PEAK AREA, SIMPSON PARK RANGE 

A Rabbit Hill Limestone fauna containing abundant 

trilobites was collected in the foothills east of W alti 

Ranch (Walti Hot Springs quadrangle) by R. E. Lehner and R. J. Roberts during reconnaissance geologic 

mapping of Eureka County. No data are available on 

the relations of these rocks to strata above and below. 

Following is a partial list of the fossils from this locality 

(M1074): 

Pleurodictyum cf. P. nevadensis n. sp. 

Syringaxon foerstei n. sp. 

Leptocoelia cf. L. occidentalis n. sp. 

Leonaspis cf. L. tuberculatus (Hall) 

Phacops sp. (large) 

Proetus sp. 

Conularia cf. C. huntiana Hall 

Conularia cf. C. lata Hall 

tentaculitids 

COAL CANYON, NORTIIERN SIMPSON PARK RANGE 

An especially important reference section for the 

Silurian and Early Devonian limestone facies of the 

westerly Monitor- Simpson Park belt is near the mouth 

of Coal Canyon, Horse Creek Valley quadrangle (fig.1). 

The stratigraphy was studied by Winterer and Murphy 

(1960), who recognized the Rabbit Hill Limestone 

overlying richly fossiliferous Late Silurian limestone 

with lenses of coarse depositional limestone breccia. 

Although this area is faulted considerably, the depositional relations of the Silurian Roberts Mountains Formation are in some ways better shown here than in the 

type section of the Roberts Mountains Formation at 

Roberts Creek Mountain, 12 miles to the southeast. In 

order to elucidate the stratigraphy and geologic structure, the Coal Creek area was mapped in some detail 

by Merriam as part of the geologic mapping of the 

Horse Creek Valley quadrangle by the U.S. Geological 

Survey. 

On the east side of Coal Canyon the upper part of 

the Roberts Mountains Formation is overlain conformably by 1,100 feet of the Rabbit Hill Limestone. 

About 500 feet of the uppermost Roberts Mountains 

along the east side of the canyon appears to be unfaulted 

and it includes Late Silurian coral zone E (fig. 4). The 

west side of the Coal Canyon is within the north-south 

Coal Canyon fault zone, which breaks the continuity 

of the Silurian column, although no great amount of 

the section appears to have been cut out by this deformation. West of the Coal Canyon fault zone the limestones of the Roberts Mountains contain a fauna similar to that of Silurian coral zone D. 

One-half mile east of Coal Canyon, the Rabbit Hill 

Limestone is repeated in a seperate fault block, greatly 

broadening the exposure of this formation. About a mile 

east of Coal Canyon, Nevada Formation unit 2 crops 

out in another fault block. No normal stratigraphic 

boundary of the Nevada upon the Rabbit Hill has been 

found in this area. 

As discussed below under age and correlation of the 

Rabbit Hill Limestone, the results of this mapping and 

stratigraphic-paleontologic work do not support the 

conclusions of Johnson (1965), Johnson and Murphy 

(1969), and Johnson (1970) regarding age and stratigraphic sequence within the Roberts Mountains Formation of this area. 

Rabbit Hill fossils listed below were collected from 

beds high in the formation. It is probable that the unit 

can be zoned here on the basis of bed-by-bed collecting. 

As at the Walti Ranch locality west of McClusky Peak, 

the Coal Canyon Rabbit Hill contains large trilobites 

in some abundance: 

Syringaxon foerstei n. sp. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Leptostrophia cf. L. becki tennesseensis Dunbar 

Strophonella cf. S. punctulifera (Conrad) 

Leptaena fremonti n. sp. 

Schuchertella cf. S. haraganensis Amsden 

Plethorhyncha andersoni n. sp. 

Meristella martini n. sp. 

Howellella cycloptera subsp. monitorensis n. subsp. 

(?)Acrospirifer kleinhampli n. sp. 

(?) Costispirifer are nos us subsp. dobbinensis n. subsp. 

·(?)Coelospira sp. (small) 
AREAL DISTRIBUTION AND STRATIGRAPHY OF THE RABBIT HILL LIMESTONE 

Monitor Range 

Rabbit Hill 

2 

Simpson Park Range Roberts Mountains 

Coal Canyon Roberts Creek Mountain 

c: 

0 

Sulphur Spring Range 

southern part 

Diamond Mountains 

Oxyoke Canyon 

Devtls Gate 

Limestone 

DD -~ I Units 1 and 2 

1.\ DFault contact 1./-~ -- -B=a~~: ;e:~(?) \V Nevada 1 1\l Dolomite', 

DD Fo~~~~:i~n t __ _ ' Member 11 

and 2 "· ,-> I 

1 Dolomite 1 "' \Dolomite\ 

Faulting and//~ / ~ \ 

Thickness 

approximate 

Woodpecker 

Limestone 

Member 

Bay State 

Dolomite Member 

Woodpecker 

Limestone 

Member 

alluvium/ / o \ 

25 

Manhattan 0 

116" 

50 MILES " 

c: 

"' 

~ Vi 

c: 

"' ·c:; 

·;; 

0 

.,... _, ,...... Dolomite/ .~ 

.,..""",..,.. I ~ / I c: ,..""' I ::I 

Top /// 0DA Rabbit I ~ unexposed Hill I 

CD Limestone G)§ 

DA Rabbit Hill ...J 

~ Quartzite 

CD Overthrust relation; upper plate is Ordovician Pogo nip Group. 

G) Sandstone resembling Oxyoke Canyon Sandstone Member. 

G) Coral zone SE unrecognized in dolomite facies. 

0 Rabbit Hill Helderbergian fossils in Beacon Peak Dolomite Member. 

0 Devonian and Silurian coral zones (DA, SD) shown on left of 

column. Limestone 

Quartzite 

Sentinel Mountain 

Dolomite Member 

Oxyoke Canyon 

Sandstone Member 

Beacon Peak 

Dolomite Member 

~~-~~~~~e---IIDisconformitv 

section 

Lone Mountain 

Dolomite 

t 

1000 FEET 

500 

0 

VERTICAL SCALE 

FIGURE 4.-Correlation diagram showing stratigraphic relations of the Rabbit Hill Limestone and inferred equivalence of Lone 

Mountain Dolomite to the Silurian Roberts Mountains Limestone. 

9 

Orthoceras sp. 

tentaculitids 

Leonaspis cf. L. tuberculatus (Hall) 

Phacops sp. (large) 

from localities along the west Cortez front. At locality 

M1083 on the southeast side of Mount Tenabo, a collection made by A. J. Boucot contains Syringaxon 

foerstei n. sp. and Pleurodictyum cf. P. nevadensis n. sp. 

(?)Phacops sp. B, cf. P. canadensis Stumm 

dalmani tid (very large) 

CORTEZ MOUNTAINS AND TUSCARORA MOUNTAINS 

Cortez Mountains.-Rabbit Hill fossils occur in the 

Wen ban Limestone of Gilluly and Masursky ( 1965, p. 

29) in the Cortez area 8 miles northwest of the Coal 

Canyon section, northern Simpson Park Range. The 

Wenban occupies large areas in the western Cortez 

Mountains, where it rests upon the Silurian Roberts 

Mountains Limestone. As described by Gilluly and 

Masursky, this unit is probably more than 2,000 feet 

thick and seems to include much of the Devonian. It 

is fairly evident that a least the lower half represents 

the Rabbit Hill interval as exposed in Coal Canyon, 

whereas the upper half probably includes the Nevada 

Formation, possibly capped by a Late Devonian equivalent of the Devils Gate Limestone. Whether the Rabbit 

Hill part of the Wenban can on a lithologic basis be 

mapped separately from the Nevada in that area 

remains to be demonstrated. Collections of poorly preserved fossils suggesting the Rabbit Hill fauna come 

Tuscarora M ountains.-Exposures of limestone containing a Rabbit Hill fauna were discovered in the 

southern Tuscarora Mountains by L. D. Cress during 

the course of geologic mapping in the Carlin Gold mine 

area. These disturbed limestones are in contact with 

the Roberts Mountains Limestone, which in that vicinity contains Silurian Coelospira. At locality M1400 near 

Maggie Creek, 9 miles northwest of Carlin, the following fossils occur: 

Favosites sp. (massive forms) 

Pleurodictyum sp. cf. P. lenticularis (Hall) 

Syringaxon foerstei n. sp. 

Billingsastraea sp. m 

Schuchertella sp. cf. S. haraganensis Amsden 

Leptaena cf. L. fremonti n. sp. 

Rhipidomella sp. 

Leptocoelia sp. (shell fragments only) 

Acrospirifer sp. 

Nucleospira sp. cf. N. ventricosa (Hall) 

Meristella sp. 

phacopid trilobite pygidium (small) 
10 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Billingsastraea sp. m (pl. 9, figs. 1, 2) is the earliest 

known coral of this genus in the Cordilleran belt and 

is one of two known occurrences of colonial Rugosa in 

the Rabbit Hill. 

BEACON PEAK DOLOMITE, 

SULPHUR SPRING RANGE 

Geologic mapping of the southern Sulphur Spring 

Range (fig. 1) under the Kobeh Valley project has disclosed many exposures of dolomite and dolomitic limestone containing a fauna similar to that of the Rabbit 

Hill Limestone in beds that conformably underlie 

Nevada Formation unit 1, which carries the Oriskany 

age ( Siegenian) fauna of Devonian coral zone B. 

Because of their stratigraphic position and lithologic 

similarity to the Beacon Peak, lowest member of the 

Nevada Formation in the Eureka mining district, these 

beds are assigned to that unit (Nolan and others, 1956, 

p. 42). In its type area, the Beacon Peak (fig. 1) rests 

disconformably upon Lone Mountain Dolomite (fig. 4) 

and has yielded no determinable fossils. Although Lone 

Mountain Dolomite, where best exposed in the southern 

Sulphur Spring Range, lies in fault contact with the 

Beacon Peak and the higher Nevada, it is with some 

confidence believed to directly underlie Beacon Peak 

beds containing elements of the Rabbit Hill fauna. 

Fossils from two of the Beacon Peak localities in this 

area are listed below. 

South Mulligan Gulch area (locality M186): 

Pleurodictyum sp. 

Favosites sp. (massive) 

Syringaxon foerstei n. sp. 

Siphonophrentis sp. B 

Levenea subcarinata subsp. antelopensis n. subsp. 

Leptocoelia occidentalis n. sp. 

Anastrophia cf. A. verneuili (Hall) 

Strophonella sp. cf. S. punctulifera (Conrad) 

Bailey Pass area· (locality M197) : 

Favosites sp. (massive) 

Syringaxon foerstei n. sp. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Leptocoelia occidentalis n. sp. 

Leptaena cf. L. fremonti n. sp. 

Anastrophia cf. A. verneuili (Hall) 

Meristella sp. (large) 

Acrospirifer sp. cf. A. kleinhampli n. sp. 

AGE AND CORRELATION 

OF THE RABBIT HILL LIMESTONE 

The Rabbit Hill Limestone is of Helderbergian 

(Early Devonian) age. When first examined in the type 

area (Merriam and Anderson, 1942, p. 1687), these 

beds were included with the Roberts Mountains Formation as a part of the Silurian System. Comparative 

study of brachiopods in 194 7 strongly favored an Early 

Devonian age. Among its abundant and distinctive 

brachiopod genera, Leptocoelia appears first in this formation (table 1); so far as is known, this genus is confined to the Devonian and is especially characteristic 

of the Early Devonian. The genus Ambocoelia in the 

Rabbit Hill confirms a Devonian age. Supporting 

TABLE !.-Characteristic fossils of the Rabbit Hill Limestone 

and Beacon Peak Dolomite Member of theN evada Formation 

Monitor 

Range 

Favosites cf. F. 

helderbergiae Hall .................... X 

Favosites sp. (massive) ............... . Striatopora cf. S. gwenesis 

Amsden ...................................... X 

Pleurodictyum nevadensis n. sp... X 

Pleurodictyum sp ....................... . Pleurodictyum dunbari n. sp ...... X 

Syringaxon foerstei n. sp ............ X 

Australophyllum sp. r ................. . 

Rhipidomella rossi n. sp ............ X 

Levenea subcarinata subsp. 

antelopensis n. subsp .............. X 

Orthostrophia strophomenoides 

subsp. newberryi n. subsp ...... X 

Leptostrophia sp. cf. L. becki 

tennesseensis Dunbar .............. X 

(?) Pholidostrophia sp. R ............ X 

Stropheodonta sp .......................... X 

Strophonella sp. cf. S. 

punctulifera (Conrad) 

Leptaena fremonti n. sp .............. X 

Schuchertella cf. S. 

haraganensis Amsden .............. X 

Plethorhyncha andersoni n. sp .. X 

M eristella martini n. sp ............ X 

M eristella sp. (large) ................. . Ambocoelia sp. a ............................ X 

Leptocoelia occidentalis n. sp .... X 

Leptocoelia sp ............................. . Trematospira mcbridei n. sp ...... X 

Kozlowskiellina nolani n. sp ...... X 

Howellella cycloptera subsp. 

monitorensis n. subsp .............. X 

Acrospirifer kleinhampli n. sp ... . Costispirifer arenosus subsp. dobbinensis n. subsp ............... . (?)Coelospira sp. (small) ........... . Anastrophia cf. A. verneuili 

(Hall) ....................................... . Platyceras sp. a ............................ X 

Platyceras sp. b .............................. X 

Platyceras sp. c .............................. X 

Orthoceras sp ................................ X 

Conularia cf. C. huntiana Hall ... . Conularia cf. C. lata Hall ........... . tentaculitids ................................... . Leonaspis cf. L. tuberculatus 

(Hall) ........................................ X 

(?) M iraspis sp .............................. X 

Phacops sp. (large) ...................... X 

(?)Phacops sp. B, cf. P. 

canadensis Stumm ................... . dalmanitid (very large) ............. . Proetus sp ..................................... . 

X 

X 

X 

---· 

X 

X 

X 

X 

X 

...... 

X 

X 

X 

X 

X 

X 

X 

X 

cf. 

X 

X 

X 

X 

X 

Simpson 

Park 

Range 

cf. 

..... 

X 

cf. 

X 

X 

X 

X 

........ 

X. 

....... 

X 

...... 

X 

X 

X 

X 

X 

X 

X 

X 

X 

cf. 

cf. 

X 

·---

X 

----

X 

X 

........ 

X 

X 

X 

X 

X 

X 

X 

X 

cf. 

X 

X 

cf. 

X 
AGE AND CORRELATION OF THE RABBIT HILL·LIMESTONE 11 

brachiopod evidence is provided by the presence of 

Devonian types of Trematospira in the Rabbit Hill and 

of Anastrophia related to A. verneuili in the correlative 

Beacon Peak Dolomite Member. Moreover, Early Devonian Acrospirifer and large Costispirifer of the Oriskany 

C. arenosus type occur in higher Rabbit Hill beds. The 

colonial rugose coral Billingsastraea sp. m of the Rabbit 

Hill at Tuscarora Mountains further supports a Devonian age, this genus not being recorded in older rocks. 

Paleontologic comparison of the Rabbit Hill and 

Beacon Peak faunas with Devonian faunas of eastern 

North America demonstrates that several distinctive 

western species and subspecies have near relatives in 

Helderbergian (Early Devonian) strata of New York, 

Tennessee, and Oklahoma. Among fossil indicators of 

eastern Helderberg affinity are two species of Pleurodictyum, the trilobite Leonaspis of the L. tuberculatus 

type, and also the brachiopods Levenea subcarinata 

subsp. antelopensis, Howellella cycloptera subsp. monitorensis, Anastrophia cf. A. verneuili, and Orthostrophia strophomenoides subsp. newberryi. 

Evidence from study of Rabbit Hill conodonts also 

supports an Early Devonian age. A conodont faunule 

extracted from samples collected by the writer in the 

upper 100 feet of the type Rabbit Hill Limestone at 

Rabbit Hill is reported on by J. W. Huddle (written 

commun., 1969) as follows: 

***Your collections M1326-1 and M1326-2 from the upper 

100 feet of Rabbit Hill Limestone at the Rabbit Hill type section, Copenhagen Canyon, Horse Heaven quad., Nevada both 

contain abundant specimens of Icriodus latericrescens n. subsp. 

B of Klapper 1969, I. latericrescens huddlei Klapper and Ziegler and single cusp conodonts generally referred to Acodina 

which seem to be associated with Icriodus latericrescens. 

These forms are characteristic of Johnson-Boucot (1968) 

Spinulosa-Zone I and Klapper et al in press Zone-5 (and Klapper, 1969) which is thought to be Siegenian. 

Further permissive evidence of Siegenian age is provided by conodonts from the uppermost part of the 

Rabbit Hill at Coal Canyon, Simpson Park Range 

(locality M1310), identified by Huddle as follows: 

Belodella resimus Philip 

Icriodus cf. I.latericrescens n. subsp. B of Klapper 

Icriodus sp. 

Ostracods from a locality near the base of the Wenban Limestone near Cortez (Gilluly and Masursky, 

1965, p. 31) have been reported on by Jean M. Berdan, 

of the U.S. Geological Survey. The lower part of the 

Wenban is with assurance the lower part of the Rabbit 

Hill Limestone of the neighboring Simpson Park 

Range. Following are the ostracods listed by Berdan: 

M esomphalus sp. 

V eli beyrichia sp. 

n. gen. aff. W elleria 

Saccarchites sp. 

506-612 0- 73 - 3 

Aechmina? sp. 

Acanthoscapha sp. 

Tricornina sp. 

Tubilibairdia sp. 

Bairdia sp. aff. B. leguminoides 

As several of the genera listed range upward from Late 

Silurian into Early Devonian, it was not found possible 

on the basis of ostracods alone to fix the age of these 

beds. 

Samples from the uppermost part of the Rabbit Hill 

Limestone at Coal Canyon (locality M1310) yielding 

Belodella resimus Philip and other conodonts reported 

on by Huddle also contain ostracods, identified by Jean 

M. Berdan as follows: 

***The ostracodes include Thlipsura sp. aff. T. furca Roth, 

Parahealdia? aff. P.? convexoris Swartz and Whitmore, and 

several unidentifiable species. Thlipsura furca was originally 

described from the Haragan Limestone of Oklahoma. Parahealdia? convexoris was described from the upper part of the 

Manlius Limestone in southeastern New York; however, there 

is an undescribed species in the Port Ewen Limestone in the 

Hudson Valley which is even closer to the form from the Rabbit Hill. These two species suggest that this part of the Rabbit 

Hill has affinities with the Helderbergian of the Appalachian 

region. 

Because of the high stratigraphic position of this ostracod and conodont locality (M1310), it is assumed that 

these beds are younger than those in the Wen ban Limestone near Cortez that yielded ostracods identified by 

Berdan. 

On the basis of fossil evidence, the westerly Rabbit 

Hill Limestone is correlated with the Beacon Peak 

Dolomite Member in the more easterly AntelopeRoberts Mountains facies belt (fig. 4). Fossils common 

to the two differing carbonate facies are similar types 

of Pleurodictyum, Syringaxon foerstei n. sp., Leptocoelia occidentalis n. sp., Levenea subcarinata subsp. 

antelopensis, and similar Acrospirifer. 

Limestones possibly correlative with the Rabbit Hill 

occur in the Mazourka Canyon area, northern Inyo 

Mountains, Calif. (fig. 1), where they lie in the upper 

part of the Vaughn Gulch Limestone and in the upper 

part of the more or less equivalent Sunday Canyon Formation (Ross, 1966, p. 31-35). These beds contain 

species of the colonial rugose coral Australophyllum 

similar to Rabbit Hill A. landerensis. The middle and 

lower parts of both formations are Silurian (Merriam, 

1973a). Late Silurian coral zone E underlies the uppermost Vaughn Gulch division, which contains Australophyllum sp. v of possible Helderbergian age. Australophyllum stevensi in upper beds of the Sunday Canyon 

Formation is also conceivably Early Devonian. As mapped by Ross ( 1966, pl. 1), the Vaughn Gulch Limestone changes northward into the more shaly Sunday 

Canyon Formation, in which Silurian graptolitic depos-
12 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

its predominate, a facies change comparable to that 

noted elsewhere in correlative Roberts Mountains 

Limestone of the major intermediate limestone belt. 

With a single exception, there are no recorded occurrences of the Rabbit Hill fauna in western North 

America outside of the Great Basin. Glacial cobbles 

collected by F. K. Miller, of the U.S. Geological Survey 

(oral commun., 1965), in the Chewelah area, Stevens 

County, northeastern Washington, contain a fauna of 

Rabbit Hill affinity. Among the fossils are Syringaxon 

sp., Pleurodictyum cf. P. lenticularis (Hall), Levenea 

cf. L. subcarinata (Hall), and a species of Leptocoelia. 

Data from stratigraphic position of the Rabbit Hill 

Limestone and correlative Beacon ·Peak Dolomite 

Member have a bearing upon the age and correlation of 

these units in a world sense. In the Sulphur Spring 

Range the Beacon Peak occupies the interval between 

the Lone Mountain Dolomite (below) and Nevada 

Formation unit 1 (above) (fig. 4). Lower beds of 

Nevada Formation unit 1 carrying Costispirifer arenasus and Acrospirifer as well as the rugose corals of 

Devonian coral zone B are of Oriskany age, or Siegenian of the European scale. Hence a pre-Oriskany or 

Helderbergian age assignment of the Beacon Peak and 

Rabbit Hill is appropriate. Presence in the topmost 

part of the Rabbit Hill Limestone at Dobbin Summit 

of the large Costispirifer arenosus subsp. dobbinensis 

and the large Acrospirifer kleinhampli strongly suggests that the fauna of these upper beds foreshadows 

and may be little older than that of Nevada Formation 

unit 1 in Devonian coral zone B with its Oriskany or 

Siegenian elements. Moreover, the reported Siegenian 

age of the uppermost Rabbit Hill based on conodont 

evidence seems to be in harmony with these findings. 

Fixing of the age of the base of the Rabbit Hill Limestone is made possible by its conformable stratigraphic 

relation to underlying coral-bearing limestones in the 

northern Simpson Park Range. At Coal Canyon (fig. 1) 

the topmost Roberts Mountains Limestone contains a 

large and diverse coral assemblage of Gotlandian 

aspect and Late Silurian (Ludlovian) age (fig. 4). These 

distinctive corals characterize Silurian coral zone E of 

the Great Basin and include the Silurian rugose corals 

Mucophyllum, Kodonophyllum, and Chonophyllum, 

and pycnostylids. They are not known in Devonian 

rocks, and, with the entire fauna of Silurian coral zone 

E, do not reappear in the Rabbit Hill. Conclusions by 

Johnson and others (Johnson, 1965; Johnson, 1970; 

Johnson and Murphy, 1969) regarding a possible Devonian age of the uppermost Roberts Mountains Limestone at Coal Canyon are not confirmed by the rugose 

coral and brachiopod studies of Merriam ( 1973a). The 

Late Silurian fauna of coral zone E has been found in 

the Toquima Range, Nev. (McKee and others, 1972), 

where it underlies limestone with a probable Rabbit 

Hill fauna. A similar relation is recognized (Merriam, 

1973a) in the Vaughn Gulch Limestone of the northern 

Inyo Mountains, Calif. 

In summary, an Early Devonian (Helderbergian) age 

for these Great Basin strata is supported by the stratigraphic position of Rabbit Hill Limestone at Coal Canyon, Simpson Park Range, above Late Silurian (Ludlovian) beds of Silurian coral zone E, by the occurrence 

of faunas of Rabbit Hill affinity below strata of Oriskany (Siegenian) age in the Sulphur Spring Range, 

and most convincingly by paleontologic similarities of 

the Rabbit Hill fauna to faunas of eastern Helderberg 

formations. 

LONE MOUNTAIN DOLOMITE 

The nam~ "Lone Mountain Limestone" originally 

applied by Hague ( 1892, p. 57-62) to a more inclusive 

section was later, as "Lone Mountain Formation," 

restricted by Merriam ( 1940, p. 13; 1963, p. 39) to 

some 1,750 feet of blocky saccharoidal dolomite overlain by the Nevada Formation and underlain by a lower 

darker gray dolomite unit. At Lone Mountain, Eureka 

County, Nev., within the designated type area, there 

has been previous to this report no fossil evidence applicable to the restricted Lone Mountain Dolomite. Presumed Silurian age was predicated upon stratigraphic 

position beneath Lower Devonian beds of Nevada unit 

1, coupled with possible correlation of underlying 

darker gray dolomite with Silurian·Iimestones named 

Roberts Mountains Formation by Merriam ( 1940, p. 

11). 

In other Great Basin areas, the name Lone Mountain 

Dolomite has been adopted rather loosely in some 

instances for lithologically comparable and usually 

rather barren dolomites beneath an assumed SilurianDevonian boundary. Whereas the Lone Mountain Dolomite was long assumed to be a westerly continuation of 

the Laketown Dolomite of the eastern Great Basin, 

there has previous to this report been no published 

fossil evidence to bear out this view. 

In recent years geologic mapping of areas within and 

bordering upon the Eureka mining district has disclosed stratigraphic sections in which the Lone Mountain Dolomite is quite fossiliferous, and where the 

stratigraphic relations to contiguous formations may be 

determined. These sections lie in the southern Diamond 

Mountains, the southern Fish Creek Range, the 

Mahogany Hills, and the southern Sulphur Spring 

Range. 

LONE MOUNTAIN DOLOMI1E, LONE MOUNTAIN 

The "Lone Mountain Formation" of the type area as 

redefined by Merriam in 1940 (p. 13, 19) included only 
LONE MOUNTAIN DOLOMITE 13 

the upper "1,570 feet" of Hague's inclusive "Lone 

Mountain Limestone" (Hague, 1892, p. 57). So 

delimited, the Lone Mountain of Merriam is underlain 

by about 750 feet of darker weathering dolomite, at 

that time considered to be a southerly dolomite facies 

of the Roberts Mountains Formation, which in its type 

area is mainly limestone rich in Silurian fossils (Merriam, 1940,pl.2,fig.2). 

Recent disclosures call for some realinement of the 

dolomite units at Lone Mountain in the interest of 

clarity and simplicity. Because of the dolomitic nature 

of the entire section upward from the Silurian basal 

chert member to the Devonian Nevada Formation, it 

is here proposed to refer to the lower 750-foot darker 

weathering dolomite in the Lone Mountain Dolomite 

as Lone Mountain unit 1, designating the upper unit or 

Lone Mountain Dolomite (restricted) of Merriam 

(1940) as Lone Mountain unit 2 (fig. 5). So reapportioned, Hague's original "Lone Mountain Limestone" 

comprises at the bottom a Late Ordovician dolomitic 

facies of the Hanson Creek Formation overlain by Lone 

Mountain Dolomite units 1 and 2. Of special stratigraphic significance at Lone Mountain (fig. 6) is the 

Silurian basal chert, which is as much as 80 feet thick 

in places and forms the bottom member of Lone 

Mountain Dolomite unit 1. 

Although no positively identifiable fossils have been 

collected from the type section of Lone Mountain 

Dolomite during these investigations, poorly preserved 

organic remains are not uncommon. Hague ( 1892, p. 59, 

61) and Walcott (1884, p. 4, 273) make reference to 

the presence at Lone Mountain of "Halysites cate.nulatus." Because Hague gives its horizon as "within 50 

feet of the quartzite," it is likely this was an halysitid 

normally occurring in the Late Ordovician Hanson 

Haque (18921 Merriam 11940) Merriam (this report) 

Nevada Limestone Nevada Formation Nevada Formation 

unit 1 * L one Mountain Lone Mountain 

Formation Dolomite 

(restricted) un it 2 

-------

Lone M ountain Roberts Mou ntains L one Mountai n 

Limestone Formation Dolomite 

(dolomite facies) u ni t 1 

--- ~~:.-:~~-..,-.'1" 

Hanson Creek Hanson Creek 

Formation Formation 

(dolomite facies) (dolomite facies) 

Eureka Quartz ite Eureka Quartzite Eureka Quartzite 

Pogonip L imestone Pogon ip Li mestone Pogonip Group 

*Beacon Peak Dolomite Member unrecog nized. 

X Silurian ba sal chert marker red . 

Early Devo n ian 

(early Emsian) 

Silurian 

Ordovician 

FIGURE 5.-Diagram illustrating history and present usage of 

the stratigraphic name Lone Mountain Dolomite. 

Creek and Ely Springs Dolomite. Walcott (1884, p. 4) 

alludes to its poor preservation in stating that doubt 

existed in the mind of James Hall, who examined the 

fossil, as to the validity of the identification. Poorly 

preserved tabulate corals were collected by Merriam 

(1940, p. 13, 20) in the 1930's at the base of Lone 

Mountain unit 2. These corals were considered more 

closely allied to Syringopora than Halysites. 

Many exposures of dark-gray dolomite showing 

conspicuous organic traces have been found in Lone 

Mountain unit 2 during detailed mapping of the Lone 

Mountain area by the U.S. Geological Survey. Carbonaceous dolomites containing the poorly preserved 

fossils are most numerous in the upper 750 feet of the 

Lone Mountain and appear to be lenses or pods surrounded by lighter gray barren rock. The dark pods 

appear to have been loci of especially prolific organic 

activity within which the magnesian recrystallization 

was somewhat less destructive of fossil structure than 

in the lighter rock. 

Definite rugose coral structures occur at two localities (M1122, M1122a) east of Charcoal Gulch on the 

southeast side of Lone Mountain, probably within the 

upper 500 feet of the Lone Mountain Dolomite. Material from locality Ml122 shows broken, partly macerated Rugosa with fairly large subcylindrical corallites 

of diameters up to three-fourths of an inch and lamellar 

septa (pl. 11, fig. 32). These fossils suggest the Silurian 

genus Entelophyllum, well represented in the higher 

Lone Mountain Dolomite of the Mahogany Hills and 

Fish Creek Range as discussed below. 

LONE MOUNTAIN DOLOMITE, 

SOUTHERN MAHOGANY HILLS 

Dark-gray carbonaceous dolomites containing abundant silicified fossils occur within the upper 500 feet of 

the Lone Mountain Dolomite 1 14 miles north of the 

summit of Wood Cone Peak and 2 miles south-southwest of Combs Peak (Merriam, 1963, p. 41). As at Lone 

Mountain in the upper part of unit 2, these fossilbearing carbonaceous dolomites are lenticular within 

the lighter gray barren dolomite and appear to occupy 

about the same stratigraphic interval (fig. 7). At 

locality Mlll2 the coral beds are quite extensive and 

are occupied almost solely by the colonial bushy 

Entelophyllum (pl. 10, fig. 11). 

