Silurian Rugose Corals 

of the Central and 

Southwest Great Basin 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 777 

Silurian Rugose Corals 

of the Central and 

Southwest Great Basin 

By CHARLES W. MERRIAM 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 777 

A stratigraphic-paleontologic investigation of rugose 

corals as aids in age detern2ination and correlation 

of Silurian rocks of the Great Basin with those 

of other regions 

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. 73-600082 

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

Washington, D.C. 20402- Price $2.15 (paper cover) Stock Number 2401-00363 
CONTENTS 

Abstract---------------------------------------------------------------------------

Introduction --------------------------------------------------------------------

Purpose and scope of investigation--------------------------------

History of investigation -----------------------------------------------

Methods of study--------------------------------------------------------

Acknowledgments-------------------------------------------------------

Identification of the Silurian System in the Great Basin----------

Areal distribution of Great Basin Silurian coral-bearing rocks--

Depositional and faunal facies of Great Basin Silurian coralbearing rocks ----------------------------------------------------------------

Great Basin Silurian reference sections ---------------------------------

Mazourka Canyon reference section--------------------------------

Ikes Canyon reference section----------------------------------------

Roberts Creek Mountain reference section-----------------------

Coal Canyon reference section---------------------------------------

Northern Panamint Range reference section--------------------

Lone Mountain reference section---------------------·--------------

Rugose coral zonation of the Great Basin Silurian-----------------

Zone A----------------------------------------------------------------------

Zone B ----------------------------------------------------------------------

Zone C ----------------------------------------------------------------------

Zone D----------------------------------------------------------------------

Zone E ----------------------------------------------------------------------

Stratigraphy and rugose corals of the Lone Mountain and 

Laketown Dolomite -------------------------------------------------------

Rugose corals and geologic correlation of Silurian rocks within 

the Great Basin -------------------------------------------------------

Zone A----------------------------------------------------------------------

Zone B ----------------------------------------------------------------------

Zone C ----------------------------------------------------------------------

Zone D----------------------------------------------------------------------

Zone E ----------------------------------------------------------------------

Great Basin Rugosa and correlation with distant Silurian rocksZone A----------------------------------------------------------------------

Zone B ----------------------------------------------------------------------

Zone C----------------------------------------------------------------------

Zone D----------------------------------------------------------------------

Zone E ----------------------------------------------------------------------

Correlation of Lone Mountain and Laketown Dolomite----------

Age conclusions based 6n Silurian Rugosa------------------~--------­

Comparison of Silurian coralline rocks in the Great Basin 

with those of other regions----------------------------------------------

Depositional features of Great Basin Silurian coralline rocks 

in relation to the reef problem -----------------------------------------

Dasycladacean algae in Great Basin Silurian coralline depositsClassification of Great Basin Silurian Rugosa -----------------------

Systematic and descriptive paleontology -------------------------------

Family Streptelasmatidae ---------------------------------------------

Rhegmaphyllum---------------------------------------------------

Brachyelasma -------------------------------------------------------

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Systematic and descriptive palaeontology-Continued 

Family Streptelasmatidae-Continued 

Page 

Dalmanophyllum ------------------------------------------------- 32 

Family Stauriidae ------------------------------------------------------- 32 

Cyathoph y llo ides-------------------------------------------------- 32 

Palaeophyllum ----------------------------------------------------- 33 

Family Pycnostylidae--------------------------------------------------- 34 

Stylopleura, new genus------------------------------------------ 34 

Family Tryplasmatidae------------------------------------------------ 36 

Try plasma----------------------------------------------------------- 36 

Solitary-rugate group -------------------------------------- 37 

Fasciculate-cylindrical group---------------------------- 37 

Rhabdocyclus------------------------------------------------------- 38 

Palaeocyclus -------------------------------------------------------- 39 

Zelophyllum -------------------------------------------------------- 40 

Family Kodonophyllidae---------------------------------------------- 40 

Subfamily Kodonophyllinae ----------------------------------- 40 

Kodonophyllum --------------------------------------------- 40 

Subfamily Mycophyllinae--------------------------------------- 41 

Mucophyllum ------------------------------------------------ 41 

Family Arachnophy llidae --------------------------------------------- 42 

Arachnophyllum -------------------------------------------------- 42 

Family Lykophyllidae ------------------------------------------------- 43 

Ryderophyllum ---------------------------------------------------- 44 

Pycnactis ------------------------------------------------------------- 45 

Family Cystiphyllidae-------------------------------------------------- 45 

M icroplasma -------------------------------------------------------- 46 

Family Goniophyllidae------------------------------------------------ 46 

Rhizophyllum ------------------------------------------------------ 46 

Family Kyphophyllidae ----------------------------------------------- 46 

Kyphophyllum ----------------------------------------------------- 47 

Petrozium------------------------------------------------------------ 47 

Entelophyllum ----------------------------------------------------- 48 

Entelophylloides--------------------------------------------------- 49 

Subgenus Prohexagonaria, new subgenus----------- 50 

Neomphyn1a -------------------------------------------------------- 51 

Tonkinaria, new genus------------------------------------------ 51 

Family Chonophyllidae ----------------------------------------------- 52 

C honop hy llum ----------------------------------------------------- 52 

Family Endophyllidae ------------------------------------------------- 54 

A us tra lop hy llu m -------------------------------------------------- 54 

Subgenus Toquimaphyllum, new subgenus-------- 54 

Family Acervulariidae-------------------------------------------------- 55 

Diplophyllum ------------------------------------------------------ 56 

Genera with no family designation-------------------------------- 56 

Salairophyllum ---------------------------------------------------- 56 

Denayphyllum, new genus------------------------------------- 56 

Locality register---------------------------------------------------------------- 57 

References ----------------------------------------------------------------------- 59 

Index------------------------------------------------------------------------------ 63 

III 
IV CONTENTS 

ILLUSTRATIONS 

[Plates follow index] 

PLATE 1. Dalmanophyllum, Brachyelasma, Rhegmaphyllum, Palaeocyclus, Rhabdocyclus, and Tryplasma. 

2. Tryplasma, Palaeophyllum?, Stylopleura, and Maikottia. 

3. Stylopleura and Palaeophyllum. 

4. Kodonophyllum, Diplophyllum?, and Crassilasma?. 

5. Mucophyllum, Arachnophyllum, and Cyathophylloides. 

6. Ryderophyllum, Crassilasma?, and Pycnactis. 

7. Tonkinaria, Microplasma?, Rhizophyllum, and Denayphyllum. 

8. Chonophyllum and Cyathactis?. 

9. Entelophylloides (Prohexagonaria) and Petrozium. 

10. Entelophyllum and Tryplasma. 

11. Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

12. Australophyllum (Toquimaphyllum), Australophyllum, and Salairophyllum?. 

13. Kyphophyllum nevadensis, n. sp., and Neomphyma crawfordi, n. sp. 

14. Kyphophyllum and Australophyllum. 

15. Stylopleura, Rhabdocyclus, Palaeocyclus, Pycnostylus, Entelophyllum, and Australophyllum (Toquimaphyllum). 

16. Brachyelasma, Stylopleura?, and Verticillopora. 

Page 

FIGlTRE 1. Index map showing principal areas of Silurian coral-bearing rocks referred to in text----------------------------------------------------- 3 

2. Map of Great Basin showing major lithologic belts, distribution of Silurian reference sections, and coral localities------------- 6 

3. Sketch of the Mazourka Canyon reference section, northern Inyo Mountains, Calif--------------------------------------------------------- 9 

4. Sketch of the Roberts Creek Mountain reference section, Roberts Mountains, Nev---------------------------------------------------------- 11 

5. Comparative diagram illustrating present usage of the stratigraphic name Lone Mountain Dolomite-------------------------------- 13 

6. Correlation chart showing Great Basin Silurian coral zones and common rugose coral genera ----------------------------------------- 15 

7 .. Correlation chart of Great Basin Silurian formations, showing lettered coral zones-------------------------------------------------------- 18 

8. Correlation chart showing Gotland stratigraphic units and rugose corals related to Great Basin forms------------------------------ 23 

9. Diagram showing stratigraphic occurrence of characteristic Great Basin Silurian rugose coral genera-------------------------------- 27 
SILURIAN RUGOSE CORALS OF THE CENTRAL AND 

SOUTHWEST GREAT BASIN 

By CHARLES w. MERRIAM 

ABSTRACT 

Corals representing 13 families of Silurian Rugosa from limestones 

and dolomites of the central and ~outhwe~t Great Basin are described, 

classified, and figured. Coral-beating Silurian beds of this province occur 

in two contrasting carbonate rock facies: the eastern dolomite belt and the 

intermediate limestone hell. A third major Silurian rock suite 

characterizes the western, or Pacific Border, belt, which extends from the 

western Great Basin to northern California and southeastern Alaska. 

On the basis of rugose corals and associated fossils, the Great Basin 

Silurian is subdivided as five coral zones, lettered A through E in 

ascending order. These provisional zones are a result of detailed stratigraphic studies and geologic mapping of reference sections in areas 

extending from the Inyo Mountains northeastward to the Roberts 

Mountains and northern Simpson Park Mountains. 

Of importance environmentally, as well as with the identification and 

correlation of Great Basin Silurian, are the large dasycladacean algae 

associated with Rugosa. As the genus r'erticillopora, these algae appear 

to have peaked in coral zone D. 

Rugose corals ot special importance in correlation with distant 

Silurian rocks are Palaeocyclus, Dalmanophyllwn, Kodonophyllwn, 

Mucophyllum, Arachnophyllwn, Toquimaphyllwn, and the 

lykophyllids. The closest foreign correlations are with the Gotland 

section, a Silurian carbonate standard for western Europe. Fairly close 

similarities are recognized with Silurian of Czechoslovakia and Eastern 

Ausu·alia. 

INTRODUCTION 

Monographic treatment of Silurian Rugosa emerges as 

a late byproduct of Great Basin Silurian and Devonian 

stratigraphy. Beginning in 1933, geologic mapping of 

middle Paleozoic exposures in the central and southwest 

Great Basin stimulated search for dependable means of 

identifying and subdividing monotonous Silurian 

carbonate rocks. Above all, there existed need for definitive criteria whereby Ordovician and Devonian dolomites 

might be separated frmn seemingly identical carbonate 

strata of the Silurian in areas of complex geologic 

structure. Rugose corals seemingly filled this need. 

Progress was slow during initial stages of the 

investigation because of discouraging internal preservation of silicified coral material from dolomite. Later 

discoveries of limestone faunas better suited to thin section 

study have largely removed these obstacles. 

Mapping in recent years over large areas of the Great 

Basin by several U.S. Geological Survey field parties has 

brought to light numerous coral-bearing Silurian 

exposures. Resultant correlation and integration of data 

from the many isolated occurrences has made possible a 

composite Silurian sequence based largely on coral 

faunas. This succession parallels, in some respects, that of 

the western European Gotland standard. 

Partly empirical, partly inferential, and assuredly 

provisional, the proposed Great Basin coral succession 

requires the field and laboratory testing which will follow 

in the course of continued mapping and stratigraphic 

study of these yet little known rocks. In its present state the 

composite scheme is nonetheless a workable, albeit looseknit, framework for evolutionary and taxonomic research 

upon Cordilleran Silurian Rugosa, the primary objects of 

this study. 

Research upon Great Basin Silurian Rugosa has 

proceeded concurrently with investigation of Pacific 

Border province Silurian corals of the Klamath Mountains 

and Alaska, and with tnonographic study of the Early and 

early Middle Devonian Rugosa of the central Great Basin. 

Collectively, these studies provide opportunity for 

comparison of coral biotas of different facies and a means 

of evaluating expected paleontologic changes near the 

Silurian-Devonian boundary. 

PURPOSE AND SCOPE OF INVESTIGATION 

This report describes and illustrates representative 

Silurian Rugosa and discusses their application to stratigraphic zoning and correlation of Great Basin Silurian 

rocks. Among ancillary objectives are classification of 

Silurian regose corals, determination of their 

environmental significance in connection with depositional facies, and application of coralline biofacies data to 

problems of geologic correlation. Finally, the Rugosa are 

considered in the light of their value to interpretation of 

Silurian historical geology in the Great Basin province 

and the Cordilleran belt generally. 

HISTORY OF INVESTIGATION 

Presence of halysitid chain corals was ample justification for Silurian age assignment by pioneer geologists 

attached to early Great Basin surveys, up to and including 

the Eureka district work by Hague and Walcott (Hague, 

1892; Walcott, 1884). Some halysitid-bearing rocks 

initially called Silurian are doubtless Late Ordovician 

1 
2 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

(Richmondian) of today; the Silurian System was more 

inclusive prior to adoption of the Ordovician as an independent system by the U.S. Geological Survey. So far as 

known, the Rugosa did not figure in determining the 

Silurian age of the Lone Mountain Dolomite (restricted) 

until current studies. Coral faunas of the Laketown 

Dolomite at Gold Hill, Utah, were known to include 

Rugosa when reported upon by Kirk (in Nolan, 1935, p. 

18). With the examination of Silurian limestones in the 

Roberts Mountains, Nev. (fig. 1), during the 1930's 

(Merriam, 1940, p. 12), rugose corals of these somewhat 

more hospitable facies became available for study. Duncan 

(1956) documented all known occurrences of Great Basin 

Silurian Rugosa up to the 1950's. 

Geologic mapping of the Cerro Gordo mining district 

beginning in 1946 (Merriam, 1963a) provided opportunity 

for stratigraphic and paleontologic study of coral-bearing 

Silurian rocks of the Inyo Mountains and the adjacent 

Panamint Range (fig. 1). At that time the Mazourka 

Canyon reference section was measured, and rugose coral 

collections from the Vaughn Gulch Limes tone were made. 

Geologic mapping and stratigraphic investigation of 

Paleozoic strata in the northern Panamint Range by J. F. 

l\IcAllister beginning in 1937 (McAllister, 1952) provided 

much of the best Silurian rugose coral material from the 

Hidden Valley Dolomite. Current mapping in the Funeral 

Mountains by McAllister for the U.S. Geological Survey 

has resulted in additional collecting of coral material from 

these rocks. 

Renewal of geologic mapping in Paleozoic rocks of 

central Nevada came with initiation of the Kobeh Valley 

study by T. B. Nolan and Merriam in 1958, giving 

opportunity for stratigraphic work and fossil collecting in 

the Lone Mountain Dolomite of areas within and adjacent 

to the Eureka mining district (Merriam, 1963b). During 

this period, comparative studies dealt also with Silurian 

coral-rich limestone facies of the Roberts Mountains, the 

Toquima Range, and the Simpson Park Mountains. 

In 1968 the U.S. Geological Survey initiated a stratigraphic study by T. E. Mullens of the Roberts Mountains 

Formation in north-central Nevada. Under a 

comprehensive program bearing upon problems of ore 

occurrence and genesis, this investigation was undertaken to support detailed geologic mapping of the 

structurally complex terrane encompassing the Cortez and 

Carlin gold mines. Participation by Merriam has entailed 

identification of rugose corals and other fossils in Silurian 

and Early Devonian strata. In these economically important areas, the Late Silurian faunas of coral zone E are 

represented and the overlying Helderbergian (Early 

Devonian) Rabbit Hill Limestone has been recognized. 

Research upon Silurian Rugosa of the Klamath Mountains, northern California, and of the islands of southeastern Alaska was in progress during this investigation. 

Comparison with these Pacific Border Silurian rugose 

corals has had an important bearing upon the coral 

taxonomy and upon correlation and facies analysis of the 

Great Basin Silurian rocks. 

Silurian Rugosa in dolomite facies of the Sandpile 

Group of northwest Canada have been investigated by 

Norford (1962), pro\'iding for the first time a basis for 

comparison of Great Basin Silurian with Silurian of the 

northern Cordilleran region. 

Oliver's (1964) contribution on the slipper coral 

Rhizophyllum brings together what is known of this diagnostic rugose coral genus in the central Great Basin, the 

Inyo Mountains, the Klamath Mountains, and Alaska. 

METHODS OF STUDY 

Stratigraphic investigation. conducted jointly with 

geologic mapping is the background of these Silurian 

coral studies. The framework of vertical succession and 

coral evolution is of necessity theoretical, but detailed 

mapping procedures help minimize the amount of 

inference which attends stacking of composite sections in 

a region of complex geologic structure and rapid facies 

change. Section measuring and fossil collecting without 

mapping control are far less dependable; experience 

demonstrates that the better and tnore complete sections 

for measurement are likely to be disclosed during later 

phases of a mapping program. 

Reference stratigraphic sections employed in zoning the 

Great Basin Silurian corals are in geologically mapped 

areas or in areas where mapping is in progress. Some of the 

fossil collections were made close to Brunton compass and 

tape traverses within mapped areas. Other collections are 

weathered surface material from outcrop bands 200 or 

more feet wide and may include float from a greater 

interval. Attempts were made to find the same species in 

situ. 

Stratigraphic and taxonomic studies of Silurian Rugosa 

depend upon comparison with species from classic 

European sections, among which are those of Gotland, 

Sweden, and of Czechoslovakia. The Gotland section (fig. 

8) is a world Silurian yardstick for the coral-bearing 

carbonate facies. Since Wedekind's 1927 treatise on 

Rugosa of northern Gotland there have been no 

comprehensive paleontologic studies of entire Gotland 

rugose coral faunas in relation to field stratigraphy. Most 

Gotland Rugosa still require photographic illustration of 

thin sections, and much additional detail is needed on 

field occurrence, stratigraphic ranges of species, and 

faunal association. The same applies to the 

Czechoslovakian Rugosa, known mainly from exterior 

figures (Po~ta, 1902) and requiring thin-section study and 

establishment of species ranges. 

Study of fine structure of the Rugosa depends on preservation of material, which ranges from retention of minute 
380 

36" 

INTRODUCTION 

' ' " ' 

Hale;(0 

IDAHO 

0 Tonopah 

•22 ' '\. 0Beatty 

21 .20 ' .18 

. ' oCerro Gordo'\. 

19. ' ~as Vegas0 

' "' ' ' Bakersfield oKingman 

0 50 100 150 MILES 

EXPLANATION 

1. Kobeh Valley at Lone Mountain 

2. Roberts Creek Mountain in the 

Roberts Mountains 

3. Simpson Park Mountains, 

north end at Coal Canyon 

4. Fish Creek Range, south end 

5. Antelope Valley 

6. Toquima Range at Ikes Canyon 

7. Carlin gold mine area 

8. Ruby Mountains, southern part 

9. Antelope Peak, Elko County 

10. Ely Springs Range 

11. Confusion Range 

12. San Francisco district 

13. Thomas Range 

14. Deep Creek Range at Gold Hill 

15. East Tintic Mountains 

16. Logan area 

17. Randolph area 

18. Bare Mountain area 

19. Funeral Mountains 

20. Panamint Range, northern part 

21. Inyo Mountains at Cerro Gordo mine 

22. Inyo Mountains at Mazourka Canyon 

23. Taylorsville area 

24. Northeast Klamath Mts; Ga:z;elle area 

FIGURE 1.-Index map showing principal areas of Siluriancoral-bearing rocks referred to in text. 

3 

Flagstaff0 
4 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

thin-section detail of wall features in unsilicified limestone material to complete loss of fine structure in 

silicified corals from dolomite. Many of the dolomite 

corals were obtained by block etching; these specimens 

usually make poor thin sections. Sections of unetched 

dolomite corals may reveal patches of fine structure where 

silica replacement is incomplete. To avoid loss of detail in 

the silicified corals, thicker slices are usually more satisfactory. 

Silicified material well enough preserved for study of 

the internal characters is uncommon; therefore, characterization is based to a considerable extent on gross external 

features, and quantitative morphoiogic studies must await 

more extensive collecting. 

Description and classification of Silurian rugose corals 

here dealt with are based on gross features of exterior and 

interior. In some families, such as the Tryplasmatidae and 

Kodonophyllidae, fine structure of wall and septa will 

eventually be useful taxonomically (Wang, 1950; Kato, 

1963). With regard to photographic illustration, enlargement of critical details to X 8 or greater is of value for 

identification and future taxonomic investigation. 

. ACKNOWLEDGMENTS 

Acknowledgment is made to those U.S. Geological 

Survey field geologists engaged in mapping of Great Basin 

Silurian rocks whose fossil collections added n1aterially to 

this report. Among these contributors and the areas of 

their mapping efforts are ]. F. McAllister, the northern 

Panamint Range and the Funeral Mountains, Calif.; D. C. 