Southwest of locality M1112, and presumably much 

lower in the section, Halysites is present in dark-gray 

dolomite that possibly represents Lone Mountain unit 

1. Still lower, in considerably faulted range-front terrane, are fossiliferous limestones of the Late Ordovician 

(Richmondian) horizons representing the Hanson 

Creek Formation (fig. 7). Walcott's original locality for 

the "Trenton" fauna, now known to be that of the Han-
14 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

FIGURE 6.-South side of Lone Mountain, showing east-dipping stratigraphic section upward from Ordovician Antelope Valley 

Limestone (Oa) on left to Devonian Nevada Formation (Dn) on right. Note color contrast differentiating darker gray Lone 

Mountain unit 1 (Sll) from lighter gray Lone Mountain unit 2 (Sl2). Oe-Eureka Quartzite; Oh-Hanson Creek Dolomite 

facies; Sib-Silurian basal chert; WP-West Peak; CP-Central Peak; FG-Fossil Gulch; CG-Charcoal Gulch. 

4 

Sulphur Spring Range 

southern part 

Lone Mountain Mahogany Hills 

southern part 

Diamond Mountains 

Oxyoke Canyon 

Confusion Range, Utah 

Ibex Hills (i) 

12d' ""' 

Thickness 

approximate 

Devils Gate 

Devils Gate Limestone 

cj_--~L~im~e~s;to;n~•-----------------------.~g~--r 

·~ Unit 5 (Bay State ~ ~ Dolomite Member) u. 

Bay State 

Dolomite Member 

Woodpecker 

L imestone 

Member 

Woodpecker Limestone 

() 

,. 

l=.,,.,u.:;;;;---.,.C~±,+---- --¥-i--1 .,. 0 

"' z

100 so 0 100 200 300 MILES 

c 

~ 

c 

0 

~ 

D 

c 

0 

E 

~ 

c 

§ 

5 

0 

:;; 

Pycnostylus 

Ha/ysites 

~ 

E 

0 

0 

D 

c 

·~ 

Unit 2 (limestone facies) .----T-hick~eSs- -------

Entelophyllum 

beds 

Un it 2 

approximate 

~ 

e 

0 

0 

D 

c 

·~ 

0 

:;; 

Nevada Formation 

units 1 and 2 

!lowell ella 

pauciplicata 

Entelophyllum 

M1112 

Faulted section 

Member 

Sentinel Mountain 

Dolomite Member 

Ox yoke Canyon 

Sandstone Member 

. B~~~~r::::k ~ ·~ "'o 1---t--M_e_m_b_•_' ____ d) Lone Mountain 

Dolomite 

Faulted 

section 

Fish Haven 

Dolomite 

48 Howellella 

pauciplicata 

46 Verticillopora, 

Holy sites, Huronia 

40 Halysites, 

Lissocoelina? 

34 Halysites 

Dolomite 

facies 0 Sandstone resembling Oxyoke Canyon 

Sandstone Member. ~ 

c 

0 

...J 

Halysites 

Pycnostyl ids 

0 

:;; ~ 

c 

0 

...J 

~~tc-'771- Eureka 

0 Measured section R.K. Hose, U.S. Geol. Survey 

(written commun., 1954). 

0 Hanson Creek Limestone fauna (Richmondian). 

Late Ordovician; locality of "Trenton fauna" 

(Haque, 1892, p. 58; Walcott, 1884, p. 273). 

@ Disconformity at base of Devonian. 

®Beacon Peak Dolomite Member with Rabbit Hill ~ 

Helderbergian fossils in Sulphur Spring Range. 

CD No field evidence of disconformity. 

·~ " 

E 

0 

Fault contact ~ 

c 

0 

...J 

Unit 1 

facies 

Eureka 

Quartzite 

Base unexposed t 

1000 FEET 

500 

0 

Quartzite 

Devonian coral zones {0, El 

shown on left of column . 

FIGURE 7.-Correlation diagram showing stratigraphic relations of the Lone Mountain Dolomite and its equivalence to the 

Laketown Dolomite of Utah. 

son Creek limestone facies, is situated here near 

BM7201, about nine-tenths of a mile north-northeast 

of Wood Cone, and one-half mile southeast of Entelophyllum locality M1112. 

Except for abundant Entelophyllum, the fauna of 

locality M1112 is small and nondiverse, including only 

the following forms: 

(?) Thamnopora sp. 

Entelophyllum engelmanni n. sp. 

Camarotoechia sp. 

?Hyattidina sp. f 

Howellella pauciplicata Waite 
AGE AND CORRELATION OF THE LONE MOUNTAIN DOLOMITE 15 

LONE MOUNTAIN DOLOMITE, 

SOUTHERN FISH CREEK RANGE 

Low-dipping, considerably disturbed Lone Mountain 

Dolomite is in contact with the Nevada Formation 3% 

miles southwest of Fish Creek Springs, where these 

Devonian rocks and overlying Devils Gate Limestone 

make up the north end of Fenstermaker Mountain. 

Blocky Silurian dolomites exposed here lie within the 

upper part of the Lone Mountain Dolomite and yield 

well-preserved silicified coral-brachiopod assemblages 

(pl. 12, fig. 25) differing somewhat from the fauna of 

locality M1112 in the southern Mahogany Hills. 

Because of complex faulting not yet mapped out, the 

relation to the Nevada Formation is not entirely clear. 

It appears probable that these fossil-bearing dolomites 

directly underlie the Nevada and occupy about the 

same stratigraphic interval as the Mahogany Hills beds 

of locality M1112 and the fossil-bearing dolomite lenses 

at Lone Mountain locality M1122 (fig. 7). 

Lone Mountain Dolomite faunas from two Fish 

Creek Range localities, both close to the south boundary of the Bellevue Peak quadrangle, are described 

here. The localities are M1113, near the range crest, and 

M1087, a quarter of a mile west. The fauna from 

locality M1087 (pl. 12, fig. 25) is listed below: 

slender ramose favositids (thin-walled) 

Alveolites sp. 

Entelophyllum engelmanni subsp. b 

Tryplasma sp. 

?Hyattidina sp. f 

Hindella sp. a 

H owellella smithi Waite 

The fauna collected at locality M1113 follows: 

massive favositids (small colonies) 

?Thamnopora sp. 

Entelophyllum eurekaensis n. sp. 

Entelophyllum sp. cf. E. engelmanni subsp. b 

Salopina sp. f 

Camarotoechia pahranagatensis Waite 

Camarotoechia sp. b 

Camarotoechia sp. f 

Atrypa sp. f 

?Hyattidina sp. f 

H owellella smithi Waite 

LONE MOUNTAIN DOLOMITE, 

SULPHUR SPRING RANGE 

Characteristic Silurian dolomites assigned to the 

Lone Mountain form the large fault block at East 

Ridge, south of Romano Ranch (fig. 1). The eastdipping blocky dolomite is in contact on the west with 

the Nevada Formation along the high-angle northsouth Romano fault. The areal geology and structure 

as mapped in this vicinity strongly suggest that Lone 

Mountain Dolomite also underlies the Early Devonian 

Beacon Peak Dolomite Member between the Romano 

fault and the parallel major Mulligan Gap fault 2 miles 

west. 

The Lone Mountain Dolomite of East Ridge is about 

1,200 feet thick. Silicified corals were collected at 

locality M1121 near the fault in lower strata of this 

block and at locality M1148 on the east in the higher 

beds. Both faunas represent a Halysites-pycnostylid 

biofacies (fig. 7). That of the lower horizon contains a 

large undescribed pycnostylid genus with flaring calice 

(pl. 11, figs. 28, 29) in association with Halysites. The 

upper fauna includes a great abundance of the slender 

phaceloid Pycnostylus (pl. 11, fig. 30) together with 

Halysites. 

Corals of the East Ridge Halysites-pycnostylid biofacies are not related to those of the higher Lone Mountain in the Mahogany Hills and Fish Creek Range, 

which are the Entelophyllum-Howellella association 

designated below as the upper Lone Mountain-Laketown biofacies. It is probable that these East Ridge 

dolomites are a lower interval of the Lone Mountain 

sequence, possibly including some of Lone Mountain 

unit 1. 

AGE AND CORRELATION 

OF THE LONE MOUNTAIN DOLOMITE 

All identifiable fossils collected during this investigation from Lone Mountain Dolomite of the type area 

are of Silurian age. They include the EntelophyllumH owellella assemblages of the Mahogany Hills and Fish 

Creek Range and those of the Halysites-pycnostylid 

facies of the Sulphur Spring Range (fig. 7). Rugose 

corals of the genus Entelophyllum and the pycnostylids 

are unknown in Devonian rocks; halysitids of the types 

occurring in the Lone Mountain are not known to have 

survived beyond the Silurian. 

Whereas studies of the Lone Mountain Dolomite at 

Lone Mountain itself have brought forth no unequivocal evidence of Silurian age in that immediate locality, 

nearby exposures of this dolomite have yielded an 

abundance of Silurian fossil material. The three 

described Entelophyllum-bearing faunas from localities 

M1112, M1087, and M1113 have species in common, 

and while differing somewhat in detail, probably all 

represent a single stratigraphic interval corresponding 

to the upper 500 feet of Lone Mountain unit 2 at Lone 

Mountain. These faunas are of Late Silurian age and 

characterize the upper Lone Mountain-Laketown biofacies (table 2). Moreover, discovery in the Lone 

Mountain Dolomite at Lone Mountain of coralline 

lenses comprising large volumes of comminuted rugose 

corals suggesting Entelophyllum (pl. 11, fig. 32) seems 

to bear out the possible equivalence of these beds in 
16 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

TABLE 2.-Characteristic fossils of the upper Lone MountainLaketown biofaces 

Massive favositids 

(small colonies) 

Ramose favositids ........................................ 

(thin-walled) ......................................... 

?Thamnopora sp ............................ Alveolites sp .................................. Entelophyllum engelmanni n. sp ............................................ Entelophyllum engelmanni subsp. b ...................................... Entelophyllum eurekaensis 

Trn.p~;;;,~-~p--~~~~~~~~~~~~~~~~~:~~:~::~~::~:~~ 

Salopina sp. f .................................. Camarotoechia sp ........................ Camarotoechia pahranagatensis 

Waite .......................................... Camarotoechia sp. b .................... Camarotoechia sp. f ...................... Atrypella carinata Johnson ........ Atrypa sp. f .................................... ?Hyattidina sp. f ............................ ?Hyattidina hesperalis Waite .... Hindella sp. a ................................ Howellella pauciplicata Waite .... Howellella smithi Waite .............. ? M eristina sp ................................ Douvillina geniculata Waite ........ 

Lone Mountain 

Dolomite 

(Upper part only) 

Cll 

bO 

~ r:: 

., ..... 

..... ~ 

;:!1 ~ :l§ Cll 

"" lE 0 

.d >. rJl 

r:: 

., i£: 

~ t-

~ 00 .d 0 ., 

::E! ~ ~ 

X 

---- X ---- X ........ X 

X 

X 

X ? 

......... X 

X ........ 

......... X 

X 

X 

X 

X 

......... X 

X X X 

......... 

......... X 

X ........ ......... 

X X 

.d 

., .2l::l Cll ·at Cllbl) 

...,r:: 

s; ·a~ 8~ .g..., 

r::r:: 0011 

~bl) 

~-Sao ;~.-o .£ ~...,.. Cllc,.; +> ·;:: e~ ,!<; r::·~ ::S.d t .-oor:: 

HO;:J ~&!z 

? 

X X 

? 

X 

X 

........ 

X 

X .. ..... ? X 

X 

X 

Lone Mountain unit 2 to the Late Silurian Entelophyllum beds of the Mahogany Hills and Fish Creek 

Range. 

Comparison of the Entelophyllum-Howellella assemblages of the Lone Mountain Dolomite with Silurian 

faunas of the higher Laketown Dolomite in the eastern 

Great Basin provides good evidence of age and correlation. A suitable Laketown reference section for present 

purposes is that of the Ibex Hills, Confusion Range, 

Utah, mapped and measured by R. K. Hose (written 

communs., 1954-1964). The Ibex Hills Laketown (fig. 

7) is about 1,200 feet thick, underlain by Late Ordovician Fish Haven Dolomite and overlain disconformably 

by probable Early Devonian beds of the Sevy Dolomite. 

Units 29 to 49 of the Hose measured section fall within 

the Laketown. Laketown unit 48, about 60 feet below 

the Sevy contact, contains the diagnostic Late Silurian 

fauna of the upper Lone Mountain-Laketown biofacies, 

whose key fossil is Howellella pauciplicata Waite. No 

Entelophyllum has yet been collected from unit 48 of 

the Ibex Hills section, although generally in the eastern 

Great Basin Laketown this rugose coral is present. 

Upper Laketown beds correlative with unit 48 occur 

in the Pahranagat Range of southern Nevada (Waite, 

1956; Johnson and Reso, 1964). In that area the characterizing Howellella is the coarser ribbed species H. 

smithi Waite, present also in the Lone Mountain of 

Fish Creek Range, but doubtfully represented in unit 

48 of the Confusion Range, where pauciplicata 

predominates . 

Other Silurian faunas characterize the greater part 

of the Ibex Hills Laketown Dolomite below unit 48. The 

faunas in units 29 upward to unit 4 7 have not yet been 

found in the Lone Mountain Dolomite. Of special interest is the abundance of the dasycladacean alga Verticillopora in unit 46, a genus that reaches its peak in Late 

Silurian coral zone D of the Silurian limestone facies of 

the westerly Great Basin. 

Halysites appears to be absent or very uncommon in 

the Great Basin higher Silurian, not having been recognized in the upper Lone Mountain-Laketown biofacies 

or in Late Silurian coral zones D and E of the westerly 

limestone facies. However, halysitids are clearly facies 

controlled and generally through the Silurian and Late 

Ordovician may be very abundant or totally lacking in 

a given assemblage where other corals are common. 

Pycnostylid Rugosa are distinctive Silurian corals, 

seemingly also subject to some degree of facies control. 

The Halysites-pycnostylid association of the Silurian 

dolomite of Sulphur Spring Range has not yet been 

identified in the lower Laketown, where it is to be 

expected. In the Silurian limestone facies of the westerly Great Basin, the pycnostylid genera range upward 

to coral zones D and E but, being absent from the 

Rabbit Hill, are not known to survive into the Early 

Devonian. 

The Lone Mountain Dolomite is assumed to be correlative for the most part with the Roberts Mountains 

Limestone, an assumption based upon stratigraphic 

position, but, because of biofacies differences, unsupported by direct paleontologic evidence (fig. 4). Conclusive evidence of lateral intertonguing of the two carbonate facies is unavailable; however, within the type 

section of the Roberts Mountains Limestone, interbeds 

of dolomitic limestone and dolomite (Winterer and 

Murphy, 1960) suggest the possibility of such a relation 

in that area. In this type section, the uppermost beds 

of the Roberts Mountains Limestone have largely 

changed over to dolomite. These uppermost strata fall 

in Late Silurian coral zone D. Above zoneD, the section 

is barren dolomite wherein highest Silurian coral zone E 

would be expected; it is not improbable that these dolomites may represent a northerly tongue of Lone Mountain Dolomite unit 2, above which lies the Beacon Peak 

Dolomite Member of Rabbit Hill (Early Devonian) 

age (fig. 8). 
RELATION OF RABBIT HILL LIMESTONE TO LONE MOUNTAIN DOLOMITE 17 

1 2 

Simpson Park 

Range 

Coal Canyon 

Roberts Mountains 

Roberts Creek 

Mountain lone Mountain 

rJ __ g_ 

0 25 50 MILES 

0

Manhattan 

CD Coral zone SE unrecognized in dolomite facies. 

c 

<0 

c 

g 

c3 

c 

<0 

~ u; 

c 

<0 

·c:; 

·~ 

"0 

0 

DA 

SE 

SD 

G) Beacon Peak Dolomite Member contains Rabb1t Hill fossils 10 miles 

east in Sulphur Spnng Range. 

CD Beacon Peak Dolomite Member unrecognized at Lone Mountain. 

Great Basin Silurian and Devonian coral zones (SA, DAl indicated 

by capital letters on left of column 

12 miles 

Roberts Mountains 

Limestone 

20 miles 

Devon1an 

Silurian 

Lone Mountain 

Dolomite 

Nevada 

Coral zones DA and DB unrecognized 

Entelophyllwn beds (Silurian) 

Lone Mountain 

unit 2 

Lone Mountain 

unit 1 

Silurian basal chert 

Hanson Creek 

Dolomite 

Eureka 

t

1000 FEET 

500 

0 

VERTICAL SCALE 

FIGURE B.-Correlation diagram showing stratigraphic relation of Rabbit Hill Limestone to Lone Mountain Dolomite 

as interpreted. 

Fossils have not been found in the uppermost Lone 

Mountain Dolomite in its type area, that is, within the 

300 feet or so between Late Silurian EntelophyllumHowellella beds and the Devonian Nevada Formation. 

Accordingly, in a negative way it is not entirely possible 

at present to rule out Early, perhaps pre-Helderberg, 

Devonian age for the highest Lone Mountain. Factors 

to be weighed are Helderbergian age of the lowest 

Nevada member, the Beacon Peak Dolomite Member, 

plus absence from the type Lone Mountain section at 

Lone Mountain of the Beacon Peak. In that section 

Nevada Formation unit 1 with post-Helderberg fossils 

rests conformably upon the Lone Mountain as mapped. 

In view of a seemingly gradational boundary, it is therefore not inconceivable that beds mapped as the highest 

barren Lone Mountain may occupy the Helderbergian 

time-stratigraphic interval. 

On tenuous evidence, the Lone Mountain Dolomite 

has in recent years been interpreted by several paleontologists as at least partly Devonian, a view seemingly 

inspired by earlier suggested lateral equivalence of the 

Rabbit Hill Limestone to the upper part of the Lone 

Mountain Dolomite (Merriam, 1963, fig. 7). A further 

complication has been added by conodont, graptolite, 

and brachiopod investigators (Clark and Ethington, 

1966; Johnson, 1970), who conclude that a not inconsiderable upper part of the Roberts Mountains Limestone is also Devonian. These age conclusions are not 

substantiated by Merriam's ( 1973a) rugose coral and 

brachiopod studies. Clearly an appraisal and adjustment of these conflicting paleontologic findings is called 

for, taking into account a review of the stratigraphic 

ranges of all fossil groups represented in the light of 

more recent structural and stratigraphic study of the 

enclosing rocks. 

CONCLUSIONS REGARDING RELATION OF 

RABBIT HILL LIMESTONE 

TO LONE MOUNTAIN DOLOMITE 

Among objectives of this investigation is elucidation 

of age and stratigraphic relation of the Rabbit Hill 

Limestone to the Lone Mountain Dolomite, the two 

units having previously been viewed as locally occupying similar or overlapping stratigraphic positions and 

never occurring in the same stratigraphic column (fig. 

8). These paleontologic studies strongly indicate that 

the Rabbit Hill fauna is of Helderbergian (Early Devonian) age and is accordingly younger than the highest 
18 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

known Lone Mountain Dolomite fossil horizon, which 

is Late Silurian and lies no more than 400 feet below 

the top of the dolomite formation. This factor greatly 

narrows down the possibility of age equivalence of any 

of the Rabbit Hill to the uppermost part of the Lone 

Mountain. 

Factors of stratigraphic significance bearing upon the 

Rabbit Hill-Lone Mountain relation are: (1) probable 

time-stratigraphic equivalence of Lone Mountain unit 

1 and much of Lone Mountain unit 2 to the Roberts 

Mountains Limestone of Silurian age as previously 

demonstrated, and (2) the stratigraphic position of the 

Beacon Peak Dolomite Member carrying a Rabbit Hill 

fauna and overlying the Lone Mountain Dolomite 

(figs. 4, 7). 

Failure to discover fossils in the uppermost type area 

Lone Mountain Dolomite leaves open the possibility 

that the beds in unit 2 carrying the Silurian (Ludlovian) upper Lone Mountain-Laketown assemblages 

might conceivably be succeeded upward by a very Early 

Devonian or Helderbergian fauna. However, the biofacies differences here might well eliminate a direct 

fossil comparison. The Lone Mountain faunas of unit 2 

include the spiriferoid genus H owellella and massive 

tabulate corals, each represented by differing species 

in the Rabbit Hill, but in general the biofacies differences are great. In fact, it would appear that the magnitude of this faunal disparity, enhanced as it is by 

facies, may be somewhat disproportionate to actual age 

difference between the two formations. 

GREAT BASIN SILURIAN AND DEVONIAN 

CORAL ZONES 

Rugose corals were used to zone Silurian and Devonian strata of the Great Basin (Merriam, 1971a, 

1971b). The five proposed Silurian zones are lettered A 

through E in ascending stratigraphic order. Zone A is 

of Early Silurian age (Llandoverian), B and C are 

Middle Silurian (Wenlockian), and D and E are Late 

Silurian (Ludlovian). The nine Devonian coral zones 

are lettered A through I; of these zones, A, B, and Care 

Early Devonian, zone D is Early and early Middle 

Devonian, zones E, F, G, and probably the lower half 

of H are Middle Devonian, and coral zone I is Late 

Devonian. In both systems, the coral zonation is best 

shown in the limestone facies (figs. 4, 7, 8). 

The Rabbit Hill Limestone is within Devonian coral 

zone A, characterized by the Syringaxon biofacies. 

There is a very profound discontinuity in rugose coral 

history between Late Silurian coral zone E of the uppermost_ Roberts Mountains Limestone and Early Devonian coral zone A of the conformably overlying Rabbit 

Hill. Following a great burst of coral evolution in 

Silurian coral zone E, nearly all of the rugose coral 

genera drop out abruptly. In most places the Rugosa 

continue to be represented in coral zone A of the Rabbit 

Hill by the one small solitary genus Syringaxon, which 

is abundant. The next great burst of rugose coral evolution took place locally in Devonian coral zone D. 

Knowledge of Rugosa in Silurian dolomite facies of 

the Lone Mountain and the Laketown Dolomite is at 

this time not sufficient for coral zonation. Rugosa are 

locally abundant in several horizons of the Laketown, 

ranging from beds with Palaeocyclus, possibly corresponding to Silurian coral zone A (Merriam, 1973a), to 

those higher in the column containing Rhabdocyclus, 

Tryplasma, lykophyllids, and Entelophyllum. 

SYSTEMATIC AND DESCRIPTIVE 

PALEONTOLOGY 

This general paleontologic study of Rabbit Hill and 

Lone Mountain faunas is concurrent with research 

upon Great Basin Silurian and Early Devonian rugose 

corals. Among its objectives are support for and 

strengthening of conclusions based on the coral studies. 

Qu·estions of stratigraphic superposition, age, and 

geologic correlation having to do with setting up of 

reliable composite reference sections for the Great 

Basin Silurian and Devonian require integration of all 

lines of paleontologic evidence derived from study of as 

much as possible of entire faunas. The rugose corals 

are by themselves insufficient for achieving these objectives. New genera and species of Great Basin Rugosa 

are in some instances unknown in distant standard 

sections of eastern North America and the Old World, 

hence at present are of no direct comparative value in 

this regard. 

Among megafossils normally associated ecologically 

with Rugosa, the brachiopods have been relied upon 

for age conclusions within the Cordilleran mid-Paleozoic. The determinative advantages of good brachiopod 

interiors, where these shells, like those of the Rabbit 

Hill and the Lone Mountain, are excellently preserved 

by silicification are well known. Among rugose corals in 

these environments, fine structures of wall and septa are 

usually damaged or nearly destroyed by the same silicification processes. Brachiopods named and described 

are those silicified and most abundant in the Rabbit 

Hill bioclastic limestones and in the dark-gray carbonaceous facies of the Lone Mountain. Other brachiopods are at this time insufficiently represented for 

naming and full description, and much remains to be 

done with the paleontology of this fossil group. Systematics of the Rugosa are entered into more fully in 

contributions dealing wholly with this Order (Merriam, 

1973a, 1973b, 1973c). Of less commonly silicified 

fossils, few have been touched upon. Mollusca, Echinoderms, bryozoans, ostracods, and most of the trilobites 
FAMILY FAVOSITIDAE DANA 19 

remain to be described. 

Rabbit Hill platy limestones and shaly-silty laminated beds are locally rich in trilobite remains and in 

places contain conularids and abundant tentaculites. 

Near Walti Ranch (locality M1074) in the Simpson 

Park Range, thin-bedded Rabbit Hill limestones yield 

well-preserved Conularia comparable to Hall's C. huntiana of the eastern Helderbergian (pl. 2, figs. 18-20). 

In the taxonomic sense, greater faunal differentiation 

of the Rabbit Hill as compared with the upper Lone 

Mountain is noteworthy. Of the Rabbit Hill silicified 

bioclastic limestone fossils from the type section, some 

26 taxa are listed here; these are only part of the total 

preserved fossil assemblages in this facies. Fossils are 

numerous in the restricted upper Lone Mountain darkgray carbonaceous dolomite facies, but the preserved 

fauna is small and nondiverse. Only 11 taxa were recognized in the most diverse of these faunas from the Fish 

Creek Range. Some upward adjustment of this species 

count would doubtless be called for, if unsilicified, and 

therefore unrecovered, shell-bearing forms were known. 

It is seemingly a safe assumption that the diagenetic 

dolomite faunas of the higher Lone Mountain were 

initially far less diverse taxonomically than the Rabbit 

Hill Limestone bioclastic facies. Marine environmental 

differences, little understood, would appear to be a 

logical explanation for these disparities in faunal 

diversity. In general, shallow-water marine conditions 

during accumulation of the richly fossiliferous Rabbit 

Hill Limestones must have been far more hospitable 

than during deposition of the diagenetic upper Lone 

Mountain dolomites. Except for the local carbonaceous 

bodies, these magnesian carbonates are sparsely fossiliferous or completely barren. 

FOSSILS OF THE RABBIT HILL LIMESTONE 

AND BEACON PEAK DOLOMITE MEMBER 

OF THE NEVADA FORMATION 

Order TABULATA Edwards and Haime, 1850 

Family FAVOSITIDAE Dana, 1846 

Tabulate corals are the abundant and usually the 

only colonial corals in the Early Devonian Rabbit Hill 

Limestone. As limestone builders, the favositids contributed much of the material in bioclastic facies, where 

they are accompanied by the small solitary rugose 

coral Syringaxon. Tabulates continue to predominate 

in coralline facies to the early Middle Devonian beds 

in the higher part of coral zone D, where colonial 

Rugosa become fairly common. In Middle Devonian 

coral zone F, colonial Rugosa outnumber Tabulata and 

the favositids are no longer common in this region. The 

local Devonian evolutionary peak of the Tabulata was 

thus reached in argillaceous limestone facies of Nevada 

Formation unit 2 and coral zone D, in which they outnumber Rugosa. As noted by earlier researchers in 

506-612 0 - 73 - 4 

corals the Paleozoic Tabulata throve better in muddy 

seas than did colonial rugose corals, especially in turbid 

bottom environments, where stromatoporoids are 

absent. Similar argillaceous sediments are present as 

interbeds in both Rabbit Hill Limestone and Nevada 

unit 2. Tabulates are numerous in each case, and in 

each the stromatoporoids are quite uncommon. 

Three subfamilies of the Favositidae are present in 

the Rabbit Hill Limestone: (1) Favositinae with the 

genus Favosites; (2) Pachyporinae with Striatopora; 

and ( 3) Micheliniinae with Pleurodictyum. Genera 

that would be expected here, but have not been identified, are Emmonsia, Alveolites, Coenites, and Cladopora. There are no Heliolitidae or Syringoporinae in 

the collections, and Halysitidae are absent. 

Of special stratigraphic significance is the abundance 

of Pleurodictyum of the P. lenticulare lineage; as noted 

by several investigators, these corals characterize rocks 

of about Helderbergian age in widely scattered parts of 

the globe. Other and distinct Pleurodictyum lineages 

occur in strata of Silurian age (Amsden, 1949, p. 100) 

and range upward to the Middle Devonian (Fenton and 

Fenton, 1936; Stumm, 1950, 1964). Neither Pleurodictyum nor Striatopora have been recognized among 

the abundant tabulate corals of Nevada unit 2 and coral 

zoneD. 

Subfamily FAVOSITINAE Dana, 1846 

Genus Favosites Lamarck, 1816 

Favosites cf. F. helderbergiae Hall 

Plate 1, :figures 16-19 

The corallum of these massive favositids ranges from 

large and globose or hemispherical more than 6 inches 

in greatest diameter to elongate, digitate, and lobose. 

Coralla with polygonal corallites 2-3 mm (millimeters) 

wide are distinguishable from those with small corallites less than 2 mm. The wall is uniformly thin, a characteristic of the genus; mural pores are moderately 

large, disposed in either one or two vertical columns per 

polygonal wall facet, have thickened rims, and may be 

covered by a pore plate. Tabulae are usually rather 

widely spaced, but in some coralla are closely set. 

Septal spines are minute and very scarce. There are no 

squamulae as in Emmonsia and certain species of the 

Favosites alpenesis group of Swann (1947). Numerous 

small reproductive offsets characterize some mature 

coralla. These are usually but not always situated internally at wall facet junction angles. 

At present there are no criteria by which these 

Rabbit Hill massive favositids may be distinguished 

from surficially similar species of Nevada unit 2 (coral 

zone D). But available material of zone D Favosites 

does not reveal the numerous reproductive offsets on 

distal surfaces of rna ture coralla. Certain species of 

Silurian Favosites like F. gothlandicus, the type species, 
20 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

attain a uniformly much greater corallite width than 

any of those in the Rabbit Hill or Nevada Formations. 

Subfamily PACHYPORINAE Gerth. 1921 

Genus Striatopora Hall. 1851 · Striatopora cf. S. gwenensis Amsden 

Plate 1, figures 1, 3-6 

1963 Striatopora sp. cf. S. gwenensis Amsden. Merriam, p. 43. 

Branching Striatopora with thick cylindrical coralla 

tapering toward tips of branches. Septal ridges prominent in polygonal calices. Corallite walls thickened 

throughout by lamellar stereoplasm; greatly thickened 

laterally around calices. Tabulae few and widely spaced, 

visible in axial vicinity only, obscured by stereoplasm 

peripherally. No mural pores or septal spines recognized. 

Presence of large and small calices suggests corallite 

dimorphism as recognized by Oliver ( 1966) for the type 

species, S. flexuosa Hall. The type species appears to 

be of more slender construction and internally the 

"a-corallites" of Oliver (1966, p. 449) are much thinner 

walled axially than in the Rabbit Hill species. 

Associated with Striatopora in the Rabbit Hill Limestone are slender ramose tabulates of similar external 

appearance, but possessing thin walls, calices without 

septal ridges, and large mural pores. Some of these 

have an external holotheca covering calices of earlier 

formed parts of a corallum. 

Striatopora has not been recognized in Devonian 

strata above the Rabbit Hill Helderbergian of the Great 

Basin. 

Subfamily MICHELINIINAE Waagen and Wentzel.1886 

Genus Pleurodictyum Goldfuss. 1829 

Type species.-Pleurodictyum problematicum Goldfuss 1829. Lower Devonian, Coblenz and Eifel districts, 

Germany. Known in the form of molds with supposed 

worm tube in basal part. 

Diagnosis.-Corallum round-ovoid transversely with 

convex upper surface; base unevenly flattened, concave or convex. Corallites large, radiating outward from 

conical initial chamber, numbering from one to more 

than 30, with thick hexagonal walls pierced by irregularly spaced large communicating pores or canals. Walls 

with as many as 36 rudimentary pseudosepta composed of vertically arranged spines. Tabulae are usually 

absent. 

Remarks.-Like P. ploblematicum, the Lower Devonian representatives of this genus are in part low, 

laterally extended encrusting forms, the shape of whose 

corallum base is more or less determined by the substratum. There are uncertainties about the structure 

of problematicum because of its preservation as moulds. 

Sardeson ( 1896, p. 292) interpreted this species as 

lacking tabulae, but later workers (Stumm, 1950), p. 

210; Hill and Stumm, 1956, p. F466) regard Pleurodictyum broadly as having tabulae. Middle Devonian 

large forms with numerous tabulae and radially elongate corallites are assigned by some workers to Michelinia de Koninck 1841 (Sardeson, 1896, p. 294; Hill and 

Stumm, 1956, p. F466). By others, Michelinia is 

regarded as a synonym. According to Stumm ( 1964, p. 

77-79), Pleurodictyum includes larger species with 

abundant tabulae, and the genus is subdivided as two 

subgenera; Pleurodictyum (Pleurodictyum) has walls 

with strong septal ridges or spines and complete or 

incomplete tabulae, and Pleurodictyum (Procteria) 

Davis has smooth to faintly striate walls, cystose 

tabellae in the larger species, and a thick papillose 

peritheca. Some Middle Devonian forms such as "P." 

stylopora (Eaton?) from the Hamilton Group of North 

America also are reported to have the tubular vermiform body of problematicum. 

Simple species of Pleurodictyum having only a few 

large corallites were present in the Silurian as represented by P. tennesseensis Amsden of the Brownsport 

Formation (Amsden, 1949, p. 100, pl. XXIII, figs. 1-3). 

Dunbar (1920, p. 118, pl. 1, figs. 5-7) has described P. 

trifoliatum, another primitive more or less encrusting 

species from the Lower Devonian Rockhouse Shale of 

Tennessee. 

If the new Rabbit Hill Helderbergian species Pleurodictyum dunbari is correctly assigned generically, it 

seems likely that these forms early developed two 

growth habits, the low encrusting one like P. lenticulare 

(Hall) of the New York Helderberg and the elongate 

stalked form like P. dunbari, which appears to be 

related to the Silurian P. tennesseensis and to the more 

abbreviated trifoliatum. 

Pleurodictyum nevadensis n. sp. 

Plate 1, figures 7-12 

1963 Michelinia sp., Merriam, p. 43. 

Type material.-Holotype, USNM 159517; paratype 

USNM 159518. Lower Devonian Rabbit Hill Limestone, locality M404. 

Diagnosis.-Pleurodictyum with large polygonal radiating corallites having a deep calice. Base usually 

shows conical apex of initial corallite and may be 

flattened, convex, or concave. Pseudosepta, as many as 

40, consist of longitudinal rows of close-set short spines. 

Wails thick, pierced by large connecting pores in common wall of adjoining chambers, about 80 openings per 

square centimeter. No tabulae, the deeper medial 

calices extending almost to proximal (basal) wall. 

Smaller newly added chambers near periphery. 

Remarks.-This form varies from encrusting individuals with roughly concave proximal surface and 

thickened peritheca to erect forms with projecting 
FAMILY LACCOPHYLLIDAE GRABAU 21 

initial corallite and very deep calices. Larger encrusting 

individuals have 36 corallites, but usually the erect 

ones have many fewer. 

Pleurodictyum nevadensis n. sp. resembles the Helderbergian P. lenticularis (Hall). Hall's figures (1887, 

pl. III, figs. 1, 2, 3, 5) show large corallites that are 

shallow with broad floor, not open nearly to the corallum base as in P. nevadensis. It is not known whether 

the broad corallite floor of lenticularis is actually a 

tabula. Beecher's ( 1893a, p. 211) studies of the development of lenticularis imply that this primitive species 

is nontabulate. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality 

M409. Dobbin Summit, Monitor Range, locality M1309 

(cf.). Petes Canyon, Toquima Range, locality M1150 

( cf.). Walti Ranch, Simpson Park Range, locality 

M1074 (cf.). Mount Tenabo, Cortez Mountains, 

locality M1083. 

Pleurodictyum dunbari n. sp. 

Plate 1, figures 13-15 

1963 Pleurodictyum cf. P. trifoliatum Dunbar. Merriam, p. 43. 

Type material.-Holotype, USNM 159522; para type 

USNM 159523. Lower Devonian Rabbit Hill Limestone, locality M409. 

Diagnosis.-Stalked, elongate, simply branching 

Pleurodictyum with one to six thick-walled large corallites with deep calice, a central calicinal boss, and about 

22 prominent pseudosepta composed of longitudinally 

alined spines. Peritheca thick, with a basal expanded 

pedal attachment. 

Remarks.-The mural pores are large and serve to 

establish this aberrant form as a tabulate coral. A 

transverse thin section of the stalk 1 em above the 

basal attachment shows parts of five closely appressed 

thick-walled corallites; these have about 12 thick 

pseudosepta or septal spines, some of which reach the 

center and are for the most part laterally in contact. 

The thick main stalk with expanded apical (or basal) 

attachment appears to be that of the initial corallite 

from which the others have budded off, more or less in 

the manner described by Beecher for Pleurodictyum 

lenticulare (Hall) (1893a, p. 207-212, pls. 9-13), but 

after the primary corallite attained large size and was 

growing erectly from its apical attachment disc. A 

silicified specimen reveals no trace of tabulae in longitudinal section of the stalk, but these structures could 

have been destroyed by the silicification. 

Pleurodictyum trifoliatum Dunbar ( 1920, p. 118, pl. 

1, figs. 5-7) of the Lower Devonian Rockhouse Shale 

in Tennessee lacks the stalk and is an encrusting form, 

but is otherwise similar toP. dunbari n. sp.; somewhat 

closer perhaps is P. tennesseensis Amsden (1949, p. 

100, pl. XXIII, figs. 1-3) of the Silurian Brownsport 

Formation, which is erect but lacks the elongate stalk. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Order RUGOSA Edwards and Haime, 1850 

Family LACCOPHYLLIDAE Grabau, 1928 

Reference form-Syringaxon siluriensis (McCoy), 

1850. 

Small solitary trochoid to subcylindrical rugose 

corals with very deep calice, straight, smooth lamellar 

septa, a narrow septal stereozone, and tubular stereoplasmic aulos. Tabulae partly complete, very strongly 

uparched; nearly flat within aulos, steeply inclined 

peripherally. No dissepiments. 

These nondissepimented, but otherwise specialized 

corals are distinguished by the strong inner ring produced by swelling of septal tips and commonly rather 

heavy addition of extraneous stereoplasm. Arching of 

tabulae is pronounced. The Laccophyllidae occur in 

the Silurian and Devonian, wherein they may be abundant in a facies lacking other Rugosa. Nearly identical 

small corals like Permia, reappearing in the Carboniferous, may be homeomorphic (Hudson, 1944, p. 360; 

Fliigel and Free, 1962, p. 232). Somewhat less convergent are the Permian Polycoeliidae as revised by 

Schindewolf (1942, p. 55). 

Syringaxon, the only member of this family recognized in the Great Basin, is the characterizing rugose 

coral of the Helderberg (Early Devonian) Syringaxon 

facies. 

Genus Syrinqaxon Lindstrom, 1882 

1882 Syringaxon Lindstrom, p. 20. 

1900 Laccophyllum Simpson, p. 201. 

1902 Nicholsonia Pocta, p. 184. Cited in plate explanations as 

Alleynia (Nicholsonia). 

1928 Laccophyllum Simpson. Grabau, p. 82. 

1928 Alleynia Pocta ANicholsonia Pocta). Grabau, p. 82 

1935 Syringaxon Lindstrom. Butler, p. 117. 

1938 Syringaxon Lindstrom (in part). Prantl, p. 21. 

1940 Syringaxon Lindstrom. Lang, Smith, and Thomas, p. 129. 

1949 Syringaxon Lindstrom. Stumm, p. 10. 

1956 Syringaxon Lindstrom. Hill, p. F258. 

1962 Syringaxon Lindstrom (in part). Fliigel and Free, p. 224. 

Type species.-By monotypy, Cyathaxonia siluriensis McCoy, 1850 (p. 281); Silurian, upper Ludlow, 

Underbarrow, Kendal, Westmorland, England. According to Butler (1935, p. 118) and Lang, Smith, and 

Thomas (1940, p. 129), Lindstrom, in naming the 

genus, gave no diagnosis, merely using McCoy's species 

siluriensis under the new generic name Syringaxon in 

his faunal lists of the Gotland Silurian (Lindstrom, 

1882, p. 20). 
22 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Diagnosis.-Small, solitary turbinate and ceratoid 

to cylindrical rugose corals with deep calice and lacking 

dissepiments. Axial ends of major septa dilated and 

laterally in contact to form an aulos. Tabulae strongly 

uparched distally, the aulos dividing them into inner 

flat or slightly sagging segments and outer segments 

that descend steeply to meet the outer wall (Fltigel 

and Free, 1962, fig. 3); tabulae either continuous from 

wall to wall through aulos stereozone, terminating 

within the aulos or abutting proximally as tabellae 

against adjacent tabulae. Stereome usually abundant 

as aulos thickening and general thickening or filling in 

brephic and neanic growth stages. Narrow fossulae 

commonly reveal quadrants in late neanic growth stages. 

Remarks.-The genus Laccophyllum was proposed 

by Simpson ( 1900, p. 201) with L. acuminatum Simpson from the Niagaran of Tennessee as type species. 

Butler's exhaustive study (1935) fixed McCoy's (1850, 

p. 281) "Cyathaxonia siluriensis" as the type species of 

Syringaxon Lindstrom, following which Lang, Smith, 

and Thomas ( 1940, p. 129) concluded that the bolotype of Laccophyllum acuminatum Simpson is assignable to Syringaxon, making Laccophyllum Simpson a 

synonym of Syringaxon Lindstrom. 

Alleynia Pocta or Alleynia (Nicholsonia) Pocta 

(Lang and others, 1940, p. 15, 129) appears to be correctly interpreted as a synonym of Syringaxon. 

Barrandeophyllum Pocta (1902, p. 190) resembles 

Syringaxon. According to Prantl (1938, p. 34), who 

studied Pocta's cotypes of Barrandeophyllum perplexum the type species, this genus is closely related to 

Syringaxon. Barrandeophyllum is distinguished by 

irregularities of the aulos, usually elliptical in transverse section, and by a sparing development of dissepiments. Stereoplasm is always present, though not 

abundant. The type species of Barrandeophyllum is 

reported from the Early Devonian Branik Limestone of 

Bohemia. Syringaxon ranges from the Tennessee Niagaran through strata of Early Devonian (Helderberg) 

age in western North America and is reported in the 

Late Devonian Independence Shale of Iowa (Stainbrook,1946,p.402). 

As noted by Hudson ( 1944, p. 360), small, rather 

simple corals resembling Syringaxon range upward to 

the Carboniferous, where they are represented by 

Permia Stuckenberg. According to Hudson, Permia 

and Syringaxon are homeomorphs. 

Small solitary corals resembling Syringaxon occur in 

the Silurian part of the Hidden Valley Dolomite of the 

northern Panamint Mountains (McAllister, 1952, p. 

15-17). Following the great proliferation of this genus 

in the Helderbergian of the Great Basin, it virtually 

disappeared from this region; scarce and fragmentary 

specimens that may belong either in Syringaxon or 

Barrandeophyllum have been found in Nevada Formation unit 2 at Lone Mountain. 

Syringaxon foerstei n. sp. 

Plate 2, figures 1-10 

1963 Syringaxon acuminatum (Simpson). Merriam, p. 43. 

Type material.-Holotype, USNM 159243; figured 

paratypes, USNM 159245-159250. Rabbit Hill Limestone, Early Devonian, Central Great Basin, Monitor 

Range. 

Diagnosis.-Syringaxon having a very deep calice, 

thick wall, prominent longitudinal grooves externally 

and on interior of calice wall, and a high septal count 

for this genus. Cardinal and alar septa differentiated in 

neanic stages. 

External features.-Corallum large for the genus, 

attaining a length exceeding 30 mm and greatest diameter of 27 mm at edge of calice; average length about 

19 mm with maximum diameter 16 mm (see table). 

Calice very deep, in large individuals 16 mm, or more 

than half the corallum length. Average specimen 

trochoid; ceratoid individuals fairly common; turbinate 

and nearly cylindrical individuals uncommon. Septal 

grooves sharply defined and distinctly pinnate with 

reference to the primary septa. Rugae weakly defined 

or absent, rarely prominent. Occasional individuals 

with talons or attachment surface at apex. Septa 

extend distally as low subequal ridges on inside of 

calice, rarely becoming obsolete. Aulos defined as ringshaped boss at bottom of calice in many individuals; in 

other specimens the aulos is ill defined and narrow 

fossulae may outline quadrants made by the primary 

septa. 

Transverse sections.-Mature sections show from 

26 to more than 30 major septa extending three-fourths 

of the distance to the axis. Minor septa normally present, but in some individuals not recognized at maturity; these septa range from mere stubs to one-third 

the length of major septa; in some instances, they are 

buried within the peripheral stereoplasm. Septa usually 

Syringaxon (foerstei) n. sp. 

Table of measurements (in mm) 

Cll Cll Cll Cll 

P,~CQ Po~""' P,~CI) P.~oo "S~~c:<l _e.z~ _e.z~ _e.z~ _e.z~ ~.§z~ 

~~~ ceooa> <'~ooa> 

~~~ !:llltlfl.l 

~ ..... ~p~ ~p~ p. i£:~P~ 

Restored corallum 

length ·------·-------- 32 17 

Calice depth -------- 16 8 

Outside diameter 

at calice 

bottom ----------·--· 12 11.5 

Number of major 

septa at calice 

bottom -------------- 28 24 

Ephebic section: 

Diameter ---------- 9.5 13 15.6 

Major septa ____ 26 24 26 
FAMILY ENDOPHYLLIDAE TORLEY 23 

dilated toward tips, laterally in contact and reinforced 

by stereoplasm to produce an aulos. Entire septum may 

be somewhat dilated. Individuals with poorly defined 

aulos show pairs of contiguous septa meeting axially 

like a tuning fork, the merged segments continuing 

toward axis; they may reveal quadrate transverse symmetry. The peripheral stereo zone may exceed 1 mm, 

but it is usually not as thick as the aulos. Amount of 

stereoplasm varies considerably; some early ephebic 

sections show entire aulos filled with this material. 

Appearance of false dissepiments may result from section cutting bulbous distal inflations of tabulae between 

aulos and outer wall. 

Longitudinal sections.-Outer segments of tabulae 

descend steeply, with upward inflection before meeting 

the stereozone. Some complete tabulae are vague 

within the aulos; others are traceable completely 

across. Aulos segments of tabulae may be thickened 

stereoplasmically. In some individuals complete tabulae have M-shape curvature with near-vertical outer 

segments. Tabular spacing nonuniform, usually fairly 

wide. 

Comparison with related forms.-Butler's ( 1935) 

figures of Syringaxon siluriensis (McCoy) show a 

maturely cerioid to subcylindrical form with fewer 

septa and poorly developed minor septa. S. foerstei 

includes externally similar subcylindrical variants, but 

the norm is a trochoid corallum. Both species are 

inclined to have heavy stereoplasmic deposits in the 

aulos and a wide septal stereozone. Of several species 

figured by Prantl ( 1938) from the Devonian of Czechoslovakia, most have a lower septal count and elongate 

subcylindrical coralla. Species described from the 

Greifensteiner Kalk (Eifelian) of Germany by Fli.igel 

and Free ( 1962) have a weaker aulos and less arching 

of tabulae. 

Occurrence.-Rabbit Hill Limestone of Helderberg 

(Early Devonian) age; Devonian coral zone A. Northern Monitor Range, Rabbit Hill vicinity, localities M48, 

M49, M187. Middle part of the Monitor Range, Dobbin 

Summit area, localities M1067, M1068, M1069. Northern Simpson Park Range: Walti Hot Springs area, 

locality M1074; Coal Canyon area, localities M1032, 

M1075, M1076. Cortez Mountains, Mount Tenabo 

area, locality M1083. 

Beacon Peak Dolomite Member of Helderberg (Early 

Devonian) age, Devonian coral zone A. Southern Sulphur Spring Range, localities M186, M197, M1081, 

M1082. 

Family STREPTELASMATIDAE Nicholson, 1889 

Genus Siphonophrentis O'Connell, 1914 

Siphonophrentis sp. B 

Plate 8, figures 1-3 

Fragmentary specimens of a nondissepimented coral 

provisionally placed in Siphonophrentis were collected 

from the Beacon Peak Dolomite Member in the southern Sulphur Spring Range. A silicified individual with 

restored corallum length of about 45 mm and greatest 

diameter of 32 mm has about 60 straight, tapering 

septa of medium length, poorly differentiated as major 

and minor. An indefinite fossula lies on the convex side 

of the corallum. The septal stereozone is narrow. 

A smaller individual, possibly the tip of the above 

described larger corallum, has short septa, a narrow 

peripheral stereozone and rather close-set tabulae, 

part of which are complete. Large elongate tabellae are 

present peripherally. 

Occurrence.-Southern Sulphur Spring Range, locality M186. Beacon Peak Dolomite Member of the 

Nevada Formation, in Devonian coral zone A with a 

Rabbit Hill Early Devonian (Helderbergian) fauna. 

Family ENDOPHYLLIDAE Torley, 1933 

Reference forms.-Endophyllum bowerbanki Edwards and Haime and E. abditum Edwards and Haime, 

1851. Devonian, Torquay, England. 

Cerioid and aphroid rugose corals with wide corallites, a broad marginarium of partly large lonsdaleioid 

dissepiments and a narrow to very wide tabularium 

comprising closely spaced tabulae. No axial structure. 

Genera assigned to the Endophyllidae are: 

Endophyllum Edwards and Haime, 1851 

Yassia Jones, 1930 

Australophyllum Stumm, 1949 

Undescribed Late Silurian corals of the Klamath 

Mountains, Calif., and the Great Basin also belong in 

this family. These include an unnamed subgenus of 

Australophyllum characterizing Great Basin Silurian 

coral zone E and an unnamed genus related to Australophyllum in the Silurian Gazelle Formation of the 

Northeast Klamath Mountains. 

Certain corals here regarded as Endophyllidae have 

previously been assigned to Spongophyllum, a homeomorphic genus not included in this family. It is proposed that the term Spongophyllum be applied only to 

species with slender corallites agreeing in general structure and proportions with the Devonian S. sedgwicki as 

originally illustrated by Edwards and Haime ( 1853, pl. 

56, figs. 2, 2a-c, 2e). 

In addition to the wide lonsdaleioid marginarium, 

Late Silurian representatives of Yassia and the undescribed subgenus ofAustralophyllum manifestadecided 

tendency to abbreviate and lose septa in mature growth 

stages, characteristics not observed in Spongophyllum. 

Genus Australophyllum Stumm, 1949 

1911 Spongophyllum cyathophylloides Etheridge, p. 7-8, pl. 

A, fig. 3, pl. C, figs.1-2. 

1949 Australophyllum Stumm, p. 34, pl. 16, figs. 1-2. 
24 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

1956 (?) Australophyllum cyathophylloides (Etheridge). Hill, 

fig. 207-4a-b. 

Type species. - Spongophyllum cyathophylloides 

Etheridge, by author designation. "Lower Middle 

Devonian"; Douglas Creek, Clermont, Queensland, 

Australia. 

Diagnosis.-Cerioid Endophyllidae with medium 

wide to narrow, closely spaced, proximally sagging 

tabulae and wide to very wide dissepimentarium comprising scattered to wholly lonsdaleioid dissepiments, 

some large. 

Remarks.-Australophyllum differs from Spongophyllum by having multiple columns of elongate, lonsdaleioid dissepiments and more closely spaced sagging 

tabulae without peripheral depression. Stumm's diagnosis of Australophyllum includes carinate septa, 

although his figures do not reveal these convincingly. 

The wall of typical Australophyllum is thickened 

stereoplasmically; septal crests do not appear to be 

characteristic, as in the undescribed Silurian subgenus. 

Australophyllum landerensis n. sp. 

Plate 9, figures 3-6 

Diagnosis.-Australophyllum with long minor septa, 

all septa thickened in tabularium and outer dissepiments steeply inclined for the genus; outer wall thickened and beaded with wall crests. Tabularium medium 

wide; close-set tabulae with pronounced sag. 

External features.-Occurs in compact cerioid heads 

6 inches or more in diameter. 

Transverse sections.-Septa about 44, all of which 

are long and usually thickened within the tabularium; 

minor septa are more than one-half the length of major 

septa. Some major septa reach the axis, where they are 

twisted. Septa may be minutely wavy, and where 

thickened show minute nodes and lateral bumps, but 

no true elbow carinae. Stereome-thickened wall with 

beaded appearance because of wall crests; other septal 

crests sparse in lonsdaleioid band. 

Longitudinal sections.-Tabularium about one-third 

the corallite width at maturity, very sharply set off 

from dissepimentarium. Tabulae 4 or 5 per millimeter, 

with pronounced sag that may be angulate axially. 

Large outer dissepiments steep for this genus, the 

smaller ones becoming vertical at tabularium margin. 

Dissepiment columns range from 7 to 12. Thickened 

axial segments of major septa reveal minute lateral 

bumps. 

Reproductive offsets.-One mature corallite shows 

three calice wall offsets internally situated. 

Fine structure.-Thickened septa may have a 

median clear trace; trabecular structure and lamination ill defined in septal stereozone. 

Comparison with related forms.-Australbphyllum 

cyathophylloides, the type species, differs by having 

fewer septa that lack thickening in the tabularium. 

Australophyllum sp. v from the upper part of the 

Vaughn Gulch Limestone, Owens Valley, Calif., 

resembles Australophyllum landerensis, but lacks 

thickened septa; Australophyllum sp. v occurs in beds 

of possible Early Devonian age immediately above Late 

Silurian coral zone E, which contains a different subgenus of Australophyllum. The coral zone E subgenus 

has broader mature corallites with a considerably 

smaller septal count and lacks septal thickening; this 

form has outer lonsdaleioid dissepiments inclined at 

a low angle, a greater number of very large dissepiments, and, unlike A. landerensis, tends to reduce and 

lose septa at maturity. 

Measurements.-Mature corallite diameter and 

major septum count: 

Holotype 

USNM 159353 

corallites 

A B C 

Diameter (in mm) ........ 13 14 10 

Major septa .................... 22 22 22 

Para type 

USNM 159354 

corallites 

A B 

13 10 

20 22 

Occurrence.-Lower Devonian Rabbit Hill Limestone, Petes Canyon, locality M1150 at north end of 

Toquima Range, southern Lander County. At locality 

M1150 this colonial coral is associated with a typical 

Rabbit Hill fauna like that of the type locality. Colonial 

corals of this kind are uncommon in the Rabbit Hill, 

which usually contains only the small solitary rugose 

coral Syringaxon. 

Australophyllum stevensi n. sp. 

Plate 9, figures 8-13 

Type material.-Holotype, USNM 165349; Sunday 

Canyon Formation, locality M1401. 

Diagnosis.-Australophyllum with few lonsdaleioid 

dissepiments, many small dissepiments, septal thickening in tabularium moderate and nonuniform. Minute 

septal spines present. 

Transverse thin sections.-Septal count about 42 in 

a corallite of 13 mm diameter; longer septa minutely 

wavy and twisted near axis. Minor septa two-thirds 

length of major septa. Carinae absent. Septa moderately to slightly thickened in tabularium and innermost 

dissepimentarium of parts of some corallites. Wall moderately thickened stereoplasmically. Lonsdaleioid septa 

present in some corallites, where they are irregular and 

confined to small segments. 

Longitudinal thin sections.-Tabularium medium 

wide to wide; tabulae close spaced and sagging. Dissepiments mostly small, with as many as eight columns 

on each side, many steeply inclined. Minute septal 

spines scattered. 
FAMILY RHIPILOMELLIDAE SCHUCHERT 25 

Comparison with related forms.-Australophyllum 

stevensi differs from A. landerensis by having fewer and 

less uniformly developed lonsdaleioid dissepiments, a 

less thickened wall, and less extensive septal thickening. The minute septal spines of A. stevensi were not 

observed in A. landerensis. Australophyllum sp. v of the 

higher Vaughn Gulch Limestone differs by having 

unthickened septa and a somewhat more uniform pattern of lonsdaleioid dissepiments. 

Occurrence.-Sunday Canyon Formation (Ross, 

1966, p. 32), Mazourka Canyon area, northern Inyo 

Mountains, Calif., locality M1401, east side of AI Rose 

Canyon. The Sunday Canyon Formation as demonstrated by Ross passes southward into the Vaughn 

Gulch Limestone. A. stevensi came from beds that may 

be of Early Devonian age about 40 feet stratigraphically below the top of the Sunday Canyon. 

Study rna terial is part of a single large corallum. 

Australophyllum sp. v 

Plate 9, figure 7 

Australophyllum sp. v. represented by a fragmentary 

corallum from the upper part of the Vaughn Gulch 

Limestone of the northern Inyo Mountains, Calif., 

shares some features of A. landerensis of the Rabbit 

Hill and some characteristics of A. stevensi of the Sunday Canyon Formation. 

Australophyllum sp. v has the thickened wall of A. 

landerensis, but its septa are unthickened. The lonsdaleioid band is somewhat better developed than in A. 

stevensi, and its septa are peripherally discontinuous 

as septal crests. 

Occurrence.-Upper part of the Vaughn Gulch Limestone, Mazourka Canyon area, northern Inyo Mountains, Calif., locality M1093. The Vaughn Gulch Limestone (Ross, 1966, p. 30) is largely Silurian, but its 

upper unit is possibly of Early Devonian age like the 

upper part of the Sunday Canyon Formation, which 

passes laterally into the Vaughn Gulch beds. Late 

Silurian limestones of coral zone E underlie the beds 

that yielded Australophyllum sp. v. 

Family DISPHYLLIDAE Hill. 1939 

Genus Billingsastraea Grabau, 1917 

Billingsastraea sp. m 

Plate 9, figures 1, 2 

Figured material.-Specimen USNM 165350; southern Tuscarora Mountains, Maggie Creek, locality 

M1400. 

Diagnosis.-Billingsastraea with unusually small 

corallites for the genus and smooth uniformly unthickened septa. 

Transverse thin sections.-Septal count about 35 in 

a corallite of 7% mm diameter; septa smooth, uniform 

and unthickened, the major septa extending to axis; 

minor septa more than three-fourths length of major 

septa. Septa slightly wavy only in tabularium. Small 

dissepiments crowded at inner edge of dissepimentarium. 

Longitudinal thin section.-Only available section 

does not pass through tabularium. Some flat dissepiments very elongate. 

Comparison with related forms.-Corallites of this 

species are about one-half the width of those of B. 

nevadensis (Stumm) and B. affinis (Billings), both of 

which have a larger septal count and minutely wavy 

septa with small zigzag carinae not present in Billingsastraea sp. m. 

Occurrence.-South end of the Tuscarora Mountains, locality M1400 near Maggie Creek northwest of 

Carlin. This coral is associated with a Rabbit Hill 

Early Devonian fauna, and appears to be the oldest 

known occurrence of Billingsastraea. 

Phylum BRACHIOPODA Dumeril, 1807 

Class ARTICULATA Huxley, 1869 

Order ORTHIDA Schuchart and Cooper, 1932 

Family RHIPIDOMELLIDAE Schuchart, 1913 

Genus Rhipidomella Oehlert. 1890 

1958 Rhipidomelloides Boucot and Amsden, p. 165, pl. XII, 

figs. 5-9, pl. XIV, figs. 10-11, text figs. 9, 42. 

The Rabbit Hill brachiopods placed in Rhipidomella 

are most similar to species previously classified by 

Boucot and Amsden (1958) as "Rhipidomelloides," a 

genus later placed in synonymy (Williams and Wright, 

1965, p. 341). 

Rhipidomella rossi n. sp. 

Plate 4, figures 15-24 

1963 Dalmanella sp. (small form); Merriam, p. 43. 

Type material.-Holotype, USNM 159556; paratypes, USNM 159555, 159557-159561. Rabbit Hill 

Limestone, locality M409. 

Diagnosis.-Orthoid brachiopods with dorsal and 

ventral valves about equally convex, rectimarginate; 

dorsal valve without sulcus. Ventral valve muscle field 

moderately large, ovoid-fan-shaped, and lacking the 

radial myophragms of some Rhipidomella. Dorsal valve 

with stout brachiophores and large thickened cardinal 

process. 

Exterior.-Outline ovoidal to subcircular. Hinge line 

about one-half maximum width of shell. Pedicle valve 

interarea curved, concave, slightly apsacline, much 

longer than dorsal valve interarea. Delthyrium large 

and open. Both valves flattened toward commisure; 

without trace of sulcus or fold. Fine radial ribs split 

anteriorly. 

Pedicle valve interior.-Delthyrial cavity large and 

deep; teeth large, supported by abbreviated but stout 

dental plates. The muscle field is bilobed, rounded 

anteriorly, and has a median septum which is promi-
26 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

nent anteriorly at the union of the two large crescentic 

diductor scars and faint or nonexistent posteriorly 

between the adductors. The more or less heart-shaped 

combined adductor areas are relatively large for the 

genus. Radiating myophragms that divide the muscle 

field of some Rhipidomella species were unrecognized. 

No pallial markings were observed. Crenulations at 

internal shell margin reported (Boucot and Amsden, 

1958, p. 165, 168) to characterize "Rhipidomelloides" 

are too poorly preserved for meaningful comment. 

Where recognizable on the silicified shells, they are 

more suggestive of those of Rhipidomella than those of 

rectangular cross section in "Rhipidomelloides." 