Ross, the northern Inyo Mountains, Calif.; H. R. 

Cornwall and F. ]. Kleinhampl, Bare Mountain, Nev.; R. 

K. Hose, the Confusion Range, Utah; and Ronald Willden 

and R. W. Kistler, the Ruby Mountains, Nev. Corals from 

the Simpson Park Mountains and the Toquima Range, 

Nev., were contributed by A.]. BoucotandJ. G. Johnson. 

The writer thanks Helen Duncan and Jean M. Berdan of 

the U.S. Geological Survey for assistance in connection 

with Entelophylloides and for material representing this 

genus collected by them from the Cobleskill and Keyser 

Limestones. 

The writer also thanks Prof. S. W. Muller and Stanford 

University for use of the McAllister thesis fossil collections from the northern Panamint Range. 

All fossil photographs are the work of Kenji Sakamoto 

of the U.S. Geological Survey. 

Thin sections used during the last 2 years of this study 

were prepared by Robert G. Shely. 

IDENTIFICATION OF THE SILURIAN SYSTEM IN 

THE GREAT BASIN 

The Silurian System in the central and eastern Great 

Basin is part of a fairly continuous saccharoidal dolomite 

section that includes Late Ordovician and Devonian strata 

as well. These somewhat n1onotonous and not infrequently barren dolomites occupy a stratigraphic 

interval between the Pogonip Group or the Eureka 

Quartzite and various horizons of the Middle Devonian. 

The lowest dolomites of this three-system sequence are 

readily distinguishable as Late Ordovician by a 

widespread Richmondian brachiopod-coral fauna containing abundant streptelasmid and halysitid corals. The 

top of the Silurian within the upper third of the sequence 

is less readily distinguishable, for above the uppermost 

fossil zone of unequivocal Silurian age no diagnostic 

faunas of Early and early Middle Devonian age have thus 

far been recognized in the dolomite facies. Most of the 

well-documented Early Devonian fossils have come from 

limestone or dolomiticiiimestone facies of the west-central 

and southwest Great Basin. 

Halysitid corals and large pentameroid brachiopods of 

the Conchidium and Virgiana types are the commonly 

accepted criteria of Silurian age in the three-system 

dolomite succession. Halysitids have been considered 

more indicative of the lower beds, and the large 

pentameroids more characteristic of the higher Silurian. 

In view, however, of the great abundance of halysitids in 

the Richmondian or Late Ordovician beds, these tabulates are not definitive unless identified generically and 

specifically. 

Silurian faunas of the Cordilleran belt have received 

little attention by the paleontologist and stratigrapher. 

Until recently, scarcity and poor preservation of fossils in 

dolomite discouraged serious paleontologic study. 

Routine fossil idenfifications for stratigraphic purposes 

were always provisional and uncertain-the species 

assigned with a query to a described fossil of a distant 

province, and the genera long-ranging and in most 

instances of doubtful value for system discrimination. 

Except possibly for graptolites in appropriate facies, there 

has been almost no paleontologic basis for zoning or 

stratigraphic subdivision of the Great Basin Silurian; in 

fact, paleontologic identification of the system itself has in 

some areas remained in doubt. Thus far, evidence from 

graptolites is lacking in the prevailingly dolomitic facies 

of the central and eastern Great Basin. 

Whereas most of the identified Silurian of the Great 

Basin is marine dolomite,'mappingiin,thewest-central and 

southwestern parts of this province discloses areas of 

Silurian and Early Devonian limestone rich in fossils, of 

which many of the more distinctive are rugose corals. 

Northwest of the Great Basin, from the north end of the 

Sierra Nevada to the Klamath Mountains, there exists a 

third Silurian stratified rock suite in which siliceous 

clastic rocks of the graywacke type prevail, and where all 

carbonate rocks are nondolomitic. In limestone lenses of 

this graywacke province, the rugose corals are again 

among the distinctive Silurian indicators. 
DEPOSITIONAL AND FAUNAL FACIES 5 

AREAL DISTRIBUTION OF GREAT BASIN 

SILURIAN CORAL-BEARING ROCKS 

Silurian marine rocks of the southwest Cordillera, 

including the Great Basin, are distributed in three belts, 

contrasted with respect to lithology and faunas. These 

belts are the (1) eastern dolomite belt, (2) intermediate 

limestone belt, and (3) western, or Pacific Border, 

graywacke belt. Paleogeographically, the boundary trends 

of these belts are poorly defined, but they appear to have 

extended across the Great Basin province in north to 

northeasterly directions (fig. 2), not necessarily in alinement with existing orographic features. A border zone 

between the intermediate limestone belt and the eastern 

dolomite belt n1ay be fairly accurately delineated in the 

vicinity of the Inyo Mountains and the Panamint Range, 

and in the Roberts Mountains and east of the Monitor 

Range. The boundary relationship of the intermediate 

limestone belt and the western graywacke belt is 

inferential, mainly because of cover by younger rocks. 

Coral faunas in the three Silurian belts differ because of 

facies and by reason of the vagaries of faunal dispersal and 

paleogeography. 

Eastern dolomite belt.-This belt includes Silurian 

strata of the southern and eastern Great Basin and much of 

the central part that have been described as Hidden Valley 

Dolomite, Lone Mountain Dolomite, and Laketown 

Dolomite. In general terms, these rocks will be referred to 

hereafter as the Lone Mountain-Laketown facies. Only in 

the east-central and southwest Great Basin have the coral 

faunas of the eastern dolomite belt been studied 

intensively. However, in several mining districts of the 

eastern Great Basin, Silurian corals are fairly abundant, 

and provisional generic identifications have been made. 

Intermediate limestone belt.-In such areas as the 

northern Inyo Mountains, Toquima Range, Monitor 

Range, Simpson Park Mountains, and the Roberts 

Mountains, the Silurian is represented by limestones. 

These limestone beds have yielded the greater part of the 

well-preserved rugose coral material herein described. 

Plotted distribution of limestone occurrences relative to 

occurrences of the eastern dolomite belt suggests that 

depositional change from dolomite to limestone took 

place in a westerly to northwesterly direction. Only in the 

Roberts Mountains is there evidence of intertonguing of 

Silurian dolomite and limestone facies, and there the 

structural conditions related to major thrusting are unfavorable for stratigraphic deductions. Recent discoveries 

of Silurian coral-bearing beds in the north-central Great 

Basin are mostly within the intermediate limestone belt, 

although those in the Ruby Mountains lie on the eastern 

dolomite side. 

Western, or Pacific Border, graywacke belt.-In the 

western Great Basin occurrence of the Pacific Border 

graywacke belt beneath younger rocks is mainly 

inferential; the nearest exposures of such beds are at the 

north end of the Sierra Nevada near Taylorsville, Calif. 

Ordovician black shales and arenaceous deposits are 

known in the western Great Basin, and clastic deposition 

may have persisted into Silurian time in that part of the 

province. From the Taylorsville area northwest through 

the Klamath Mountains of northernmost California, the 

Silurian rocks of the Pacific Border province cmnprise 

argillite, graywacke, conglomerate, bedded chert, and 

fairly pure limestone. There is no dolomite. Much of the 

graywacke was probably derived from more or less contemporaneous volcanic rocks. Silurian strata of the Pacific 

Border graywacke suite are best exposed in southeastern 

Alaska, where they resemble those of the northern California region. In southeastern Alaska, mafic volcanic rocks 

with pillow structure are interbedded with the Silurian 

graywacke. All carbonate rocks are, again, nondolomitic. 

Silurian rugose coral faunas of the Pacific Border province differ to a considerable degree from those of the 

adjoining intennediate limestone belt on the east and 

probably to a greater extent from those of the eastern 

dolomite belt. The Rugosa of the Klamath Mountains 

Sililurian are described in a separate report (Merriam, 

1972.) 

DEPOSITIONAL AND FAUNAL FACIES OF GREAT 

BASIN SILURIAN CORAL-BEARING ROCKS 

Two contrasting marine depositional and faunal facies 

are recognized in many parts of the world where the 

Ordovician and Silurian Systems are well represented. 

Faunally speaking, these are referred to in England as the 

graptolitic facies and the shelly facies (Jones, 1933, p. 474). 

The graptolitic facies in both geologic systems is commonly black, organic clay shale; the shelly 

facies-characterized by predon1inance of heavier shelled 

organisms, such as Mollusca, brachiopods, and the 

corals-is typified by carbonate rock and marls tone. Facies 

contrasts of this kind are especially impressive in the Great 

Basin Ordovician, where black shales, siltstones, cherts, 

and minor limestones of graptolitic sequences, such as the 

Vinini Formation, occupy separate outcrop belts and form 

thrust sheets of exceedingly complex structure. Carbonate 

shelly facies, being more competent structurally, have 

been less intensely deformed. In places the two Ordovician 

facies come together in thrust fault contact. Wholly 

graptolitic facies of the Silurian, although poorly understood, appear to be less extensive than other facies in the 

Great Basin. Limestone and dolomite, which include 

shelly facies only, make up the greater part of the known 

Silurian. Graptolitic facies of this system are mainly 

calcareous shale and thinly bedded calcareous siltstone 

that are lithologically unlike the very extensive noncalcareous clay shale, argillite, and chert of the Ordovician 

graptolitic sequences. In the western part of the Great 
6 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Flagstaff0 

0 50 100 150 MILES 

FIGURE 2.-Major lithologic belts, distribution of Silurian reference sections, and coral localities in the Great Basin. 

Basin, some of the localized outcrops of Silurian limy 

shale and platy siltstone yield only graptolites. Other 

Silurian graptolite deposits are more sporadic, occurring 

as occasional calcareous shale tongues or interbeds in 

limestone units wherein the shelly facies predominate. In 

some areas of almost exclusively graptolitic facies, such as 

the Ordovician Vinini, it is not improbable that 

graptolite-bearing clay shale and chert deposition 

persisted on into Silurian time. 

Eastern dolomite belt.-Silurian dolomites of this belt 

(Staatz and Osterwald, 1959) range in thickness from 2,500 

feet at Lone Mountain, Nev., to 1,200feetin western Utah. 

Thick-bedded blocky gray dolomite of saccharoidal texture is characteristic; most of these dolomites have a rather 

uniform and monotonous appearance and lack easily 

recognizable and persistent lithologic changes by which 

they might conveniently be subdivided into map units. 

Argillaceous beds are uncommon within the eastern 
DEPOSITIONAL AND FAUNAL FACIES 7 

EXPLANATION 

G Type areas of Silurian marine rock units 

1. Lone Mountain Dolomite 

2. Laketown Dolomite 

3. Bluebell Dolomite (Silurian part) 

4. Hidden Valley Dolomite (Silurian part) 

5. Laketown Dolomite: four described 

members in Thomas Range, Utah 

6. Roberts Mountains Formation 

7. Masket Shale of Kay and Crawford (1964) 

8. Vaughn Gulch Limestone 

9. Montgomery Limestone 

10. Gazelle Formation 

11. Trail Creek Formation 

Silurian rugose coral genera 

o Late Silurian 

!I Toquimaphyllum and related corals 

~ Rhizophyllum 

1:!1 Entelophyllum 

101 Stylopleura 

o Lykophyllids 

m Zelophyllum 

t:>. Middle Silurian 

A Lykophyllids 

"' Zelophyllum 

o Lower Silurian 

Q Palaeocyclus 

<D Arachnophyllum 

e Dalmanophyllum 

Silurian dasycladacean algae 

Late Silurian 

• V erticillopora 

Middle Silurian 

• Verticillopora 

Prevailing lithology 

Sssl, shale, sandstone, and limestone 

Sss, shale and sandstone 

Sl, limestone 

Sd, dolomite 

Sdq, dolomite and quartzite 

Silurian localities 

1. Mazourka Canyon, northern Inyo Mts 

dolomite belt; toward the west occur sporadic lenses of 

clean lime-cemented quartz sandstone or quartzite. 

Continuous diagenetic dolomite accumulation without 

significant stratigraphic discontinuity during most of the 

Silurian suggests a stable m.arine environment, little 

disturbed by crustal deformation, under conditions commonly ascribed to the "stable shelf." 

Fossils are scarce or absent throughout most of the 

eastern dolomite. Silicified fossil material is locally 

abundant, especially in scattered bodies of dark-gray 

carbonaceous dolomite surrounded by the normal, lighter 

gray rock. Within these highly organic lenses and pockets, 

corals and brachiopods became silicified early and 

mysteriously survived destruction during the magnesian 

recrystallization. Fossil assemblages of these carbonaceous 

2. Cerro Gordo area, southern Inyo Mts 

3. Ubehebe Peak area, northern Panamint Range 

4. Andy Hills, northern Panamint Range 

5. Whitetop Mtn., northern Panamint Range 

6. Funeral M ts 

7. Bare M tn. area 

8. Pahranagat Range 

9. Ely Springs Range 

10. Sunnyside 

11. Dobbin Summit 

12. lkes Canyon 

13. Austin area 

14. Copenhagen Canyon 

15. Southern Fish Creeks Range 

16. Southern Mahogany Hills 

17. Lone Mountain, Eureka County 

18. Southern Sulphur Spring Range 

19. Roberts Creek Mountain 

20. Coal Canyon, northern Simpson Park Mts 

21. Ruby Mts 

22. Maggie Creek, Eureka County 

23. Antelope Peak, Elko County 

24. Pequop Mts 

25. San Francisco district 

26. Ibex Hills 

27. Kings Canyon, Confusion Range 

28. Confusion Range, southern part 

29. Thomas Range 

30. East Tintic Mts 

31. Gold Hill district 

32. Stockton and Fairfield areas 

33. Logan area 

34. Randolph area 

35. Elbow Canyon 

36. Rock Creek, Lost River Range 

37. Grouse Creek, Lost River Range 

38. Bayhorse quadrangle, east-central part 

39. Bay horse quadrangle, north-central part 

40. Bayhorse quadrangle, central part 

41. Trail Creek 

42. Mount Morrison area 

43. Northeast Klamath Mts, Willow Creek area 

44. Northeast Klamath Mts, Horseshoe Gulch area 

45. Taylorsville area 

46. Weaverville quadrangle, Douglas City area 

47. Knownothing Creek, Cecilville area, 

Klamath Mts 

dolomite lenses differ in character from those in approximately correlative limestone facies of the intermediate limestone belt. Among rugose corals, 

Entelophyllum is the best known in the eastern dolomite 

belt; in terms of biofacies the eastern dolomites are referred 

to as the Entelophyllum facies, as this coral genus is not a 

common element of the intermediate limestone belt to the 

west. 

Intermediate limestone belt.-Medium- to dark-gray 

and bluish-gray limestones of this Silurian belt have been 

traced from the northern Inyo Mountains, Calif., to the 

Tuscarora Mountains of northern Nevada. Ranging in 

thickness from 1,200 feet in the Inyos to more than 2,000 

feet in the Simpson Park Mountains and the Roberts 

Mountains, the limestones of this belt are here and there 
8 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

rich in well-preserved rugose corals and other fossils. In 

these facies are to be found the more continuous marine 

reference sections. Platy and flaggy to thick-bedded limestones are characteristic, with relatively few massive 

members. Bioclastic facies are common; the contributing 

organisms are crinoids, stromatoporoids, corals, 

brachiopods, calcareous algae, and Mollusca, in 

approximate order of decreasing abundance. Bedded darkgray chert is widespread at the base of these limestone 

successions. 

Calcareous shaly interbeds and partings are most 

numerous in the lower parts of stratigraphic sequences in 

the intermediate limestone belt. There is little wholly noncalcareous clay shale in these strata. Graptolites are most 

obvious to the collector in these lower, shaly intercalations. The higher and more thickly bedded parts of 

Great Basin Silurian limestone sequences have thus far 

yielded relatively few graptolites. 

Limestones of the intermediate limestone belt contain 

dolomite tongues in the type section of the Roberts Mountains Limestone (Winterer and Murphy, 1960). It is 

possible that we have here a boundary relationship with 

the eastern dolomite belt. A lateral interfingering relationship between the coral-rich Vaughn Gulch Limestone 

of the intermediate limestone belt and graptolitic facies 

can be observed in Mazourka Canyon, northern Inyo 

Mountains. There, the Sunday Canyon Formation (Ross, 

1966, p. 32), a calcareous but partly shaly graptolitic unit, 

reveals probable northward tongues of the Vaughn Gulch 

Limestone, which has yielded no graptolites. 

No exposures which bridge the gap between facies of the 

intermediate limestone belt and the Pacific Border 

graywacke belt are known in the western Great Basin. 

Rocks of the Pacific Border graywacke belt have thus far 

disclosed no diagenetic dolomite; coral-bearing limestones of this belt are quite subordinate to the siliceous 

clastics of which the source material is in considerable part 

volcanic. 

GREAT BASIN SILURIAN REFERENCE SECTIONS 

Because of structural complexity and lack of continuous 

exposure, Silurian rock sequences with depositional 

contact at bottom and top are a rarity in the central and 

southwest Great Basin. Faults are the common system 

boundaries. Hence, vertical and evolutionary order of 

faunas is partly dependent upon composite sequences, the 

reliability of which is within the limits of accuracy 

imposed by physical or fossil correlation between separate, 

but theoretically overlapping, partial sections. 

Of the many Silurian outcrop areas mapped or 

examined during the course of these studies, few are sufficiently inclusive to serve as reference sections for the 

system. Those so designated within the intermediate limestone belt are as follows: The Mazourka Canyon section, 

northern Inyo Mountains; the Ikes Canyon section, 

Toquima Range; the Roberts Creek Mountain section; 

and the section in Coal Canyon, northern Simpson Park 

Mountains. Reference sections for the eastern dolomite 

belt are those of the northern Panamint Range near 

Ubehebe Peak and Whitetop Mountain, the Funeral 

Mountains section, California, and the Lone Mountain 

section, Eureka County, Nev. The section at Bare 

Mountain near Beatty, Nev., n1ay eventually be suitable 

for reference purposes; like the Roberts Creek Mountain 

section, it also lies near the border between the eastern 

dolomite and intermediate limestone belts. 

MAZOURKA CANYON REFERENCE SECTION 

At Mazourka Canyon a continuous limestone sequence 

about 1,500 feet thick rests conformably upon the Late 

Ordovician Ely Springs Dolomite and is overlain 

disconformably by Mississippian conglomerate and 

quartzites (fig. 3). Named the Vaughn Gulch Limestone 

by Ross ( 1963, p. B81), this formation has been a subject of 

paleontological investigation since 1912, at which time 

these strata were considered to be Devonian (Kirk, 1918; 

Stauffer, 1930). Mapping of the Cerro Gordo mining 

district in 1946 brought renewed interest in these beds, 

when it became fairly evident that the Silurian and Lower 

Devonian Hidden Valley Dolomite (McAllister, 1952) of 

the southern Inyo Mountains near Cerro Gordo changes 

northward into limestone (Merriam, l963a). Rugose coral 

studies of Vaughn Gulch material from what is now called 

coral zone E indicated correlation with coral faunas in 

central Great Basin Silurian limestones. 

The Vaughn Gulch Limestone appears to be an 

unbroken sequence of well-bedded medium- to dark-gray, 

partly bluish-gray, impure carbonaceous limestone, argillaceous limestone, and calcareous siltstone, including 

many fossil-rich beds. Some of the more argillaceous and 

silty interbeds weather in subdued fashion to a light gray, 

stained pink or orange in places. Black chert zones are 

stratigraphically significant, occurring at the base and top 

of the formation; elsewhere, minor chert is present as 

scattered nodules or thin lenses. Platy and flaggy exposures predominate, with limestone beds ranging in 

thickness from 1 to 6 inches separated by calcareous shaly 

or siltstone partings. Thicker limestone beds, some more 

than 3 feet thick, are fairly common, and many of them are 

bioclastic. These weather out prominently and are the 

most numerous in the upper middle part of the formation. 

Readily mappable lithologic divisions (Ross, 1965, 

1966) have not been recognized within the Vaughn Gulch 

Limestone. For faunal distribution, however, the column 

can be divided into a lower part 350 feet thick, a middle 

part 720 feet thick, and an upper part 460 feet thick. 

More uniformly bedded and having fewer bioclastic and 

fossil beds than higher parts of this formation, the lower 

350 feet consists largely of platy to flaggy, partly laminated 

dark-gray or bluish-gray argillaceous limestone that 
GREAT BASIN SILURIAN REFERENCE SECTIONS 9 

Type section of 

Vaughn Gulch Limestone 

1530 ft 

c:: 

ro 

~ ~ ;:s ·- .......... 