Brachial valve interior.-Median ridge varies from 

very heavy to rather faint; extends to middle of valve. 

Transverse ridge separating anterior from posterior 

adductor scars well defined to faint; anterior scar is 

larger. Stout shaft of cardinal process simple, may be 

coBstricted beneath myophore that has one to several 

tubercles. 

Comparison with related forms.-Rhipidomella 

rossi appears to be related to both R. oblata (Hall) of 

the Haragan Limestone and R. henryhousensis Amsden of the Henryhouse Formation (Boucot and 

Amsden, 1958, pl. II, figs. 1-16; pl. XII, figs. 1-9; pl. 

XIV, figs. 10-11). R. rossi seems to be more nearly 

equivalved in transverse profile than oblata; the brachiophores and cardinal process of henry housensis are 

less stout. Some specimens of oblata have well-defined 

radiating myophragms in the ventral-valve muscle field 

not noted in rossi, and the cardinalia of oblata are less 

heavy. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Family DALMANELLIDAE Schuchert, 1913 

Genus Levenea Schuchert and Cooper, 1931 

1931 Levenea Schuchert and Cooper, p. 246. 

1932 Levenea Schuchert and Cooper, p. 123, pl. 18, figs. 19-23., 

25-32. 

Type species.-Orthis subcarinata Hall, 1857 (by 

author designation). Early Devonian (Helderbergian); 

New York and Tennessee. 

Diagnosis.-Dalmanellid brachiopods with subcircular outline, hinge line narrower than greatest width, 

ventral interarea longer than dorsal; delthyrial cavity 

of ventral valve deep, dental plates thickened on inside 

to form fossette, diductor tracks deeply impressed. 

Cardinal process prominent with lobate myophore; 

adductor field or dorsal valve subcircular, or elliptical. 

This genus, though reported from the Silurian, is 

especially characteristic of the Early Devonian (Helderberg) rocks. 

Levenea subcarinata subsp. antelopensis n. subsp. 

Plate 4, figures 1-14 

1963 Levenea n. sp. cf. L. subcarinata (Hall). Merriam, p. 43. 

Type material.-Holotype, USNM 159547; paratypes, USNM 159548, 159551, 159552, locality M409. 

Paratypes, USNM 159549, 159550, locality M186. 

Paratype, USNM 159553, locality M1309. Paratype, 

USNM 159554, locality M1312. Rabbit Hill Limestone 

and Beacon Peak Dolomite Member of the Nevada 

Formation. 

Diagnosis.-Large unequally biconvex Levenea with 

well-defined brachial valve sulcus and medially subcarinate pedicle valve. Brachiophore blades thick. 

Adductor scars of brachial valve large and deeply 

impressed on shelly platform with medial ridge. Cardinal process elongate and narrow to large with swollen 

bifid termination at myophore. 

Pedicle valve interior.-Delthyrial cavity deep; 

diductor tracks deeply impressed in thickened shell 

platform and separated by a wide flat-topped ridge 

which may have a median groove. Diductor and adjustor scars not differentiated. Teeth stout; dental plates 

short and merging with anteriorly projecting wall of 

delthyrial cavity. Dental plates may be thickened on 

medial side above umbonally directed grooves in wall 

of delthyrial cavity. Large rounded pit may develop 

just anterior to muscle platform. Pallial markings not 

well defined. 

Brachial valve interior.-The large subquadrate, 

quadripartite muscle field is sharply impressed in a 

thickened shelly platform having prominent raised 

rim; the median dividing ridge is usually stout and 

rounded from the cardinal process shaft through the 

posterior adductor pair, becoming more narrowly carinate anteriorly. Brachiophores are thick blades joining 

the raised outer muscle field rim dorsally. Sockets deep 

and rounded. In some individuals there is a weakly 

defined transverse lateral groove, the prolongation of 

that between anterior and posterior adductor scars. 

External features.-Subcarinate pedicle valve much 

more deeply convex than sulcate brachial valve in this 

biconvex shell. Valves ornamented by fine, close-set, 

more or less equal radial costellae that split anteriorly. 

Outline subrounded in commissure plane, greatest 

width anterior to hinge line. 

Comparison with related forms.-Within its variation range, subsp. antelopensis includes individuals 

whose brachial interior features may be matched 

closely with those of typical subcarinata as figured by 

Schuchert and Cooper (1932, pl. 18, figs.19, 25, 31, 32), 

and in general the new subspecies is morphologically 

quite similar to the eastern Helderberg species. Typi-
FAMILY STROPHEODONTIDAE CASTER 27 

cal subcarinata, unlike subsp. antelopensis, seemingly 

does not have a marked tendency toward bifurcation of 

the cardinal process, whereas antelopensis lacks the 

secondary shaft of the cardinal process over the median 

ridge (Schuchert and Cooper, 1932, p. 124) shown by 

subcarinata s.s. 

Occurrence.-Early Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, localities M1309, 

M1311. Petes Canyon area, Toquima Range, locality 

M1150. Coal Canyon, Simpson Park Range, locality 

M107 5. Early Devonian Beacon Peak Dolomite Member. Southern Sulphur Spring Range, localities M186, 

M197, M1312. 

Family ORTHIDAE Woodword. 1852 

Genus Orthostrophia Hall. 1883 

Orthostrophia strophomenoides subsp. newberryi n. subsp. 

Plate 3, figures 4, 5; plate 8, figures 6-9 

1963 Orthostrophia sp. cf. 0. strophomenoides (Hall), Merriam, p. 43. 

Type material.-Holotype, USNM 159540; paratypes, USNM 159616, 159617. Rabbit Hill Limestone, 

locality M409. 

Diagnosis.-Orthostrophia of the strophomenoides 

(Hall) type, large for the genus, with transverse outline, ventral fold, and dorsal sulcus. Sulcus well developed on posterior half only, becoming obsolete toward 

the commissure in mature shells. Strength of radial 

ornamentation medium to coarse for the genus. Dental 

plates abbreviated as anterolateral rims of delthyrial 

cavity. 

External features.-Shell with biconvex lateral profile; outline transverse-subquadrate. Hinge line wide 

and straight. Ventral interarea apsacline, longer than 

dorsal interarea, which is orthocline. Ornamentation 

multicostellate with heavier radial ribs rather coarse 

for the genus (5-7 ribs within 6 mm on mature part). 

Concentric incremental ridges widely spaced and rather 

subdued. 

Pedicle valve interior.-Muscle field small, of triangular outline, deeply impressed and terminating 

anteriorly as an elevated shelf. The dental lamellae 

develop as abbreviated anterolateral rims of the delthyrial cavity. Pallial markings and margins of adductor 

and diductor scars indefinite on available silicified 

specimens. 

Brachial valve interior.-Brachiophores moderately 

thick at edge of wide and fairly deep notothyrial cavity. 

Sockets small. Cardinal process simple, swelling anteriorly to merge with prominent rounded medial ridge 

that divides the muscle field. Adductor muscle scars 

deeply impressed on a raised shelly platform. Transverse ridges separating anterior from posterior adductor scars weakly developed. Pallial markings poorly 

shown. 

Comparison with related forms.-Orthostrophia 

strophomenoides newberryi resembles 0. strophomenoides (Hall) quite closely, judged by the illustrations 

of Schuchert and Cooper ( 1932, p. 70-71, pl. 6, figs. 22, 

24, 25, 27, 28) and of Hall and Clarke (1892, pt. 1, pl. 

V, figs. 24-27). The hinge plate and brachial valve 

muscle scar features are similar, but the available specimens of newberryi do not reveal the strong pallial 

markings of typical strophomenoides and the costellae 

of newberryi seem on the whole slightly heavier. 

Orthostrophia strophomenoides subsp. parva Amsden (1958a, p. 41-45, pl. 1, figs. 22-32) seems to be a 

smaller subspecies, with somewhat less coarse radial 

costellae than subsp. newberryi. Amsden's illustrations 

( 1958a, pl. 1, fig. 30, 31, 32) show a better separation of 

anterior from posterior adductor scars of the brachial 

valve than in newberryi and strongly developed vascular markings not known in the new species, possibly 

because of preservation by silicification. 

Occurrence.-Early Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Order STROPHOMENIDA Opik. 1934 

Family STROPHEODONTIDAE Caster, 1939 

Genus Leptostrophia Hall and Clarke. 1892 

Leptostrophia sp. cf. L. becki tennesseensis Dunbar 

Plate 3, figures 1-3; plate 8, figure 5 

Fragmentary ventral valves of this genus from the 

Rabbit Hill type section reveal interior details and surface ornamentation. Ventral interiors have large triangular diductor scars with bounding lateral ridges; 

the ventral process is large and where widest shows a 

median groove. Externally the ventral valve is slightly 

convex near the umbo, flattening laterally and anteriorly. The surface is finely costellate, with about eleven 

costellae per width of 5 mm. Concentric rugae weak, 

recognizable only about halfway between umbo and 

shell perimeter. 

The Rabbit Hill shells resemble specimens from the 

Bois d'Arc Limestone of Oklahoma and from the Birdsong Shale of Tennessee referred by Amsden ( 1958a, 

p. 78-80; pl. 3, figs. 15-20; pl. 6, fig. 1; pl. 11, figs. 27, 

28) to this subspecies. Those illustrated by Amsden are 

much less strongly rugate concentrically than the possibly aberrant representative of tennesseensis described 

and figured by Dunbar (1920, p. 129, pl. 3, fig. 18). 

The Rabbit Hill Leptostrophia resembles more completely an undescribed species from the lower part of 

the Nevada Formation (unit 1), where it occurs in 

post-Rabbit Hill beds of Oriskany age. This form has 

a less expanded ventral process with a less conspicuous 

median groove. 
28 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1309. 

Genus Pholidostrophia Hall and Clarke, 1892 

(7}Pholidostrophia sp. R 

Plate 3, figures 6, 7 

This distinctive, possibly aberrant, stropheodont is 

represented in the collections by a single silicified 

pedicle valve. The outer surface is smooth and without 

pseudonacreous texture, probably because of replacement by siliceous matter. This valve is deeply convex, 

with greatest width near hinge line; interarea wide, 

short, orthocline, and denticulate. The poorly preserved 

pseudodeltidium is thick, largely closing the delthyrium, and probably had a median fold. 

The muscle field is rather deeply impressed; the large 

fan-shaped diductor scars, unlike normal Pholidostrophia, have strong lateral bounding ridges. Cardinal 

process receiving pits are large and deep, suggesting 

that the cardinal process of the brachial was thick. A 

long ventral process is split by a median groove 

throughout, this groove extending almost to the anterior shell margin. Adductor scars unusually large and 

oval. Pseudoteeth present. 

This form differs markedly from normal Pholidostrophia by having diductor scar bounding ridges and a 

very elongate median groove of the ventral process. It 

may represent a distinct genus, but fuller characterization must await collecting of more material. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Genus Strophonella Hall, 1879 

Strophonella cf. S. punctulifera (Conrad} 

Plate 3, figures 10, 11 

A large Strophonella with exterior features intermediate between S. punctulifera and S. bransoni Amsden occurs at several localities in the southern Sulphur 

Spring Mountains in association with Rabbit Hill Helderberg species. The resupinate curvature is within the 

range of that illustrated by Amsden (1958a, p. 70) for 

bransoni, but the radial ornamentation is perhaps more 

like that of the New York Helderberg punctulifera 

(Hall and Clarke, 1892, pl. XII, fig. 10), which reveals 

finer costellae than the Haragan species bransoni. 

Strophonella has been recognized only in the Lower 

Devonian of Nevada, where two other forms occur in 

Nevada Formation, unit 1; of these, one occurs in the 

Oriskany age beds of coral zone B and another slightly 

higher in the beds of coral zone C together with Papiliophyllum and Acrospirifer kobehana. 

This genus was not found in limestone facies of the 

typical Rabbit Hill Limestone. 

Occurrence.-Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation. Southern Sulphur Spring Range, localities M186, M197, M1081. 

Family LEPTAENIDAE Hall and Clarke, 1894 

Genus Leptaena Dalman, 1828 

Leptaena fremonti n. sp. 

Plate 3, figures 16, 17, 19 

1963 Leptaena sp. cf. L. rhomboidalis (Wilckens). Merriam, 

p.43. 

Type material.-Holotype, USNM 159544; paratype, USNM 159545. Rabbit Hill Limestone, locality 

M409. 

Diagnosis.-Medium-sized Leptaena with fairly regular transversely subquadrate, moderately alate outline. Valves sharply geniculate anteriorly; externally 

the valves have few medium to heavy concentric rugae 

for the genus. Radial costellae may be subdued. 

External features.-Proportions and outline of this 

slightly alate, but not strongly mucronate shell, are 

characteristic. The trail bears only radial ornamentation; ribs are coarse on the interior of both dorsal and 

ventral valve trail surfaces. Concentric rugae of pedicle 

valve exterior range from 6 to 9, few for this genus when 

mature. The trail is usually long, fairly even, and bends 

abruptly almost 90°, as shown on pedicle valve exterior. 

Pedicle valve interior.-Muscle field deeply impressed, with evenly rounded raised rim and median 

septum; configuration like that of many species of 

Leptaena. 

Brachial valve interior.-Lobes of the bifid cardinal 

process of medium to large size, with extensive ovoidtriangular myophore surfaces. Median ridge between 

adductor scars may extend beyond valve middle as a 

weak septum. Broadened radial ribs prominent on inner 

trail surface. Inner valve surface may be strongly 

postulose. 

Comparison with related forms.-Leptaena fremonti 

resembles Leptaena cf. L. rhomboidalis (Wilckens) of 

Amsden (1958c, pl. II, figs. 12-15) from the Bois d'Arc 

Limestone of Oklahoma, which has a more irregular outline. Leptaena acuticuspidata Amsden of the Oklahoma 

Haragan (Amsden 1958a, pl. III, figs. 1-9) is also similar, but shows greater irregularities in and around the 

muscle field of both valves. Leptaena ventricosa (Hall) 

from the Frisco Limestone of Oklahoma as figured by 

Amsden and Ventress (1963, pl. II, figs. 9-14) is more 

elongate, less alate, and has a larger number of concentric rugae. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1311. Coal 

Canyon, Simpson Park Range, locality M1075. Specimens compared to this species occur in the Southern 

Sulphur Spring Range in the Beacon Peak Dolomite at 

locality M197. 
FAMILY UNCINULIDAE RZHONSNITSKA YA 29 

Family SCHUCHERTELLIDAE Williams, 1953 

Genus Schuchertella Girty, 1904 

Schuchertella cf. S. haraganensis Amsden 

Plate 3, figures 12-15 

1963 Schuchertella sp. (large form). Merriam, p. 43. 

The genus Schuchertella is represented in the Rabbit 

Hill collections by several silicified pedicle valves 

resembling that of S. haraganensis; these are of medium 

to large size for the genus, rather coarse ribbed and 

lack dental lamellae. With the larger shells, the valve 

is nearly flat or shallowly convex; the stout hinge teeth 

are buttressed by a thickened ridge beneath the palintrope, but not projecting anteriorly along the floor as 

dental lamellae. One smaller deformed individual is 

much more convex and narrower at the hinge line, has 

more elongate interarea, and shows evidence of possible 

beak attachment (Stehli, 1954, p. 298). 

Pedicle valves of the Rabbit Hill Schuchertella have 

coarser ribbing than S. nevadensis Merriam from 

Nevada Formation unit 2. An undescribed species 

resembling nevadensis occurs in Nevada unit 1 with 

Acrospirifer kobehana; this undescribed form has incipient but very short dental lamellae in most but not all 

individuals and accordingly might be assignable to 

Schellwienella Thomas, rather than to Schuchertella 

(Amsden, 1958a, p. 90-91). 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

A similar Schuchertella occurs in these beds at Dobbin 

Summit, Monitor Range, locality M1311. 

Order PENTAMERIDA Schuchert and Cooper, 1931 

Family PARASTROPHINIDAE Ulrich and Cooper, 1938 

Genus Anastrophia Hall, 1867 

Anastrophia cf. A. verneuili (Hall) 

Plate 5, figures 15-19 

Several brachial valves of a possible new species of 

Anastrophia were collected in the southern Sulphur 

Spring Range at localities M186 and M197 in association with a fairly large fauna of Rabbit Hill Helderberg 

age. No pedicle valves were found. The internal features 

of these shells are quite similar to those of verneuili as 

illustrated by Schuchert and Cooper ( 1932, pl. 25, figs. 

33, 36, 38, 39). 

The Nevada species is of medium size to large, with 

coarse radial costae and deeply convex brachial valve; 

the fold is weakly defined in some individuals, well 

defined in others. On the anterior part of large mature 

shells, the number of costae occuping the fold ranges 

from 5 to 7. The radial ornamentation of this form also 

resembles that of Anastrophia grossa Amsden (1958a, 

p. 65-68, pl. II, figs. 18-28). 

Presence of Anastrophia is significant in fixing the 

Helderbergian age of this fauna, bec~use as in the New 

York area, this genus is not known above that interval 

(Amsden, in Amsden and Ventress, 1963, p. 194; text 

figs. 10, 51). 

Occurrence.-Lower Devonian Beacon Peak Dolomite Member of the Nevada Formation. Southern Sulphur Spring Range, localities M186 and M197. 

Order RHYNCHONELLIDA Kuhn, 1949 

Family UNCINULIDAE Rzhonsnitskaya 

Genus Plethorhyncha Hall and Clarke, 1894 

Plethorhyncha andersoni n. sp. 

Plate 6, figures 1-7 

Type material.-Holotype, USNM 159574; paratypes, USNM 159575-159578. Rabbit Hill Limestone, 

locality M409. 

Diagnosis.-Large Camarotoechiacea with broad 

shallow fold and sulcus; brachial valve more convex 

than pedicle valve. No dental plates. Rather small posteriorly situated pedicle valve muscle field. Brachial 

valve hinge plate (septalium) with median triangular 

pit bordered by adventitious thickenings. 

External features.-Lateral profile biconvex; brachial valve with greater convexity. Shape transversely 

elliptical to subquadrate. Fold and sulcus broad and 

flatly rounded at commissure of mature shells; width 

one-half that of valves; these features developed only 

in anterior half of mature individuals. Pedicle valve 

flattened posteriorly. Shells ornamented by medium 

to fine subequal radial ribs, of which there are 8-12 in 

the sulcus at commissure of large individuals. Beaks 

small and subdued. 

Pedicle valve interior.-Hinge narrow; teeth are 

modifications of wall and without dental plates. No deltidium covering recognized. Muscle field rather small, 

moderately impressed and flabellate, with thin median 

partition posteriorly; adductor scars partly differentiated. Pallial markings indistinct. 

Brachial valve interior.-Hinge plate and prominent 

median septum united as a continuous element (septalium). The hinge plate is thickened laterally to form 

rims or ventral socket plates and has a triangular 

median pit with lateral thickenings. In available specimens there is no indication of a cardinal process or 

myophore. The median septum extends about one-half 

the distance to the anterior edge of the shell. 

Comparison with related forms.-Plethorhyncha 

andersoni differs from P. speciosum (Hall), the type 

species (Amsden and Ventress, 1963, p. 94), by having 

more numerous and finer radial ribs and a well-defined 

fold and sulcus, these last being poorly developed in 

speciosum. P. speciosum is more elongate anteroposteriorly. The hinge plate of some individuals of speciosum 

carries a bifid cardinal process, although young specimens are reported to lack this structure (Amsden and 

Ventress, 1963, p. 95), in this respect resembling our 

specimens of andersoni. Havlicek (1961, p. 127-131) 
30 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

calls attention to progressive filling of the pit ("SeptaIiumholung") during ontogeny by shell material. It is 

possible that such a filling, together with the bifid 

cardinal process and myophore, were destroyed in our 

silicified specimens of andersoni, leaving only the pit. 

Most species previously assigned to Plethorhyncha 

such asP.? welleri ·(Stewart), P.? salinensis (Stewart), 

and P. barrandi (Hall) have, like speciosum (Hall), a 

coarser pattern of radial ribbing (see Amsden and Ventress, 1963, pls. III and XII). Such a pattern is present 

in the foreign species P. diana (Barrande) and P. altera 

Barrande as figured by Havlicek (1961, pls. XV and 

XVI). Actually the surface ornamentation of P. andersoni is somewhat more suggestive of species placed in 

Uncinulus and Costellirostra than Plethorhyncha (see 

Amsden and Ventress, 1963, pl. III; Schmidt, 1941, pl. 

1; Havlicek, 1961, pl. XXII), but the marked differences in internal structure do not support a direct relation. For example, Uncinulus as established by Schmidt 

(1941, p. 15-25) and by Havlicek (1961, p. 139-149) 

has in the rna ture growth stages a comb like structure 

(Havlicek, 1961, p. 142, p. 56) that develops medially 

on the ventral surface of the hinge plate, a feature not 

known in Plethorhyncha. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1311. Coal 

Canyon, Simpson Park Range, locality M1075. 

Order SPIRIFERIDA Waagen, 1883 

Family MERISTELLIDAE Waagen, 1883 

Genus Meristella Hall, 1860 

Meristella martini n. sp. 

Plate 7, figures 23-27 

1940 (?)Meristella cf. robertsensis Merriam, pl. 6, figs. 13-16. 

Type material.-Holotype, USNM 159606; paratypes, USNM 159607, 159608. Rabbit Hill Limestone, 

locality M409. 

Diagnosis.-Of small to medium size. Outline of 

pedicle valve umbo acutely angulate posteriorly; curvature of wings in plane of commissure rather abrupt for 

the genus. Lateral surfaces of pedicle valve slope 

steeply just anterior to foramen and are not flattened 

toward hinge line as a false interarea. Pedicle beak not 

abruptly in curved or hooked. 

External features.-Shell smooth except for concentric incremental lines that are conspicuous only toward 

front of mature individuals. Lateral profile subsequally 

biconvex; some individuals have a deeper brachial valve 

with convexity exceeding that of pedicle valve. Steep 

sides are characteristic, pitching abruptly in front of an 

acutely angulate pedicle valve beak. Outline in commissure plane more subtriangulate than subrounded, 

with abrupt curvature at greatest shell width, which is 

commonly anterior to middle. Brachial valve fold only 

near front of mature shells, where it is evenly rounded 

or slightly angulate at commissure. Pedicle valve sulcus 

only on anterior third of valve, where it is shallow 

except near commissure of larger individuals. Ventral 

valve beak prominent for genus, but not hooked 

anteriorly. 

Pedicle valve interior.-Muscle field wide, striated, 

and deeply impressed for this genus. Teeth large and 

posteriorly hooked. Mature shells with dental plates 

developed as short inconspicuous ridges which are suppressed with umbonal thickening. 

Brachial valve interior.-Hinge plate triangular, 

merging in front with a high, sharp median septum 

which usually extends more than one-half the valve 

length. Socket large. The brachiophores converge 

toward the beak outlining the large median triangular 

pit characteristic of M eristella. Some specimens reveal 

a process or thickening toward the apex that may be 

cardinal process myophore. Others have bilobed shelly 

fillings toward broader edge of pit, whereas some have 

pit filled by shelly material. 

Comparison with related forms.-Meristella n. sp. 

differs from M eristella robertsensis in shape and proportions of the pedicle valve, especially that part just 

anterior to the beak; M. robertsensis is also a larger 

form. Individuals figured by Merriam ( 1940, pl. 6, figs. 

13-16) from Oriskany beds in the Lower Devonian of a 

horizon lower than those yielding the typical robertsensis are quite similar to the new species and may be 

assignable to it (see also Cooper, 1944, pl. 127, figs. 24, 

25, but not fig. 23). Meristella atoka Girty (Amsden 

1958a, pl. X, figs. 1-15) is similar to martini but 

appears to differ in details of the hinge plate and 

includes numerous variants with acute fold and sulcus 

at the commissure. Meristella arcuata Hall and M. 

laevis Hall are similar externally, but too little is known 

of the internal features of these two species to make 

comparison meaningful. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1311. Coal 

Canyon, Simpson Park Range, locality M1075. 

Family AMBOCOELIIDAE George, 1931 

Ambocoelia sp. a 

Plate 7, figures 28-31 

Figured material.-USNM 159609-159612; Rabbit 

Hill, Copenhagen Canyon, locality M409. 

Several pedicle valves of Ambocoelia from the Rabbit Hill type section are of special interest in supporting 

the Devonian age of this formation, as the genus is 

unknown in older rocks. 

The pedicle valve resembles that of A. umbonata 

(Conrad), the type species, by having prominent 
FAMILY RETZIIDAE WAAGEN 31 

thickened hinge teeth unsupported by dental plates. 

However, the teeth are buttressed by a shelly thickening beneath the delthyrium margin that merges toward 

the beak with extensive umbonal filling by shell material. The sulcus is broad and shallow for the genus. 

Occurrence.-Rabbit Hill Limestone. Rabbit Hill, 

Copenhagen Canyon, locality M409. 

Family LEPTOCOELIIDAE Boucot and Gill, 1956 

Genus Leptocoelia Hall, 1857 

Leptocoelia occidentalis n. sp. 

Plate 5, figures 1-14 

1963 Anoplotheca sp. cf. A. acutiplicata (Conrad). Merriam, 

p.43. 

1964 (?) Leptocoelia sp. Boucot, Johnson, and Staton, pl. 125, 

fig. 19. 

Type material.-Holotype, USNM 159562; paratypes, USNM 159563, 159565-159570, locality M409. 

Paratype, USNM 159564, locality M197. 

Diagnosis.-Thick-shelledLeptocoelia with biconvex 

lateral profile and well-defined sulcus and fold. Hinge 

plate and cardinal process massive. Older shells have 

prominent pit just anterior to strongly impressed 

muscle field of pedicle valve. 

External features.-Size, medium to large for this 

genus; 3 or 4 prominent, rather sharply rounded radial 

costae lateral to the brachial fold and 3 or 4 lateral to 

the strong rib defining the pedicle valve sulcus. Outline 

nearly round, with subdued beaks. Hinge line narrow. 

The two strongest costea, which occupy the fold, rise 

above the lateral rib as they approach the commissure; 

fold not defined on posterior half of valve. Pedicle valve 

with strong median rib in sulcus, opposing interspace 

between the pair of fold ribs. Concentric incremental 

frills strong and closely spaced toward commissure of 

mature shells. 

Pedicle valve interior.-Hinge teeth large, separated 

from lateral walls by a rounded groove. Muscle field 

large, fan shaped, and rather deeply impressed. Pair 

of small ovoidal adductor scars separated by a narrow 

ridge that thickens posteriorly. The usually large 

rimmed pit in front of muscle field is distinctive. 

Brachial valve interior.-Hinge plate broad and 

thick, brachiophores merging basally with strong ventral socket ridges that converge posteriorly at edge of 

plate. Cardinal process thick and elongate-triangular in 

outline with long, dorsally inclined posterior grooves 

constituting the myophore. Heavy median ridge extends anteriorly from hinge plate, narrowing to form 

dividing ridge of the large anterior adductor scars. 

Sockets large and ovoidal. 

Comparison with related forms.-Leptocoelia {labellites (Conrad) Hall is regarded as the type species 

(Amsden and Ventress, 1963, p. 178). The new species 

differs from L. flabellites by having a highly convex 

brachial valve, whereas that of the former is flat; there 

are also marked differences in hinge-plate structure. 

Leptocoelia acutiplicata (Conrad) as figured by Kindle 

(1912, pl. VI, figs. 1-15) is much less convex than 

occidentalis and differs in hinge-plate structure. Leptocoelia infrequens (Walcott) is externally the closest to 

occidentalis, but is less convex; its internal features are 

not well enough known to make further comparison 

possible (Amos and Boucot, 1963, pl. 63, figs. 5-9). 

Leptocoelia occidentalis resembles species assigned to 

Australocoelia Boucot and Gill, 1956, but differs with 

respect to internal features, especially the cardinal 

process by which the genus is distinguished from the 

externally homeomorphic Leptocoelia (Boucot and 

Gill,1956,p. 1174). 

Leptocoelia sp. (Boucot and others, 1964, pl. 125, 

fig. 19) from lower beds of the Nevada Formation is a 

brachial valve whose interior is quite similar to that of 

occidentalis in nearly all structural details. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1311. Walti 

Ranch, Simpson Park Range, locality M1074 (cf. occidentalis). Beacon Peak Dolomite Member of the 

Nevada Formation. Southern Sulphur Spring Range, 

localities M186, M197. 

Family RETZIIDAE Waagen, 1883 

Genus Trematospira Hall, 1859 

Trematospira mcbridei n. sp. 

Plate 6, figures 8-15 

1963 Trematospira sp. cf. T. equistriata Hall and Clarke. Merriam, p. 43. 

Type material.-Holotype, USNM 159579; paratypes, USNM 159580-159585. Rabbit Hill Limestone, 

locality M409. 

Diagnosis.-Finely, uniformly ribbed Trematospira 

with well-developed sulcus; dorsal fold absent or very 

weakly defined. Pedicle valve with narrowly flabellate 

rather deeply impressed muscle field. Hinge plate subquadrate, thick and prominent, projecting about 2 mm 

posteriorly beyond beak. Sockets large. 

External features.-Shape transversely elliptical, 

with small subdued beaks. Lateral profile moderately 

biconvex; hinge line narrow. No interareas. The sulcus 

begins near the beak, remains shallow and fairly broad 

to commissure of larger shells. Brachial valve convexity 

changes anteriorly with slight medial swelling toward 

front, but usually without development of a discrete 

fold. Radial ribs close spaced, subequal, evenly rounded, 

separated by interspaces of comparable width. Splitting 

of ribs anteriorly uncommon. Concentric striations 

inconspicuous. About 9 radial ribs in sulcus of pedicle 

valve, with 18 to 21 ribs on each flank. 
32 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Pedicle valve interior.-Dental plates short and 

inconspicuous. Muscle field triangularly flabellate and 

rather deep, especially where its acute apex is 

impressed medially in floor of delthyrial cavity, forming 

wide lateral shelves. Adductor scars not differentiated. 

Pallial markings unrecognized. 

Brachial valve interior.-Thickened hinge plate variable, invariably projects prominently beyond valve 

edge in a posterior direction; this plate is a paired structure including stout brachiophores that merge anterodorsally with thick socket plates or brachiophore 

support plates. The medial ridge may be either strong, 

tapering anteriorly from the brachiophores along the 

valve inner surface as a ridge, or subdued and narrow. 

The cardinal process is a somewhat indefinite feature 

without a well-defined shaft and is bordered laterally 

by two posterior brachiophore projections. 

Comparison with related forms.-Externally T. mcbridei bears strong resemblance to T. equistriata Hall 

and Clarke 1894, especially as figured by Schuchert 

( Schuchert and Maynard, 1913, p. 430, pl. 73, figs. 

8-9). The interior of equistriata is unknown but may 

be related to T. deweyi (Hall) assigned by Hall and 

Clarke (1894, p. 128, pl. 49, figs. 40-46) to Parazyga, 

the interior of which has been figured. The hinge plate 

of deweyi is similar to that of some individuals of 

mcbridei, although this structure is quite variable. 

Trematospira multistriata Hall has heavier radial ribbing than mcbridei, and there are differences in hingeplate details (Hall and Clarke, 1894, pl. 49, figs.13, 14). 

Trematospira mcbridei resembles T. cooperi Merriam (1940, p. 82, pl. 6, fig. 12) externally and may be 

a subspecies. Because the interior of cooperiis unknown, 

however, the relation of these two Early Devonian 

forms must await preparation of suitable material. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Family DELTHYRIDIDAE Waagen, 1883 

Genus Kozlowskiellina Boucot, 1958 

1957 Kozlowskiella Boucot, p. 318. 

1958 Kozlowskiellina Boucot, p. 1030. 

1842 Delthris raricosta Conrad, pl. 14, fig. 18. 

1857 Spirifer perlamellosus Hall, p. 57. 

1858 Kozlowskiella Boucot, Amsden and Boucot, p. 121. 

1963 Kozlowskiellina Boucot, Amsden and Ventress, p. 114. 

Type species.-By original designation, Kozlowskiella strawi Boucot, 1957. Wenlock Limestone, Great 

Britain; west of Wren's Nest, Dudley, England, middle 

nodular beds of the Wenlock Limestone. 

Diagnosis.-Coarse-ribbed spiriferoid brachiopods 

having frilled growth lamellae, uncomplicated fold and 

sinus, a strong median septum in the pedicle valve, and 

a large distinctive double cardinal process. Interarea of 

pedicle valve long and extensive, that of the dorsal 

valve insignificant. 

Remarks.-As noted by Boucot (1957, p. 318-319), 

the pedicle valve of Kozlowskiellina is more convex than 

the brachial. The heavy ribs and interspaces are ornamented by fine radial riblets that project over the concentric lamellae as fringes of small spines. In mature 

individuals, the deltidial plates are conjunct except for 

an apical foramen. Dental plates are usually short but 

stout; in older individuals, these become partly 

embedded in secondary shell material deposited in the 

umbonal and delthyrial cavities. The strong median 

septum extends from one-half to two-thirds the distance to the anterior margin of the pedicle valve. The 

double cardinal process may be deeply striated. 

Hedeina Boucot, 1957 is externally similar to Kozlowskiellina, but lacks the pedicle valve median septum; the cardinal process is not of the distinctive 

double type found in Kozlowskiellina. Delthyris Dalman, 1828 possesses a thinner median septum in the 

pedicle valve and differs from Kozlowskiellina by lacking the frilly external lamellae, as well as the distinctive 

double cardinal process and by having relatively longer 

and thinner dental lamellae. 

Kozlowskiellina occurs in rocks of Middle Silurian 

age in England (Wenlock Limestone), in the higher 

parts of the Roberts Mountains Formation of the type 

section, which is either Middle or Upper Silurian, and 

is especially characteristic of the Helderberg (Early 

Devonian) beds of the Rabbit Hill Limestone. 

Kozlowskiellina nolani n. sp. 

Plate 6, figures 16-24 

1963 Kozlowskiellina sp. a, Merriam, p. 43. 

Type material.-Holotype, USNM 159589; paratypes, USNM 159586-159588, 159590, 159591, Rabbit 

Hill Limestone, locality M409. Paratype, USNM 

159592, Rabbit Hill Limestone, locality M1309. 

Diagnosis.-Kozlowskiellina with narrow hinge line, 

subquadrangular outline in plane of commissure, and 

few heavy radial ribs. Ventral valve greatly thickened 

by adventitious material in umbonal region. Dorsal 

hinge plate large, with strong bifid cardinal process 

flanked by thick brachiophore supports. 

External features.-Size medium to large for this 

genus. Hinge line width usually exceeds anteroposterior length. Width of fold at commissure may be more 

than one-third hinge line width. Fold and sinus broad, 

deep and rather evenly rounded. Lateral profile 

strongly biconvex; pedicle valve usually deeper than 

brachial. Radial costellae limited to one on either side 

of fold and one lateral to heavy ribs which border the 

sulcus. Concentric frills usually well developed; threadlike minor ribbing and spines at frill edges are not preserved. Pedicle valve interarea long and apsacline; del-
FAMILY DELTHYRIDIDAE WAAGEN 33 

thyrial notch makes angle of about 28 °. Brachial valve 

interarea insignificant. Conjunct deltidial plates and 

foramen not preserved. 

Pedicle valve interior.-Muscle fields not distinguishable in mature shells. Median septum high, usually extending more than half the distance from beak 

to commissure. In early mature stages, septum thin, 

following floor of delthyrial cavity as a low plate separated from the dental lamellae; with older individuals 

having umbonal adventitious deposits, the median 

septum is much thickened posteriorly and merges with 

thick, short dental plates to form a troughlike pseudospondylium. The median septum commonly swells to 

an elongate boss on floor of delthyrial cavity. One or 

more pairs of apically trending grooves occur below 

teeth along the walls of the delthyrium, converging 

toward the beak. 

Brachial valve interior.-Hinge plate large, slightly 

less than one-third valve width at hinge line; a bifid 

cardinal process, lateral to which are expanded brachiophore supports that make up most of the plate. Muscle 

impressions poorly defined, small, with low dividing 

ridge just anterior to hinge plate. Spiralia unknown. 

Comparison with related forms.-Kozlowskiellina 

nolani differs from K. strawi, the type species, in the 

narrowness of the shell and convexity of the brachial 

valve; the brachial valve of K. strawi is nearly flat. 

Compared with K. nolani, most described species have 

a more alate shell and are not known to have the excessive thickening of the pedicle valve median septum on 

the floor of the delthyrial cavity of older individuals. 

Perhaps the most closely related is K. velata Amsden 

(Amsden 1958a, p. 121, pl. VIII, figs. 1-13), though it 

is more alate and has more major costellae and a more 

angulate fold and sinus. An undescribed species of 

Kozlowskiellina in the upper Roberts Mountains Silurian is alate and has numerous major costellae and a 

smaller hinge plate. 

Occurrence . ....:....Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1309. Petes 

Canyon area, N orthem Toquima Range, locality 

M1150. 

Genus Howellella Kozlowski. 1946 

Howellella cycloptera (Hall) subsp. monitorensis n. subsp. 

Plate 7, figures 17-22; plate 8, figure 10 

1963 Spirifer sp. a, cf. as." cylopterus Hall, Merriam, p. 43. 

Type material.-Holotype, USNM 159604; paratype, USNM 159603; Rabbit Hill Limestone, locality 

M409. Paratype, USNM 159605; Rabbit Hill Limestone, locality M1311. 

Diagnosis.-Howellella with evenly curved fold and 

sulcus, lateral to which are 5 to 7 prominent evenly 

rounded radial ribs on each flank. Dental plates short. 

Ventral muscle field flabellate, usually impressed, 

markedly striated, with low median partition. Interior 

of pedicle valve pitted lateral to muscle field. Valve 

surfaces ornamented by fine radial riblets that are 

prominent and possibly spinose at concentric incremental edges. 

External features.-Lateral profile moderately biconvex, the two valves subequal. Hinge line width 

usually exceeds length. Shape in commissure plane 

subovoidal; cardinal extremities rounded. Fold and 

sulcus uncomplicated. Pedicle valve interarea short, 

concave-orthocline with hooked beak. Delthyrial notch 

making angle about 55°. Deltidial plates unknown. 

Dorsal interarea very short. 

Pedicle valve interior.-The fan-shaped impressed, 

longitudinally striate muscle field undifferentiated 

except for median ridge, which varies from broad to 

weak or undefined. Dental lamellae short and ventrally 

divergent. Pitting of inner valve sui-face S'trongest near 

muscle field, but may extend to valve edge. 

Brachial valve interior.-Hinge plate wide, divided 

and open, with small cardinal process and thin, widely 

divergent, bladelike brachiophore supports. Muscle 

attachments weak or unrecognized. 

Comparison with related forms.-The Nevada specimens herein classified as a subspecies of cycloptera 

(Hall) resemble Hall's figures of the New York Helderbergian types rather closely and are quite similar to 

the Oklahoma Bois d'Arc individuals figured by Amsden (Amsden 1958a, pl. VIII, figs. 14-26). The New 

York specimens reveal the striated pedicle muscle field 

and the pitting as in subsp. monitorensis and the exterior pattern of fine surface ornamentation present upon 

the Bois d'Arc individuals. The Bois d'Arc form reveals 

a suggestion of a weak median sulcus on the dorsal fold 

not recognized in subsp. monitorensis. The new subspecies differs markedly from the Silurian Lone Mountain Dolomite species Howellella smithi Waite, which 

has a flattened fold and sinus near the commissure, 

fewer lateral plications, and longer, more slender dental 

plates. Howellella pauciplicata Waite, also of the Lone 

Mountain, is smaller and has very weak lateral 

plications. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Rabbit Hill, Copenhagen Canyon, locality M409. 

Dobbin Summit, Monitor Range, locality M1311. Coal 

Canyon, Simpson Park Range, locality M1075. 

Genus Acrospirifer Helmbrecht and Wedekind.l923 

1923 Acrospirifer Helmbrecht and Wedekind, p. 952. 

1944 Acrospirifer Wedekind. Cooper, p. 323. 

1963 Hysterolites (Acrospirifer) Helmbrecht and Wedekind, 

1923. Amsden and Ventress, p.105. 
34 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Type species.-Spirifer primaevus Steininger 

(Cooper, 1944, p. 323; Amsden and Ventress, 1963, p. 

108). Lower Devonian, Germany. 

Diagnosis.-Cooper (1944) characterizes Acrospirifer as follows: "***Subsemicircular to transversely 

semielliptical, costate and lamellose spiriferoids; fold 

and sulcus noncostate; dental plates strong, muscular 

field large, elongate-oval; dorsal interior with thick 

socket plates.'' 

Remarks.-Amsden and Ventress (1963,p.105-111) 

have reviewed the present status of Acrospirifer in connection with the relations of A. murchisoni (Castelnau). These writers treat Acrospirifer as a subgenus of 

Hysterolites Schlotheim 1820, following the usages of 

Maillieux (1941) and Havlicek (1959). 

Acrospirifer kleinhampli n. sp. 

Plate 7, figures 9-12 

Type material.-Holotype, USNM 159599; paratype, USNM 159600. Rabbit Hill Limestone, locality 

M1309. 

Diagnosis.-Large Acrospirifer with rather narrow 

hinge line for the genus, short dental lamellae, and 6 

or 7 radial ribs on either side of the ventral sulcus. 

Mature individuals may show a tendency toward splitting of radial ribs anteriorly. 

External features.-Cardinal extremities sub rounded 

to subangulate. Radial ribs rounded, rather closely 

spaced and numerous for the genus. Pedicle sulcus deep 

and usually subangular toward the commissure of 

mature shells; brachial fold prominent and sub rounded. 

Concentric lamellae not prominent, obscured because 

of silicification. Splitting or doubling of radial ribs 

toward the anterior margin of large individuals appears 

to be characteristic. Beak of pedicle valve slightly 

hooked. Pedicle interarea well defined but less extensive laterally than in other species of this genus. No 

trace of deltidial plates was noted. 

Pedicle valve interior.-Dental lamellae short and 

obtuse for this genus. Muscle field large, rather deeply 

impressed and striated. 

Brachial valve interior.-Hinge plate with thin dorsally projecting flange medial to brachiophore as in 

Acrospirifer kobehana (Merriam); flange does not 

meet internal valve surface. 

Comparison with related forms.-Acrospirifer kleinhampli differs from A. kobehana (Merriam) by being 

somewhat smaller, with narrower hinge line and laterally less extensive ventral interarea. The dental lamel~ 

lae of kobehana are longer and thinner. The radial ribs 

of kobehana are heavier, fewer, and more widely spaced. 

Acrospirifer kleinhampli resembles A. murchisoni 

(Castelnau) but appears to be narrower (see Amsden 

and Ventress, 1963, pl. VI) and less alate. The complex 

pattern of concentric lamellae shown by murchisoni is 

not known in kleinhampli, possibly because of preservation by silicification. 

Occurrence.-Rabbit Hill Limestone. Dobbin Summit, Monitor Range, locality M1309 in the higher beds 

of this formation. 

Family COSTISPIRIFERIDAE Termier and Termier, 1949 

Genus Costispirifer Cooper, 1942 

1942 Costispirifer Cooper, p. 230. 

1944 Costispirifer Cooper, p. 323, pl. 122, figs. 27-31. 

1963 Costispirifer Cooper, Amsden and Ventress, p. 111-114, 

pl. 5, figs. 3-11, text-fig. 35. 

Type species.-Spirifer arenosus planicostatus 

Swartz (1930, p. 56-57, pl. 9, figs. 13-15) by author 

designation. From cherts in the upper part of the Giles 

Formation near Saltville, Va. Lower Devonian. Cooper 

(1942) regarded Costispirifer planicostatus (Swartz) 

as a distinct species. 

Diagnosis.-Large spirifers with costate fold and 

sulcus. The costae are broad and flat with narrow interspaces; costae ornamented with fine radial lines. Dental 

plates strongly developed. In brachial valve, tbe crural 

bases cup shaped and welded to sides of valve; notothyrial cavity broad and moderately deep. Delthyrium 

covered by a short convex pseudodeltidium. 

Remarks.-Spirifers similar to the eastern Oriskany 

Costispirifer are nos us (Conrad) are the most diagnostic and abundant brachiopods of Early Devonian 

(Siegenian) beds of the Great Basin, where they occur 

with large horn corals belonging to the Subfamily 

Papiliophyllinae. First recognized in the Roberts 

Mountains (Merriam, 1940, p. 50, pl. 7, fig. 17, pl. 11, 

fig. 17), these spirifers have been collected in large 

numbers from arenaceous limestones of Nevada formation unit 1 in the Sulphur Spring Range. Most specimens are pedicle valves that exhibit flattening of ribs 

toward the anterior margin of large shells; otherwise 

the costae are rounded. Fine, delicate costellae were 

not observed on ribs of unpeeled valves. A high percentage of these shells appear to be especially wide at 

the hinge line as compared with more elongate figured 

specimens from the eastern Oriskany ( Schuchert and 

Maynard,1913,pl.71,figs.3,8,9). 

In silicified pedicle valves from the upper part of the 

Hidden Valley Dolomite, Panamint Mountains, Calif., 

the teeth are small and the short dental plates especially heavy where they form a buttress beneath the 

interarea. 

No far-western Costispirifers showing the very wide, 

flattened costae of Costispirifer arenosus var. planicostatus Swartz (1930, pl. 9, figs. 13, 14) have been recognized. Cooper ( 1942, p. 232) elevated Swartz's 

variety to a species separate from C. arenosus (Conrad) upon designating planicostatus as type species of 
FAMILY CONULARIIDAE WALCOTT 35 

Costispirifer. 

Amsden and Ventress (1963, p. 111-114) have 

reviewed the relations and distribution of American 

Costispirifer, noting the taxonomic importance of flat 

costae and narrower interspaces. 

On the whole, differences in shell and ornamentation 

are not great when the New York, Oklahoma, and 

Great Basin forms are compared. The various geographic taxa might reasonably be regarded as subspecies; some selected Nevada specimens are quite 

similar morphologically to some of those from the 

Appalachian belt as well as Oklahoma. 

Appearance of Costispirifer of the arenosus type in 

the higher Rabbit Hill fauna at Dobbin Summit, 

Monitor Range, suggests that these beds are probably 

little older than Nevada unit 1, in which very similar 

brachiopods become dominant. 

Costispirifer arenosus (Conrad) subsp. dobbinensis n. subsp. 

Plate 7, figures 1-7 

Type material.-Holotype, USNM 159594; paratypes, ·usNM 159593, 159595-159597. Rabbit Hill 

Limestone, locality M1309. 

Diagnosis.-Large Costispirifer arenosus with shallow to moderately deep pedicle valve sulcus, large 

deeply impressed ventral muscle field, short dental 

lamellae, and heavy dental lamella buttresses beneath 

the palintrope. The convex pseudodeltidium beneath 

the incurved beak is short and rather heavy. 

Remarks.-The Dobbin Summit pedicle interiors 

reveal deeply impressed muscle scars and very short 

dental plates, except for the greatly thickened buttress 

beneath the interarea. The convex pseudodeltidium 

beneath the beak is short and rather heavy. 

This subspecies, judged by pedicle valve exterior 

features, is specifically like C. arenosus from Nevada 

unit 1. Wide individuals of subspecies dobbinensis 

resemble wide shells of the Hidden Valley Dolomite 

form, which have a somewhat more slender dental 

lamella buttress. 

The dorsal features of subspecies dobbinensis, like 

the Nevada unit 1 form, are poorly known, because 

most of the preserved shells are pedicle valves. Validity 

of dobbinensis as a subspecies must therefore await 

comparison of brachial valve features, likewise poorly 

known in the Hidden Valley representatives. The likelihood that dobbinensis is ancestral suggests that differences in the ventral interior may be borne out in the 

rest of the shell when that is better understood. 

Occurrence.-Lower Devonian Rabbit Hill Limestone. Upper beds of the Rabbit Hill Limestone, Dobbin Summit, Monitor Range, locality M1309. Fragmentary shells possibly belonging to this subspecies 

have been collected from higher beds of the Rabbit 

506-612 0 - 73 - 6 

Hill Limestone at Coal Canyon, Simpson Park Range, 

locality M1076. 

TENTACULITIDS AND CONULARDDS 

OF THE RABBIT HILL LIMESTONE 

Shells of Conularia are locally associated with abundant tentaculitids in platy limestones and calcareous 

shale interbeds of the Rabbit Hill Limestone. Southeast of Walti Ranch (locality M1074) in the Simpson 

Park Range, such platy beds with Conularia contain 

small slender tentaculitids (pl. 8, fig. 18) having the 

ornamentation of Nowakia acuaria Richter. Trilobites 

Leptocoelia, Pleurodictyum, and Syringaxon also occur 

in this assemblage. Similar tentaculitids are present in 

platy Rabbit Hill interbeds at Coal Canyon, northern 

Simpson Park Range. In the Devonian of the Great 

Basin, N owakia-like shells are most abundant in the 

Middle Devonian strata of Nevada Formation unit 4, 

where smooth Styliolina also is common. No large 

coarsely ribbed benthonic tentaculites like those of 

shaly interbeds of Nevada Formation unit 2 were 

observed in the Rabbit Hill. 

Subclass CONULATA Moore and Harrington 

Order CONULARIIDA Miller and. Gurley 

Family CONULARIIDAE Walcott 

Conularia sp. cf. C. huntiana Hall 

Plate 2, figures 18-20 

Figured material.-USNM 159536, 159537; Rabbit 

Hill Limestone, locality M1074, Walti Ranch, Simpson 

Park Range. 

Flattened shells of this delicate Conularia range in 

length from 30 mm to more than 400 mm. The sharply 

sculptured transverse ribs are uniform, about 40 per 

mm, and ornamented by close-spaced small tubercles. 

In some individuals these tubercles are round, in others 

elongate and drawn out longitudinally toward the 

interspaces, but not to the extent shown in Hall's figure 

(1859-61, pl. 72A, figure 2b) of the Helderbergian C. 

huntiana. 

Similar Conularia occurs in the Early Devonian 

Hunsriickschiefer of Bundenbach, Germany. 

Occurrence.-Rabbit Hill Limestone, locality M1074 

southeast of W alti Ranch, Simpson Park Range. 

MOLLUSCA OF THE RABBIT HILL LIMESTONE 

Mollusca, greatly outnumbered by the brachiopods, 

are generally not conspicuous in the Rabbit Hill Limestone. Residues from hydrochloric acid solution of 

Rabbit Hill bioclastic limestones yielded few lamellibranchs; their shells evidently were less amenable to 

silicification than were those of brachiopods, corals, 

and gastropods. Most gastropods so obtained are allied 

to Platyceras. Fragmentary straight Orthoceras-like 

shells of small size were the only cephalopods recog-
36 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

nized. No identification of the fragmentary lamellibranchs was attempted. 

Family PLATYCERATIDAE Hall 

Genus Platyceras Conrad 

Three kinds of Platyceras occur in the type Rabbit 

Hill bioclastic limestones; these range in configuration 

from nearly planospiral through openly planospiral to 

somewhat helicospiral and disjunct. None of the large, 

excessively spinose forms of Platyceras like those that 

characterize lower beds of the Nevada Formation (unit 

1) were found in the Rabbit Hill. 

Platyceras sp. a 

Plate 1, figures 20, 21 

Platyceras sp. a (USNM 159524) is nearly planospiral, smooth, comprises two whorls and has an ovoidal 

aperture and open umbilicus. 

Occurrence.-Rabbit Hill Limestone. Rabbit Hill, 

Copenhagen Canyon, locality M409. 

Platyceras sp. b 

Plate 1, figures 22, 23 

Platyceras sp. b (USNM 159525) is more typical of 

the genus, a small form with a single open whorl. The 

aperture is nearly round with generating curve increasing rapidly in diameter. Sinuosity of the growth line 

conforms to an irregular aperture margin with five 

minor embayments. 

Occurrence.-Rabbit Hill Limestone. Rabbit Hill, 

Copenhagen Canyon, locality M409. 

Platyceras (Orthonychia) sp. c 

Plate 1, figure 24 

Platyceras (Orthonychia) sp. c (USNM 159526) is 

a small disjunct species comprising two whorls with the 

character of the subgenus Orthonychia and having a 

very elongate, straight body whorl. Growth lines and 

aperture margin show two broad embayments. 

Occurrence.-Rabbit Hill Limestone. Rabbit Hill, 

Copenhagen Canyon, locality M409. 

TRILOBITES OF THE RABBIT HILL LIMESTONE 

Trilobites of the families Odontopleuridae and 

Phacopidae are the common fossils at some exposures 

of the Rabbit Hill Limestone. This is especially true of 

the platy limestones in the Simpson Park Range west 

of McClusky Peak and at Coal Canyon. In the type 

area at Rabbit Hill, Monitor Range, and at Dobbin 

Summit, trilobite remains are abundant in some beds, 

whereas in the richly fossiliferous bioclastic lenses 

where the brachiopods and corals are silicified, the trilobites are not replaced by silica and do not appear in the 

acid residues. Thin beds in which trilobite remains are 

the common fossils yielded a few weathered specimens. 

Some of these beds are a virtual "trilobite hash" from 

which, by repeated splitting of large amounts of rock, 

well-preserved but disarticulated fragmentary trilobites may be prepared (pl. 8, figs. 12, 13). Most of these 

are small spiny Odontopleuridae; it is unlikely that 

articulated or complete specimens can be obtained 

from these bioclastic beds. 

Material available is not sufficient to justify more 

than a cursory review of the Rabbit Hill trilobites, 

referring the few kinds collected to the nearest described species. Trilobite beds yielding better material 

will doubtless be found by careful search of the Simpson Park exposures, in particular those at Coal Canyon 

and near McClusky Peak (Walti Ranch), where fragmentary larger phacopids are abundant. It is probable 

that most of the Rabbit Hill trilobites are undescribed 

species, in view of the lack of study of far-western 

Devonian trilobites. 

Family ODONTOPLEURIDAE Burmeister 1843 

Spiny trilobites of this family predominate in some 

trilobite beds of the Rabbit Hill Limestone. Leonaspis 

is the abundant genus, long-forked structures indicate 

the presence of other genera such as Miraspis and 

Odontopleura. Trilobites of this family seem to be 

uncommon in the Devonian section of this province 

above the Rabbit Hill; none were found in the Lower 

Devonian beds of Oriskany age in Nevada Formation 

unit 1. Leonaspis occurs sporadically somewhat higher 

in Nevada unit 2 of the southern Sulphur Spring Range 

northwest of Romano Ranch, where it was found associated with Spirifer pinyonensis in very sandy limestones. 

Genus Leonaspis Richter and Richter, 1917 

Leonaspis cf. L. tuberculatus (Hall), 1859 

Plate 2, figures 15-17 

1859 Acidaspis tuberculatus Hall, p. 36~70; pl. 79, figs. 1-14. 

1956 Leonaspis tuberculatus (Hall, 1859). Whittington, p. 507-

509, pl. 57, figs.1-9. 

1963 Leonaspis sp. cf. L. tuberculatus (Hall). Merriam, p. 43. 

Collections from the Rabbit Hill Limestone in its 

type section include a number of isolated free cheeks, 

pygidia, and hypostomas of this form well enough preserved for identification. No cranidea were found. Free 

cheeks have been identified at most Rabbit Hill collecting localities. 

The mature free cheek is similar to those illustrated 

by Hall (1859)., having 12 or 13 lateral spines, a marginal row of rather coarse tubercles and sea ttered 

tubercles on the convex part of the cheek, these being 

more numerous internally. The lateral spines are less 

acute than on Hall's illustrations and more like those 

shown by Whittington (1956, pl. 57, fig. 7; pl. 58, figs. 

3, 4) for Leonaspis tuberculatus and L. williamsi. 

The pygidium has a general pattern quite similar 

to L. tuberculatus as illustrated by Whittington ( 1956, 

pl. 57, fig. 4), but the paired tubercles are smaller on 

the Rabbit Hill specimens and the median tubercle at 
FAMILY TRYPLASMATIDAE ETHERIDGE 37 

the axial tip of L. tuberculatus is weak or absent. The 

differences in the two pygidia suggest only subspecific 

differences. 

Genus Miraspis Richter and Richter, 1917 

(?)Miraspis sp. 

Plate 2, figure 14 

Elongate paired or forked occipital ring spines are 

associated with Leonaspis in trilobite beds of the Rabbit Hill Limestone. These spines probably came from 

an odontopleurid genus such as Miraspis or possibly 

Odontopleura, two genera believed to be limited to the 

Silurian. 

Family PHACOPIDAE Hawle and Corda, 1847 

Trilobites of this family are common in certain beds 

of the Rabbit Hill Limestone in its type section. In 

some platy limestones of the Simpson Park Range, 

phacopids are the most numerous fossils. Only one 

genus, Phacops, has been recognized. There is some 

specific diversity, as between those with a genal spine 

and those lacking this feature. Although some of the 

material is fairly well preserved, most of the specimens 

are fragmentary. In this region phacopids are numerous 

in the Lower and lower Middle Devonian through 

Nevada Formation unit 2, but material available is 

insufficient for detailed species comparison. 

Genus Phacops Emmrich, 1839 

Phacops sp. A, cf. P.logani Hall, 1861 

Plate 8, figures 16, 17 

This form is represented at Rabbit Hill by fragmentary small to medium-sized pygidia that are not conspicuously postulose and do not show a rim. The 

cephalon is unknown. The pygidia also resemble those 

of var. gaspensis and var. birdsongensis as figured by 

Delo (1940, pl.1, figs. 10-12, 13-15). 

(?)Phacops sp. B, cf. P. canadensis Stumm 

Plate 2, figures 11-13 

Large phacopids with well-defined pygidial rim occur 

at Coal Canyon, Simpson Park Range. They are represented in the collections by a nearly complete articulated specimen and by a partial crushed cephalon. 

The inflated glabella and short pygidium indicate 

that this form is probably related to the genus Phacops. 

There are, however, decided differences, among them a 

narrowness behind the swollen frontal glabellar lobe 

and the presence of genal spines. 

Among the described Phacopidae, Phacops canadensis Stumm( 1954, p. 213, pl. IV, figs. 7, 15, 18) possesses a short genal spine but differs in features behind 

the swollen frontal lobe. The thorax and pygidium of 

P. canadensis are unknown. 

Pygidia associated with the cephalon of this species 

are of medium to rather larger size and have a narrow 

rim not recognized in Phacops sp. A. 

Family DALMANITIDAE Vogdes, 1890 

The remains of larger trilobites from the Rabbit Hill 

Limestone include a large incomplete dalmanitid cephalon from the Coal Canyon section, Simpson Park 

Range. This individual was about 60 mm wide in the 

anterior part of the thorax. Although possibly a species 

of Dalmanites, preservation is too imperfect for a definite generic assignment. 

Order RUGOSA Edwards and Haime, 1850 

Family TRYPLASMATIDAE Etheridge, 1907 

Genus Tryplasma Lonsdale, 1845 

1845 Tryplasma Lonsdale, p. 613. 

1871 Pholidophylum Lindstrom, p. 925. 

1894 Spiniferina Penecke, p. 592. 

1907 Tryplasma Lonsdale. Etheridge, p. 76-77. 

1927 Tryplasma Lonsdale. Lang and Smith, p. 461. 

1927 Pholidophyllum Lindstrom. Wedekind, p. 25. 

1927 Stortophyllum Wedekind, p. 30. 

1936 Tryplasma Lonsdale. Hill, p. 204. 

1940 Tryplasma Lonsdale. Lang, Smith, and Thomas, p. 135. 

1940 Pholadophyllum Lang, Smith, and Thomas, p. 99. 

1940 Tryplasma Lonsdale. Hill, p. 405. 

1950 Tryplasma Lonsdale. Schouppe, p. 80-84. 

1952 Tryplasma Lonsdale. Stumm, p. 841-843. 

1956 Tryplasma Lonsdale. Hill, p. F312. 

1960 Tryplasma Lonsdale. Oliver, p. 96. 

1962 Tryplasma Lonsdale. Oliver, p. 13. 

Type species.-Try plasma aequabile Lonsdale, 1845; 

by subsequent designation (Etheridge, 1907, p. 42). 

Silurian near Bogoslovsk; east of northern Ural Mountains, Russia. 

Diagnosis.-Solitary and fasciculate rugose corals 

with acanthine septa that are vertical columns of trabecular spines. Corallites elongate or subcylindrical. 

Septal stereozone medium wide to narrow. No dissepiments. Tabulae mostly complete, commonly straight 

and widely· spaced. 

Remarks.-Tryplasma and related corals with acanthine septa have been the subject of special studies by 

Hill ( 1936), Schouppe ( 1950), Stumm ( 1952), and 

Oliver ( 1960). Species of this genus are characteristic 

of Silurian deposits in Europe, Australia, and North 

America; as noted by Duncan ( 1956, p. 226-227; figs. 

3a-b), they are among the common fossils in the Silurian of western North America. Oliver (1960, p. 96) 

notes that Try plasma extends its range into the Lower 

Devonian of Europe, Australia, and eastern North 

America. 