- :I ;:.,.._ 

Middle unit 

720ft Lower unit 

350ft 

·a. 

a. 

...s:: ·-

§- ~ Coral I 1! ~ zone 1 

Coral zone 

·~ 

~~ 

~ 

I 

c:: 

0 

·;; 

ro 

Upper unit 

460ft 

Upper Silurian or 

Lower Devonian 

...... a. E I 

~ ::> Verticillopora beds 

~ Toquima-i 

phyllum 1 N 

O'l 

0 (!) 

--..:::: 

0 

t:: 

A Ely Springs Eureka Quartzite 

Dolomite equivalent' 

c:: 

c:: .~ ro u ·;: ·:;; 

275ft 380ft 

c:: 

ro 

I :ogonip Gcoup equivalent' 

ro 

'(3 

·:;; 

0 

'0 

E 

0 

u. 

~I 

:=t 

~I 

00 

~ .- 0- O'l .- I'"'\ 0 ~ ....... .-

~ 

:I 0 ==-o en .... .... 0 Q) .... $ Q) 

0 a. ....J a. 

'(3 

·:;; 

0 

'0 

0 

.... 

Q) 

a. 

a. 

::> 

0 

~ 

'0 

~ 

~ 

I 

Barrel Spring and Johnson Spring are local names (Ross, 

1966) applied to units of the Eureka Quartzite interval; 

normal Eureka Quartzite occupies this interval along the 

west I nyo Mountains front 15 miles to the south (Merriam 

1963a). Ranges from Middle to possibly Late (Richmond) 

Ordovician age. 

0 200 

::> 

400 FEET 

2 

Local names have been given to these strata (Ross, 

1963, 1966). 3 Disconformity at top of Vaughn Gulch Limestone 

(Merriam, 1963a, p. 15). 

4800' 

4700' 

4600' 

FIGURE 3.-Mazourka Canyon reference section, showing type section of the Vaughn Gulch Limestone. Section extends 

northeasterward along divide between Vaughn Gulch and Willow Springs Canyon, Indepencence quadrangle, California. 

Based on unpublished geologic mapping by Merriam. 

weathers light gray in places. A persistent dark-gray chert 

member at the bottom, some 15 feet thick, corresponds to 

that forming the base of the Silurian System elsewhere in 

the Great Basin. Weak partial dolomitization and nodular 

chert decrease upward to the lowest fossil bed of coral zone 

A, which lies 130 feet above the thick basal chert. The few 

fossil beds in this division contain abundant Heliolites 

and favositids; more distinctive zone indicators, such as 

Dalmanophyllum, are uncommon. 

The 720 feet of limestone constituting the middle part of 

the Vaughn Gulch includes the prominent medium- to 

dark-gray richly fossiliferous coralline and bioclastic beds 

in its upper half, of which the uppermost 200 feet falls 

within Great Basin Silurian coral zone E. The thicker, 

darker gray beds, ranging in thickness form 10 inches to 

more than 3 feet, are generally the biogenic beds; the~~e are 

commonly sculptured into prominent ribs separated by 

subdued intervals of silty or argillaceous limestone that 

weather lighter gray. Crinoidal debris is much of the 

bioclastic material of these thicker fossil ribs. Some of the 

fossils which weather in relief are complete but are 

partially silicified and limonite in1pregnated. Below the 

middle of this 720-foot division, most of the limestones are 

thinner bedded and show fewer bioclastic members. No 

fossil accumulations with true biohermal relief were 

found. Chert is a minor constituent. About 300 feet of beds 

in the middle of this 720-foot division contain an 

abundance of the large dasycladacean alga Verticillopora. 

Though long-ranging, these calcareous algae appear to be 

most numerous in Great Basin Silurian coral zone D. 

A 460-foot upper interval of the Vaughn Gulch includes 

those beds between the top of Silurian coral zone E and the 

Mississippian disconfonnity. Bioclastic beds within the 

topmost 75 feet contain abundant poorly preserved fossils. Contorted layers of dark-gray chert in the upper 30 feet 

are associated with massive dark-bluish-gray crinoidal 

limestone which contains silicified, partly macerated, 

limonite-stained brachiopods, favositids, and large rugose 

corals, both solitary and colonial. Below the upper beds, 

the limestone is partly laminated and platy down to the 

lower strata adjoining coral zone E, where thicker bioclastic and coralline beds become more numerous. As 

noted elsewhere under correlation, there is inconclusive 

paleontologic evidence of Early Devonian age for the 4()0-

foot upper interval. 

IKES CANYON REFERENCE SECTION 

Silurian limestone, calcareous shale, and siltstone some 

500 feet thick at Ikes Canyon, northern Toquima Range, 

Nev., are rich in well-preserved coral material at several 

stratigraphic horizons. Mapping by Kay and Crawford 

(1964) shows this area to be structurally very complex; 

measurable stratigraphic sections are uncommon because 

of the many thrust and normal faults. Fairly abrupt facies 
10 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

changes from graptolite-bearing calcareous shale to shelly 

facies and coralline limestone further complicate stratigraphic and structural interpretation. The strata in 

question were assigned by Kay and Crawford (1964, p. 

43 7-441) to the Masket Shale and Diana Limestone of 

Silurian age, and the McMonnigal Limestone was 

assigned to the Devonian. 

Fossil collections upon which Merriam's appraisal is 

based came from the west side of Copper Mountain, north 

of Ikes Canyon, where coral-bearing medium- to darkbluish-gray limestones crop out at successive horizons 

across strata mapped by Kay and Crawford as Masket, 

overlain by McMonnigal. The lower coral collections 

representing Great Basin Silurian coral zones A and D 

came from sites within the Masket; the upper collections, 

those of coral zone E, appear to fall within the 

McMonnigal. 

Appraisal of Silurian and Ordovician stratigraphy at 

Ikes Canyon suggests that the upper chert member of Kay 

and Crawford's (1964, p. 437) prevailingly dolomitic 

Gatecliff Formation beneath the Masket is actually the 

widespread Great Basin basal Silurian chert, whereas the 

underlying dolomitic members of the Gatecliff correspond to the Ely Springs Dolomite of Late Ordovician 

(Richmondian) age. 

ROBERTS CREEK MOUNTAIN REFERENCE SECTION 

The Roberts Creek Mountain reference section is 1Yz 

miles west-northwest of the summit of Roberts Creek 

Mountain on the spur between the north and middle forks 

of Pete Hanson Creek. The type sections of the Late 

Ordovician (Richmondian) Hanson Creek Formation and 

the conformably overlying Roberts Mountains Formation 

of Silurian age are included. 

About 2,200 feet thick, the Roberts Mountains 

Formation is approximately 80 percent limestone with a 

prominent cherty member at the base and dolomitic limestone and dolomite beds in the upper 450 feet (fig. 4). 

Stratigraphic relationships are clearly shown in the lower 

l ,500 feet of this column; the higher part, being closer to 

the Roberts Mountains thrust, is 1nore deformed, and the 

beds in this direction become increasingly more dolomitic. 

The Roberts Creek Mountain reference section was 

measured in 1934 (Merriam, 1940) and has more recently 

been mapped by Winterer and Murphy ( 1960, p. 120) in 

connection with study of intertonguing dolomite and 

limestone. In the immediate type area, lithology and 

paleontology make feasible a three-unit division as unit 1 

(180ft), unit 2 (l,100ft), and unit 3 (900ft), in ascending 

stratigraphic order. 

Unit 1, a cherty division. comprises a basal chert overlain 

by fine-textured thin-bedded or laminated dark-gray 

limestone that weathers platy and flaggy with shaly 

partings. The limestones weather light gray. The 

distinctive basal chert is bluish black; its lowermost 10 feet 

is 75 percent chert containing subordinate limestone 

lenses. The chert decreases upward, occurring in Yz to 2-

inch layers separated by laminated limestone. The chert 

largely disappears toward the top of unit 1. The basal 

chert, conformable with underlying Hanson Creek 

Formation, is the widely recognized basal chert of the 

Great Basin Silurian. Fossils are scarce in the laminated 

limestone, but shaly partings yield poorly preserved 

graptolites. In other areas correlative basal cherts contain 

pentameroid brachiopods. 

Unit 2 comprises platy to flaggy dark, sometimes 

bluish-gray, limestones and heavier limestone interbeds 

up to 2 feet thick. Calcareous shaly partings separate the 

limestone layers, many of which are coarse textured and 

highly fossiliferous, much of the debris being crinoidal. 

The absence of chert and the introduction of the thicker, 

coarsely bioclastic and crinoidal beds distinguish unit 2 

from unit 1. Scattered black chert lenses are, however, 

present above the middle of unit 2. In the upper part are a 

few light-gray recrystallized carbonate layers that appear 

to be somewhat dolomitic. Tabulate corals and 

pentameroids and other brachiopods are abundant in the 

many bioclastic beds, but rugose corals are in the minority. 

Unit 3 is gradational with unit 2 through an interval in 

which the coarser textured crinoidal layers containing 

abundant Conchidium-like brachiopods pass upward 

into a thicker bedded sequence of light- and dark-gray 

blocky Jeathering limestones which include coralline 

beds. These coral beds contain large colonial Rugosa and 

represent ~reat Basin Silurian coral zone C. Some 250 feet 

above the base, this unit becon1es prevailingly lighter gray 

and less well bedded as it passes into the magnesian limestone and dolomite of the upper half. Light-gray weathering magnesian limestones in the n1iddle part of this unit 

contain abundant silicified corals of Great Basin Silurian 

coral zone D. Bedding is poorly defined and blocky 

through the upper 400 feet, where fossils become fewer and 

the rock passes into dolomite of the overlying unit. 

Some 1,600 feet of blocky dolomite between unit 3 and 

the richly fossiliferous beds of the Devonian Nevada 

Formation· were initially correlated with the Lone 

Mountain Dolomite (Merriam, 1940, p. 32). No 

identifiable fossils were obtained from this interval. It 

probably includes not only a partial equivalent of the 

Lone Mountain but also higher dolomitic limestones and 

dolomites which elsewhere represent the lowermost 

Nevada containing the Helderbergian Rabbit Hill fauna 

and faunas of Oriskany age. 

COAL CANYON REFERENCE SECTION 

The Coal Canyon reference section, at the north edge of 

the northernmost Simpson Park Mountains, includes 

5,000 feet of east-dipping strata ranging in age from Late 

Ordovician to Middle Devonian. Along the east slopes of 

Coal Canyon near its mouth are the best known exposures 
GREAT BASIN SILURIAN REFERENCE SECTIONS 11 

c Undifferentiated c 

·;: 

ttl -~ Lone Mountain c ::l 0 

Dolomite and > (/) Q) 

.... Beacon Peak Cl Q) 

Q) Eureka Hanson Creek c 

~ Quart- Formation Q) zite 650ft 

-~ 500ft ...J c c c ttl ttl Unit 1 Unit 2 Unit 3 

900ft 

a. 

a. Dolomite Member .... 

Q) 

s: Roberts Creek -~ :::J Mtn. ·u "<::) 

"tJ ·:; ·:; 

0 0 0 

"tJ 

180ft 1100 ft 

0 

(.!) 0 "E 

0 ..... 

.... 

Q) 

~ 

() 

Coral zones 

.... .... Q) Q) C D 

s: a. 0 a. ...J :::J 

iii 

Direction of structure section S 80° E 

.-N 

00 

1 

Upper 500 feet of this undifferentiated dolomite may 

include the Beacon Peak Dolomite Member of the Nevada 

Formation, which 10 miles east in the Sulphur Spring 

Range contains the Rabbit Hill fauna of Helderberg Early 

Devonian age. 

0 

0 

0 

of Nevada 0 

Formation I ...J 

9219 ft 

1000 FEET 

2 Expected position of Great Basin Silurian coral zone E; 

corals of this zone absent possibly because of dolomite 

facies. 3 Acrospirifer kobehana and Eurekaspirifer pinyonensis 

faunas in Nevada Formation of lower plate below Roberts 

Mountains thrust. 

10,000' 

9000' 

8000' 

FIGURE 4.-Roberts Creek Mountain reference section, showing type section of the Roberts Mountains Formation and 

type section of the underlying Hanson Creek Formation. Section extends S. 80° E. between south and middle forks of 

Pete Hanson Creek, Roberts Creek Mountain quadrangle, Nevada. 

of uppermost Roberts Mountains Formation in normal 

stratigraphic contact with overlying Rabbit Hill 

Limestone of Early Devonian age. The strata of this 

section probably occupy the lower plate of an overthrust. 

One-half mile southeast of the mouth of Coal Canyon, a 

flat-lying discordant outcrop of brecciated Ordovician 

Vinini chert and shale probably represents the upper plate 

of the thrust. All strata of this area are cut by later northtrending high-angle faults which exert topographic 

control and hamper measurement of continuous 

stratigraphic sections. A north-trending shear zone along 

the west side of Coal Canyon is several hundred feet wide 

and separates the less disturbed upper beds of the Roberts 

Mountains Formation along the east wall of the canyon 

from the dislocated limestone and calcareous shale of 

probable Silurian age to the west. On the east of the 

canyon, the uppermost 250 feet of the Roberts Mountains 

Formation below the Rabbit Hill boundary comprises 

flaggy to thick-bedded dark-bluish-gray limestone 

containing lenses and interbeds of coarse depositional 

limestone breccia (Winterer and Murphy, 1960). Clasts and 

matrix of these breccia bodies contain well-preserved 

corals and brachiopods representing Silurian coral zone E 

of this report. 

The Roberts Mountains-Rabbit Hill contact is drawn 

where the thicker coralline beds and lenses of Silurian 

coral zone E pass upward into thinner bedded and platy, 

somewhat darker gray limestone and calcareous shale of 

the Rabbit Hill. This boundary appears to be gradational 

and is without recognized features of disconformity, such 

as might be expected along a tradational system boundary. 

The Helderbergian Rabbit Hill of this eastern structural 

block has a minimum thickness of 900 feet. Allowing for 

probable duplication of Rabbit Hill strata by faulting, the 

total width of outcrop, which exceeds half a mile, suggests 

that this formation may be more than 1,000 feet thick in 

this area. 

The easternmost and stratigraphically uppennost 

exposures in the Coal Canyon section are the argillaceou~ 

limestones of Merriam's Nevada Formation unit 2 

(Merriam, 1973c). Alluvial cover prevents determination 

of true stratigraphic relationship of the Rabbit Hill 

Limestone to the contiguous Nevada. No strata of the 

Early Devonian (Siegenian) unit 1 of Merriam (l973c) of 

the Nevada Formation were recognized. 

The Roberts Creek Mountain stratigraphic section 

appears fairly continuous in the structural block west of 

the Coal Canyon shear zone. Johnson and Murphy (1969) 

used the name "Windmill Limestone" for upper beds of 

this block and have included in this unit not only the Coal 

Canyon shear zone but also the uppermost Roberts 

Mountains Formation below the Rabbit Hill contact in 

the contiguous eastern structural block. Johnson and 

Murphy (1969, fig. 2) regarded their Windmill Limestone 

as Early Devonian on the basis of somewhat controversial 

evidence from graptolites, conodonts, and brachiopods. 

This rugose coral investigation, together with 

concurrent detailed geologic mapping of the Coal Canyon 

area by Merriam, fails to support the conclusions of 

Johnson and Murphy (1969) with respect to Devonian age 

assignment of the uppermost Roberts Mountains 

Formation 1n this reference column. Clearly, the 
12 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

{(Quadrithyris zone' of Johnson and Murphy is Merriam's 

Silurian coral zone E, which contains here, as elsewhere in 

the Great Basin, a large and distinctive rugose coral 

assemblage of Gotlandian character. Rationalization of 

this question should await the completion of detailed 

geologic mapping in this area. Other structural and 

paleontologic problems engendered by the JohnsonMurphy stratigraphy call for review of fossil identifications and fossil ranges. As presently interpreted by these 

workers, the lower part of their Windmill Limestone, 

dated as Early Devonian by species of Monograptus (M. 

hercynicus and M. praehercynicus) with support from 

conodont and brachiopod evidence, underlies their 

"Quadrithyris zone," which brackets Merriam's Silurian 

coral zone E. 

The Coal Canyon reference section supplements the 

type section of the Roberts Mountains Formation 12 miles 

to the southeast (Merriam, 1940, p. II). Both occupy 

structural belts of thrusting and subsequent high-angle 

faulting. In detail the two sections present both similarities and differences. Dolomite, present as tongues and 

interbeds in the type section, has not been found at Coal 

Canyon, whereas the coral-rich depositional limestone 

breccias of Coal Canyon are unrecognized in the type 

section of the Roberts Mountains Formation. Graptolitic 

facies are better shown and probably more extensive in the 

Coal Canyon Silurian. Most noteworthy is the failure to 

recognize the Helderbergian Rabbit Hill beds where they 

are to be expected above the type Roberts Mountains 

Formation on Pete Hanson Creek. However, in this 

section these Helderbergian strata may well be represented 

in the thick dolomites occupying the interval between the 

Silurian Roberts Mountains beds and the Devonian 

Nevada Formation at Roberts Creek Mountain. 

NORTHERN PANAMINT RANGE REFERENCE SECTION 

The Silurian strata of the northern Panamint Range 

reference section are a part of the Hidden Valley Dolomite 

in its type locality 272 miles north of Ubehebe Peak 

(McAllister, 1952, p. 15 ). There, the Hidden Valley is 1,365 

feet thick and rests conformably upon Late Ordovician 

(Richmondian) Ely Springs Dolomite. In neighboring 

areas to the east, higher beds of this dolomite formation 

contain Early Devonian (Oriskany) fossils. Only Silurian 

fossils are known in the type area, and a system boundary 

cannot be indicated within the unbroken sequence. 

McAllister (1952, p. 15, 16) defined three lithologic units. 

Only in the lower unit, or unit I, having a thickness of 435 

feet, are Silurian fo~sils abundant. The thick-bedded 

saccharoidal dolomites of this division weather blocky 

and medium to light gray and are cherty. Coral-rich beds 

of Great Basin Silurian coral zone B occur in the upper 

part of unit 1, about 300 feet above its base. Few fossils have 

been found in the 730 feet of dolomite in overlying unit 2. 

A faulted Hidden Valley Dolomite sequence at 

Whitetop Mountain, 10 miles northeast of the type 

section, shows the lowermost beds of unit 1, which contain 

the fauna of Great Basin Silurian coral zone A. A similar 

zone A assemblage was collected by McAllister in the Andy 

Hills 672 miles east of the type locality. Thus far, the Early 

Silurian zone A fauna has not been found below coral zone 

B, where it would be expected, in the lowermost dolomites 

of the Hidden Valley in its type locality. 

LONE MOUNTAIN REFERENCE SECTION 

The Lone Mountain Reference section is on the southwest side of Lone Mountain, Eureka County, Nev., where 

the entire carbonate sequence from the top of the Eureka 

Quartzite to the base of the Nevada Formation of 

Devonian age is diagenetic dolomite. Detailed geologic 

mapping of Lone Mountain, which is within the type 

area of the Lone Mountain Dolomite, was carried out 

under the Kobeh Valley project of Nolan and Merriam; 

this mapping called for stratigraphic revision, in 

accordance with which the name Lone Mountain 

Dolomite is applied to the entire 2,500 feet of section from 

the bottom of the Silurian basal chert directly overlying 

the Hanson Creek Formation to the base of the Nevada 

Formation. Merriam's (1940, p. 13, 21) earlier redefinition 

of Hague's (1892, p. 57) Lone Mountain Limestone had 

used the term Roberts Mountains Formation for the lower 

750 feet of darker weathering dolomite now designated as 

Lone Mountain unit I. Thus revised and reapportioned 

(fig. 5 ), Hague's original Lone Mountain Limestone 

comprises, at the bottom, a Late Ordovician dolomitic 

facies of the Hanson Creek Formation, overlain by unit I 

and unit 2 of the Silurian Lone Mountain Dolomite. 

Stratigraphy and paleontology of the Lone Mountain 

Dolomite are treated in a separate paper (Merriam, 1973a). 

Approximately 80 feet thick in places, the lower chert 

member of Lone Mountain unit I is much thicker than 

usual for the basal Silurian chert in limestone facies; together, the basal chert and the overlying darker gray 

saccharoidal dolomite total about 750 feet thick. Although 

barren of identifiable fossils, Lone Mountain unit l 

probably correlates with the basal chert and limestone of 

Roberts Mountains Formation unit I and part of unit 2 in 

the richly fossiliferous Silurian limestone facies of the 

Roberts Mountains area to the north. 