The genus Try plasma as understood includes species 

that differ considerably in growth habit, ranging from 

solitary ones with elongate corallum showing repeated 

rejuvenescence rims to bushy phaceloid colonies whose 

slender branches are cylindrical and relatively smooth. 

These corals are well represented in the Silurian 

limestone facies of the west-central and southwest 
38 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

parts of the Great Basin but are poorly known in the 

dolomite facies. 

Tryplasma sp. f 

Plate 11, figures 24, 25 

Isolated nondissepimented, cyclindrical corallites in 

the upper part of the Lone Mountain Dolomite of the 

Fish Creek Range are assigned to Tryplasma. The 

complete tabulae range from straight to undulant and 

sagging. Moderately long acanthine septal spines are 

well shown in both transverse and longitudinal thin 

sections. 

Occurrence.-Upper Silurian, upper part of the Lone 

Mountain Dolomite. Southern Fish Creek Range, 

locality M1087 in association with Entelophyllum 

engelmanni and the H owellella brachiopod fauna. 

Family KYPHOPHYLLIDAE Wedekind, 1927 

Reference form.-Kyphophyllum lindstromi Wedekind. Silurian, Gotland, Sweden. 

The Kyphophyllidae are mostly colonial phaceloid, 

less commonly cerioid genera among which the fasciculate species with long subcylindrical corallites predominate. Long lamellar septa are characteristic, with one 

to several dissepiment columns, the outer of which are 

lonsdaleioid in some species. Tabulae are fairly wide, 

arched in some genera; in a few species a flaring calice 

rim is present. 

Described genera provisionally included in this 

family are: 

Kyphophyllum Wedekind, 1927 

Strombodes Schweigger, 1819 

Petrozium Smith, 1930 

Entelophyllum Wedekind, 1927 

Entelophylloides Rukhin, 1938 

Neomphyma Soshkina, 1937 

At least two generic or subgeneric groups within the 

Kyphophyllidae of the Great Basin Silurian remain 

undescribed. All members of this family appear to be 

restricted to the Silurian System. 

Genus Entelophyllum Wedekind, 1927 

1927 Entelophyllum Wedekind, p. 22-24, pls. 2, figs. 11-12, 

pl. 7, figs. 7-10, pl. 29, figs. 18-51. 

1927 Xylodes Lang and Smith, p. 461-462, figs. 13-14. 

1929 Xylodes Lang and Smith. Smith and Tremberth, p. 362-

367, pl. 7, figs. 1-6, pl. 8, figs. 2-4. 

1933 Xylodes rugosus Smith, p. 516, figs. 6-7. 

1940 Entelophyllum Wedekind. Lang, Smith, and Thomas, p. 

57-58. 

1940 Entelophyllum Wedekind. Hill, p. 411. 

1940 Xylodes articulatus (Wahlenberg). Prantl, p. 10-13, pl. 

1, figs. 1-3, pl. 2, figs. 1, 3, 4. 

1956 Entelophyllum. Duncan, pl. 23, figs. 5c-d. 

1956 Entelophyllum Wedekind. Hill, p. F275, fig. 187, 2a-c. 

1962 Entelophyllum Wedekind. Oliver, p. 15, pl. 6, figs. 11-12. 

1962 Entelophyllum Wedekind. Stumm, p. 2-3, pl. 1, figs. 6-8, 

pl. 2, figs. 9-11. 

1964 Entelophyllum Wedekind. Stumm, p. 32, pl. 22, figs. 9-21. 

Type species.-Madreporites articulatus Wahlenberg=Entelophyllum articulatum (Wahlenberg); by 

subsequent designation, Lang, Smith, and Thomas 

(1940, p. 57, 140). Silurian, Gotland, Sweden. According to Smith and Tremberth ( 1929, p. 366), this species 

occurs in strata of Wenlock and Ludlow ages on the 

Island of Gotland and is recorded from the Wenlock 

Limestone in England. 

Diagnosis.-Phaceloid, possibly in part solitary 

rugose corals with elongate subcylindrical corallites. 

Major septa thin, slightly thickened near outer wall 

only; longer septa approach the axis. Tabularium wide, 

typically with close-spaced flat tabulae or tabellae and 

narrow peripheral sag bordering dissepimentarium. 

Dissepimentarium having few to many columns of small 

steeply inclined globose dissepiments. Outer wall thin, 

lacking a stereozone. No fossulae or other indication of 

bilateral symmetry in mature stages. Septa slightly to 

moderately wavy; well-developed elbow carinae not 

present in typical form. Attachment wall outgrowths 

characterize some species. Five or six reproductive offsets, marginal to calice. 

Remarks.-Not all Entelophyllum species have the 

well-defined peripheral depressed zone of the tabularium shown by the type species. Entelophyllum 

pseudodianthus (Weissermel) of the English Wenlock 

has zigzag thickened and carinate septa and less elongate cylindrical corallites (Smith and Tremberth, 1929, 

p. 361-362; Lang and Smith, 1927, p. 475, fig. 15); possibly subgenerically or even generically distinct from 

Entelophyllum sensu stricto. 

Disphyllum of the Middle Devonian resembles 

Entelophyllum externally, but differs by having generally slender corallites that lack the thick attachment 

outgrowths of Entelophyllum. Disphyllum also lacks 

the peripheral depressed tabular zone of typical Entelophyllum, has more even septa without carinae, and 

commonly has a somewhat wider tabularium. Transverse sections of Disphyllum show a more uniform and 

even concentric distribution of axially concave dissepiment traces. Some species of Entelophyllum have a 

cycle of reproductive offsets at the calice margin, a 

characteristic not found in Disphyllum. 

Entelophyllum engelmanni n. sp. 

Plate 10, figures 5-11 

Type material.-Holotype, USNM 159413; paratypes, USNM 159414-159418. 

Diagnosis.-Phaceloid Entelophyllum forming large 

laterally extensive bushy colonies of nearly straight 

cylindrical corallites joined by lateral outgrowths. 
FAMILY KYPHOPHYLLIDAE WEDEKIND 39 

Tabularium wide, tabulae mostly complete, subparallel, 

usually lacking the peripheral sag of typical Entelophyllum. Tabulae with axial-periaxial sag or slightly 

arched distally. Tabellae uncommon. Major septa withdrawn from axis, slightly wavy and without carinae; 

minor septa short, usually less than one-half the length 

of major septa. Septa thin toward axis, but with wedge 

thickening peripherally. No stereozone. 

External features.-Very elongate cylindrical mature 

corallites, large for this genus, with well-defined septal 

grooves crossed by annular incremental striations. 

Coarse annular folds or rugae few. Some corallites have 

thick irregular lateral attachment outgrowths distributed vertically along one side. 

Transverse sections.-Major septa about 28, thinned 

axially and slightly withdrawn from the axis. Minor 

septa less than one-half the length of major septa. All 

septa thicken rather abruptly in wedge fashion toward 

outer wall, which is very thin. Septa slightly wavy, lack 

carinae. Dissepiments not numerous, somewhat irregular as chevrons, forks, and simple traces that are either 

almost straight or slightly concave axially. 

Longitudinal sections.-Tabularium wide, about 

two-thirds of corallite diameter. Tabulae mostly complete, varying from straight or slightly arched axially 

and periaxially with or without peripheral depression 

to those with axial-periaxial sag and no peripheral 

depression. A few broad, flat tabellae peripherally. Dissepiments globose in one to three columns, steeply 

inclined, and of small, medium, and large size. 

Comparison with related forms.-Entelophyllum 

engelmanni differs from E. eurekaensis in the unevenness of its tabulae, which usually lack the peripheral 

depression. The extensively developed lateral connecting excrescences of this species were not observed in 

E. eurekaensis. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; upper Lone Mountain-Laketown 

biofacies. Southern Mahogany Hills, locality M1112. 

Northern Fish Creek Range, locality M1087. A similar 

Entelophyllum occurs in Silurian dolomite of the Ruby 

Mountains. 

Entelophyllum eJ;tqelmanni subsp. b 

Plate 10, figures 12, 13; plate 11, figures 26, 27 

Entelophyllum engelmanni with subcylindrical corallites attaining large size and having diameters exceeding 1 % inches or about twice normal for the species. 

The large corallites have some 38 major septa, steeply 

inclined dissepiments, no septal stereozone, and in 

some instances unusually thick and prominent external 

attachment processes. External rugae and protuberances more prominent than in typical form. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite. Southern Fish Creek Range, 

locality M1087. 

Entelophyllum eurekaensis n. sp. 

Plate 10, figures 1-4 

Type material.-Holotype, USNM 159412; paratype, USNM 159419. . 

Diagnosis.-Subcylindrical to ceratoid Entelophyllum with wide tabularium and closely spaced, straight, 

nearly continuous tabulae and flat peripheral tabellae. 

Peripheral zone of tabularium proximally depressed as 

in typical Entelophyllum. Septa slightly thickened, 

longer major septa approach axis. In transverse sections, the small to medium sized dissepiments show as 

axially concave and chevron traces. 

External features.-This species, known only from 

isolated pieces, is assumed to have been bushy and 

phaceloid like E. engelmanni of the same beds. However, available specimens of eurekaensis are more 

nearly ceratoid than cylindrical in shape. 

Transverse sections.-Major septa about 30; most 

are withdrawn, but a few approach the axis. Minor 

septa range from short wedge stumps to about one-half 

the length of major septa. Septa somewhat thicker than 

in most Entelophyllum species and show only a little 

waviness. No carinae recognized. Dissepiments inClude 

herringbone and chevron traces as well as concentric 

and axially concave. Septa thicken markedly in wedge 

fashion toward outer wall, but there is no continuous 

septal stereozone. Epitheca rather thin. 

Longitudinal sections.-Tabularium width about 

two-thirds corallite diameter. Most tabulae nearly 

complete, axially-periaxially very flat, peripherally 

depressed as in typical Entelophyllum. Flat peripheral 

tabellae present. Dissepiments in as many as five 

columns, of which the outer may have nearly horizontal 

basal planes; larger dissepiments elongate. 

Comparison with related forms.-This species has 

much flatter, more even tabulae than engelmanni; 

tabulae are more closely spaced and have a well-defined 

peripheral sag. Dissepiments of eurekaensis are on the 

whole less steeply inclined, occur in more numerous 

columns, and are less globose. The bushy and cylindrical growth habit of engelmanni is not known in this 

species. No individuals of eurekaensis with prominent 

external attachment processes are known. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; upper Lone Mountain-Laketown 

biofacies. Southern Fish Creek Range, locality M1113; 

associated with the Howellella-Camarotoechia-Atrypa 

brachiopod assemblage of this facies. 
40 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

Phylum BRACHIOPODA 

Class ARTICULATA Huxley. 1869 

Order ORTHIDA Schuchert and Cooper, 1932 

Family ENTELETIDAE Waagen. 1884 

Genus Salopina Boucot, 1960 

Salopina sp. f 

Plate 11, figures 16-23 

Small Dalmanellacea possessing an elongate ventral 

palintrope and a variously extended dorsal valve 

median septum are among common brachiopods in 

Silurian and Early Devonian rocks of the Great Basin. 

Need for taxonomic revision within this large and complex orthoid group has recently been indicated by 

detailed studies of dalmanellid morphology and systematics (Williams and Wright, 1963). Recently proposed generic names possibly applicable to certain of 

these taxa in the Great Basin Province are Salopina 

Boucot (1960), Protocortezorthis Johnson and Talent 

(1967b), and Muriferella Johnson and Talent (1967a). 

Salopina sp. f is known mainly from silicified shells 

with valves articulated and showing only external 

features. Among newly described dalmanellid species, 

the closest similarities appear to be with the Late Silurian Salopina? sp. of Boucot (1960, pl. 1, figs. 1-5), 

from Devon Island, Northwest Territories, Canada, 

and Salopina cf. S. crassiformis (Kozlowski) of Johnson and Talent (1967a) from the Roberts Mountains. 

Better preserved interiors are required to fully establish these relations. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; Southern Fish Creek Range, 

locality M1113. 

Order RHYNCHONELLIDA Kuhn, 1949 

Family CAMAROTOECHIIDAE Schuchert and Levene, 1929 

Genus Camarotoechia Hall and Clarke, 1893 

Brachiopods of the Camarotoechia group are among 

the abundant and diverse fossils of the upper part of 

the Lone Mountain Dolomite. At least three forms are 

recognized, Camarotoechia pahranagatensis Waite, a 

related form designated as C. sp. b, and a finely ribbed 

species resembling C. bieniaszi Kozlowski of the Polish 

Borszczow beds to- which the designation C. sp. f is 

applied here. Camarotoechia-like brachiopods similar 

to sp. b and pahranagatensis have been described by 

Johnson and Reso (1964) from correlative Late Silurian beds of the Pahranagat Range. 

Camarot!)echia pahranagatensis Waite 

Plate 11, figures 7-9 

1956 Camarotoechia pahranagatensis Waite, pl. 3, figures 1-5. 

The shell assigned to this species agrees well in general proportions, strength, and number of radial ribs, 

and emargination of the anterior commissure with 

Waite's figures of the holotype. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; Southern Fish Creek Range, 

locality M1113. 

Camarotoechia sp. b 

Plate 11, figures 10-13 

This form is characterized by a pair or, less commonly, three prominent radial ribs in the fold and 

sulcus; these ribs are more pronounced than in C. pahranagatensis. Ferganella? lincolnensis Johnson (Johnson and Reso, 1964, pl. 19, figs. 5-12) differs by having 

three or more prominent ribs in fold and sulcus. 

Occurrence.-Same as C. pahranagatensis at locality 

M1113. 

Camarotoechia sp. f 

Plate 11, figures 5, 6 

This finely ribbed form with weakly developed fold 

and sulcus is with some hesitation referred to as Camarotoechia; it is rather certainly unrelated to the other 

brachiopods of the upper Lone Mountain fauna placed 

in that genus, sharing some of its external features with 

·Trematospira and Atrypa. Externally similar brachiopods have been described by Kozlowski ( 1929, p. 158, 

pl. V, figs. 12-14) as Camarotoechia bieniaszi from the 

Borszczow beds of Poland. 

Occurrence.-Same as C. pahranagatensis and sp. b 

at locality M1113. 

Order SPIRIFERIDA Waagen, 1883 

Family MERISTELLIDAE Waagen, 1883 

Genus Hyattidina Schuchert, 1913 

?Hyattidina sp. f 

Plate 12, figures 30-33 

Small, smooth biconvex Hyattidina-like and Nucleospira-:-like brachiopods, most less than 8 mm wide, are 

very abundant in the upper Lone Mountain faunas. 

Most of these articulated shells are probably immature 

growth stages of such Spiriferacea as Hyattidina and 

Hindella. Brachial valves from Mahogany Hills locality 

M1112 have hinge-plate features suggestive of Hyattidina congesta (Conrad); larger shells from locality 

M1087 in the Fish Creek Range reveal spiralia with 

lateral apices and pedicle valve muscle fields similar to 

?Hyattidina hesperalis (Waite) of the Laketown Dolomite. Larger and more robust shells in these Lone 

Mountain faunas are assigned to the genus Hindella 

and are described separately. 

?Hyattidina hesperalis (Waite) was initially placed 

in Protathyris Kozlowski (Waite, 1956) and later 

referred to Hyattidina Schuchert by Johnson and Reso 

(1964). ?Hyattidina sp. f from the Lone Mountain 

Dolomite has no well-defined fold and sulcus, differing 

in this respect from mature Hyattidina congesta and 

the Laketown hesperalis. The largest shells of ?H. sp. f 

show a slight emargination of the commissure suggesting incipient fold-sulcus development. 

Externally very similar shells are described and 

illustrated by Norford (1962) from the Silurian Sand-
FAMILY DELTHYRIDIDAE WAAGEN 41 

pile Dolomite of Northern British Columbia. The 

Sandpile species is assigned by N orford to Glassia 

variabilis Whiteaves. ?Hyattidina sp. f has a spiralium 

like that of the Meristellidae, with lateral apices of 

cones; Glassia Davidson by definition has the spiralium 

apices situated at the middle of the brachial cavity 

(Schuchert, 1913, p. 409). 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; upper Laketown-Lone Mountain 

biofacies. Southern Mahogany Hills, locality M1112, in 

association with Howellella pauciplicata and Entelophyllum engelmanni. Southern Fish Creek Range, 

locality M1087, in association with Howellella smithi 

and Entelophyllum engelmanni. 

Genus Hindella Davidson. 1882 

Hindella sp. a 

Plate 12, figures 34-37 

Hindella with valves about equally convex, length 

but slightly greater than width. Anterior commissure 

conspicuously bowed; fold of dorsal valve very weak 

anteriorly, ventral valve with incipient sulcus. Shell 

smooth except for incremental lines that are numerous 

near the commissure. This species is relatively wider 

than both H. prinstana and H. umbonata, and depth of 

the dorsal valve is more nearly that of the ventral valve. 

The interior of H. sp. a is unknown, leaving the 

generic assignment uncertain. Some of the small and 

possibly immature shells found in association and here 

interpreted as belonging to ?Hyattidina sp. f may be 

the young of H indella sp. a. 

Atrypella carinata Johnson (Johnson and Reso, 

1964) has similar features in the beak vicinity, a more 

elongate shell with better defined fold and sulcus. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite, locality M1087, Southern Fish 

Creek Range. 

Family ATRYPIDAE Gill. 1871 

Genus Atrypa Dalman. 1828 

Atrypa sp. f 

Plate 11, figures 1-4 

Small to medium-sized Atrypa with coarse radial 

costae, moderate even upward bowing of the anterior 

commissure, and rather weakly defined growth lamellae 

which produce small costal nodes. Costae may bifurcate 

anteriorly. Convexity of brachial valve does not greatly 

exceed that of pedicle valve. 

Among described American Silurian atrypas, this 

species appears closest to A. tennesseensis Amsden of 

the Brownsport and Henryhouse, but differs by having 

less prominent growth lamellae. Atrypa sp. of Johnson 

and Reso (1964) from the Silurian of the Great Basin 

has similar ornamentation and possibly represents the 

same species as Atrypa sp. f. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite, Southern Fish Creek Range, 

locality M1113. 

Family DELTHYRIDIDAE Waagen. 1883 

Genus Howellella Kozlowski. 1946 

Small and medium-sized spiriferoids of this genus are 

the most distinctive fossils of the Late Silurian dolomites of the Great Basin. These shells have a conspicuous fold and sulcus and strong dental lamellae, and 

lack a ventral valve median septum. The coarse radial 

costae which characterize this genus may become 

nearly obsolete laterally in some species. Howellella 

ranges from Late Silurian into the Helderbergian Rabbit Hill Limestone, where it is represented by a larger 

species allied to H. cycloptera. 

Howellella pauciplicata Waite 

Plate 12, figures 20-24 

1956 Howellella pauciplicata Waite, p. 17, pl. 3, figs. 6-10. 

1964 Howellella pauciplicata Waite. Johnson and Reso, pl. 20, 

figs. 8, 10-12. 

1964(?)Macropleura? sp. Johnson and Reso, p. 82, pl. 20, figs. 

1-7. 

This species is characterized by obsolete or nearly 

obsolete ribbing on the flanks of the valves. A large 

suite of individuals from Laketown Dolomite unit 48 

of Hose in the Confusion Range, Utah (R. K. Hose, 

written commun., 1954) show a range in dorsal valves 

from those that are nearly smooth on either side of the 

fold to those having the fold flanked by a single coarse 

but subdued rib. In some individuals, the fold itself is 

rather weak. 

The upper Lone Mountain specimens have at least 

one subdued rib lateral to the fold, apd the shell flanks 

are somewhat less smooth than in Waite's holotype and 

other Confusion Range specimens. There is no indication of continuous variation from the pauciplicata 

lineage into coarsely plica ted H owellella smithi, also of 

the upper Lone Mountain. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; southern Mahogany Hills, locality 

M1112, associated withEntelophyllum engelmanni and 

?Hyattidina sp. f. 

Howellella smithi Waite 

Plate 12, figures 1-19 

1956 Howellella smithi Waite, p. 17, pl. 3, figs. 16-19. 

This coarsely ribbed species, large for the genus, is 

abundantly represented in two fossil localities of the 

upper Lone Mountain Dolomite of the Fish Creek 

Range. The hinge line is narrow and the shell width 

considerably greater than the shell length. Fold and 

sulcus are prominent, flattened medially toward the 

commissure. Two coarse costae occupy the flanks of 

both valves, lateral to which are one or more subdued 
42 RABBIT HILL LIMESTONE AND LONE MOUNTAIN DOLOMITE OF CENTRAL NEVADA 

ribs. Dental lamellae are well developed, but only moderately long; there is no suggestion of a pedicle valve 

median septum. In the brachial valve, the dental 

rockets and other hinge-plate features are similar to 

those of Howellella crispa (Risinger) as illustrated by 

Hall and Clarke (1894, pt. II, pl. 36, fig. 4). Some 

individuals of this species, however, reveal a very weak 

incipient median septum in the brachial valve not 

known in crispa. 

A suite of specimens in various growth stages gives 

no indication of intergradation of Howellella smithi 

with pauciplicata of about the same stratigraphic 

horizon. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; Southern Fish Creek Range, 

localities M1087 and M1113. Waite's holotype is 

reported from Laketown beds "below the Sevy dolomite" in the Pahranagat Range. Howellella smith was 

not found in unit 48 of the Confusion Range, Utah, 

Laketown Dolomite which yielded abundant H. pauciplicata. 

LOCALITY REGISTER1 

Fossils of the Rabbit Hill Limestone and correlative strata 

Inyo Mountains, Calif. 

Locality M1093.-Independence quadrangle, California. 

NE% sec. 8, T. 13 S., R. 36 E.; at mouth of Mazourka Canyon east of Kearsarge. At measured stratigraphic section 

VG-1 (Ross, 1966, pl. 1) 450 feet below top of Vaughn 

Gulch Limestone. 

Locality M1401.-Independence quadrangle, California. Mazourka Canyon area, east side AI Rose Canyon, %o mile 

N. 78° E. of SE cor. sec. 36, T. 11 S., R. 35 E., on measured 

section SC-5 (Ross, 1966, pl. 1) 40 feet below top of Sunday Canyon Formation. 

Monitor Range, Nev. (middle part) 

Locality M1311.-East side of Monitor Range near Dobbin 

Summit, northern Nye County. East side of road east of 

East Dobbin Summit Spring, altitude 8,500 ft (Army Map 

Service, Tonopah sheet, NJ 11-5). Lower part of Rabbit 

Hill Limestone. Same locality as M1067. 

Locality M1068.-Same locality as M1311; in middle part 

of Rabbit Hill Limestone. 

Locality M1309.-Same locality as M1311; in upper part of 

Rabbit Hill Limestone. Same locality as Ml069. 

Monitor Range, Nev. (northern part) 

Locality M409.-Horse Heaven Mountain quadrangle. 

Southeast side of Rabbit Hill near junction of Whiterock 

Canyon with Copenhagen Canyon; altitude 7,080 ft. Type 

section of Rabbit Hill Limestone. Other locality numbers 

same site: M48, Ml87, M1326. 

Locality M49.-Horse Heaven Mountain quadrangle; %o 

mile north-northwest of Rabbit Hill; altitude 7,300 ft. Rabbit Hill Limestone with same fauna as type section. 

Toquima Range, Nev. (northern part) 

Locality M1150.-Wildcat Peak quadrangle. Petes Canyon 

area, northernmost Toquima Range. SW% sec. 16, T. 16 

1Locality numbers with M prefix (for example M1093) used in this report 

refer to U.S. Geological Survey fossil localities listed in the Paleozoic locality ledgers of the Menlo Park, Calif. center. 

N., R. 46 E.; on top of spur 1,600 feet south of summit 

7,188, and 2,800 feet east of Petes Canyon road. Small isolated exposure of Rabbit Hill Lime~tone in contact with 

graptolitic shale. Same locality as M1147. 

Simpson Park Range, Nev. (middle part) 

Locality M1074.-Walti Hot Springs quadrangle. Foothills 

half a mile southeast of Walti Ranch and west of 

McClusky Peak, altitude 6,000 ft. Rabbit Hill Limestone. 

Simpson Park Range, Nev. (northern part) 

Locality M1032.-Horse Creek Valley quadrangle. Coal Canyon area; east side of Coal Canyon in NW% sec. 21, T. 25 

N., R. 49 E., altitude 6,600 ft. Rabbit Hill Limestone. 

Locality M1075.-Horse Creek Valley quadrangle. Coal 

Canyon area, near canyon mouth on east side. Limestone 

beds near top of ridge 6909 on west side. Upper part of 

Rabbit Hill Limestone. 

Locality M 1076.-Same as M1075, mostly float material 

below ridge top 6909 down slope to west. Rabbit Hill Limestone. 

Locality M1310.-Horse Creek Valley quadrangle. Coal Canyon area; SE:lf4 sec. 17, T. 25 N., R. 49 E. West side of 

ridge 6909 near top. Upper 200 feet of the Rabbit Hill 

Limestone, in platy limestone with abundant trilobites. 

Cortez Mountains, Nev. 

Locality M1083.-Cortez quadrangle. Cortez Mountains, 

southeast side of Mount Tenabo, near head of Horse 

Canyon, 1,000 feet north, 700 feet west of SE cor. sec. 4, 

T. 26 N., R. 48 E.; altitude 7,900 ft. Rabbit Hill Limestone 

fauna. 

Tuscarora Mountains, Nev. 

Locality M1400.-East side of Tuscarora Mountains near 

south end (Army Map Service, Winnemucca sheet NK 

11-11). Nine miles northwest of Carlin, near top of bluff 

on east side of Maggie Creek; T. 34 N., R. 51 E. Rabbit 

Hill Limestone overlying Roberts Mountains Limestone. 

Sulphur Spring Range, Nev. (southern part) 

Locality M186.-Garden Valley quadrangle. South Mulligan 

Gulch area; east side South Mulligan Gulch near mouth; 

2,000 feet southwest of summit 6927, altitude 6,560 ft. 

Beacon Peak Dolomite Member with Rabbit Hill fauna 

below beds with Oriskany-age fossils, and above probable 

Lone Mountain Dolomite. 

Locality M 197.-Garden Valley quadrangle. Bailey Pass 

area; 3f4 mile south of Bailey Pass on main ridge crest 

1 000 feet southeast of summit 7107. Beds with Rabbit Hill 

f~ssils below Oriskany -age faunas of the Nevada Formation. 

Locality M1081.-Garden Valley quadrangle. South Mulligan Gulch area; east side of range 1 mile east of Mulligan 

Gap, 2,600 feet northeast of summit 7446; altitude 6,800 ft. 

Beacon Peak Dolomite Member with Rabbit Hill fauna. 

Locality M1082.-Garden Valley quadrangle. South Mulligan Gulch area; due west of BM 5867, 1o/to miles on top of 

spur, altitude 6,440 ft; 1,400 feet east-northeast of summit 

6474. Beacon Peak Dolomite Member with Rabbit Hill 

fossils. 

Locality M1312.-Garden Valley quadrangle. Near M186. 

Beacon Peak Dolomite Member with Rabbit Hill fossils. 

Locality M1319.-Garden Valley quadrangle. Prince of 

Wales mine area; southeast of Prince of Wales mine and 

northwest of summit 7530; altitude 7,200 ft. Beacon Hill 

Dolomite Member with Rabbit Hill fossils, below beds 

with Oriskany-age fauna. 

Fossils of the Lone Mountain Dolomite 

Lone Mountain, Eureka County, Nev. 
SELECTED BIBLIOGRAPHY 43 

Locality M 1122.-Whistler Mountain quadrangle. Southeast 

side Lone Mountain, east side Charcoal Gulch, %o mile 

due south of summit 7360; altitude 6,840 ft on top of spur. 

Dark-gray carbonaceous Lone Mountain Dolomite with 

fragmentary rugose corals. 

Locality M1122a.-Same area as M1122, 3,200 ft southsoutheast of summit 7360; altitude 6,600 ft. Dark-gray 

Lone Mountain Dolomite with fragmentary corals. 

Mahogany Hills, Nev. (southern part) 

Locality M1112.-Bellevue Peak quadrangle. About 1If4 

miles due north of top of Wood Cone Peak and half a mile 

north-northwest of BM 7201; in foothill exposures of Lone 

Mountain Dolomite. Altitude 7,300 ft. Dark-gray carbonaceous dolomite with silicified corals. 

Fish Creek Range, Nev. (southern part) 

Locality M1087.-Bellevue Peak quadrangle. North end of 

Fenstermaker Mountain on west side at south boundary of 

quadrangle; about 2,000 feet due south of summit 7232, 

altitude 7,000 ft. Dark-gray Lone Mountain Dolomite with 

silicified fossils. 

Locality M1113.-Bellevue Peak quadrangle. Same area as 

M1087; %0 mile south-southeast of summit 7232. Altitude 

7,080 feet. Dark-gray Lone Mountain Dolomite with silicified fossils. 

Sulphur Spring Range, Nev. (southern part) 

Locality M1121.-Garden Valley quadrangle. East margin 

of range in East Ridge, 2 miles south-southwest of Romano 

Ranch, and %0 mileS. 60° W. of BM 5825; altitude 6,440 

ft near top of ridge, Lower part of Lone Mountain Dolomite with silicified corals. 