Lone Mountain Dolomite unit 2, having a thickness of 

about 1, 750 feet, is lighter gray, more massive, and blockier 

weathering than unit I. Although coarse saccharoidal 

texture is characteristic of unit 2, the finer textured 

dolomite members occur toward the top. In the type 

section, Lone Mountain Dolomite unit 2 appears to be 

gradational with the overlying, richly fossiliferous 

dolomitic Lower Devonian sandy limestone of Nevada 

Formation unit I. No trace of the Helderbergian Rabbit 

Hill fauna has been found where it would be expected near 

this boundary. 
RUGOSE CORAL ZONATION OF THE GREAT BASIN SILURIAN 13 

Hague ( 1892) Merriam (1940) Merriam (this report) 

Nevada Limestone Nevada Formation Nevada Formation Early Devonian 

unit 1 (early Emsian) 

Lone Mountain 

Lone Mountain Dolomite 

Formation (restricted) unit 2 

Lone Mountain 

Silurian ~ 

Limestone Roberts Mountains Lone Mountain 

Formation Dolomite 

(dolomite facies) unit 1 

--/~/~/~/--/~/~/~/-'" 

Hanson Creek Hanson Creek 

Formation Formation 

(dolomite facies) (dolomite facies) 

Ordovician 

Eureka Quartzite Eureka Quartzite Eureka Quartzite 

~ All known fossils of the Lone Mountain Dolomite type area are Silurian. 

*Silurian basal chert marker. 

FIGURE 5.-Comparative diagram illustrating present usage of the stratigraphic name Lone Mountain 

Dolomite in its type area. 

Fossils are scarce and very poorly preserved because of 

magnesian recrystallization through the Lone Mountain 

Dolomite type section. In the upper 500 feet of unit 2, 

scattered very dark gray carbonaceous dolon1ite lenses 

contain fairly abundant but fragmentary and partly 

macerated colonial rugose corals probably of the Silurian 

genus Entelophyllum, a common and well-preserved 

silicified fossil in neighboring Lone Mountain Dolomite 

exposures. 

Supplementary Lone Mountain exposures yielding 

Entelophyllum and well-preserved Silurian brachiopods 

have recently been mapped in the Mahogany Hills, 16 

miles southeast of Lone Mountain, and in the Fish Creek 

Range, 25 miles southeast of Lone Mountain. Other 

outcrops of Lone Mountain Dolomite have been mapped 

in the southern Sulphur Spring Range, 20 miles northeast 

of Lone Mountain. There, the large dolomite fault block 

of East Ridge, near Ron1ano Ranch, contains Silurian 

coral faunas probably representing lower horizons of the 

Lone Mountain Dolomite. As discussed below under 

correlation of Great Basin Silurian coral zones, the higher 

Lone Mountain in the Mahogany Hills and the Fish Creek 

Range pertains to the Late Silurian upper Lone 

Mountain-Laketown Dolomite faunal facies. 

In the Sulphur Spring Range, the large East Ridge 

dolomite fault block near Romano Ranch includes about 

l ,200 feet of blocky Lone Mountain with two coral 

horizons-one about 250 feet above the base, and the other 

504-634 0 - 73 - 2 

near the top. Abundant Halysites and Silurian 

Pycnostylus (pl. 15, fig. 11) andStylopleura? (pl. 16, figs. 3, 

4) occur in these horizons. These dolomites may be partly 

correlative with Lone Mountain unit 1. In a separate fault 

block west of the East Ridge block occur dolomitic limestones with a Helderbergian Rabbit Hill fauna. These 

beds lie above the Lone Mountain Dolomite at the base of 

Nevada Formation unit l (Merriam, 1973a). Mapping of 

these dolomitic Helderberg beds in the Sulphur Spring 

Range has led to the conclusion that they are correlative 

with the Beacon Peak Dolomite Member, the lowest 

member of the Nevada Formation in the Eureka mining 

district (Nolan and others, 1956, p. 38). Southeast of 

Eureka in its type section, the fine-textured Beacon Peak is 

separated from coarse-textured subjacent Lone Mountain 

Dolomite by a sharply incised undulant erosion surface 

unrecognized in the type section of the Lone Mountain 

Dolomite. 

RUGOSE CORAL ZONATION OF THE GREAT 

BASIN SILURIAN 

Study of the stratigraphic distribution of Silurian 

Rugosa in correlative and overlapping reference sections 

makes possible a hypothetical fivefold paleontologic 

zonation based on ranges of species and genera. 

Provisional zones are designated by capital letters A 

through E, in ascending stratigraphic order. Gaps in the 

coral record within a single reference section may be filled 
14 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

in the correlative sections to complete the overlapping 

composite zonal schen1e. At present, no more than three 

coral zones have been recognized within any one reference 

column; additional collecting is expected to eliminate 

some of these local gaps. 

Ranging in age from late Early to Late Silurian, the five 

coral zones are as follows: 

Age 

Late Silurian 

Middle Silurian 

Late Early Silurian 

Great Basin 

Silurian 

coral zone 

E 

D 

c 

B. 

A 

British Series 

Ludlovian 

Wenlockian 

Late Llandoverian 

As noted elsewhere, there is inconclusive evidence of 

biofacies or ecologic difference between the rugose corals 

in diagenetic dolomite and those in approximately 

correlative limestone deposits. Rugosa of the upper part of 

the Lone Mountain Dolomite and of the Laketown 

Dolomite are, in a biofacies sense, unlike those of the more 

or less equivalent limestones and cannot, therefore, be 

included at present in the fivefold zonal arrangement. 

Silurian coral zone A is based on rugose coral genera 

present in both dolomite and limestone facies, as well as 

on forms collected only in the dolomites (fig. 6). Coral 

zone B assemblages have been collected only in the 

dolomites. Coral zones C and E are established on the basis 

of limestone faunas, whereas coral zoneD indicators have 

been found in both carbonate facies. 

ZONE A 

Early Silurian faunas of coral zone A occupy lower beds 

of the Hidden Valley Dolomite in the reference section of 

the northern Panamint Range. These are the lowest 

known Silurian shelly faunas of the Great Basin, 

occurring in the lower I 00 feet of Hidden Valley unit I and 

above the Ely Springs Dolomite with a Richmondian 

fauna. Rugose corals in basal Silurian beds of Whitetop 

Mountain, northern Panamint Range, are as follows: 

Rhegmaphyllum sp. h 

Dalmanophyllum sp. A 

Palaeocyclus porpita subsp. mcallisteri 

Rhabdocyclus sp. d 

Arachnophyllum kayi 

Other diagnostic Rugosa present in limestone facies 

coral zone A of the Toquima Range are Cyathophylloides 

fergusoni and N eomphyma crawfordi, there in association 

with Arachnophyllum kayi. Palaeocyclus, a small button 

coral, is the distinctive fossil of this zone. However, it 

seemingly has facies-restricted distribution, having been 

collected only in dolomites of the Panamint Range, the 

Characteristic Rugosa of the Great Basin Silurian coral zones 

Age Characteristic rugose corals of 

Great Basin Siluriar 

Stylopleura berthiaumi, n. gen., n. sp. 

Stylopleura neuadensis, n. gen., n. sp. 

Mucophyllum oliveri, n. sp. 

Kodonophyllum mulleri, n. sp. 

Rhizophyllum d. R. enorme 

Rhizophyllum sp. D 

Chonophyllum simpsoni, n. sp. 

Australophyll~m (Toqwmaphyllum) johnsoni, 

n. subgen., n. sp. 

Kyphophyllum nevadensis, n. sp. 

Salairophyllum?'" sp: 

Stylopleura berthiaumi, n. gen., n. sp. 

Tryplasma duncanae, n. sp. 

Tonkinaria simpsoni, n. gen .. n. sp. 

Denayphyllum denayensis, n. gen., n. sp. 

Tryplasma newfarmeri, n. sp. 

Entelophylloides (Prohexagonaria) occidentalis, 

n. subgen., n. >p. 

Small streptelasmid coral> 

Brachyelasma sp. B 

Ryderophyllum ubehebensis, n. sp. 

Pycnactis sp. k 

Petrozium mcallisteri, n. sp. 

Rhegmaphyllum sp. h 

Dalmanophyllum sp. A 

Cyathophylloides fergusoni, n. sp. 

Palaeocyclus porpita subsp. mcallisteri, n. subsp. 

Rhabdocyclus sp. d 

Arachnophyllum kayi, n. sp. 

Neomphyma crawfordi, n. sp. 

Great Basin 

Silurian coral 

zone 

E 

D 

c 

B 

A 

* Salairophyllum? material from uncertain stratigraphic horizon at Coal Canyon, 

Simpson Park Mountains, Nev., probably from beds in coral zone E. 

Ruby Mountains of north-central Nevada, and the 

Confusion Range of western Utah. 

Tabulate corals, thus far unstudied, are the common 

corals of Silurian coral zone A. These include massive 

favositids, Cladopora, Heliolites, andHalysites. Silicified 

brachiopods associated with this assemblage are assigned 

to Dicaelosia, Dalmanella, Camarotoechia, and Atrypa. 

Of the Rugosa in coral zone A, only Arachnophyllum 

and N eomphyma are known in strata above the Lower 

Silurian, but in regions other than the Great Basin. 

Cyathophylloides is more commonly a Late Ordovician 

genus. 

ZONEB 

Of early Middle Silurian age, coral zone B includes the 

following Rugosa; 

Small streptelasmid corals 

Brachyelasma sp. B 

Ryderophyllum ubehebensis 

Pycnactis sp. k 

Petrozium mcallisteri 

Corals of zone Bare known in dolomites of the Great 

Basin Silurian reference sections north of Ubehebe Peak, 

Panamint Range, and in the Funeral Mountains. At the 
RUGOSE CORAL ZONATION OF THE GREAT BASIN SILURIAN 15 

Great 

Basin Characteristic Location of reference sections, Silurian coral zones, Silurian rugose coral central and southwest Great Basin coral genera 

Geologic zones 

1 2 3 4 5 6 age Northern Northern Toquima Northern Roberts Mts, Fish Creek 

Panamint lnyo Mts, Range, Nev. Simpson Park Nev. Range, Nev. 

Range, Calif. Calif. Mts, Nev. 

Australoph_vllum c Q) 

(Toquimaph_J·l/um) ........ Mucophyllum 

E E E ~·E 

E Rhi:ophyllum 

Kodonophyllum Q) 

c0 En tela- C/wnophyllum ~ 0 0 phyllum ~ Kyphophyllum ...JO 

Sty/opleura c facies Ctl 0 ...J .... c c ... 0 0 

0 Stylopleura Ctl Q) ·.::; 0 Tonkinaria a. c ·.::; 0 0 ~ ... ~ Ctl Ctl .E -- -?-- Tr_vplasma Q) E E c ~ Q) 0 0 0 0 

c .2 E LL LL ·.::; 0 Ctl - ::i "' Ctl 0 '§ "' E Entelophylloides ~ c c 0 c (Prohexagonaria) .E ..c 

u; c '§ '§ c '§ Try plasma ~ LL 0 ::J c c Q) Denayphyllum ::J ::J "' c 

=c 0 (.!) 0 0 c ::J 

0 c ~ ~ '§ 0 

:'2 ..c ~ 

::: Ryderoph_J•l/um > Cl "' "' c Q) ~ ::J .... ..... ::J Pvcnactis ... ... c Petrozium a; Ctl Q) Q) 0 0 B Try plasma > B > .c .c ~ ...J 0 0 Brachvelasma c 0: 0: "' Palae~phyllum .... Q) ... "C Q) 

:'2 .c 

0 Palaeocrclus I 0: > Dahna,;ophyllum 

-.::: A Ctl Arachnophyllum A A A w Cyathoplzylloides 

Brachyelasma 

FIGURE 6.-Great Basin Silurian coral zones and common rugose coral genera and subgenera. 

former locality in the type area of the Hidden Valley 

Dolomite, the zone B fauna occurs in McAllister's (1952, p. 

15) unit l, about 325 feet above the base of the fonnation. 

Tabulates are the abundant fossils, as in coral zone A. 

These include Halysites, Heliolites, andSyringopora. The 

halysitids are diverse, ranging from the large Halysites 

(Cystihalysites) of the magnitubus type to species with 

medium and small corallites. Brachiopods are relatively 

scarce; only the genus Atrypa has been recognized. 

Dasycladacean algae first make their appearance in 

coral zone B, where they are represented in some 

abundance by a species of Verticillopora with narrow 

shaft; these do not attain the large size of the Verticillopora 

in coral zone D. 

ZONEC 

Coral zone C of late Middle Silurian age is characterized 

by the following Rugosa: 

Denayphyllum denayensis 

Tryplasma newfarmeri 

Entelophylloides (Prohexagonaria) occidentalis 

Coral zone C is proposed for the richly coralline beds near 

the base of unit 3 of the Roberts Mountains Formation 

(fig. 4) in the type section of that formation on Pete 

Hanson Creek. No associated brachiopods or other fossils 

were found in these beds. 

ZONED 

Great Basin Silurian coral zoneD of Late Silurian age 

includes the following rugose corals: 

Stylopleura berthiaumi 

Tryplasma duncanae 

Tonkinaria simpsoni 

The reference section for this zone is also the type section for the Roberts Mountains Formation on Pete 

Hanson Creek (fig. 4), where these corals and associated 

tabulates and brachiopods occupy dolomitic limestones in 

the upper 250 feet of unit 3. Beds of coral zone D lie about 

500 feet above coral zone C in the same section. Between 

the two intervals this section is penetrated by mafic dikes, 

but it appears to be otherwise unbroken; toward zoneD the 

limestones become progressively more dolomitic, passing 

upward into a thick blocky dolomite unit. All fossils 

obtained in coral zoneD are silicified. Predominant in the 

coral beds are n1assive and digitate favositids, followed in 

order of abundance by Rugosa, brachiopods, and 

calcareous algae. Among the silicified brachiopods prepared by acid etching are Dicaelosia, Homoeospira, 

Kozlowskiellina, and Atrypa. 

One of the more distinctive elen1ents of the coral zoneD 

assemblage in this section is the dasycladacean alga 

Verticillopora. 

ZONEE 

Uppermost of the five zones is coral zone E of Late 

Silurian age, which is characterized by the following 

Rugosa: 

Stylopleura berthiaumi 

Stylopleura nevadensis 
16 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Mucophyllum oliveri 

Kodonophyllurn mulleri 

Rhizophyllum cf. R. enorme 

Chonophyllum simpsoni 

Australophyllum (Toquimaphyllum) johnsoni 

Ryderophyllum? sp. 

Cyathactis? sp. 

Coral zone E is proposed for the diverse assemblage 

occurring in the uppermost beds of the Coal Canyon 

reference section, northernmost Simpson Park 

Mountains. The zone fossils come from a limestone 

interval which includes bodies of breccia-conglomerate; 

some were extracted from clasts of the depositional 

breccia. 

Other than Rugosa, the com1non fossils of coral zone E 

at Coal Canyon are stromatoporoids, massive Favosites 

with medium and small corallites, chaetetids, A lveolites, 

and Cladopora. Much of this limestone is bioclastic, is 

dark, slightly bluish-gray, and contains abundant 

crinoidal debris and large columna! seg1nents. Wellpreserved silicified brachiopods prepared by acid etching 

are as follows: 

Orthostrophia sp. 

Schellwienella? sp. 

Barrandella? sp. 

Sicorhyncha? sp. 

Rhynchospirina sp. 

Plectatrypa? sp. 

Atrypa? sp. 

Kozlowskiellina sp. 

Meristella sp. 

The large dasycladacean alga Verticillopora is present 

but very uncommon in coral zone E at Coal Canyon. 

Other than fossils removed from breccia clasts or the 

limestone in place, most collections made on this outcrop 

band are surface weathered material and float, some of 

which may be derived from upslope overlying exposures 

of the Early Devonian Rabbit Hill Limestone. Surface 

rubble of this kind, which cannot with full assurance be 

ascribed to coral zone E, yielded the following fossils: 

Orthostrophia? sp. 

Cymostrophia sp. 

Rafinesquina sp. 

Howellella? sp. 

Atrypa? sp. 

Leonaspis sp. 

Harpid trilobite 

Proetid trilobite 

Phacopid trilobite 

Orthoceras-like cephalopod 

Conocardium sp. 

Leperditia sp. (large) 

Large crinoid columnals and abundant crinoid debris 

A complex solitary rugose coral (pl. 12, figs. 6-8) placed 

provisionally in the Russian genus Salairophyllum was 

collected at Coal Canyon locality Mlll7 and was probably 

derived from uppermost beds of the Roberts Mountains 

Formation, Silurian coral zone E. This coral resembles an 

undescribed species from Kuiu Island, southeastern 

Alaska, where it occurs at locality Mll86 with the Late 

Silurian Conchidium alaskense. 

The subgenus Toquimaphyllum is the most diagnostic 

fossil of coral zone E, occurring at all sites where this zone 

has been recognized. At Ikes Canyon in the Toquima 

Range, Toquimaphyllum is associated with large 

phaceloid Kyphophyllum, found also in coral zone E of 

the Mazourka Canyon reference section. Coral zone E is 

known only in the intermediate limestone belt of the Great 

Basin. 

STRATIGRAPHY AND RUGOSE CORALS OF THE 

LONE MOUNTAIN AND LAKETOWN DOLOMITE 

The Lone Mountain Dolomite of the central Great 

Basin and the Laketown Dolomite of the eastern Great 

Basin are comparable lithologic units in which silicified 

fossils occur sporadically, most exposures being devoid of 

identifiable material. Stratigraphy and fossils of the Lone 

Mountain are dealt with in a separate contribution 

(Merriam, 1973a). 

In the eastern Great Basin where Silurian limestone 

facies are as yet unknown, the term Laketown Dolomite 

has been applied locally to most of the rocks believed to be 

of Silurian age. Possible time-stratigraphic equivalence of 

the entire Laketown to the entire Lone Mountain in its 

type area as redefined herein remains unsupported by 

paleontologic evidence. Like faunas of the Lone 

Mountain those of the Laketown Dolomite seemingly 

represent biofacies differing from those of Great Basin 

Silurian limestones in which the fivefold rugose coral 

zonation here proposed is best shown. Fossils and 

stratigraphy of both Silurian dolomite formations are at 

present insufficiently known for coral zoning. 

Equivalence of the upper part of unit 2 of the Lone 

Mountain Dolon1ite to upper beds of the Laketown is 

convincingly supported by occurrence in both of the 

Howellella pauciplicata brachiopod fauna, the precise 

stratigraphic position of which is established in unit 48 

(fig. 7, col. 10) of the Confusion Range, Utah, stratigraphic column (R. K. Hose, writtencommuns., 1954-64). 

These correlative Silurian dolomites are referred to 

faunally as upper Lone Mountain-Laketown biofacies. 

Fossils of this biofacies have not been recognized in 

Silurian limestones. 

Adjacent to the Lone Mountain Dolomite type area, 

strata in the upper 500 feet of this formation contain 

faunas of the upper Lone Mountain-Laketown biofacies 

with the Silurian rugose coral Entelophyllum. At Lone 

Mountain itself, macerated corals of this kind are too 

poorly preserved for positive identification. As unit 2 of 
GEOLOGIC CORRELATION WITHIN THE GREAT BASIN 17 

the Lone Mountain Dolomite is traced southeastward 

from the Lone Mountain area through the Mahogany 

Hills to the Fish Creek Range, scattered bodies of darkgray to black carbonaceous dolomite become increasingly 

numerous within the lighter, barren blocky phase. Wellpreserved silicified fossils in these dark dolomites 

represent the upper Lone Mountain-Laketown biofacies. 

Coral beds largely made up of favositids with associated 

Entelophyllum engelmanni and E. eurekaensis are 

extensive. Associated brachiopods are Howellella 

pauciplicata Waite, H. smithi Waite, Camarotoechia 

pahranagatensis Waite, and Protathyris hesperalis Waite, 

together with undescribed species of ?Hyattidina, 

Hindella, Salopina, and Atrypa. The Confusion Range 

(Ibex Hills) unit48 (fig. 7, col. 10) Howellella pauciplicata 

brachiopod assemblage described in part by Waite (1956) 

has more recently been elucidated in the Pahranagat 

Range of southeastern Nevada by Johnson and Reso 

( 1964). 

Coral faunas in the lower part of the Lone Mountain 

Dolomite or Lone Mountain unit I are little known, as are 

those in the lower part of the Laketown. Halysites and 

pycnostylid genera of the East Ridge dolomite block near 

Romano Ranch, Sulphur Spring Range, are believed to 

occur in lower beds of this formation. Beds containing an 

Early Silurian coral zone A assemblage with Palaeocyclus 

in the Confusion Range, Utah (loc. Mll29), occupy an 

isolated fault block whose position in the Laketown 

section remains uncertain. 

RUGOSE CORALS AND GEOLOGIC 

CORRELATION OF SILURIAN ROCKS 

WITHIN THE GREAT BASIN 

Interpretation of overall vertical and evolutionary order 

among Great Basin Silurian corals depends upon 

reliability of interarea geologic correlation within the 

province, as well as upon paleontologic ties with distant 

reference columns, such as those of eastern North America, 

Gotland (Sweden), England, and eastern Europe. Within 

the province, lithologic criteria exclusive of fossils also 

have value in this connection (fig. 7). Among pertinent 

factors are lateral continuity of bedded cherts at the system 

base and wide areal persistence of other distinctive sedimentary rock types, such as continuity in particular directions of diagenetic dolomite or the contrasting limestone 

lithofacies. 

Contrasting facies belts distinguished by predominance of either graptolitic or shelly biofacies have 

long been recognized in Ordovician and Silurian Systems 

of the Great Basin. Facies differences of this order greatly 

complicate or obviate direct paleontologic correlation 

from basin to basin and justify the multiplication of 

separate local stratigraphic columns. No better example of 

such facies variance may be cited than the Ordovician 

Vinini graptolitic sequences as compared with those of the 

Pogonip Group, thus far recognized together in fault 

relationship only. Facies isolation is but slightly less of a 

deterrent to correlation in the Silurian System of this 

province. 

Because of wide acceptance and growing dependability 

of the remarkable British graptolite sequence, worldwide 

Silurian stratigraphy and correlation lean heavily upon 

these fossils. Some belts of Great Basin Silurian exposure 

have thus far yielded only graptolite evidence, such as the 

calcareous shales of the Monitor Range stratigraphically 

below the Helderbergian type Rabbit Hill Limestone. 

Conversely, much of the Silurian in this province has thus 

far disclosed no graptolites, as throughout the eastern 

dolomite belt. By comparison, the intermediate limestone 

belt with its calcareous shales and platy limestone is 

graptolite bearing in some places. Graptolites are most 

abundant in lower horizons, where the shales and 

laminated limestones readily disclose their graptolitic 

nature to the collector. Higher in son1e of the same stratigraphic sections, where limestone bedding is generally 

thicker and more massive, graptolites are either less 

evident to the collector or seemingly absent. It is in upper 

beds of limestone reference sections, as in Coal Canyon, 

Simpson Park Mountains, in the type Roberts Mountains 

Lin1estone area, and in the Mazourka Canyon area, Inyo 

Mountains, Calif., that the greatest possibilities exist for 

future discovery of intercalated graptolitic and shelly biofacies. In the northwestern part of the Great Basin, approaching the Pacific Border graywacke belt (Pacific 

Border province), graptolitic shales may theoretically be 

expected to become even more widespread. 

Geologic correlation by means of a single biologic 

group may be misleading; use of corals alone in this respect would doubtless lead to error. Correlation of 

seemingly equivalent or identical coral assemblages from 

place to place is the equating of ecologically comparable 

coralline biofacies. In the present state of knowledge of 

these assemblages, it cannot be said with confidence that 

they do not have greater value as environmental indicators than of time equivalence. Little is yet known of the 

vertical ranges of Silurian coral genera and species. Data 

from research upon associated fossils are essential in support of rugose coral evidence. A1nong these, brachiopods 

are usually common and closely associated in the coral 

biota. Their supplementary use facilitates greater resolution of correlation problems. Studies of other associated 

fossil groups are needed; among these are trilobites, 

ostracodes, conodonts, and calcareous algae. A test of the 

correlation value of any one of these groups individually is 

the degree of adjustment required to bring data and the 

specialist's conclusions based upon these data into reasonable accord with evidence from independent study of the 

other stratigraphically associated groups. 

At best, a standard Silurian paleontologic sequence for 

the Great Basin will always be composite. Thus, for the 
18 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

2 

WASHINGTON 

--------

OREGON 

I 

\. 

I 

\ 

I 

0 Boise 

0 100 

MONTANA 

\ ,------

' \.r-- - J\! cQ. 

16 I 

\ WYOMING 

Pocat~llo 

200 MILES 

1 

NORTHERN INYO MTS 

Mazourka Canyon 

NORTHERN PANAMINT RANGE 

Ubehebe Peak area, 

3 

FUNERAL MTS 

4 

TOQUIMA RANGE 

lkes Canyon 

5 

MONITOR RANGE 

Dobbin Summit 

Andy Hills, Whitetop Mtn 

/ 

/ 

Perdido 

Formation / Formation --~---------~~--

460 It 

Vaughn Gulch 

Limestone 

1530 ft 

Ely Springs 

Dolomite 

Eureka 

Quartztte 

equtvalent 

Lower Devonian or 

-~p~il~nE Toquimaphyllum 

Rhizophyllum 

Verticillopora 

Hidden Valley 

Dolomite 

1365 ft 

Ely Springs 

200 ' It 

"'-< _/ 

_/ 

'Z'>< 

~$.<>$ ~-~o 

Lost Burro / _/ 

Formation / 

730 It "'" ~? 

" Hidden Valley 

Dolomite 

Ryderophyllum 

Petrozium 

Verticillopora 

Dalmanophyllum 

Arachnoph_l•llu1n 

Palaeocvclus 

Ely Springs 

Dolomite 

_,____ ____ Toquimaphyllum 

-~f·b--\ 

Stylof?lt:ura \ Rabbit Htll 

Tonkmana L' 

~ir:t:~~~ee Jrerticillopora \ tmestone 

8 Rydcrnphyllum A ___L_ _ __j_J 

Pvcnactis .·trach11ophyllum 

J~erticillopora ~l~:~::~-;:loides Limeston-:-ie 

Gatecliff Formation of Kay Hanson Creek 

/C~r ~~!-;;f ~e~-'+~--t-----~Fo::rm~a~t~lon, 

/ g~;::for~1 l1~)~d -!------ ___ - 940 It 

Eureka 

Quartzite ----- Eureka 

Quartzite 

6 

NORTHERN SIMPSON 

PARK MTS 

Coal Canyon 

Rabbot Hill 

Limestone 

Silurian 

Ordovician 

FiGURE 7.-Correlation chart of Great Basin 
GEOLOGIC CORRELATION WITHIN THE GREAT BASIN 

7 

ROBERTS CREEK MTN 

8 

LONE MTN 

9 

FISH CREEK RANGE 

11 

GOLD HILL 

6 

NORTHERN SIMPSON 

PARK MTS 

Coal Canyon 

\ • · ada Nevada 

~io_n +----+- _____ Fo_r_m_atio_n+--"'-""-~'--"D.!!!ev!!fO!!!Jni!!!!an!___, 

10 

CONFUSION RANGE 

Ibex Hills section 

of R.K. Hose 

/ 

/ 

/ 

/ / Dolomite 

_ _ ("Toquimaphyllum 7 

Rhizophyllum /' 

r---'-..§!Jl'!f!!.~_/ 

D Tonkinaria 

Stylop/eura 

Try plasma 

Roberts Mountains 

Formation 

2200 It 

r---

D Tonkinaria 

Stylopleura 

Try plasma 

Verticillopora 

Unit 3 

900 It 

Lone Mountain 

Dolomite 

1750ft 

C Tryplasma 

Prohexagonaria 

I----

Unit 2 

1100ft 

-Unit1 

Dolomite 

741ft 

Coral beds with 

debris of probable 

Entelophyllum 

Lone Mountain 

Dolomite 

Silurian 

Upper part of one 

Mountain-Laketown 

b1ofac1es with 

Ente/ophyllum and 

Howe/leila pauciplicata 

fauna l Sevy 

Dolomite 

mite, _____ , u-""""'~"- . 

~- ..... ----~ 

Laketown 

Dolomite 

1200 ft 

Silurian I Unit48 ne\10~ 

Howe/lelia paucip/icata L.......lv-."""'-+-- ~(\&" 

fauna 

Umt 46 

Verticillopora 

Huronia 

Lissocoelina Laketown 

Dolomite 

970 It 

A Palaeocyc/us {Ml129) 

=~ Basa.,_l""ch..,er'-'-t ___ _ ~ ~~21 ~hert ~ Bas_a_l c_he_rt_m_e_m_be_r __ ....,,..,~dc,::'~::.c;i:=i:inc...an-------- -+----+- Fish Haven 

11 

GOLD HILL 

Hanson Creek 

Formation 

Fish Haven Dolomite 

Hanson Creek 

Formaton 

~~i~e 

D~~o ";~te 250 It -4--+-

----·-----=-- -+--+- -----

-+--1- -4----~ 

Eureka / Quartzite 

~ 

12 13 

THOMAS RANGE EAST TINTIC MTS 

Sevy 

Dolomite 

4 

243ft 

3 

---, 

? Zelophyllum 

Halysite1s magnitubus 

Pinyon Peak 

Limestone 

85ft 

14 

RANDOLPH AREA 

Jefferson 

Dolomtte 

1200 ft 

Laketown 

I 

I 

I 

I 

I 

I 

I 

Eureka 

Quartzite 

537ft 

15 16 

BAYHORSE AREA BORAH PEAK AREA 

I 

I 

I 

I 

Laketown 

Dolomtte 

3000ft± 

\ 

\ 

\ 

I 

\ 

? 

\ 

\ 

\ Entelophyllum 

Lykop~yll1d coral 

I 

\ 

\ 

I 

Jefferson 

Dolomtte 

800ft+ 

L Devonian 

--srfUrian Laketown f-----

Dolomite 

1228ft 

I Victoria Formation 

278ft 

L ~vonian _ 7 

Dolomite 

1000 ft Lykophyllid corals 

411ft 

1 

135ft 

Fish Haven 

Dolomite 

300ft 

Silurian · 

Bluebell Dolomite 

Ente/ophyl/um 491 ft 

Pvcnactis 

· Silurian 

ordovician Fish Haven 

Dolomtte 

285ft 

? Polyorophe 

'Ze/ophyllum 

Ftsh Haven 

Dolomite 

500ft 

------- Saturday Mountain 

Formation 

300ft+ 

Laketown 

Dolomite 

600ft+ 

Silurian 

Ordovician 

Saturday Mountatn Entelophyllum 

Lykophyllld 

~ corals 

-1--~-

Silurian formations, showing lettered coral zones. 

19 
20 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

proposed coral zonation, no single measureable reference 

section has been found to include all five of the zones in 

succession. Piecing together of zonal units in partial, overlapping sections passing from one mountain area to 

another of structurally deformed beds calls for integration 

of physical-stratigraphic and paleontologic data, not only 

from coral and graptolite research but also from investigation of all associated organic groups, toward a converging pattern of geologic dating evidence. 

ZONE A 

Mazourka Canyon reference section, California.-Comparative thicknesses suggest that the 

Vaughn Gulch Limestone occupies about the same stratigraphic interval as the Hidden Valley Dolomite to the 

southeast. The lowest Vaughn Gulch beds contain the 

zone A solitary rugose coral Dalmanophyllum sp. A, together with a small tryplasmid, a pycnostylid, favositids, 

Heliolites, and the brachiopod Camarotoechia. The 

primary zone A indicator Palaeocyclus of the basal Hidden 

Valley Dolomite was not found in the Vaughn Gulch 

Limestone. 

Detailed geologic mapping of the Independence quadrangle by Ross (1966) demonstrates that northward in 

Mazourka Canyon the stratigraphic interval normally occupied by the Vaughn Gulch Limestone is in considerable 

part occupied by calcareous shale, siltstone, and argillaceous limestone in which Monograptus is a common 

fossil. Named separately as the Sunday Canyon Formation 

by Ross (1963), these graptolitic beds may be compared to 

wholly graptolitic facies equivalents of the Roberts 

Mountains Formation of the central Great Basin. The 

Sunday Canyon graptolite beds probably represent 

horizons above coral zone A. Corals in the uppermost beds 

of this unit are discussed below under correlatives of Great 

Basin Silurian coral zone E. 

Tuscarora Mountains, Nev.-Graptolite beds perhaps 

slightly younger than coral zone A are known in the 

Tuscarora Mountains, 75 miles north of Roberts Creek 

Mountain (Berry and Roen, 1963). The graptolites a few 

feet above the basal chert corresponding to the basal chert 

of unit 1 in the type Roberts Mountains Formation were 

considered to be early Wenlockian by Berry and Roen, representing the British zone of Monograptus 

riccartonensis. No associated coral or other shelly faunas 

were reported. 

Carlin mining district, Nevada.-Strongly defonned 

Silurian rocks assigned to the Roberts Mountains 

Formation underlie large areas in the Carlin mine vicinity 

of the southernmost Tuscarora Mountains. Coral and 

brachiopod faunas from localities along Maggie Creek for 

the most part probably represent horizons in the upper 

part of the formation. A Silurian fossil assemblage of unknown horizon contains Cyathophylloides similar to C. 

fergusoni of coral zone A. Associated brachiopods are 

small Coelospira, Fardenia, Ptychopleurella, and small 

coarse-ribbed Conchidium-like pentamerids. The 

brachiopods suggest that this assemblage may be younger 

than coral zone A. 

Ruby Mountains, Nev.-Crinoidal dolomitic limestone containing the button coral Palaeocyclus occurs at 

locality Ml336, on the north side of the north fork of 

Mitchell Creek, 3 miles northeast of Mitchell Ranch. Associated are Halysites, favositids, Atrypa, and 

Camarotoechia-like brachiopods in a fauna probably representing coral zone A. 

Confusion Range, Utah.-lsolated exposures of 

Silurian dolomite in this area (loc. Mll29) contain a large 

zone A fauna. Beds in question (R. K. Hose, written 

commun., 1964) do not form part of a continuous Laketown Dolomite section but crop out in a minor fault block. 

Rugose corals of this assemblage are Palaeocyclus d. P. 

porpita, Brachyelasma sp., and Tryplasma d. T. 

hedstromj. Tabulate corals include favositids, A lveolites, 

Heliolites, and Halysites. Other fossils are Encrinurus, 

Hesperorthis, Atrypa, and Atrypina. 

Ikes Canyon reference section, Nevada.-Platy limestone and calcareous shale in the lower part of the Masket 

Shale of Kay and Crawford ( 1964, p. 439) are correlative 

with coral zone A and share with it the colonial rugose 

coral Arachnophyllum kayi. Other rugose corals in these 

lower beds are Cyathophylloides fergusoni and 

Neomphyma crawfordi. The primitive cerioid genus 

Cyathophylloides is more commonly Late Ordovician. 

Sitnilar Arachnophyllum was reported in the lowermost 

Gotland Silurian by Lindstrom ( 1884, p. 7). This genus 

ranges upward as high as the Brownsport Forn1ation of 

eastern North America, but in Gotland and the Great 

Basin it is known only in Early Silurian beds. 

Roberts Creek Mountain reference section, 

Nevada.-The 300-foot interval of unit 1 and the lowermost part of unit 2 in the type Roberts Mountains 

Formation probably includes the time-stratigraphic 

equivalent of coral zone A, but it has yielded no 

Palaeocyclus, Dalmanophyllum, or Arachnophyllum. 

Other than poorly preserved Monograptus, these beds contain pycnostylids, Orthophyllum, favositids, Cladopora, 

Heliolites, and Halysites. Among the brachiopods are 

small Conchidium-like pentamerids,Dicaelosia,Eatonia?, 

Atrypa, and Merista?. 

ZONEB 

Funeral Mountains section, California.-Coral zone B 

faunas have been collected by J. F. McAllister 3 miles 

south-southwest of Schwaub Peak (Ryan quadrangle), 110 

feet above the base of the Hidden Valley Dolomite. Rugose 

corals are Ryderophyllum, Pycnactis, and Brachyelasma, 

together with favositids, Heliolites, Hesperorthis, and the 

cephalopods Huronia and Huroniella. Also present is the 

large dasycladacean alga Verticillopora. About 300 feet 

above the base in the same section occurs another fauna 
GEOLOGIC CORRELATION WITHIN THE GREAT BASIN 21 

characterized by Try plasma, Halysites, A lveolites, 

Romingerella, and Cladopora. Associated brachiopods include Leptaena, Fardenia, Rhipidium, Atrypa, Atrypina, 

and Eospirifer (Striispirifer ). Lykophyllids, generally to 

be expected in coral zone B, were not found in this upper 

horizon. 

Roberts Creek Mountain reference section, 

Nevada.-Fossils of coral zone Bare to be expected in the 

middle and upper beds of unit 2 of the type Roberts 

Mountains Formation. Possibly because of limestone 

facies, the zone B indicators Ryderophyllum, Pycnactis, 

and Petrozium of the Hidden Valley Dolomite have not 

been found in this section. Rugose corals occurring here 

are Tryplasma, Palaeophyllum, Diplophyllum, and 

Microplasma, together with the tabulates Halysites, 

Heliolites, Cladopora, and Aulopora. 

Brachiopods abundant in the higher part of unit 2, 

possibly within the range of coral zone B, are Coelospira, 

Pytchopleurella, and finely ribbed Conchidium-like 

pentamerids. Of the last one species superficially resembles the Norwegian Conchidium milnsteri Kiaer, as 

described and figured by St. Joseph (1938, p. 301); this 

species has been reported in southern Norway Silurian 

zone 5b and is considered Early Silurian (Llandoverian). 

ZONEC 

The distinctive rugose coral fauna of zone C in the 

Roberts Creek Mountain reference section has not been 

recognized elsewhere in the Great Basin. In California, 

that part of the Hidden Valley Dolmnite above 

McAllister's (1952, p. 15) unit 1 and above coral zone B of 

the type area Hidden Valley has yielded no significant 

fossiltnaterial. Likewise the Vaughn Gulch Limestone in 

Mazourka Canyon is sparingly fossiliferous within the interval where zone C indicators would be expected. In other 

areas studied, lithologic equivalents of the Roberts Mountains Formation, possibly correlative with zone C, belong 

to the platy graptolitic facies and, therefore, have yielded 

no Rugosa. 

ZONED 

Mazourka Canyon reference section, California.-Abundant fossils below coral zone E in the middle of the Vaughn Gulch Limestone are the large dasycladacean algae Verticillopora. These are similar to 

Verticillopora associated with the zoneD coral biota in the 

Roberts Creek Mountain and Ikes Canyon reference 

sections. 

Ikes Canyon reference section, Nevada.-Stylopleura, 

Tonkinaria, and large Verticillopora occupy an interval 

considerably above the horizon of coral zone A in the 

Masket Shale of Kay and Crawford ( 1964, p. 439) at Copper 

Mountain. Intermediate strata have not yielded the indicators of coral zones Band C, but coral zone E is present 

in higher strata, which Kay and Crawford included in 

their McMonnigal Limestone. 

Confusion Range, Utah.-Abundance of the 

dasycladacean alga Verticillopora in the upper part of the 

Laketown Dolomite of the Confusion Range, Utah (fig. 7, 

col. 10), suggests that the time-stratigraphic interval of 

coral zone D may be represented. Verticillopora is 

especially common elsewhere in limestone facies of coral 

zone D, during which time the genus appears to have 

peaked. The horizon of prolific Verticillopora lies in unit 

46, 330 feet below the top of the Laketown in a stratigraphic section measured by R. K. Hose, of the U.S. 

Geological Survey, in the Ibex Hills, Confusion Range, 

Utah (written commun., 1954). In this section the Laketown Dolomite is 1 ,203 feet thick and lies between the Fish 

Haven Dolomite of Late Ordovician age below and the 

Sevy Dolomite of Early Devonian age above. The distinctive Howellella pauciplicata fauna is present in beds 87 

feet below the top of the Lake.town in unit 48 of the Hose 

measured section. This fauna also characterizes the higher 

beds of Lone Mountain Dolomite unit 2 in Nevada and occupies the upper Lone Mountain-Laketown biofacies. 