Locality M1148.-Garden Valley quadrangle. East margin of 

range, east slope of East Ridge in northeast corner sec. 35, 

T. 23 N., R. 52 E.; half a mile north-northwest of BM 

5867. Altitude 6,100 ft on top east-west spur. Lone Mountain Dolomite with corals. 

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INDEX 

[Italic page numbers indicate both major references and descriptions] 

A Page 

abditum, Endophyllum____________________________________ 23 

Abstract ------------------------------------------------------------ 1 

Acanthoscapha SP-------------------------------------------- 11 

Acidaspis tuberculatus ---------------------------------- 36 

Acknowledgements ---------------------------------------- 2 

A codina -------------------------------------------------------------- 11 

Acrospirifer ------------------------------------ 7, 11, 12, 33, 84 

kleinhampli -------------------- 7, 8, 10, 12, 34,· pl. 7 

kobehana -------------------------------------------- 28, 29, 34 

murchisoni ---·--------------··-·----------····--------···· 34 

sp. D ---------------------------------------------------------- pl. 7 

sp ----------------------·-·------------------------------- 9, 10; pl. 7 

(Acrospirifer), Hysterolites ----·------------------- 33, 34 

acuaria, N owakia -------------------------------------------- 35 

acuminatum, Laccophyllum ------------------------ 22 

acuticuspidata, Leptaena ------------------------------ 28 

acutiplicata, Anoplotheca ---------------------------- 31 

Leptocoelia ---------------------------------------------- 31 

Aechmina sp ---------------------------------------------------- 11 

aequabile, Tryplasma ------------------------------------ 37 

affinis, Billingsastraea ------------------------------------ 25 

Alleynia ------------------------------------------------------------ 21, 22 

(Nicholsonia) ------------------------------------------ 21, 22 

alpenesis, Favosites ------------------------·---------·----- 19 

altera, Plethorhyncha ----------------··-·---------------- 30 

Alveolites ------··-----------·------------------····----····-------· 19 

sp --------------------------------------------------------··------ 15, 16 

A mbocoelia ------------------··--------------····---------------- 30 

umbonata -------------------------------------------------· 30 

sp. a ------------------------------------·-·----- 7, 10, 30; pl. 7 

Ambocoeliidae ------------------------------···----------------- 90 

Anastrophia ·-------------------------------··------------ 10, 11, 29 

grossa ----------------------------------------------------·--- 29 

verneuili ·--------------------------------· 10, 11, 29; pl. 5 

andersoni, Plethorhyncha ··-------- 7, 8, 29, 30; pl. 6 

A noplotheca acutiplicata ----····-------------------··· 31 

sp ·--------------·-··-----···--····-·····-----------······-------- 31 antelopensis, Levenea subcarinata .......... 7, 8, 10, 

11, 26; pl. 4 

Antelope-Roberts Mountains facies belt.... 5, 11 

arcuata, Meristella ------------···--------------------------- 30 

Areal distribution ···-·-----···-····--·-----·····--··----··· 5 

arenosus, Costispirifer ------·-····-··-···· 11, 12, 34, 35 

dobbinensis, Costispiri!er ············--···· 7, 8, 12, 

35; pl. 7 

planicostatus, Costispirifer --····-··----···-· 34 

Spirifer ·------·-··---------·------··---····-··-------·-···· 34 

Articulata ·--------------------·----··-···-----··---····-------··· 25, 40 

articulatum, Entelophyllum ·---·-··-··-··-------··· 38 

articulatus, Madreporites ·-----·--····---·······---···· 38 

Xylodes ··-------···----------------····------······---------- 38 

atoka, Meristella ·--------··-------------------------------···· 30 

Atrypa -------·-··----------------------------·-·-··-------------···· 40, 41 

tennesseensis -----------------··--·------···-··---···--·· 41 

sp. f ------------------·-····---------···-·-· 15, 16, 41; pl. 11 

sp ------------------···------------------------·····--····-------- 41 

Atrypella carinata -------------------··-----··--·-··--·-··-- 16, 41 

Atrypidae --------····-------------------------------------·--·-·--· 41 

A ustralocoelia ···---------------------··--···-----····-··---···· 31 

Australophyllum ··-----------····---··-··-·--------··· 11, 29,24 

cyathophylloides --------·····--·--·-·····------------- 24 

landerensis ----···----------------·-· 8, 11, 24, 25; pl. 9 

stevensi ------------·-··-------------···-··· 11, 24, 25, pl. 9 

sp r -------------------------------------------- 11, 24, 25; pl. 9 

B Page 

Bailey Pass ------------------------------------·---------····---- 10 

Bairdia leguminoides ·-·---------------·········----······· 11 

sp ···-------------------·-····------------····-···-----·-···-·---- 11 

Barrandeophyllum ----···---------····-···----··---·-------· 22 

perplexum ·-------------------------------···------------- 22 

barrandi, Plethorhyncha ···--------------------------- 30 

becki tennesseensis, Leptostrophia -------- 7, 8, 27; 

pls. 3, 8 

Belodella resimus -----····-··------·-----····----··--···-···· 11 

Berdan, Jean M., quoted-------------·----------·----··· 11 

bieniaszi, Camarotoechia ·----····----··-····-··-···--· 40 

Billingsastraea ·-----·--··-----···-·--------·--····--··----···· 25 

affinis -----···------···--·-···---·---····--··-·---·---·---·--- 25 

nevadensis -------------·-------··--····--·-----·······-··· 25 

sp. m ---------··--··--·----------------·· 9, 10, 11, 25,· pl. 9 

birdsongensis, Phacops ·---------------·-·---------··-- 37 

Birdsong Shale, Tennessee-------··----·--···----··--- 27 

Bogoslovsk, Russia -----··-··--------·-·---···-··-·-···---- 37 

Bois d'Arc Limestone, Oklahoma .......... 27, 28, 33 

Borszczow beds, Poland·--····-····-----·-------·-··--··----· 40 

bowerbanki, Endophyllum ······--····-·------··--···· 23 

Brachiopoda --------···--····--··············-················-- !85, 40 

brachiopods --···---···--·----·-······ 2, 7, 10, 11, 17, 18, 35 

Branik Limestone, Bohemia ----··--·----·---····--· 22 

bransoni, Strophonella ········----····-·-----··········· 28 

Brownsport Formation ··-----------··-··---·------···· 21, 41 

c 

Camarotoechia ·-·------------·--··--------·····-··------------ 40 

bieniaszi ---------------------------------·------··--········ 40 

pahranagatensis ···--···--------·· 15, 16, 40; pl. 11 

sp. b ·····--·------·-·---·-······-----·----·· 15, 16, 40; pl. 11 

sp. f --------····--··-·--------·--··-·---···· 15, 16, 40; pl. 11 

sp -------·-···---------··-------·---··-------··--··· 14, 16; pl. 11 

Camarotoechiidae ·---·········----·--···----··---·-········ 40 

canadensis, Phacops ·-----------··-··-··········-· 9, 87, pl. 2 

carinata, Atrypella ·---········-··-·-··-···--·-----········ 41 

catenulatus, H alysites ···-····----···-·····-·----------- 13 

Chewelah area, Stevens County, Wash....... 12 

Chronophyllum ··----------···--···-····--·----·-·-·-------···· 12 

Cladopora --------·------------------------------------------------· 19 

Coal Canyon ------------------------ 4, 8, 11, 12, 35, 36, 37 

fault zone ----···--··-----··----·-------·-··---···-····--·-- 8 

Coblenz and Eifel districts, Germany........ 20 

Coelospira -----------···------····----·········---·-·-····-··--·-· 9 

sp -----------------------------------------·--------·------·------ 8, 10 

Coenites ----------------------------------------------------·------- 19 

Conclusions -----·-------··--··---·--··-···----··-------····-····· 17 

congesta, Hyattidina ··------·----···-·------··--····-···-· 40 

conodonts --------------·-·-------····--------·-··--·· 2, 6, 7, 11, 17 

Conularia ---------··-----·----···----··---·-----·---··· 8, 10, 19, 95 

huntiana ··-·----··---------------····- 8, 10, 19, 35; pl. 2 

lata -------------··-----·---··--·-·----·-··-·······-·-·····--,-· 8, 10 

sp ·-----····--------------·---------·----··--··-----··--·-·· 95; pl. 2 

Conulariidae ---···--------------··----··-·-··---···-----------·· 95 

conularida ·-----···--··---------·-······----------···-···--------· 19, 95 

Conulata ----------·-----·--·-···----···-----···········-····-···---- 95 

convexoris, Parahealdia -··-----····-·······-··-·-······ 11 

Cooper, G. A., quoted ... ·-----··-··--------·--·--···-··-- 34 

cooperi, Trematospira --···------------··-···--····----· 32 

Copenhagen Canyon, Horse Heaven 

Mountain quadrangle ····-·····-- 6 

coral-brachiopod assemblages ·········---·········- 15 

Page 

corals -···----------------····--·-·---·--···---------···--·· 2, 13, 15, 19 

Coral Zones --·---·-----·---·-··-···················---··········· 18 

Cordilleran geosyncline ···---··---··---····-·····-····· 4, 5, 6 

Cortez Mountains ----···-----·--------···-···--·-···· 2, 9, 21,42 

Costellirostra -----·-----------------------··-··-·----····-·····-- 30 

Costispiri!er ---·--------··--····-------·---·------··-· 7, 11, 84, 35 

arenosus ----------··---·---··-··--··-·--·---·· 11, 12, 34, 35 

dobbinensis -··--------- 7, 8, 10, 12, 95; pl. 7 

planicostatus ···-····-------·········--·········· 34 

planicostatus --------····-···------·--------·····-···--·· 34 

Costispiriferidae -··--··-···-··-·---·----·---····-····-·-···· 84 

crassiformis, Salopina ····---··-·--··--··--··-·--······· 40 

crinoidal debris --------·-------···---···-···-···-··--·----··--· 7 

crispa, H owellella ---------··---···-··-·············--···--- 42 

Cyathaxonia siluriensis ----·---····--····-··----···---- 21, 22 

cyathophylloides, Australophyllum --··--··---- 24 

Spongophyllum --------····-··-··-·-·-·-----···-·--··-· 23, 24 

cycloptera monitorensis, Howellella ........ 7, 8, 11, 

38; pl. 8 

H owellella ····-··-----··----·-----··--··---··-·----··--··· 41 

cyclopterus, Spiri!er ·----------------------------------··· 33 

D 

Dalmanella sp ------------···---------···-····--···---··--·-···· 25 

Dalmanellidae ··--····--··------······-·····················-··· !86 

Dalmanites --·---······--··------·---·······-·--···········--······ 37 

dalmanitid ····--------·-·-----·····························-··--·· 9, 10 

Dalmanitidae -·-··---···-··········-·-····················-······ 9'! 

Delthyrididae ····--····--··········--·······---················ 9!8, 41 

Delthyris -----------··---····--····---··---·····-········---·····-· 32 

raricosta ------------·-------····--················--········ 32 

Devils Gate Limestone.·---··--··-··-·---··-·----··-·-···· 9, 15 

Devon Island, Northwest Territories, 

Canada ····-····---········----···-····-····- 40 

deweyi, Trematospira ···--··-·----··-·······-·······-···· 32 

diana, Plethorhyncha ·········------·········--·········· 30 

Disphyllidae ---------··---------------··----·---····-····---···· S5 

Disphyllum --------···-·····-·--·---·········---······--········· 38 

dobbinensis, Costispirifer arenosus ·-·-···· 7, 8, 12, 

85; pl. 7 

Dobbin Summit --···--···--·---··---·---··---····-··--··· '!, 35,36 

Douvillina geniculata ······--·-··-··--····--··--·······-· 16 

dunbari, Pleurodictyum ·-------···---···· 7, 20, !81; pl. 1 

E 

Ely Springs Dolomite ----·--·-········-·-------·-·--···-- 13 

Emmonsia -----·-·-··----··-·-··-······-·-····----·······-········ 19 

Endophyllidae ·-------·------··---·----·····-········-···---···- sa 

Endophyllum --·····-····--····--···---·----·---·····-····-···-·- 23 

abditum ·-----··----··-··--····-------··---······-·········· 23 

bowerbanki --·-----------····----·----····-···-·-·····-·· 23 

engelmanni, Entelophyllum ···--·--····-··· 14, 88, 41; 

pls. 10, 11 

engelmanni b, Entellophyllum -----···-····--···-· 15, 39 

Enteletidae ··-·--·······--····-··········-·····-·-·····-···--···· 40 

Entelophylloides ·-··---···--···-······--··--·--······-········ 38 

Entelophyllum ·····----··-············ 3, 13, 14, 16, 18, 38 

articulatum ·-------··-·--····-···--··········-··--·-····· 38 

engelmanni ··--···--··· 14, 16, 88, 41, pls. 10, 11 

b --------------·----···--·--··--·---·-----·-··--··· 15, 16, 89 

eurekaensis ---··-··················--·· 10, 15, 39; pl. 10 

pseudodianthus ·········-·····-····-·-·····-··········· 38 

sp ·---···---·-·-···----····-··············-·-····················· 15 

47 
48 

Page 

Entelophyllum-HoweUella assemblages 15, 16, 17 

equistriata, Trematospira .......................... 31, 32 

eurekaensis, Entelophyllum ............ 15, 99; pl. 10 

Eureka mining district ........................ 1, 2, 3, 10 

F 

Favosites .............................................. 6, 7, 8, 10, 19 

alpenesis .................................................... 19 

gothlandicus .............................................. 19 

helderbergiae .................... 6, 7, 8, 10, 19; pl. 1 

sp ................................................................ 9, 10 

Favositidae ........................................................ 19 

favositids .......................................................... 15, 16 

Favositinae ...................................................... 19 

Ferganella lincolnensis .................................. 40 

Fish Creek Range .... ........................ 15, 38, 40, 43 

Fish Haven Dolomite .................................... 16 

flabellites, Leptocoelia .................................. 31 

flexuosa, Striatopora .................................... 20 

foerstei, Syringaxon ........ 7, 8, 9, 10, 11, ~~;pl. 2 

fremonti, Leptaena ................ 7, 8, 9, 10, ~8; pl. 3 

Frisco Limestone, Oklahoma ...................... 28 

fucoids .............................................................. 7 

furca, Thlipsura 11 

G 

gaspensis, Phacops ........................................ 37 

Gazelle Formation, Klamath Mountains .... 23 

geniculata, Douvillina .................................. 16 

Giles Formation, Virginia .......................... 34 

Glassia variabilis ............................................ 41 

gothlandicus, Favosites .................................. 19 

Gotland, Sweden .............................................. 38 

graptolites ............................................ 2, 3, 6, 7, 17 

Great Basin .................................. 1, 2, 4, 12, 18, 40 

Silurian and Devonian depositional 

systems of ................................ 1, 2, 4 

Early Devonian coral zone B 7, 10, 12, 18, 28 

Early Devonian coral zone C .............. 18, 28 

Late Silurian coral zone D ........ 4, 8, 16, 18 

Late Silurian coral zone E ...... 4, 6, 7, 8, 11, 

12, 16, 18, 19, 24 

Middle Devonian coral zone F ............ 18, 19 

Silurian basal chert .............................. 3 

Greifensteiner Kalk, Germany.................... 23 

grossa, Anastrophia ...................................... 29 

gwenensis, Striatopora .................... 6, 8, ~0; pl. 1 

H 

Halysites .................................................... 13, 15, 16 

catenulatus .............................................. 13 

Halysites-pycnostylid biofacies .................. 15, 16 

Halysitidae ...................................................... 19 

Hamilton Group .............................................. 20 

Hanson Creek Limestone ............................ 3, 13 

Haragan Limestone, Oklahoma .................. 26, 28 

haraganensis, Schuchertella ...... 7, 8, 9, ~9; pl. 3 

Hedeina ............................................................ 32 

helderbergiae, Favosites ............ 6, 7, 8, 19; pl. 1 

Heliolitidae ...................................................... 19 

Henryhouse Formation ................................ 26, 41 

henryhousensis, Rhipidomella .................... 26 

hesperalis, Hyattidina .................................. 40 

hexactinellid sponge spicules ...................... 7 

Hidden Valley Dolomite, Panamint 

Mountains, Calif .............. 22, 34, 35 

HindeUa ............................................................ 40,41 

prinstana .................................................. 41 

umbonata .................................................. 41 

sp. a ........................................ 15, 16, 41; pl. 12 

History of investigation .............................. 9 

Howellella ................................ 3, 15, 18, 99, 38, 41 

crispa ........................................................ 42 

cycloptera .................................................. 41 

monitorensis .......... 7, 8, 10, 11, 99; pl. 8 

pauciplicata .............. 14, 16, 33, 41, 42; pl. 12 

smithi ........................ 15, 16, 33, 41, 42; pl. 12 

INDEX 

Page 

H owellella-Camarotoechia-A trypa 

brachiopod assemblage .......... 39 

huddlei, Icriodus latericrescens .................. 11 

Huddle, J. W., quoted .................................. 11 

Hunsriickschiefer Formation, Germany .... 35 

huntiana, Conularia ...................... 8, 19, 95; pl. 2 

Hyattidina ........................................................ 40 

congesta ...... .............................................. 40 

hesperalis ................................................ 16, 40 

sp. f ............................ 14, 15, 16, 40, 41; pl. 12 

sp ................................................................ pl. 12 

Hysterolites (Acrospirifer) .......................... 33, 34 

Icriodus 11 

latericrescens B ...................................... 11 

huddlei .............................................. 11 

sp ................................................................ 11 

Ikes Canyon .................................................... 7 

Independence Shale, Iowa ............................ 22 

infrequens, Leptocoelia ................................ 31 

Introduction .................................................... 1 

Inyo Mountains, Calif.................................... 42 

K 

kleinhampli, Acrospirifer .... 7, 8, 10, 12, 94; pl. 7 

Kobeh Valley project .................................... 2, 10 

kobehana, Acrospirifer .......................... 28, 29, 34 

Kodonophyllum ................................................ 12 

Kozlowskiella .................................................. 32 

strawi ........................................................ 32 

Kozlowskiellina .............................................. 92 

nolani .............................. 7, 8, 10, 9~, 33; pl. 6 

strawi ........................................................ 33 

velata ........................................................ 33 

sp. a............................................................ 32 

Kyphophyllidae .............................................. 98 

Kyphophyllum ................................................ 38 

lindstromi ................................................ 38 

L 

Laccophyllidae ................................................ B1 

Laccophyllum .................................................. 21 

acuminatum ............................................ 22 

laevis, Meristella ............................................ 30 

Laketown Dolomite, Confusion Range, 

Utah .......................... 4, 16, 18, 40, 41 

landerensis, Australophyllum ........ 8, 11, ~4.· pl. 9 

lata, Conularia .............................................. 8 

latericrescens huddlei, Icriodus .................. 11 

B, Icriodus ................................................ 11 

leguminoides, Bairdia .................................... 11 

lenticularis, Pleurodictyum ........ 9, 12, 19, 20, 21 

Leonaspis .............................. 7, 8, 9, 10, 11, 96, 37 

tuberculatus .......................... 7, 8, 9, 10, 11, 96 

williamsi .................................................... 36 

sp ................................................................ 36 

Leptaena .................................................. 7, 9, 10, 28 

acuticuspidata .......................................... 28 

fremonti ............................ 7, 8, 9, 10, ~8; pl. 3 

rhomboidalis ............................................ 28 

ventricosa .................................................. 28 

sp .......................................................... 28; pl. 3 

Leptaenidae ...................................................... ~8 

Leptocoelia ............................................ 8, 12, 91, 35 

acutiplicata .............................................. 31 

flabellites .................................................. 31 

infrequens ................................................ 31 

occidentalis ...................... 7, 8, 10, 11, 91; pl. 5 

sp ................................................ 8, 9, 10, 31, 35 

Leptocoeliidae .................................................. 91 

Leptostrophia .................................................. 8, ~7 

becki tennesseensis ........ 7, 8, 10, ~7.· pis. 3, 8 

sp .......................................... 7, 10, 27; pis. 3, 8 

Levenea ............................................................ 12, ~6 

subcarinata .............................................. 12, 26 

antelopensis ............ 7, 8, 10, 11, f6; pl. 4 

Page 

lincolnensis, Ferganella ................................ 40 

lindstromi, Kyphophyllum .......................... 38 

Locality register ............................................ .u 

logani, Phacops .............................................. 37 

Lone Mountain ................................ 1, 3, 1f, 13, 42 

Lone Mountain Dolomite ...... 2, 10, 12, 19, 15, 16, 

17, 33, 38, 40 

age and correlation of .......................... 3, 15 

fossils of .......................... 4, 16, 17, 18, 19, 42 

relation to Rabbit Hill Limestone .... 3, 17 

Unit 1. ............................................... 13, 15, 18 

Unit 2 .......................................... 13, 15, 16, 18 

Lone Mountain Formation .......................... 3, 12 

Lone Mountain-Laketown biofacies ........ 15, 16, 

18,41 

Lone Mountain Limestone .......................... 3, 13 

lykophyllids ...................................................... 18 

M 

mcbridei, Trematospira .................. 7, 91, 32; pl. 6 

McClusky Peak ................................................ 8 

Macropleura .................................................... 41 

Madreporites articulatus .............................. 38 

Mahogany Hills ........................................ 18, 40, 43 

martini, Meristella ...................... 7, 8, 10, 30; pl7. 

Meristella .......................................................... 7, 90 

arcuata ...................................................... 30 

atoka .......................................................... 30 

laevis .......................................................... 30 

martini .................................. 7, 8, 10, 80; pl. 7 

robertsensis ...... ........................................ 30 

sp ................................................................ 9, 10 

Meristellidae .................................................... 80, 40 

Meristina sp .................................................... 16 

Mesomphalus sp .............................................. 11 

Methods ............................................................ • 

Michelinia ........................................................ 20 

sp ................................................................ 20 

Micheliniinae .................................................. 19, ~0 

Miraspis ...................................................... 35, 36, 87 

Moll~~c~··:::::::::::::::::::::::::::~::::::::::::::::: .. ~: .. ~-~: .. ; pla~ monitorensis, Howellella cycloptera 7, 8, 11, 88, 

pl. 8 

Monitor Range ........................................ 2, 7, 21, 42 

type area .................................................. 2 

Monitor-Simpson Park belt ........................ 4, 5, 8 

Monograptus .................................................. 6, 7 

Mucophyllum .................................................... 12 

Mulligan Gap fault ........................................ 15 

Mulligan Gulch ................................................ 10 

multistriata, Trematospira .......................... 32 

murchisoni, Acrospirifer .............................. 34 

Murifella .......................................................... 40 

musculosa, Rhipidomella .............................. pl. 8 

N 

N eomphyma .................................................... 38 

Nevada Formation .................... 2, 6, 13, 17, 19,31 

Beacon Peak Dolomite Member .... 10, 15, 16, 

17, 18 

fossils .......................................... 3, 5, 6, 19 

unit 1 .... 6, 7, 10, 12, 17, 27, 28, 29, 34, 35, 36 

unit 2 .......................... 8, 19, 22, 29, 35, 36, 37 

unit 4 ........................................................ 35 

nevadensis, Billingsastraea ........................ 25 

Pleurodictyum ................ 7, 8, 9, 20, 21; pl. 1 

Schuchertella ............................................ 29 

newberryi, Orthostrophia strophomenoides 

7, 11, 27; pis. 3, 8 

Niagaran Formation, Tennessee ................ 22 

Nicholsonia ...................................................... 21 

(Nicholsonia), Alleynia ................................ 22 

nolani, Kozlowskiellina .............. 7, 8, 82, 33; pl. 6 

N owakia acuaria .......................................... 35 

Nucleospira ...................................................... 40 

ventricosa ................................................ 9 

sp ................................................................ 9 
0 Page 

oblata, Rhipidomella ...................................... 26 

occidentalis, Leptocoelia .... 7, 8, 10, 11, 31; pl. 5 

Odontopleura .................................................. 36, 37 

Odontopleuridae .............................................. 36 

Orthidae ............................................................ 17 

Orthis subcarinata ........................................ 26 

Orthoceras ...................................................... 7, 9, 35 

sp ································································ 10 

(Orthonychia) sp. c, Platyceras ........ 7, 36; pl. 1 

Orthostrophia .................................................. 17 

strophomenoides ...................................... 7, 27 

newberrui .............. 7, 10, 11, £7; pls. 3, 8 

parva ................................................. . 

sp ································································ ostracods ......................................................... . 

p 

27 

27 

11 

Pachyporinae .................................................. 19, 10 

pahranagatensis, Camarotoechia .. 15, 40; pl. 11 

Pahranagat Range .......................................... 40 

Palaeocyclus .................................................... 18 

Papiliophyllum ................................................ 28 

Parahealdia ...................................................... 11 

convexoris ................................................ 11 

Parastrophinidae ............................................ 19 

Parazyga .......................................................... 32 

parva, Orthostrophia strophomenoides .... 27 

pauciplicata, Howellella 14, 16, 33, 41, 42; pl. 12 

perlamellosus, Spirifer .................................. 32 

Permia ............................................................. . 

perplexum, Barrandeophyllum ................... . 

Petes Canyon ................................................. . 

21,22 

22 

8 

Petrozium ........................................................ 38 

Phacopidae ...................................................... 36, 37 

Phacops ............................................................ 37 

birdsongensis .......................................... 37 

eanadensis .................................. 9, 10, 37; pl. 2 

gaspensis .................................................. 37 

logani ........................................................ 37 

sp. A ...................................................... 37;pl. 8 

sp. B .......................................... 9, 10, 37; pl. 2 

sp ........................................................ 7, 8, 9, 10 

Pholadophyllum .............................................. 37 

Pholidophylum ................................................ 37 

Pholidostrophia .............................................. !8 

sp. R ............................................ 7, 10, 18; pl. 3 

pinyonensis, Spirifer .................................... 36 

planicostatus, Costispirifer ........................ 34 

arenosus ............................................ 34 

Spirifer arenosus .................................... 34 

Plat11ceras .............................. .......................... 35, 36 

sp. a ............................................ 7, 10, 36; pl. 1 

sp. b ............................................ 7, 10, 36; pl. 1 

(Orthonychia) sp. c ................ 7, 10, 36; pl. 1 

Platyceratidae ................................................ 36 

Plethorhyncha .................................................. 19 

altera .......................................................... 30 

andersoni ........................ 7, 8, 10, 19, 30; pl. 6 

barrandi .................................................... 30 

diana .......................................................... 30 

salinensis . ................................................. 30 

speciosum .................................................. 29 

welleri ........................................................ 30 

Pleurodictyum .............. 8, 9, 11, 12, 19, 10, 21. 35 

dunbari ................................ 7, 10, 21, 20; pl. 1 

lenticulare ................................................ 19, 20 

lenticularis .......................................... 9, 12, 21 

nevadensis .................. 7, 8, 9, 10, £0, 21; pl. 1 

(Pleurodictyum) .................................... 20 

problematicum ........................................ 20 

(Procteria) .............................................. 20 

stylopora .................................................... 20 

tennesseensis ............................................ 20 

trifoliatum ................................................ 20, 21 

sp .............................................................. 8, 9, 10 

Pogonip Group ................................................ 6 

Polycoeliidae .................................................... 21 

INDEX 

Page 

primaevus, Spirifer ...................................... 34 

prinstana, Hindella ........................................ 41 

problematicum, Pleurodictyum .................. 20 

(Procteria) Pleurodictyum .......................... ZO 

Proetus sp ........................................................ 8, 10 

Protathyris ...................................................... 40 

Protocortezorthis ............................................ 40 

pseudodianthus, Entelophyllum .................. 38 

punctulifera, Strophonella .......... 8, 10, 28; pl. 3 

Purpose and scope of investigation .......... 2 

pycnostylids .............................................. 12, 15, 16 

Pycnostylus ...................................................... 15 

sp ................................................................ pl. 11 

R 

Rabbit Hill 6, 36 

Rabbit Hill Limestone .......................... 2, 5, 18, 42 

age and correlation of ........................ 3, 10 

areal distribution and stratigraphy of 5 

type area ......................................... 6 

conularids of ............................................ 35 

fossils of ............................ 3, 4, 6, 7, 8, 19, 42 

mollusca of .............................................. 35 

relation to Lone Mountain Dolomite 3, 17 

tentaculitida of ........................................ 35 

trilobites of .............................................. 36 

raricosta, Delthyris ........................................ 32 

~resimus, Belodella .......................................... 11 

Retziidae .......................................................... 31 

Rhabdocyclus .................................................... 18 

Rhipidomella .................................................... 25, 26 

henryhousensis ........................................ 26 

musculosa .................................................... pl. 8 

oblata ........................................................ 26 

rossi ...................................... 7, 10, 25, 26; pl. 4 

sp ................................................................ 9 

Rhipidomellidae .............................................. 25 

Rhipidomelloides ............................................ 25, 26 

rhomboidalis, Leptaena ................................ 28 

robertsensis, Meristella .................................. 30 

Roberts Mountains ................................ 1, 3, 33, 40 

Formation ................................ 2, 7, 10, 13, 32 

Limestone .................................... 3, 4, 5, 12, 18 

Rockhouse Shale, Tennessee ........................ 20, 21 

Romano fault .................................................. 15 

rossi, Rhipidomella .......................... 7, 25, 26; pl. 4 

rugosa, Xylodes .............................................. 38 

rugose corals .......... 2, 8, 11, 12, 13, 15, 16, 17, 18 

s 

Saccarchites sp .............................................. 11 

salinensis, Plethorhyncha .............................. 30 

Salopina ............................................................ 40 

crassiformis .............................................. 40 

sp. f ........................................ 15, 16, 40; pl. 11 

sp ................................................................ 40 

Sandpile Dolomite, British Columbia, 

Canada ...................................... 41 

Schellwienella .................................................. 29 

Schuchertella ........................................ 7, 8, 10, 29 

haraganensis .................... 7, 8, 9, 10, 29; pl. 3 

nevadensis ................................................ 29 

sp ................................................ 9, 29; pls. 3, 8 

Schuchertellidae .............................................. 19 

sedgwicki, Spongophyllum .......................... 23 

Selected bibliography .................................... 49 

Sevy Dolomite .................................................. 16 

siluriensis, Cyathaxonia .............................. 21, 22 

Syringaxon .............................................. 21, 23 

Simpson Park Range, Nevada ........ 1, 2, 4, 8, 21, 

36, 37, 42 

Siphonophrentis .............................................. 29 

sp. B ············-~································ 10, 23; pl. 8 

smithi, Howellella ............ 15, 16, 33, 41, 42; pl. 12 

speciosum, Plethorhyncha ............................ 29 

Spiniferina ...................................................... 37 

Spinulosa ......................................................... . 

Spirifer arenosus planicostatus ................. . 

cyclopterus ............................................... . 

perlamellosus ......................................... . 

pinyonensis ............................................. . 