Perhaps because of facies differences, the Rugosa of coral 

zone D do not occur in the Vertic i llopora beds of the Laketown or the Lone Mountain. 

ZONE E 

Roberts Creek Mountain reference section, Nevada. -Strata above coral zoneD in the upper part of unit 3 

in the type Roberts Mountains Formation are sparsely 

fossiliferous dolomite, passing upward into barren 

dolomite beneath the Nevada Formation. Within this undifferentiated and barren dolomite, coral zone E may well 

be represented, together with an Early Devonian Rabbit 

Hill equivalent. Certain zoneD corals, such as Stylopleura 

berthiaumi, are very similar to zone E species, suggesting 

that zones D and E may overlap; however, as presently 

known they represent somewhat different biofacies. 

Ikes Canyon reference section, Nevada.-Australophyllum (Toquimaphyllum) johnsoni, a limestone facies 

occupant and the n1ost distinctive zone E indicator, is associated with Kyphophyllum on the northwest side of 

Copper Mountain. The beds appear to lie within the 

McMonnigal Limestone of Kay and Crawford ( 1964). 

Lower horizons in the same section on the southwest contain corals of zones D and A. Exposures east of Copper 

Mountain contain Rhizophyllum and probably also fall 

in coral zone E. 

Carlin mine area, Nevada.-Mapping and stratigraphic investigation in progress by the U.S. Geological 

Survey in this part of northern Eureka County and adjoining Elko County, Nev., has disclosed strongly deformed rugose-coral-bearing strata of Late Silurian and 

Early Devonian ages. These coralline beds are provisionally assigned to the Roberts Mountains Formation 

and to the Rabbit Hill Limestone. At the Bootstrap mine, 

north of the open-pit Carlin mine, upper .beds of the 
22 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Roberts Mountains Formation contain large heads of 

Australophyllum (Toquimaphyllum), n. sp., having 

smaller and more slender corallites than A. 

(Toquimaphyllum) johnsoni, n. sp., of Silurian coral 

zone E. Other exposures in the Carlin mine area yield 

another type of Australophyllum and fragmentary corals 

classified as Entelophyllum, Palaeophyllum, and Chonophyllum. The Bootstrap mine Toquimaphyllum is very 

similar to Australophyllum (Toquimaphyllum) 

originalis (Zhn1aev) from the Ural Mountains, Russia 

(Shurygina, 1968, pl. 59, figs. 3a, b). The Ural species 

originalis is reported to occur with Gotlandian type 

Silurian corals, this association being interpreted by 

Russian paleontologists as Early Devonian. 

Antelope Peak, Elko County, Nev.-Rugose corals from 

this area north of Wells, collected by B. L. Peterson, 

include Toquimaphyllum similar to johnsoni of coral 

zone E and pycnostylids resembling Stylopleura. 

Mazourka Canyon reference section, California.-Great Basin Silurian coral zone E occupies a 200-

foot interval at the top of the middle unit of the Vaughn 

Gulch Limestone (fig. 3 ). The interval contains a large 

and diverse but rather poorly preserved coral biota. The 

common coral is Toquimaphyllum, which closely resembles Australophyllum (Toquimaphyllum) johnsoni; 

occurring with this are Australophyllum sp., Kyphophyllum, Chonophyllum-like forms, and Crassilasma? 

sp. Float material of Rhizophyllum sp. D doubtless came 

from these beds. Plectatrypa is the only associated brachiopod identified. Strata just below coral zone E carry abundant large Vertici llopora (pl. 16 ); this dasycladacean alga 

ranges up into zone E, appearing also in the lowest beds of 

the upper unit of the Vaughn Gulch Limestone at locality 

M1093. The upper unit is considered to be Upper Silurian 

or Lower Devonian. The Verticillopora-rich beds beneath coral zone E may represent Silurian coral zoneD, as 

these large dasycladaceans appear to have peaked at about 

that time-stratigraphic interval. Rugose coral indica.tors 

of coral zone D were not found in this section. 

The lowest beds of the Vaughn Gulch upper unit at 

locality M1093 contain, in addition to Verticillopora, the 

rugose corals Australophyllum sp. (pl. 12, fig. 5), Kyphophyllum similar to K. nevadensis (pl. 14), Ryderophyllum 

sp. (pl. 6, fig. 8), Crassilasma sp. (pl. 6, fig. 9), and Chonophyllum sp. (pl. 8, fig. 8). 

The Sunday Canyon Formation (Ross, 1966) exposed 

north of the Vaughn Gulch area in Mazourka Canyon is 

largely a graptolitic facies. However, a cerioid rugose coral 

collected in 1969 by C. H. Stevens in the upper 40 feet of the 

Sunday Canyon is provisionally assigned to Australophyllum; this coral resembles Australophyllum sp. from 

locality Ml093 in the upper Vaughn Gulch unit just above 

Silurian coral zone E. In both places these higher strata are 

provisionally classified as Upper Silurian or Lower 

Devonian (fig. 3 ). 

GREAT BASIN RUGOSA AND CORRELATION 

WITH DISTANT SILURIAN ROCKS 

Most Great Basin Silurian rugose corals are congeneric 

with forms known in Europe, Australia, and eastern 

North America. Several special researches and 

monographs upon Silurian Rugosa of Great Britain, 

Gotland, Czechoslovakia, and Russia facilitate fossil 

comparison and correlation with reference sections in 

these distant regions. 

The Gotland column is an incmnparable yardstick for 

the coral·bearing carbonate Silurian of western Europe and 

for the rest of the world; it is with Rugosa of this large 

island that many of the closest paleontologic comparisons 

are made (fig. 8). Correlation with the standard British 

Silurian sequence is indirect and places a premium upon 

graptolite evidence. Neither in the Great Basin nor in 

Gotland does the known Silurian graptolite succession 

approach completeness. Hede's (1942) evaluation of the 

Gotland column in terms of British graptolites provides a 

circuitous avenue of geologic comparison between the 

Great Basin and British sequences, through the medium of 

associated Gotland rugose corals. Noteworthy comparisons of Great Basin Rugosa with American and Old 

World Silurian species are dealt with below in accordance 

with the proposed fivefold zonal scheme. 

ZONE A 

Northwest Canada and A laska.-Palaeocyclus, reported 

by Norford (1962, p. 12) from the dolomitic Sandpile 

Group of northern British Columbia, suggests the 

presence of an Early Silurian horizon. However, the rather 

extensive coral assemblages dealt with by Norford appear 

on the whole to be somewhat younger and are perhaps 

representative of coral ;zone B. Palaeocyclus kirbyi Meek 

from Porcupine River, Alaska, was reported by Bassler 

(1937, p. 190, pl. 30, figs. 7-9) as Devonian; this occurrence 

has not been confirmed, and an Early Silurian age seems 

plausible. 

New York State.-The diagnostic button coral 

Palaeocyclus of coral zone A suggests correlation with the 

Clinton Group of New York State and eastern Canada, 

where species of this coral are fairly common (Bassler, 

1937, p. 190). A species of Palaeocyclus from the Michigan 

Silurian is reported to be somewhat younger. 

Gotland, Sweden.-Early Silurian (Llandoverian) 

deposits include the Lower Vis by Marl, Upper Visby Marl 

(fig. 8), and reddish marl stratigraphically beneath the 

Lower Visby. Oldest of the Gotland rugose corals is a 

species of Arachnophyllum similar to A. typus (McCoy) 

which occurs at Visby below the low-water line in the 

reddish marl underlying the Lower Visby (Lindstrom, 

1884, p. 7; Hill, 1958, p. 153). The genusArachnophyllum 

is not reported above the reddish marl horizon in Gotland. 

In North America it continues upward to younger beds of 

the Niagara Group and the Brownsport Formation 
CORRELATION WITH DISTANT SILURIAN ROCKS 23 

jc ~ ~ 

Q) 

·.::: ~-~ c ~ Gotland rugose corals having affinity to Great Basin Silurian Q) 

co .!!1 0 Gotland grapolites Gotland rock (/) .._ N 

~:l- species in coral zones as indicated by symbols and (Hede, 1942) units ~ 

e~~ numbers ·.;:; 

(.9 8 ~ 

I ? Sundre 

I I 

I Hamra 

I I Burgsvik E Toquimaphyllum I I s ..... .5 Eke Q) rectiseptatum5 I I a. Entelophyllum 0 

a. 5. :0 • I fasciculatum * Monograptus Hemse ::::) I :l 

Rhizo~hyllum I I I nilssoni Klinteberg ...J 

I I I I I 

I 0 I I I 

I I I I I Cyrtograptus Mulde I-- I Kodonophyllum•5 I I I I richteri I I 

I 

lundgreni 

I I I 

I I I c c I I I I 

Halla 

.!!1 I :l I I I I I Phaulactis .::t (/) I u 

E .!!: I cyathophylloides Chonophyllum •5 c -c I •2 Cyrtograptus ellesi Slite Q) 

~ 

• 

I flabellata I Pycnactis• 2 ~ :;;! I mitrtfta 

B I I I I 

I 

Tofta 

I I .2 I I I 

I I I I I I I I I 

f..-- Dalmanophyllu~ 1 Kodonophyllum •5 I I I Hogklint e--

I I dalmani I truncatum 

Phaula'ctis-2 I 

Schlotheimophyllunz"l Monograptus Upper Visby ~ Q:i angusta I spiralis Q) 

patella tum > s A I 0 

0 .6.1 -c ...J c I 10 

Palaeocyclus & 1 I Lower Visby ::i 

porpita Arachnophyllum~ 

typus 

\1 Schlotheimophyllum is probably related 

to Mucophyllum of Great Basin 

Silurian coral zone E 

* Entelophyllum of upper Lone MountainLaketown biofacies 

FIGURE 8.-Gotland stratigraphic units and rugose corals related to Great Basin forms. 

(Amsden, 1949, p. 104; Stumm, 1964, p. 30) 

Arachnophyllum kayi of Great Basin Silurian coral zone 

A is similar to A. typus. 

Palaeocyclus porpita subsp. mcallisteri of coral zone A 

rather closely resembles the Lower Visby P. porpita, and 

Dalmanophyllum sp. A is close to D. dalmani of the 

Hogklint Group (fig. 8), which is earliest Wenlockian 

(Hede, in Regnell and Hede, 1960, p. 55). 

The Llandoverian Upper Visby Marl contains 

lykophyllid corals (Phaulactis) and kodonophyllids 

(Schlotheimophyllum) not present in great Basin coral 

zone A, the lykophyllids appearing in coral zone Band the 

kodonophyllids in coral zone E. 

In terms of the classic Gotland sequence (fig. 8), Great 

Basin Silurian coral zone A fits in the interval bracketing 

the Llandoverian reddish marl below the Lower Visby 

Marl and the early Wenlockian Hogklint Group. 

ZONEB 

Klamath Mountains, Calif.-Lykophyllid Rugosa 

assigned to Cyathactis and the kyphophyllid genus 

Petrozium are present in upper beds of the Gazelle 

Formation, which is considered to be Ludlovian on the 

basis of brachiopod evidence, supported by similarity of its 

endophyllid corals to Great Basin zone E 

Toquimaphyllum. 

Northwest Canada.-Solitary lykophyllids suggesting 

zone B Ryderophyllum occur in the Sandpile Group of 

northern British Columbia (Norford, 1962, pl. XIV, figs. 

5-8). Palaeocyclus reported here presumably comes from 

lower strata representing coral zone A. 

Gotland, Sweden.-Lykophyllid corals characterizing 

zone B are common in the Lower and lower Middle 

Silurian beds of Gotland, where they are represented by the 

genera Phaulactis and Pycnactis. Zone B lykophyllids are 

assigned to Ryderophyllum, which, in mature growth 

stages, closely resembles Phaulactis. In Gotland the 

lykophyllids appear to have peaked in Wenlockian time. 

Russia.-A lykophyllid frorri Podolia assigned by 

Bulvanker (1952, pl. 2) to Phaulactis cyathophylloides 

Ryder resembles zone B Ryderophyllum. The Podolian 
24 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

species comes from beds reported to range in age from 

middle Wenlockian to Ludlovian. 

Shropshire, England.-Petrozium mccallisteri of zone 

B resembles P. dewari, the type species, described from the 

Shropshire, England, Early Silurian (Smith, 1930, p. 307). 

This colonial genus ranges through the Silurian, to judge 

from the Gazelle occurrence (Klamath Mountains, Calif.), 

here considered to be Ludlovian. 

ZONEC 

New York State.-Entelophylloides (Prohexagonaria) 

occidentalis is not cl0sely related to Rukhin's type species 

of Entelophylloides, which is the American Cobleskill 

Late Silurian Columnaria inequalis (Hall). It appears 

doubtful that Great Basin coral zone C is as young as the 

New York Cobleskill. 

Gotland, Sweden.-An undescribed Entelophylloides 

(Prohexagonaria) from the Visby vicinity, figured only in 

transverse section by Smith and Tremberth (1939, pl. VIII, 

fig. I), rather closely resembles zone C occidental is. The 

Gotland species, to judge from its recorded geographic 

occurrence, came from beds somewhere in the interval of 

the Lower Visby Marl to the Hogklint Group and is, 

therefore, high Llandoverian to early Wenlockian. 

Ural Mountains and Siberia.-Cerioid Rugosa 

resembling Entelophylloides (Prohexagonaria) occidentalis are known from middle and Upper Silurian beds 

of the Ural Mountains and Siberia (Sytova, 1952, p. 140, pl. 

IV; Soshkina, 1955, p. 126, pl. XIII, figs. 2a, 25; Ivanovsky, 

1963, p. 86-90, pl. XXII, figs. I a, I b, and pl. XXIV, figs. 2a, 

2b). These were initially assigned to Entelophyllum 

Wedekind, Evenkiella Soshkina, and Tenuiphyllum 

Soshkina. Species classified as Entelophyllum and 

Evenkiella are closest to the Great Basin occidentalis. 

Evenkiella has more of a tendency to develop lonsdaleioid 

dissepiments, a character not usual with Entelophyllum 

or Entelophylloides. Entelophyllum is normally 

phaceloid, not cerioid; thus, some of the Russian and 

Siberian species in question may belong in Rukhin's 

Entelophylloides. 

Eastern Australia.-Tryplasma newfarmeri of coral 

zone C, a smooth, cylindrical, phaceloid tryplasma, is 

rather close morphologically to Tryplasma lonsdalei 

Etheridge, as figured by Hill (1940, p. 406, pl. XII, figs. 

l3a-c) from the Yass-Bowning district. The host rocks are 

reported to be Wenlockian, possibly including early 

Ludlovian (Hil1, 1940, p. 388-390), and therefore younger 

than coral zone C. Several Yass-Bowning Rugosa are, in 

fact, very similar to species in Great Basin coral zone E, 

here considered to be Ludlovian. 

ZONED 

Kentucky and Tennessee.-Externally rugate 

Tryplasma as represented by T. duncanae of coral zone D 

occurs in the Louisville Limestone of Kentucky and the 

Brownsport formatiOn of Tennessee. The Louisville 

species is T. prava (Hall) as figured by Stumm (1964, pl. 6, 

fig. 8); T. brownsportensis Amsden is the Brownsport 

representative (Amsden, 1949, pl. XXVII, figs. 7-13). It is 

probable that both species are older than Great Basin 

Silurian coral zone D. 

Gotland, Sweden.-Tryplasma hedstromi Wedekind 

(1927, pl. 29, figs. I, 2) is externally suggestive of T. 

duncanae. The Gotland species comes from the Visby area, 

probably from strata ranging in age from late 

Llandoverian to early Wenlockian (fig. 8) and therefore 

considerably older than coral zone D. 

ZONEE 

Klamath Mountains, Calif.-Rugose corals related to 

species of Great Basin coral zone E occur in the higher beds 

of the Gazelle Formation of the northeast Klamath region; 

other Rugosa in these strata are closer to zone B species. 

Similar species of the brachiopod Plectatrypa are present 

in coral zone E and the upper Gazelle beds. 

Of the Rugosa, Gazelle species of Kodonophyllum, 

Kyphophyllum, and undescribed endophyllids are allied 

to zone E species. The Gazelle endophyllids are the 

analoguelof the new subgenus Toquimaphyllum. Gazelle 

lykophyllids assigned to Cyathactis resemble zone B 

Ryderophyllum and Gotland Phaulactis. Gazelle 

Petrozium differs specifically from P. mcallisteri of coral 

zone B. Brachiopod ties between the Gazelle Formation 

and the Alaskan Silurian favor Ludlovian age and bring 

these beds more in line with Great Basin Silurian coral 

zone E. 

Southeastern Alaska. -A complex solitary coral 

collected in Coal Canyon, Simpson Park Mountains, and 

assigned provisionally to the Russian genus 

Salairophyllum Besprozvannikh, 1968 (pl. 12, figs 6-8) is 

similar to undescribed Salairophyllum in Late Silurian 

beds of northern Heceta Island and Kuiu Island, Alaska. 

Collections from locality Mll86, Kuiu Island, also include 

this form in direct association with Late Silurian 

Conchidium alaskense. 

Gotland, Sweden.-Three zone E rugose genera are represented in Gotland (fig. 8) by similar species. Chonophyllum simpsoni resembles C. flabellata (Wedekind) of 

the Slite Group (Wenlockian), Kodonophyllum mulleri 

resembles K. richteri Wedekind from Lilla Karlso Island 

off Gotland, and Rhizophyllum cf. R. enorme Etheridge 

may be compared to Rhizophyllum of the Hemse Group 

(Ludlovian). Patellate corals of coral zone E assigned to 

Mucophyllum oliveri have certain features of Gotland 

Schlotheimophyllum patellatum (Schlotheim) from the 

Visby Marl, as figured by Smith ( 1945, p. 18, pl. 32), but are 

generically different. 

Spongophyllum rectiseptatum Dybowski ( 1873a, p. 

479, pl. IV, figs. 3, 3a) is probably Toquimaphyllum. The 
SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 25 

locality of Dybowski's material suggests a horizon near the 

Eke Marl of Gotland (fig. 8), and therefore a Ludlovian 

age. 

Gotland Rugosa comparable to species of coral zone E 

occur within the age range of late Llandoverian for 

Schlotheimophyllum to early Ludlovian or Monograptus nilssoni zone for the Hemse Group Rhizophyllum (Hede, 1942, p. 22). Kodonophyllum from Lilla 

Karlso Island is high Wenlockian or low Ludlovian in 

age. 

Czechoslovakia. -A ustralophyllum (Toquimaphyllum) fritschi (Novak, in Po~ta, 1902, pl. 102, figs. 6-8) 

resembles the undescribed Gazelle Formation endophyllids but is probably more closely allied to A ustralophyllum (Toquimaphyllum) johnsoni of Great Basin 

coral zone E. The Czechoslovakian analogue is considered to be Ludlovian, occurring in strata at Kozel 

("Bande e2"). Prantl ( 1940, p. 9) tc·nned these beds the "e(3" 

zone. 

Ural Mountains.-Newly described rugose corals from 

the Ural Mountains (Shurygina, 1968) resemble species 

known in the Gotland Silurian, in Silurian rocks of the 

Cordilleran belt of North America, in southeastern 

Alaska, in Eastern Australia, and in eastern Europe. 

Among these Russian corals are species of -,Toquimaphyllum, several forms of Tryplasma, Neomphyma, 

Rhizophyllum, Spongophylloides, Holmophyllum, 

pycnostylids, and lykophyllids. Others among these Ural 

corals are possible Kodonophyllum and Kyphophyllum 

as well as an undescribed cerioid genus occurring in the 

Silurian Gazelle Formation of the Klamath Mountains, 

Calif. Strata containing these Russian Silurian-Devonian 

boundary coral assemblages are in part classified by 

Shurygina as Early Devonian; in general, all have a 

decidedly Gotlandian aspect in terms of Rugosa. A ustralophyllum (Toquimaphyllum) giganteum (Shurygina) resembles Toquimaphyllum johnsoni of Great Basin 

Silurian coral zone E. Australophyllum (Toquimaphyllum) originalis (Zhmaev) is strikingly similar to the 

undescribed Toquimaphyllum earlier mentioned from 

the higher beds of the Bootstrap mine Silurian section, 

Carlin mine area. 

Eastern Australia.-Several rugose corals in Silurian 

beds of the Yass-Bowning district, as figured by Hill 

(1940), reveal fairly close morphologic similarities to 

species of coral zone E. Among these is Australophyllum 

(Toquimaphyllum) spongophylloides (Foerste), which 

shows features of Great Basin johnsoni. Also comparable 

to corals of Great Basin zone E are Yass-Bowning species 

of Mucophyllurn and Rhizophyllum. Tryplasrna 

lonsdalei of these Australian beds resembles a Great Basin 

Silurian coral zone C Tryplasma. The Yass-Bowning beds 

were considered by Hill to range in age from high 

Wenlockian to Ludlovian. 

CORRELATION OF LONE MOUNTAIN 

AND LAKETOWN DOLOMITE 

Silurian dolomite in the Ruby Mountains, Nev.(Ronald 

Willden and R. W. Kistler, written commun., 1967), is 

lithologically comparable to Lone Mountain Dolomite. 

The distinctive button coral Palaeocyclus collected by 

Willden and Kistler suggests that lower dolomites of this 

sequence are correlative with Hidden Valley Dolomite 

coral zone A and n1ay accordingly be equivalent by inference to lower beds of the Roberts Mountains Formation 

in the intermediate limestone belt. Other and probably 

higher dolmnite of the Ruby Mountains contains 

Entelophyllum like that of the upper Lone 

Mountain-Laketown biofacies in the eastern dolon1ite 

belt. 

As noted elsewhere, isolated dolomite exposures of the 

Confusion Range, Utah, doubtless pertaining to lowermost Laketown, contain a large coral zone A assemblage. 

Few of the rugose corals from other Laketown exposures 

in the eastern Great Basin have been sufficiently studied 

for generic identification. However, the published lists 

suggest that some are lykophyllids; others are probably 

Entelophyllum and the pycnostylids. None suggest the 

prolific colonial Rugosa of the intermediate limestone 

belt to the west. 

Rugose corals provide but n1eager evidence for correlation of the Lone Mountain and Laketown Dolomites 

with the Silurian of eastern North America. Palaeocyclus 

of the Confusion Range Laketown and the Ruby Mountains suggests a Silurian Clinton equivalence for lowermost Laketown. Entelophyllum of the upper Lone 

Mountain-Laketown biofacies reveals no intimate or 

specific relationship to described Entelophyllum of the 

eastern Louisville Limestone and the Brownsport (Smith, 

1933; Amsden, 1949; Stumm, 1964), all of which are 

geologically older. 

Gotland Entelophyllum ranges upward from Visby 

Marl (Wedekind, 1927) to the Eke Marl and Hemse Group. 

Upper Lone Mountain-Laketown Entelophyllum is 

closer to Gotland species from the higher Wen lockian and 

to those of the Eke and Hemse (Ludlovian). A1nong these, 

Entelophyllum articulatum (Wahlenberg) resembles the 

Lone Mountain E. eurekaensis, and E. fasciculatum 

Wedekind is similar to E. engelmanni of the Lone 

Mountain Dolomite. 

Ludlovian age of the upper Lone Mountain-Laketown 

biofacies containing Entelophyllum, as concluded on the 

basis of the Howellella pauciplicata fauna, suggests that 

this higher Silurian zone may fall within the interval of 

combined coral zones D and E. In possible support of this 

conclusion, the dasycladacean alga Verticillopora seems 

t.o have peaked in about the interval of coral zoneD and occurs abundantly in unit 46 beneath the Howellella 

pauciplicata beds of Confusion Range unit 48. (See fig. 7, 

col 10.) 
26 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

AGE CONCLUSIONS BASED 

ON SILURIAN RUGOSA 

Provisional age determinations are based largely upon 

rugose coral comparison with European and Australian 

faunas, especially those in formations of the Gotland section. Of supplementary value are coral and brachiopod 

compansons with Kla1nath Mountains and Alaskan 

Silurian, as well as with Silurian of eastern North 

America. 

Base and top of the Great Basin Silurian are fixed 

paleontologically with some assurance by coral faunas of 

zones A and E, of which zone A is the firmer in terms of 

European correlation (fig. 9). Zone A is late Llandoverian; 

zone E is considered to be late Ludlovian. Intermediate 

zones Band Care Wenlockian; zoneD is provisionally regarded as early Ludlovian. Supporting evidence is needed 

from detailed study of associated brachiopods, as well as 

from graptolites collected in established sections where 

graptolitic and shelly facies are both represented. 

Stratigraphic ranges of Silurian rugose coral genera are 

little known. A few, such as Palaeocyclus and Dalmanophyllum, seem restricted to the lower part of the system, 

but most carry through the middle Silurian Wenlockian to 

the Late Silurian. Peaks or regional bursts within certain 

generic lineages and confined to given stages may have age 

significance, as among the lykophyllids. In Gotland the 

Lykophyllidae peak, or attained an evolutionary acn1e, 

within early and middle Wenlockian time. Gotland 

Rhizophyllum reveals but a single burst-that of the 

Ludlovian Eke and Hemse (fig. 8). 

The subgenus Toquimaphyllum and related endophyllids have thus far been recognized only in Ludlovian 

and Early Devonian (Helderbergian) rocks. Mycophyllidae range upward from the late Llandoverian 

(Upper Visby) to Great Basin coral zone E (Ludlovian). 

The Upper Visby Schlotheimophyllum is generically distinct from the higher Wen lockian and Ludlovian 

Mucophyllum of Australia, the Klamath Mountains, and 

the Great Basin. 

Long-ranging as a big genus, Entelophyllum will 

eventually lend itself to taxonomic subdivision. In 

Gotland (fig. 8), Entelophyllum is common and diverse in 

the Eke Marl (Ludlovian), as it is in the Great Basin upper 

Lone Mountain-Laketown biofacies, also considered to be 

Ludlovian. Eastern representatives of this group in the 

Louisville and Brownsport are older. 

Great Basin Silurian coral zone A.-Late Llandoverian 

age of coral zone A harmonizes with the Gotland occurrence of Palaeocyclus porpita and pre-Lower Visby 

Arachnophyllum (fig. 9). Great Basin Dalmanophyllum 

sp. A is related to HogklintDalmanophyllum dalmani, an 

early Wenlockian coral in Gotland. 

Great Basin Silurian coral zone B.-Wenlockian age of 

coral zone B is supported by fairly conclusive superposition above the interval of coral zone A and by the presence 

of the lykophyllids Ryderophyllum and Pycnactis. In 

Gotland this fan1ily peaks in the Wenlockian. Petrozium 

of coral zone B resembles the high Llandoverian P.' dewari 

of Shropshire, England, but is also similar toPetrozium of 

the Ludlovian beds in the upper part of the Gazelle 

Formation in the Klamath Mountains. 

Great Basin Silurian coral zone C.-Probable Wenlockian age of coral zone Cis neither strongly supported 

nor controverted by two rugose corals, Tryplasma newfarmeri and Entelophylloides (Prohexagonaria) occidentalzs, or by its stratigraphic position in the Roberts Creek 

Mountain reference section (fig. 4) below coral zone D. 

Try plasma newfarmeri is similar toT. lonsdalei of the late 

Wenlockian and Ludlovian Y ass-Bowning beds of 

Australia. The Entelophylloides resembles a species from 

Visby, Gotland, which is probably no younger than 

Wenlockian. 

Study of the abundant brachiopod fauna of Roberts 

Mountains unit 2 just beneath coral zone Cis expected to 

shed light on the age of these beds. Conchidium-like pentamerids seemingly differ from all known Late Silurian 

Conchidium of the Pacific Border province in the 

Klamath Mountains and in southeastern Alaska. 

Great Basin Silurian coral zone D.-This coral zone is 

provisionally regarded as early Ludlovian, pending 

elucidation of the stratigraphic relationship of coral zone 

D to Ludlovian coral zone E within the Roberts Creek 

Mountain reference section. The two zones share the distinctive pycnostylid genus Stylopleura and may overlap in 

the time-stratigraphic sense. Occurrence of Verticillopora 

in type coral zone D suggests that it may predate zone E; 

this dasycladacean is especially. abundant immediately below coral zone E of the Mazourka Canyon reference section (fig. 3). The rugate Try plasma duncanae of coral zone 

D suggests a somewhat greater age, as it resembles 

probable Wenlockian T. prava of the Louisville Limestone (Stumm, 1964, pl. 6, fig. 8) and the Gotland T. 

hedstromi from strata that are probably also Wenlockian 

(Wedekind, 1927, pl. 29, figs. 1, 2). 

Great Basin Silurian coral zone E.-Coral zone E of late 

Ludlovian age includes the uppermost Silurian beds of the 

Great Basin within the intermediate limestone belt. Overlying beds in the Coal Canyon reference section carry the 

Helderbergian (Early Devonian) Rabbit Hill fauna. Endophyllid corals of the subgenus Toquimaphyllum are 

characteristic and related to an undescribed men1ber of this 

family in Ludlovian upper members of the Klamath 

Mountains Gazelle Formation. Australophyllum (Toquimaphyllum) johnsoni of zone E is comparable to 

Spongophyllum rectiseptatum Dybowski of the Gotland 

Ludlovian Eke Marl, as well as to species of Toquimaphyllum 1n the Late Silurian of Czechoslovakia. 

Australian species in the Yass-Bowning beds are reported 

to be of late Wenlockian and Ludlovian age. 
COMPARISON OF SILURIAN CORALLINE ROCKS 27 

c: 

.~ 

c: 

0 

> Ql I I I 

a I I 1 

I I I 

E j Kodonophyllum ToquJaphyllum Rhizophyllum 

I I Kyphophyllum Chonophyllum .

~ 1 I Mucophyltm l 'I 1 gr---~-----------------+------~--J_ ____ _L __ ~I_L----~----~------~~------~ 

: : : I I I 

stylrura \ TonTria j 

D 

c: 

Ctl 

·;: 

~ 

U5 

~ 

"C 

"C 

~ 

f---

..... 

Ql 

~ 

0 

_J 

c: 

Ctl ..... ·c:; Ql 

·:; a. 0 a. "C ::::> 

0 

c 

8 

A 

I 

I 

I 

I 

I I 

Palaeophyllum 

I 

I 

Brachyelasma I Cyathophylloides 

nazmarphyllum 

I 

I 

rryprsma 

Ryderophyllum 

I Pyr'i' 

I 

I 

I 

I 

I 

I 

FIGURE 9.-Stratigraphic occurrence of characteristic Great Basin Silurian rugose coral genera. 

The Ludlovian burst of Rhizophyllum in the Hemse 

and Eke horizons of Gotland (fig. 8) is more or less paralleled by Rhizophyllum of Silurian coral zone E. However, 

the stratigraphic range of this genus extends at least from 

the Brownsport of eastern North America to the Early 

Devonian Konieprus of eastern Europe. In Australia and 

in Alaska, also, this coral is reported to have survived into 

the Devonian Period. 

COMPARISON OF SILURIAN CORALLINE ROCKS 

IN THE GREAT BASIN 

WITH THOSE OF OTHER REGIONS 

Morphologic and taxonon1ic comparisons of Great 

Basin Silurian corals with corals of the classic Silurian regions provide a basis for geologic correlation; at the same 

time, these studies invite comparative treatment of depositional and environn1ental conditions under which the 

coral-bearing strata accumulated. In this connection, two 

types of n1arine environment, broadly speaking, are 

considered: the environment of tectonically active geosynclinal belts, represented by the graywacke belt of the 

Pacific Border province, and the shelf environment, represented by the Niagara Series of the Great Lakes and the 

Gotland Silurian. 

In the Pacific Border graywacke belt, great volumes of 

siliceous conglon1erate, graywacke, bedded chert, and submarine volcanics rnanifest recurrent crustal movement 

and vulcanism. Depositional environments such as this 

might be expected to inhibit limestone accumulation and 

therefore to provide few benthonic sites favorable for extensive coral growth. Coralline rocks of the Klamath 

Mountains, Calif., and of southeastern Alaska fall within 

this province. Limestones of these regions are mostly 

lenses within the "dirty" siliceous clastics. Surprisingly 
28 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

enough, however, many of these circumscribed carbonate 

bodies are fairly pure, and many are coral bearing. 

Diagenetic dolomitization processes were not in operation 

here. Rugose corals of colonial growth habit are more 

abundant in the Klamath Mountains than in southeastern Alaska, where Silurian coralline life in general appears to have been son1ewhat less diverse and prolific. So 

far as known, the unstable tectonic-volcanic conditions of 

this belt did not foster environments required for widespread patch reef or biohermal growth like those of shelf 

seas. Silurian corals of the Pacific Border graywacke belt 

and the rocks in which they occur are treated in a separate 

report (Merriam, 1972). 

Coral faunas of the Great Basin Silurian appear to be 

less closely related to those of the Middle Silurian Niagara 

shelf seas than to those of either the Pacific Border province or the Gotland Silurian. However, the lack of wellpreserved Niagara coral comparative material makes possible only the vaguest of generalizations in this regard. 

Taxonomically and environmentally, the western faunas 

appear to differ appreciably. Unlike the Great Basin 

Silurian seas, shallow Niagara carbonate seas of th~ Great 

Lakes area were optimal for proliferation of 

bioherm-patch-reef con1plexes characterized by unstratified, altered core rock, inclined flank beds, and 

partial dolomitization, especially of the core rock 

(Lowenstam, 1948, 1950). 

For purposes of this investigation, the coral faunas of 

Gotland, Sweden, have provided a most valuable standard 

of morphologic and taxonomic comparison. In terms of 

deposition and environment, the Gotland column is, 

likewise, the best yardstick for the world Silurian marine 

carbonate rocks. 

In Gotland, the Silurian System is about 1,600 feet thick 

(Regnell and Hede, 1960, p. 46), a thickness comparing 

favorably with the Great Basin Silurian average thickness. 

Both sequences have the carbonate depositional characteristics of shelf seas, and both have a comparatively small 

thickness for the Silurian System in a world sense. For 

example, the geosynclinal Silurian of southeastern Alaska 

is about 20,000 feet thick, or 12 times the thickness of the 

system in carbonate stable-shelf columns. Conceivably, 

the greater part of Silurian time is recorded by sedi1nents 

and faunas of the Gotland reference column, which comprises 13 primary map units that are defined on the basis of 

physical rock differences and supported by paleontological evidence. Whereas the Gotland strata and those of the 

Great Basin Silurian are predominantly carbonate, much 

argillaceous matter was pervasively admixed during the 

course of sedimentation in Gotland. The argillaceous debris, evidently of terrigenous derivation, occurs throughout the section as argillaceous limestone, marls tone, claystone, and shale. Associated with these sediments in 

Gotland are biohermallimestone, sandstone, oolitic limestone, and minor bentonitic deposits. Unlike Great Basin 

Silurian and unlike the Great Lakes Niagaran, the 

Gotland Silurian includes very little dolomite. Major lime 

contributors in Gotland were the crinoids, stromatoporoids, calcareous algae, and corals. 

Especially distinctive of the Gotland Silurian are innumerable bioherms in which the corals are associated 

with other lime contributors. These depositional features 

are found in some 10 of the 13 Gotland units. Typically, 

the Gotland bioherms have unstratified limestone cores of 

inverted cone shape which intertongue laterally with reef 

detritus (Hadding, 1941, 1950; Jux, 1957; Regnell and 

Hede, 1960). Unlike the Niagara bioherms, those of 

Gotland do not ordinarily have core-rock dolomitization. 

Greenish-gray or red argillaceous limestones occur with 

some Gotland biohenns. 

Although the Gotland Silurian is mainly of shelf-sea 

character, these lithologically diverse strata were repeatedly influenced during accumulation by landward 

crustal disturbances. Hinterland deformation acting upon 

the terrigenous debris source areas is manifested in the 

complex record of Gotland marine-sediment discontinuities, both vertical and lateral. Bioherm growth on the 

shallow sea floor was markedly influenced by frequent 

marine current changes, together with landward or seaward shift of the shore zone as a result of deformation. 

DEPOSITIONAL FEATURES OF GREAT BASIN 

SILURIAN CORALLINE ROCKS IN 

RELATION TO THE REEF PROBLEM 

Field studies of Great Basin Silurian coral-bearing 

strata have thus far failed to disclose complex bedding 

structures like the classic bioherms or patch reefs of the 

Niagara and Gotland sequences. Coral-rich limestones of 

the intermediate limestone belt are usually mediumcoarse-grained jun1bled bioclastics in which bedding is 

fairly even and crinoidal debris predominates. All fossils 

in such facies are obviously transported, the corals commonly showing little evidence of wear and having scattered, random distribution. Such deposits appear to have 

formed as banklike accumulations to which the fossils had 

been carried only short distances from their growth sites. 

Generally lacking in these limestones are in situ organicgrowth depositional structures which possessed initial 

bottom relief. Unstratified core rock and inclined flank 

beds like those of the Niagara and Gotland patch reefs 

have not thus far been recognized in the Great Basin 

Silurian strata. 

In the Great Basin Silurian, few exposures have been observed which reveal corals entombed in their original 

growth positions, but among these exposures are certain 

Entelophyllum beds in Lone 1\!Iountain Dolomite of the 

:Mahogany Hills and the Fish Creek Range. There, large, 

laterally extended colonies of a rather open colonial form 

occupy fairly even beds and seemingly existed in thin, 

dispersed coral fields. None of these in situ growths were 
CLASSIFICATION OF GREAT BASIN SILURIAN RUGOSA 29 

observed to have the wave-resistant mound, or dome configuration, which might have developed as a result of 

continued upward accretion of corals, algae, and other organisms, aided by sediment-binding agents. 

Theoretically, the Silurian shelf seas of the Great Basin 

in both limestone and dolomite belts would be expected to 

favor bioherm or patch-reef complexes in ecologically 

suitable places. The coral-rich bioclastics earlier discussed are perhaps interreef facies; the Entelophyllum 

fields may be reef-marginal or lagoonal. Another suggestion of reef proximity is the lenticular occurrence of 

contemporaneous depositional limestone breccias containing abundant corals. These have been described in the 

topmost Roberts Mountains limestone of the Simpson 

Park Range, Nev. (Winterer and Murphy, 1960, p. 126). At 

Coal Canyon the limestone clasts and matrix of these depositional breccias have yielded much of the Silurian coral 

study material from that vicinity. In theory, coarse depositional breccias of this kind might form as a product of 

wave action along a reef front. Other reefal features, such 

as inclined flank beds and unstratified core rock, were not 

observed in association. Similar coarse coral-rich limestone breccia-conglomerates are known also in the Klamath Mountains Silurian within the tectonically active 

Pacific Border graywacke belt; here again there is no 

further supporting evidence of reef origin (Merriam, 

1972). 

In comparison with the great stratigraphic and facies 

complexities of the shelf sea Gotland Silurian with its 

numerous patch reefs, the Great Basin Silurian of the 

eastern dolomite belt is on the whole far more uniform, as 

it has fewer abrupt lithofacies discontinuities. Tectonically, the marine environmental conditions appear to have 

been more stable in the Great Basin dolomite belt than in 

the Gotland nondolomitic, commonly very muddy seas. 

From these environmental assumptions, one can perhaps 

speculate that the more uniform, dolomitic deposition in 

the eastern dolomite belt served in some manner to arrest 

the development of reefal structures. 

Fairly stable tectonic conditions, again without proven 

marine reefal manifestations, prevailed also to the west 

within the Great Basin intermediate limestone belt. Decreasingly stable tectonic conditions probably prevailed in 

the westernmost part of the limestone belt as the hypothetical transition to the Pacific Border graywacke belt of 

active Silurian tectonism is approached. Hence, marine 

environments more like those of Gotland may conceivably have existed in buried and unexplored terrane in 

the northwestern part of the Great Basin province. 

DASYCLADACEAN ALGAE IN GREAT BASIN 

SILURIAN CORALLINE DEPOSITS 

Plate 16, figures 5-17 

Calcareous algae of the family Dasycladaceae were 

among the major limestone builders and played a 

504-634 0 - 73 - 3 

significant role in the economy of Great Basin Silurian 

seas. Dasycladaceae are represented here by Verticillopora 

Rezak, the conical to cylindrical thalli of which were long 

confused with sponges or with large crinoid stalks, either 

of which they may closely resemble. In 1954, P. E. Cloud 

called the writer's attention to plant affiliation of these fossils, following which the collections were intensively 

studied by Rezak (1959). Intimate ecologic association of 

Great Basin Silurian Rugosa with dasycladaceans calls for 

a brief reference to these plants. 