49 

Page 

11 

34 

33 

32 

36 

primaevus ................................................ 34 

sp. a .......................................................... 33 

Spongophyllum ................................................ 23 

cyathophylloides .................................... 23, 24 

sedgwicki .................................................. 23 

stevensi, Australophyllum .......... 11, 24, 25; pl. 9 

Stortophyllum -~·-············································ 37 

strawi, Kozlowskiella .................................... 32 

Kozlowskiellina ...................................... 33 

Streptelasmatidae .......................................... 29 

Striatopora ...................................... 6, 8, 10, 19, 20 

flexuosa -~·················································· 20 gwenensis .............................. 6, 8, 10, 20; pl. 1 

sp ................................................................ 20 

Strombodes ...................................................... 38 

Stropheodonta sp .................................. 7, 10; pl. 3 

Stropheodontidae ............................................ 27 

s trophomenoides newberryi, 

Orthostrophia .... 7, 11, 27; pls. 3, 8 

Orthostrophia .......................................... 7, 27 

parva, Orthostrophia ............................ 27 

Strophonella .................................................... 8, 28 

bransoni .................................................... 28 

punctulifera .............................. 8, 10, 28; pl. 3 

sp ................................................................ 10 

Styliolina .......................................................... 35 

stylopora, Pleurodictyum .............................. 20 

subcarinata antelopensis, Levenea .. 7, 8, 10, 11, 

26; pl. 4 

Levenea .................................................... 12, 26 

Orthis ........................................................ 26 

Sulphur Spring Range 2, 10, 15, 28, 29, 36, 42, 43 

Sunday Canyon Formation, Vaughn 

Gulch Limestone, Mazourka 

Canyon, Inyo Mountains, 

Calif .................................... 11, 12, 24 

Syringaxon .......................................... 18, 19, 21, 35 

foerstei ................ 7, 8, 9, 10, 11, 22, 23; pl. 2 

siluriensis .................................................. 21, 23 

sp ................................................................ 12 

Syringopora .................................................... 13 

Syringoporinae ................................................ 19 

Systematic and descriptive paleontology .. 18 

T 

Tabulata ............................................................ 19 

tennesseensis, Atrypa .................................... 41 

Leptostrophia becki .......... 7, 8, 27; pis. 3, 8 

Pleurodictyum ........................................ 20 

tentaculitida ...................................... 8, 9, 10, 19, 35 

Thamnopora sp ........................................ 14, 15, 16 

Thlipsura furca .............................................. 11 

sp ................................................................ 11 

Toquima Range .............................. 2, 7, 12, 21, 42 

Torquay Formation, England .................... 23 

Trematospira ............................................ 11, 91, 40 

cooperi ...................................................... 32 

deweyi ........................................................ 32 

equistriata ................................................ 31, 32 

mcbridei .............................. 7, 10, 91, 32; pl. 6 

multistriata .............................................. 32 

sp ................................................................ 31 

Tricornina sp .................................................. 11 

trifoliatum, Pleurodictyum ........................ 20, 21 

trilobites .......................................... 8, 11, 19, 35, 36 

Tryplasma ........................................................ 18, 97 

aequabile .................................................. 37 

sp. f ...................................................... 38; pl. 11 

sp ................................................................ 15, 16 

Tryplasmatidae .............................................. 97 

tuberculatus, Acidaspis ................................ 36 

Leonaspis .................................... 7, 8, 9, 11, 96 

Tubilibairdia sp .............................................. 11 

Tuscarora Mountains .................... 2, 9, 11, 25, 42 
50 

u 

umbonata, A mbocoelia ----------------------------------

Hindella ----------------------------------------------------

Uncinulidae ------------------------------------------------------

Uncinulus ----------------------------------------------------------

v 

variabilis, Glassia ------------------------------------------

velata, Kozlowskiellina ----------------------------------

Page 

30 

41 

29 

30 

41 

33 

INDEX 

Page 

Velibeyrichia sp ---------------------------------------------- 11 

ventricosa, Leptaena ------------------------------------ 28 

N ucleospira ---------------------------------------------- 9 

verneuili, Anastrophia ---------------- 10, 11, 29; pl. 5 

Verticillopora -------------------------------------------------- 16 

w 

W alti Ranch, W alti Hot Springs 

quadrangle -------------------------- 8, 35, 36 

Welleria ------------------------------------------------------------ 11 

Page 

welleri, Plethorhyncha --------·--·--------------········ 30 

Wenban Limestone-------------------------------·-------- 9, 11 

Wenlock Limestone, England -----------·-·------ 32, 38 

williamsi, Leonaspis ----------------------------·····----- 36 

x. y 

Xylodes 

articulatus ----------------------·---·-----··-----·····----

rugosa ------------------------------------·------···----·-···· 

Yassia --------------------·-----·-------··--·-----·········---

38 

38 

38 

23 
PLATES 1-12 

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

Geological Survey Photographic Library, Federal Center, Denver, Colorado 80225] 
PLATE 1 

FIGURES 1, 3-6. Striatopora cf. S. gwenensis Amsden. 

1. Lateral view ( x 11f2); USNM 159475. 

3. Lateral view ( x 2); USNM 159476. 

4. Transverse thin section ( x 2); USNM 159514. 

5, 6. Longitudinal thin sections ( x 2); USNM 159515, 159516. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hall, Copenhagen Canyon, Nev. Locality M409. 

2. Digitate favositid sp. a. 

Lateral view ( x 11f2); USNM 159513. Locality M409. (Seefigs.1, 3-6.) 

7-12. Pleurodictyum nevadensis n. sp. 

7, 8. Calice and lateral views of holotype (X 1¥2); USNM 159517. 

9. Lateral view of broken paratype ( x 3); USNM 159518, showing pore distribution. 

10. Interior view of wall ( x 2); USNM 159519, showing pore pattern. 

Locality M409. (See figs.1, 3-6.) 

11. Calice view ( x 11f2); USNM 159520. Upper part of Rabbit Hill Limestone, Dobbin Summit, Monitor 

Range, Nev. Locality M1309. 

12. Calice view ( x 1); USNM 159521. Lower Devonian, Rabbit Hill Limestone; Horse Canyon, Cortez 

Mountains, Nev. Locality M1083. 

tains, Nev. Locality M1083. 

13-15. Pleurodictyum dunbari n. sp. 

13. Lateral exterior of holotype ( x 1¥2); USNM 159522. 

14. Calice view of holotype ( x 21f2); USNM 159522. 

15. Calice view of paratype ( x 21f2); USNM 159523. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

16-19. Favosites cf. F. helderbergiae Hall. 

16. Surface of massive colony ( x 1). 

17. Longitudinal thin section ( x 2). 

18. Transverse thin section ( x 2). 

19. Longitudinal thin section ( x 2). 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

20, 21. Platyceras sp. a. 

Umbilical and aperture views ( x 1); USNM 159524. Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, 

Copenhagen Canyon, Nev. Locality M409. 

22, 23. Platyceras sp. b. 

Lateral and aperture views ( x 1¥2); USNM 159525. Locality M409. (See figs. 20, 21.) 

24. Platyceras (Orthonychia) sp. c 

Elongate surface of body whorl ( x 1%); USNM 159526. Locality M409. (See figs. 20, 21.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 1 

8 

4 

3 

9 

2 6 

11 

17 

22 

15 

18 

23 

20 

19 16 24 

STRIATOPORA, PLEURODICTYUM, FA VOSITES, AND PLATYCERAS 
PLATE 2 

FIGURES 1-10. Syringaxon foerstei n. sp. 

1. Oblique calice view of holotype ( x 11f2) ; USNM 159243. Lower Devonian, Rabbit Hill Limestone; Rabbit 

Hill, Copenhagen Canyon, Nev. Locality M409. 

2, 3. Lateral view (X 11f2) and calice view (X 1) of paratype USNM 159245. Locality M409. (See fig. 1.) 

4. Lateral view of paratype ( x 2) ; USNM 159527. Locality M409. (See fig. 1.) 

5. Transverse thin section ( x 4); USNM 159248. Lower Devonian, Rabbit Hill Limestone; Coal Canyon, 

Simpson Park Range, Nev. Locality M1032. 

6. Transverse thin section of paratype ( x 4); USNM 159246. Locality M409. (See fig. 1.) 

7. Calice view ( x 2); USNM 159528. Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring Range, Nev. Locality M 197. 

8. Calice view of paratype ( x 21f2) ; USNM 159244. Locality M409. (See fig. 1.) 

9, 10. Longitudinal thin section of two paratypes ( x 4); USNM 159529, 159247. Locality M409. (See fig. 1.) 

11-13. (?)Phacops sp. B, cf. P. canadensis Stumm. 

11. Dorsal surface of nearly complete specimen ( X 1) ; USNM 159530. 

12. Cephalon showing right genal spine (X 1); USNM 159531. 

13. Latex impression of pygidium ( x 1) ; USNM 159532. Rabbit Hill Limestone, Coal Canyon, Simpson 

14. (?)Miraspis sp. 

Forked occipital ring spine ( x 2) . Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen 

Canyon, Nev. Locality M409. 

15- 17. Leonaspis cf. L . tuberculatus (Hall). 

15, 17. Pygidium ( x 4); USNM 159533 and free cheek ( x 4); USNM 159534. Locality M409. (See fig. 14.) 

16. Free cheek (X 2); USNM 159535. Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor 

Range, Nev. Locality M1311. 

18-20. Conularia sp., cf. C. huntiana Hall. 

18. Lateral view ( X 2); USNM 159536. 

19. Surface of large individual ( x 2); USNM 159537. 

20. Enlargement of part of fig. 19 ( x 8). 

Lower Devonian, Rabbit Hill Limestone; southeast of Walti Ranch, Simpson Park Range, Nev. Locality 

M1074. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 2 

3 

2 

5 

7 8 4 

12 

10 

9 

11 13 

14 15 

16 17 

18 

SYRJNGAXON, (?)PHACOPS,(?)MIRASPJS, LEONASPIS, AND CONULARIA 
FIGURES I-3. 

4, 5. 

6, 7. 

8, 9. 

IO, II. 

I2-I5. 

I6,I7, I9. 

I8. 

PLATE 3 

Leptostrophia sp. cf. L . bee hi tennesseensis Dunbar. 

I , 2. Exterior and interior of pedicle valve ( x 2); USNM 159538. 

3. Exterior of pedicle valve ( x 2) ; USNM 159539. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

Orthostrophia strophomenoides subsp. newberryi n. subsp. 

Exterior and interior ( x 2) of holotype; USNM I59540. Locality M409. (See figs. 1-3.) 

(?) Pholidostrophia sp. R. 

Exterior ( x I) and interior ( x 2) of pedicle valve; USNM 159541. Locality M409. (See figs. 1--3.) 

Stropheodonta sp. 

Exterior ( x I) and interior ( x 1%) of same pedicle valve. Locality M409. (See figs. 1-3.) 

Strophonella cf. S. punctulifera (Conrad). 

IO. Latex impression of probable pedicle valve ( X 2). 

11. Latex impression of brachial valve exterior ( x 1) . 

Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring Range, 

Nev. Locality M197. 

Schuchertella sp., cf. S. haraganensis Amsden. 

I2-I4. Pedicle valve exterior, interior and hinge views ( x I%); USNM I59542. 

I5. Pedicle valve exterior ( x 1%); USNM 159543. Locality M409. (See figs. I-3.) 

Leptaena fremonti n. sp. 

I6, 17. Pedicle valve exterior and interior ( x I), holotype; USNM I59544. 

19. Pedicle valve interior ( x I), paratype; USNM 159545. Locality M409. (See figs. I-3.) 

Leptaena sp., cf. L. fremonti n. sp. 

Pedicle valve exterior ( x 1%); USNM I59546. Lower Devonian, Beacon Peak Dolomite Member of the 

Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 3 

8 

4 

7 

5 

2 

11 

3 

10 13 

18 16 

19 17 15 

LEPTOSTROPHIA, ORTHOSTROPHIA, (?) PHOLIDOSTROPHIA, STROPHEODONTA, 

STROPHONELLA, SCHUCHERTELLA, AND LEPTAENA 

6 

14 

12 
PLATE 4 

FIGURES 1-14. Levenea subcarinata subsp. antelopensis n. subsp. 

1-3. Exterior, interior, and umbonal views ( x 2), holotype pedicle valve; USNM 159547. 

4-6. Umbonal view ( x 2), exterior and interior ( x 1%), para type brachial valve; USNM 159548. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

7. Brachial valve interior (X 2), para type; USNM 159549. Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M186. 

8. Umbonal view of articulated shell ( x 1%), paratype; USNM 159550. Locality M186. (See fig. 7.) 

9. Dorsal interior ( x 2), paratype; USNM 159551. Locality M409. (See figs. 1-6.) 

10. Pedicle interior ( x 2), para type; USNM 159552. Locality M409. (See figs. 1-6.) 

11, 12. Brachial valve exterior and interior ( x 1%), paratype; USNM 159553. Rabbit Hill Limestone, 

Dobbin Summit, Monitor Range, Nev. Locality M1309. 

13, 14. Pedicle valve interior and exterior ( x 1%), para type; USNM 159554. Lower Devonian, Beacon 

Peak Dolomite Member of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M1312. 

15-24. Rhipidomella rossi n. sp. 

15-17. Dorsal valve exterior, lateral and umbonal views ( x 2), paratype; USNM 159555. 

18, 19. Dorsal valve exterior and interior ( x 2), holotype; USNM 159556. 

20. Dorsal valve interior ( x 2%), para type; USNM 159557. 

21. Ventral valve interior ( x 2%), para type; USNM 159558. 

22. Ventral valve interior ( x 2), paratype; USNM 159559. 

23. Ventral valve interior ( x 2%), paratype; USNM 159560. 

24. Dorsal valve interior ( x 2%), paratype; USNM 159561. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 4 

2 

3 

5 11 

6 

12 

9 

17 8 14 13 

15 18 20 

19 

21 22 23 24 

LEVENEA AND RHIPIDOMELLA 
PLATE 5 

FIGURES 1-14. Leptocoelia occidentalis n. sp. 

1, 2, 4. Pedicle valve, brachial valve, and lateral exterior views ( x 2), holotype; USNM 159562. 

3, 5. Anterior (X 2) and umbonal (X 1%) views, paratype; USNM 159563. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

6, 7. Brachial valve and pedicle valve exterior ( x 1%) , paratype; USNM 159564. Lower Devonian, Beacon 

Peak Dolomite Member of the Nevada Formation, southern Sulphur Spring Range, Nev. Locality M197. 

8, 9. Brachial valve exterior ( x 2) and interior ( X 3), para type; USNM 159565. Locality M409. (See 

figs. 1-5.) 

10. Pedicle valve interior ( x 2), paratype; USNM 159566. Locality M409. (See figs. 1-5.) 

11, 12. Pedicle valve interior of two paratypes ( x 2) ; USNM 159567, 159568. Locality M409. (See figs. 1-5.) 

13, 14. Brachial valve interior of two para types ( x 3); USNM 159569, 159568. Locality M409. (See figs. 1-5.) 

15-19. Anastrophia cf. A. verneuili (Hall) . 

15, 18, 19. Pedicle valve exterior ( x 1%) and two views of interior of same individual; USNM 159571. 

Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring 

Range, Nev. Locality M186. 

16. Pedicle valve exterior ( x 1); USNM 159572. Lower Devonian, Beacon Peak Dolomite Member of the 

Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197. 

17. Pedicle valve exterior ( x 1%); USNM 159573. Locality M197. (See fig. 16.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 5 

6 7 

2 

5 

8 4 

14 15 

13 

16 17 20 

LEPTOCOELlA AND ANASTROPHJA 
PLATE 6 

FIGURE. I-7. Plethorhyncha andersoni n. sp. 

I, 2. Brachial valve exterior and anterior view ( x I); holotype, USNM I59574. 

3, 5. Pedicle valve exterior of two paratypes ( x I) ; USNM I59575, I59576. 

4, 7. Brachial valve exterior ( x I) and interior ( x 2); paratype, USNM I59577. 

6. Pedicle valve interior ( x I); paratype, USNM I59578. 

Lower Devonian, Rabbit llill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

8-I5. Trematospira mcbridei n. sp. 

8, IO. Pedicle valve exterior ( x I) and interior ( x 2) ; holotype, USNM I59579. 

9. Pedicle valve exterior ( x I%) ; paratype, USNM I59580. 

II. Pedicle valve interior ( x 2) ; paratype, USNM I59581. 

I2. Pedicle valve interior ( x 2); para type, USNM I59582. 

I3-I5. Brachial valve interior of three para types ( x 2) ; USNM I59583, I59584, I59585, showing details of 

the cardinal process. 

Locality M409. (See figs. I-7.) 

I6-24. Kozlowskiellina nolani n. sp. 

I6. Brachial valve exterior ( x I%); paratype, USNM I59586. 

I7. Brachial valve interior ( x I%); paratype, USNM I59587. 

I8. Brachial valve interior ( x 3) ; paratype, USNM I59588. 

I9. Pedicle valve exterior ( x 2) ; holotype, USNM I59589. 

20, 21. Pedicle valve interior of two paratypes ( x I%); USNM I59590, I59591. 

Locality M409. (See figs. I-7.) 

22. Pedicle valve interior ( x I%) ; paratype, USNM I59592. Rabbit Hill Limestone; Dobbin Summit, 

Monitor Range, Nev. Locality MI309. 

23. Oblique posterior view ( x I%) . Locality M409. (See figs. I-7.) 

24. Pedicle valve interior ( x 2); holotype, USNM I59589. Locality M409. (See figs. I-7.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 6 

2 

13 

4 14 

7 

8 

15 

11 16 

23 

17 

22 18 24 

PLETHORHYNCHA, TREMATOSPIRA, AND KOZLOWSKIELLJNA 
PLATE 7 

FIGURES 1-7. Costispirifer arenosus subsp. dobbinensis n. subsp. 

1, 4. Pedicle valve exterior ( x 1%) and posterior view ( x 1); paratype, USNM 159593. 

2,3. Pedicle valve exterior (x 1) and interior (x 1%); holotype, USNM 159594. 

5. Brachial valve exterior ( x 1); paratype, USNM 159595. 

6, 7. Pedicle valve exterior of two paratypes; USNM 159596, 159597. 

Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor Range, Nev. Locality M1309. 

8. Acrospirifer sp. 

Pedicle valve exterior ( x 2); USNM 159598. Locality M1309. (See figs. 1-7.) 

9-12. Acrospirifer kleinhampli n. sp. 

9, 10. Pedicle valve exterior and interior ( x 1%); holotype, USNM 159599. 

11, 12. Pedicle valve exterior and interior ( x 1%); paratype, USNM 159600. 

Locality M1309. (See figs. 1-7.) 

13, 14. Acrospirifer sp. D. 

Brachial valve exterior and interior ( x 1%); USNM 159601. Locality M1309. (See figs. 1-7.) 

15, 16. Acrospirifer cf. A. kleinhampli n. sp. 

Pedicle valve exterior and interior ( x 1%); USNM 159602. Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring Range, Nev. Locality M197. 

17-22. Howellella cycloptera subsp. monitorensis n. subsp. 

17. Brachial valve interior ( x 2); paratype, USNM 159603. 

18, 19. Pedicle valve interior and exterior ( x 1%); holotype, USNM 159604. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

20-22. Pedicle valve, brachial valve, and anterior views ( x 1%); paratype, USNM 159605. 

Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor Range, Nev. Locality M1311. 

23-27. M eristella martini n. sp. 

23, 24. Pedicle valve exterior and interior ( x 1); holotype, USNM 159606. 

25, 26. Pedicle valve interior ( x 1%) and exterior ( x 1); paratype, USNM 159607. 

27. Brachial valve interior ( x 1%); paratype, USNM 159608. 

Locality M409. (See figs. 17-19.) 

28-31. Ambocoelia sp. a 

28. Pedicle valve exterior ( x 3); USNM 159609. 

29-31. Three pedicle valve interiors ( x 3); USNM 159610, 159611, 159612. 

Locality M409. (See figs. 17-19.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 7 

5 

3 

7 

2 

6 

8 

17 28 

29 

30 

20 

21 22 23 31 

COSTJSPIRJFER, ACROSPIRIFER, HOWELLELLA, MERJSTELLA, AND AMBOCOELJA 
FIGURES 

PLATE 8 

1-3. Siphonophrentis sp. B 

Calice and lateral views ( x 1), and longitudinal thin section ( x 3) ; USNM 159613. Lower Devonian, 

Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring Range. Locality 

M186. 

4. Schuchertella sp. 

Brachial valve interior ( x 2); USNM 159614. Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, 

Monitor Range, Nev. Locality M1311. 

5. Leptostrophia sp. cf. L . becki tennesseensis Dunbar. 

Brachial valve interior ( x 2); USNM 159615. Lower Devonian, upper part of Rabbit Hill Limestone; 

Dobbin Summit, Monitor Range, Nev. Locality M1309. 

6-9. Orthostrophia strophomenoides subsp. newberryi n. subsp. 

6, 7. Brachial valve exterior and interior ( x Ph); paratype, USNM 159616. 

8, 9. Pedicle valve exterior and interior ( x 11;2) ; paratype, USNM 159617. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

10. Howellella cycloptera subsp. monitorensis n. subsp. 

Latex impression of shell bed ( x 1). Lower Devonian, Rabbit Hill Limestone; Dobbin Summit, Monitor 

Range, Nev. Locality M1311. 

11. Rhipidomella cf. R . musculosa (Hall) . 

Ventral valve muscle field ( x 1). Lower Devonian, upper part of Rabbit Hill Limestone; Dobbin Summit, 

Monitor Range, Nev. Locality M1309. 

12, 13. Laminated Rabbit Hill chert bed overlain by trilobite coquinite ( x 1). 

12. Weather surface of coquinite showing parts of Leonaspis head shields. 

13. Edge view showing chert layer overlain by trilobite coquinite. 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

14. Weathered surface of platy calcareous siltstone showing "fucoids" ( x 1). 

15. Weathered surface of coquinite composed mainly of bryozoans, brachiopods, and crinoidal debris ( X 1). 

Lower Devonian, Rabbit Hill Limestone; Rabbit Hill, Copenhagen Canyon, Nev. Locality M409. 

16, 17. Phacops sp. A 

16. Anteroventral edge of cephalon, showing glabella and one eye ( x 11;2) . 

17. Latex impression, showing dorsal surface of pygidium and several pleura ( x 11;2) . 

Lower Devonian, Beacon Peak Dolomite Member of the Nevada Formation; southern Sulphur Spring 

Range, Nev. Locality M197. 

18. Weathered surface of a tentaculite ( x 8). Early Devonian, Rabbit Hill Limestone; southeast of Walti Ranch, 

Simpson Park Range, Nev. Locality M1074. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 8 

12 

13 

6 7 

14 

15 

SJPHONOPHRENTIS, SCHUCHERTELLA, LEPTOSTROPH!A, ORTHOSTROPHJA, 

IJOWELLELLA, RHIPIDOMELLA, AND PHACOPS 

5 

8 

9 

11 

17 

18 
PLATE 9 

FIGURES 1, 2. Billingsastraea sp. m. 

Transverse and longitudinal thin sections ( x 3); USNM 165350. Early Devonian, Rabbit Hill Limestone, 

south end of Tuscarora Mountains at Maggie Creek, locality M1400. 

3-6. Australophyllum landerensis n. sp. 

3, 4. Transverse and longitudinal thin sections ( x 21;2) of holotype, USNM 159353. 

5, 6. Transverse and longitudinal thin sections ( x 2) of paratype, USNM 159354. 

Early Devonian, Rabbit Hill Limestone, north end of Toquima Range near Petes Summit, locality Ml150. 

7. Au.stralophyllum sp. v. 

Transverse thin section ( x 2). Mazourka Canyon, northern Inyo Range, Calif.; locality M1093. Upper part 

of Vaughn G.ulch Limestone. From beds of possible Early Devonian age above Silurian coral zone E. 

8-13. Australophyllum stevensi n. sp. 

8, 9. Transverse thin sections ( x 2) of holotype, USNM 165349. 

10-13. Longitudinal thin sections ( x 2) of holotype, USNM 165349. 

Mazourka Canyon area, northern Inyo Range, Calif.; locality M1401, east side of AI Rose Canyon. From beds 

of possible Early Devonian age in upper part of the Sunday Canyon Formation. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 9 

3 

5 

2 

4 

6 

7 

9 8 

12 

11 13 

BILLINGSASTRAEA AND A USTRALOPHYLLUM 
PLATE 10 

FIGURES 1-4. Entelophyllum eurekaensis n. sp. 

1, 2. Transverse and longitudinal thin sections of holotype ( x 4); USNM 159412. 

3, 4. Longitudinal and transverse thin sections of paratype ( x 2); USNM 159419. 

Late Silurian, upper part of Lone Mountain Dolomite, southern Fish Creek Range, Nev. Locality M1113. 

5-11. Entelophyllum engelmanni n. sp. 

5. Transverse thin section ( x 4), holotype; USNM 159413. 

6, 7. Longitudinal thin section ( x 2, x 3%), para type; USNM 159415. 

8. Longitudinal thin section ( x 3), paratype; USNM 159477. 

9. Longitudinal thin section ( x 4), paratype; USNM 159414. 

10. Longitudinal thin section ( x 2), para type; USNM 159478. 

11. Lateral view of paratype (slightly reduced); USNM 159417. 

Late Silurian, upper part of Lone Mountain Dolomite; southern Mahogany Hills, Eureka County, Nev. 

Locality M1112. 

12, 13. Entelopliyllum engelmanni subsp. b. 

12. Lateral view of attached corallites ( x 1) ; shows attached Howellella smithi. 

13. Lateral view of attached corallites ( X 1%). 

Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 10 

6 

5 

8 

2 7 

9 

10 

3 

4 

ENTELOPHYLLUM 
PLATE 11 

FIGURES 1-4. Atrypa sp. f. 

1-3. Ventral, dorsal, and lateral views ( x 2); USNM 159479. 

4. Dorsal view ( x 2); USNM 159480. 

Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1113. 

5, 6. Camarotoechia sp. f. 

Dorsal and ventral exterior ( x 2); USNM 159481. Locality M1113. (See figs. 1-4.) 

7-9. Camarotoechia pahranagatensis Waite. 

Dorsal, ventral, and anterior views ( x 2); USNM 159482. Locality Mll13. (See figs. 1-4.) 

10-13. Camarotoechia sp. b. 

10-12. Dorsal, ventral, and anterior views ( x 2) ; USNM 159483. Locality Mlll3. (See figs. 1-4.) 

13. Dorsal view ( x 2); USNM 159484. Locality M1113. (See figs. 1-4.) 

14, 15. Camarotoechia sp. 

Dorsal and anterior views ( x 2); USNM 159485. Locality M1113. (See figs. 1-4.) 

16-23. Salopina sp. f 

16, 17. Oblique dorsal and ventral views ( x 2); USNM 159486. 

18, 19. Dorsal valve exterior and interior views ( x 3); USNM 159487. 

20. Dorsal valve exterior ( X 3); USNM 159488. 

21, 22. Dorsal and ventral exterior ( x 3); USNM 159489. 

23. Dorsal exterior ( x 21f:z); USNM 159490. 

Late Silurian, upper part of Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087. 

24, 25. Tryplasma sp. f. 

Transverse and longitudinal thin sections ( x 2) ; USNM 159491. Locality M1087. (See figs. 16-23.) 

26, 27. Entelophyllum engelmanni subsp. b. 

Lateral exterior ( x 11f:z) and transverse thin section ( x 11f:z) ; USNM 159492. Locality M1087. (See figs. 

16-23.) 

28, 29. Pycnostylid coral. 

Calice views of same corallite ( x 1, x 1 1f:z). Silurian, lower part of Lone Mountain Dolomite; southern 

Sulphur Spring Range, Nev. Locality M1121. 

30. Pycnostylus sp. 

Longitudinal thin section ( x 1 1f:z) . Silurian, lower part of Lone Mountain Dolomite, southern Sulphur 

Spring Range, Nev. Locality Ml148. 

31. Medium-dark-gray carbonaceous Lone Mountain Dolomite containing silicified Entelophyllum engelmanni 

subsp. b ( x lf:z) . Locality M1087. (See figs. 16-23.) 

32. Dark-gray carbonaceous Lone Mountain Dolomite containing fragmentary rugose corals, probably Entelophyllum (slightly reduced)_ Upper part of Lone Mountain Dolomite; east side of Charcoal Gulch, Lone 

Mountain, Eureka County, Nev. Locality M1122_ 
GEOLOGICAL SURVEY 

5 

6 

16 

20 

23 

28 

PROFESSIONAL PAPER 808 PLATE 11 

3 

2 

4 

9 7 8 

18 15 

14 

19 

27 

24 

26 

29 30 

ATRYPA, CAMAROTOECHIA, SALOPINA, TRYPLASMA, ENTELOPHYLLUM, 

PYCNOSTYLID CORAL AND? PYCNOSTYLUS 

10 

'.1/J;'l' // .. ·\ ; J I ~ ' (} I .~ 

11 

12 

13 

32 

31 
PLATE 12 

FIGURES 1-19. Howellella smithi Waite. 

1-3. Oblique posterior, anterior, and dorsal views ( x 1%); USNM 159493. 

4, 5. Dorsal and ventral views ( x 1%); USNM 159494. 

6, 7. Ventral valve interiors showing dental lamellae ( x 2); USNM 159495. 

8. Dorsal valve interior ( x 2); USNM 159496. 

9, 10. Dorsal and ventral views ( x 1%); USNM 159497. 

11, 12. Dorsal and ventral views ( x 2); USNM. 159498. 

13. Dorsal exterior ( x 2); USNM 159499. 

14. Dorsal exterior ( x 2); USNM 159500. 

15. Dorsal exterior ( x 1%); USNM 159501. 

16. Dorsal exterior ( x 4); USNM 159502. 

17. Dorsal exterior ( x 2); USN M159503. 

18. Dorsal exterior ( x 2); USNM 159504. 

19. Dorsal exterior ( x 3); USNM 159505. 

Late Silurian, upper part Lone Mountain Dolomite; southern Fish Creek Range, Nev. Locality M1087. 

20-24. Howellella pauciplicata Waite. 

20-22. Dorsal, ventral, and posterior views ( x 2) ; USNM 159506. 

23, 24. Dorsal and ventral views ( x 6); USNM 159507. 

Late Silurian, upper part Lone Mountain Dolomite; southern Mahogany Hills, Nev. Locality M1112. 

25. Medium-dark-gray upper Lone Mountain Dolomite containing abundant silicified Howellella smithi ( x %) . 

Locality M1087. (See figs. 1-19). 

26, 27. ?Hyattidina sp. 

Dorsal and posterior views ( x 2); USNM 159508. Late Silurian, upper part of Lone Mountain Dolomite; 

southern Fish Creek Range, Nev. Locality M1113. 

28, 29. ?Hyattidina sp. 

Dorsal and lateral views ( x 2); USNM 159509. Locality M1113. (See figs. 26, 27.) 

30-32. ?Hyattidina sp. f. 

Dorsal, anterior, and lateral views ( x 3); USNM 159510. Locality M1087. (See figs. 1-19.) 

33. ?Hyattidina sp. f. 

Ventral view of peeled shell ( x 4) showing part of spiralium with lateral apices. USNM 159511. Locality 

M1087. (See figs. 1-19.) 

34-37. Hindella sp. a. 

Dorsal, ventral, lateral, and anterior views ( x 2); USNM 159512. Locality M1087. (See figs. 1-19.) 

U. S. GOVEHNMENT PRINTING OFFICE: 1973 0 - 506 · 612 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 808 PLATE 12 

2 29 

28 

26 30 

4 3 27 

31 

32 

33 

5 34 35 36 37 

6 8 20 21 23 

16 

7 9 22 

24 

17 

11 

10 15 

18 

12 13 14 19 25 

HOWELLELLA, ? HYATTIDINA, AND HINDELLA