As in the Gotland Silurian (Rothpletz, 1908, 1913), calcareous algae are known to have contributed much lime in 

the Great Basin and the Pacific Border seaways. Johnson 

and Konishi (1959) and Rezak (1959) showed that 

Dasycladaceae, Solenoporaceae, and other algal families 

were active in the Klamath Mountains Silurian; however, 

the large Vertici llopora was not recognized in that region. 

The Great Basin Verticillopora ranges upward from 

coral zone B through coral zone E. It is, however, in about 

the interval of coral zone D that this fossil is most 

abundant. Verticillopora annulata develops to large size 

and in a variety of cylindrical, conical, and irregular 

turbinate shapes. In some beds of the Vaughn Gulch 

Limestone below coral zone E, this alga outnumbers the 

rugose corals. Similar large thalli occur with Rugosa in 

zone D of the Ikes Canyon reference section. In the Roberts 

Creek Mountain reference section, Verticillopora of coral 

zone D is smaller and more like that of unit 46 in the 

Laketown of the Confusion Range. (See fig. 7, col. 10.) 

Verticillopora of coral zone B is. narrowly cylindrical, 

strongly suggestive of a crinoid stalk, and may represent a 

distinct species. 

CLASSIFICATION OF GREAT BASIN 

SILURIAN RUGOSA 

Great Basin Silurian rugose corals here described are 

classified in 13 families. The usage and content of several 

families depart from Hill's 1956 classification, the most 

comprehensive and authoritative published thus far. Departures from Hill's scheme include the elevation of certain subfamilies to independent family status, the restoration of the family Pycnostylidae, and the shift of certain 

genera from one family to another believed to be more appropriate. Of three new genera proposed, Denayphyllum 

is not assigned to a family. 

Family Streptelasmatidae Nicholson, 1 1889 (as Streptelasmidae). 

Genus Rhegmaphyllum Wedekind, 192'1 

Rhegmaphyllum sp. h 

Genus Brachyelasma Lang, Smith, and Thomas, 1940 

Brachyelasma sp. B 

Genus Dalmanophyllum Lang and Smith, 1939 

Dalmanophyllum sp. A 

Family Stauriidae Edwards and Haime, 1850 

Genus Cyathophylloides Dybowski, 1873 

Cyathophylloides fergusoni, n. sp. 

1ln Nicholson and Lydekker (1889). 
30 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Family Stauriidae Edwards and Haime, 1850-Con. 

Genus Palaeophyllum Billings, 1858 

Palaeophyllum sp. b 

Palaeophyllum? sp. c 

Family Pycnostylidae Stumm, 1953 

Genus Stylopleura, n. gen. 

Stylopleura berthiaumi, n. sp. 

Stylopleura nevadensis, n. sp. 

Family Tryplasmatidae Etheridge, 1907 

Genus Tryplasma Lonsdale, 1845 

Group 1: Solitary-rugate Tryplasma 

Tryplasma duncanae, n. sp. 

Group 2: Fasciculate-cylindrical Tryplasma 

Tryplasma newjarmeri, n. sp. 

Tryplasma sp. R 

Genus Rhabdocyclus Lang and Smith, 1939 

Rhabdocyclus sp. B 

Rhabdocyclus sp. d 

Rhabdocyclus sp. K 

Genus Palaeocyclus Edwards and Haime, 1849 

Palaeocyclus porpita subsp. mea/listen, n. subsp. 

Genus Zelophyllum Wedekind, 1927 

Family Kodonophyllidae Wedekind, 1927 

Subfamily Kodonophyllinae, new subfamily 

Genus Kodonophyllum Wedekind, 1927 

Kodonophyllum mulleri, n. sp. 

Subfamily Mycophyllinae, new subfamily 

Genus Mucophyllum Etheridge, 1894 

Mucophyllum oliven, n. sp. 

Family Arachnophyllidae Dybowski, 1873 

Genus Arachnophyllum Dana, 1846 

Arachnophyllum kayi, n. sp. 

Family Lykophyllidae Wedekind, 1927 

Genus Pycnactis Ryder, 1926 

Pycnactis sp. k 

Genus Cyathactis Soshkina, 1955 

Cyathactis? sp. 

Genus Ryderophyllurn Tcherepnina, 1965 

Ryderophyllum ubehebensis, n. sp. 

Family Cystiphyllidae Edwards and Haime, 1850 

Genus Microplasrna Dybowski, 1873a 

Microplasrna? sp. R 

Family Goniophyllidae Dybowski, 1873a 

Genus Rhiwphyllurn Lindstrom, 1866 

Rhiwphyllurn sp. D, Oliver 

Family Kyphophyllidae Wedekind, 1927 

Genus Kyphophyllum Wedekind, 1927 

Kyphophyllum nevadensis, n. sp. 

Genus Petrozium Smith, 1930 

Petroziurn mcallisteri, n. sp. 

Genus Entelophyllurn Wedekind, 1927 

Entelophyllum eurekaensis, n. sp. 

Enteloplzyllum engelmanni, n. sp. 

Genus Entelophylloides Rukhin, 1938 (as subgenus) 

Subgenus Prohexagonaria, n. subgen. 

Enteloplzylloides (Prohexagonaria) occidentalis, n. sp. 

Genus Neomphyma Soshkina, 1937 

Neornphyrna crawfordi, n. sp. 

Genus Tonkinaria, n. gen. 

Tonkinaria simpsoni, n. sp. 

Family Chonophyllidae Holmes, 1887 

Genus Chonophyllum Edwards and Haime, 1850 

Chonophyllum simpsoni, n. sp. 

Family Endophyllidae Torley, 1933 

Genus Australophyllum Stumm, 1949 

Subgenus Toquimaphyllum, n. subgen. 

Australophyllum (Toquimaphyllum) johnsoni, 

n. subgen., n. sp. 

Family Acervulariidae Lecompte, 1952 

Genus Diplophyllum Hall 1852 

Diplophyllum? sp. m 

No family assignment 

Genus Salairophyllum Bresprozvannikh, 1968 

Salairophyllum? sp. 

Genus Denayphyllum, n. gen. 

Denayphyllum denayensis, n. gen., n. sp. 

SYSTEMATIC AND 

DESCRIPTIVE PALEONTOLOGY 

All 35 rugose coral species treated in this report were 

previously undescribed. Five are classified in the new 

genera Stylopleura, Tonkinaria, and Denayphyllum; two 

are assigned to the new subgenera Entelophylloides 

(Prohexagonaria) and Australophyllum (Toquimaphyllum). Twenty of the new species are given formal 

names, being represented in our collections by wellpreserved material considered appropriate for complete 

diagnosis. Fifteen species, mostly solitary Rugosa, are 

designated provisionally and informally by letter; whereas 

these lettered taxa have prime stratigraphic value, they are 

represented by rather poorly preserved, mostly incomplete specimens judged too few and inadequate to warrant 

formal species naming at present. In general, the stratigraphically more important unnamed species are assigned 

capital letters. Regretfully, with all of the studied species, 

the number of sectioned coralla is insufficient for 

quantitative variation techniques, which by modern 

standards is a part of any species characterization. 

The Great Basin Silurian coral zone is indicated under 

occurrence of most species. Locality numbers, such as 

Ml097, are recorded in the U.S. Geological Survey Menlo 

Park Paleozoic fossil locality catalogue; also, a register of 

these locality numbers accompanies this report. 

Descriptive terminology used in this report is largely 

that proposed by Hill in 1935 and 1956. 

Family STREPTELASMATIDAE Nicholson, 1889 2 

(as STREPTELASMIDAE) 

Reference genus and species.-Streptelasma cornzculum Hall. Ordovician, New York. 

Mostly solitary rugose corals lacking dissepiments, and 

with a septal stereozone; tabulae and tabellae usually but 

not always arched, and involved with septal ends as an 

axial structure in some species. In genera with a wide 

stereozone, tabulae may be obscure. 

This diverse and long-ranging family is probably ancestral to a large number of the post-Ordovician rugose 

2ln Nicholson and Lydekker (1889). 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 31 

corals and will probably eventually lend itself to subfamily taxonomic subdivision. Rhegmaphyllum, 

Brachyelasma, and Dalmanophyllum are the Great Basin 

Silurian Rugosa here classified. 

Genus RHEGMAPHYLLUM Wedekind, 1927 

1831. Turbinolia turbinata Hisinger (in part), p. 128. 

1868. Zaphrentis. conulus Lindstrom. p. 428; pl. 6, fig. 8. 

1927. Rhegmaphyllum Wedekind, p. H, pl. 24, figs. 6-8. 

1940. Rhegmatophyllum Lang, Smith, and Thomas, p. 114. 

1956. Rhegmaphyllum Wedekind. Hill, p. F269, fig. 182,9b, 9c. 

Type species.-Rhegmaphyllum turbinatum 

(Hisinger); by subsequent designation (Soshkina, 1937, p. 

85; see also Lang, Smith, and Thomas, 1940, p. 114). 

Silurian, Wenlockian, Slite group, Gotland, Sweden. 

Diagnosis.-Sn1all, solitary ceratoid-trochoid rugose 

corals with long, smooth major septa, some of which extend to axis; minor septa less than half the length of major 

septa. Septal stereozone narrow. Tabulae arched, some 

complete; may be weakly developed. Exterior nearly 

smooth; septal grooves weak or absent. 

Remarks.-These small and rather simple solitary 

streptelasmid corals are smaller than Streptelasma and 

have a narrower stereozone and a more discrete fossula. 

Orthophyllum of Po~ta (1902, pl. 112, figs. 5-7) has few or 

no minor septa and lacks a well-defined fossula. (See also 

Smith, 1930, p. 304, fig. 4.) 

In the Great Basin province, corals of this kind occur in 

the lower part of the Silurian. 

Rhegmaphyllum sp. h 

Plate 1, figures 7, 8 

Small silicified corals assigned to Rhegmaphyllum sp 

h occur in the lower part of the Hidden Valley Dolomite of 

southwest Great Basin. Only the exterior is known because the material is inadequate for thin-section preparation. 

Figured corallum with 26 smooth major septa in a deep 

conical calice, at the bottom of which most major septa 

meet the axis. Cardinal septum abbreviated in its fossula. 

Outer surface is almost smooth, with faint traces of 

longitudinal grooves. 

Occurrence.-In lower beds of the Hidden Valley 

Dolomite, Early Silurian, coral zone A northern Panarnint 

Range, where it is associated with Dalmanophyllum, 

Tryplasma, and Palaeocyclus. Whitetop Mountain, 

northern Panamint Range, locality M1096. Study material 

consists of three silicified coralla. 

Genus BRACHYELASMA Lang, Sn. l!:J4U 

1927. Dybowskia Wedekind, p. 18, pl. 1, figs. 10, 11 [not Dall, 1876]. 

1940. Brachyelasma Lang, Smith, and Thomas, p. 28. 

1956. Brachyelasma. Hill, p. F268, fig. 182,5a, 5b. 

Type species.-Dybowskia prima Wedekind; by 

original designation (Lang, Smith, and Thomas, 1940, p. 

28). Stavnestangen, Tyrifjord, Norway; in strata of either 

Late Ordovician or Early Silurian age. 

Diagnosis.-Trochoid-ceratoid solitary rugose corals 

lacking dissepiments and having subhorizontal, straight, 

or slightly arched tabulae, some of which are complete. 

Tabulae bent downward as they approach the wall. Major 

septa not meeting the axis, though commonly extending 

more than half that distance. Minor septa· short. Septal 

stereozone narrow. A fossula recognizable in some species. 

Remarks.-Brachyelasma shares some of the characteristics of Devonian siphonophrentids, especially the 

subgenus Breviphrentis which differs in possessing an 

elongate subcylindrical corallum and has amplexoid septa 

together with a wider stereozone (Merriam, 1973c). 

Siphonophrentis (Breviphrentis) commonly undergoes 

repeated rejuvenescence to give the corallum a narrow segmented appearance. 

Brachyelasma occurs in rocks of Late Ordovician, Early 

Silurian, and early Middle Silurian age. The type species, 

B. prima, is reported by Lang, Smith, and Thomas (1940, 

p. 28) to be Llandoverian, although Hill (1956, p. F268) 

implied a Late Ordovician age. In the Toquima Range of 

the Great Basin this genus has been found in the lower part 

of the Gatecliff Formation of Kay and Crawford (1964, p. 

437), which may be pre-Richmondian; Brachyelasma is 

found also in the Ely Springs Dolomite of Richmondian 

age, and in Silurian coral zones A and B. 

Brachyelasma sp. B 

Plate 1, figures 9-11; plate 16, figures 1, 2 

Silicified corals upon which this description is based 

were collected from the lower part of the Hidden Valley 

Dolomite in the northern Panamint Range and in the 

Funeral Mountains, Calif. 

About 32 major septa, thickened peripherally, tapering 

axially, and withdrawn from the axis; minor septa short. 

Septal stereozone very narrow. Tabulae complete, close 

spaced, and straight except for peripheral downward 

bend. No suggestion of a fossula, in transverse thin sections. One weathered specimen (pl. 16, fig. 2) shows a discrete fossular down-bend of the calice tabula in the 

position of a primary septum. 

Occurrence.-Early Middle Silurian, coral zone B; 

lower part of the Hidden Valley Dolomite. Northern 

Panamint Range: Ubehebe Peak area, locality M1094; 

Andy Hills, locality M1095. Funeral Mountains, Pyramid 

Peak area, localities M1097, Ml127. A somewhat different 

Brachyelasma occurs at locality M1098 in the Schwaub 

Peak area, Funeral Mountains (pl. 1, figs. 5, 6). Study 

material consists of two cm·alla (M1094), one corallum 

(M1095), one corallun1 (M1097), and one corallum 

(M1127). 
32 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

In the Confusion Range, Utah (loc. Mll29), 

Brachyelasma of this same general type is associated with 

Palaeocyclus and a large fauna indicative of Silurian coral 

zone A. Brachyelasma like the sp. B occurs elsewhere in 

beds of probable Late Ordovician age, such as the Gatecliff Formation of Kay and Crawford ( 1964) in the 

Toquima Range and beds in the Tuscarora Mountains of 

northern Eureka County, Nev., where this coral genus is 

associated with Catenipora, Palaeofavosites, and 

H espero_rth is. 

Genus DALMANOPHYLLUM Lang and Smith, 1939 

1933. Tyrza Scheffen, p. 33, pl. V, figs. 2, 3. 

1939. Dalmanophyllum Lang and Smith, p. 153. 

1940. Dalmanophyllum. Lang, Smith, and Thomas, p. 49. 

1956. Dalmanophyllum. Hill, p. F269, fig. 182.6a-6c. 

1961. Dalmanophyllum Lang and Smith. Minato, p. 81-86, text figs. 

20-23; pl. XI, pl. XIX, figs. 2-5. 

Type species.-Cyathaxonia dalmani Edwards and 

Haime, 1851; by original designation (Lang and Smith, 

1939, p. 153). Silurian, Hogklint Group, early 

Wenlockian, Gotland, Sweden. 

Diagnosis.-Small solitary rugose corals of trochoid 

shape with solid bladelike axial structure projecting upward in bell-shaped calice; transverse outline of calice rim 

broadly ovoidal and nonangulate. Fossula in line with 

median plane of axial structure. Major septa project axially to columella in early adult and younger growth stages. 

Minor septa short; major septa dilated. Septal stereozone 

narrow. Tabulae largely suppressed by septal thickening. 

Dissepiments absent. 

Remarks.-Dinophyllum differs from Dalmanophyllum in having a loose and open axial structure rather 

than a solid columella; its major septa are usually less 

dilated and are twisted toward the axis. Dinophyllum 

commonly does not develop well-defined short minor 

septa and is more often ceratoid than trochoid. 

The Late Ordovician Bighornia (Duncan, 1957) resembles Dalmanophyllum, but it normally is flattened 

apically, and the mature transverse section is commonly 

angulate. Bighornia may show even more dilated major 

septa than Dalmanophyllum, and minor septa are more 

weakly developed. 

Dalmanophyllum sp. A 

Plate 1, figures 1-3 

Dalmanophyllum sp. A is known only from exteriors; 

available material is insufficient for sectioning. Externally, this species closely resembles D. dalmani (Edwards and 

Haime), as figured by them (1851, pl. 1, fig. 6); a copy of 

one holotype figure of dalmani is here reproduced for 

comparison (pl. l, fig. 4). 

Epitheca with faint longitudinal striations, but no pronounced septal grooves; moderate rugae developed. Major 

septa in mature calice about 36; septa straight and smooth 

peripherally, becoming periaxially wavy where they join 

the laterally compressed columella. Solid columella projecting upward 3 millimeters in calice and elongate-ovoid 

in cross section, with long axis in cardinal-counter plane. 

Short septum in fossula probably the cardinal septum; 

fossula situated on convex side of corallum. 

Occurrence.-Early Silurian, coral zone A. Basal beds of 

Hidden Valley Dolomite, Whitetop Mountain, northern 

Panamint Range; locality Ml096. Basal part of Vaughn 

Gulch Limestone, Mazourka Canyon, northern Inyo 

Mountains, locality Ml09l. Study material consists of the 

two complete silicified figured specimens and fragments 

of coralla from Whitetop Mountain (loc. Ml096). 

Comparable columellate solitary corals assignable 

either to Dalmanophyllum or to Dinophyllum occur in 

the lower part of the Silurian section, Gazelle area, northeastern Klamath Mountains, Calif., and in the Montgornery Limestone near Taylorsville, Calif. 

Family STAURIIDAE Edwards and Haime, 1850 

Reference genus and species.-Stauria astreiformis Edwards and Haime. Silurian, Gotland, Sweden. 

Fasciculate and cerioid rugose corals having slender 

corallites mostly without dissepiments; tabulae straight or 

arched, and long lamellar major septa commonly extend 

to the axis. In some lineages of this family, dissepiments in 

a single column or sporadically in a broken column. 

Two of the species here described are placed in genera 

classified as Stauriidae; these are Cyathophylloides and 

Palaeophyllum. 

Genus CYATHOPHYLLOIDES Dybowski, 1873 

1851. Columnaria gothlandica Edwards and Haime, p. 309, pl. 14, 

figs. 2, 2a. 

1873. Cyathophylloides Dybowski, p. 334, 379. 

1940. Cyathophylloides Dybowski. Lang, Smith, and Thomas, p. 43. 

1950. Cyathophylloides Dybowski, Bassler, p. 274 (in part). 

1956. Cyathophylloides. Duncan, pl. 24, figs. 6a, 6b. 

1956. Cyathophylloides Dybowski, Hill, p. F296, fig. 202,3a,3b? 

1961. Cyathophylloides Dybowski, Flower, p. 83, pl. 43, figs. 1-10; 

pl. 44, figs. 1-5. 

Type species.-Cyathophylloides kassariensis Dybowski, 1873; by subsequent designation (Sherzer, 1891, p. 

278). Island of Kassar, Estonia, from beds believed to be 

Upper Ordovician (Bassler, 1950, p. 274). 

Diagnosis.-Massive cerioid rugose corals having 12-14 

smooth, simple lamellar major septa which meet axially, 

where they may be twisted but do not form a discrete axial 

structure or columella. Tabulae complete, highly variable 

from straight to arched distally with median sag or 

sagging slightly overall; widely spaced to closely set. 

Minor septa short to rather long. No dissepiments. 

Remarks.-Cyathophylloides is closely related to 

"Favistella" or Favistina Flower, a new generic term 

(Flower, 1961, p. 77) which, in adjustment of a nomenclatural problem, may appropriately cover species previously assigned to "Favistella." Characters such as 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 33 

arching of tabulae and axial meeting of septa are, however, 

not overly constant in Cyathophylloides, which also, as 

here interpreted, may have some straight or nearly 

horizontal tabulae and whose major septa may in places be 

shorter, as in normal Favistina. Nonetheless, there is 

evidently a recognizable group of these Rugosa with the 

septal arrangement of Cyathophylloides which ranges 

from Late Ordovician into the Silurian and is represented 

by the lower Masket Cyathophylloides fergusoni, n. sp. 

Cyathophylloides gothlandicus (Edwards and Haime) 

(1851, p. 309, pl. 14, figs. 2, 2a), one of the few described 

Silurian species, is insufficiently known internally. 

Bassler's (1950, pl. 18, figs. 10, 11) figures of gothlandicus 

do not show long, axially meeting septa. The stratigraphic horizon of gothlandicus is not known, but 

presumably the type material may have come from the 

vicinity ofVisby, Gotland, in the lower part of the Silurian 

column. 

In a comprehensive study of Late Ordovician colonial 

Rugosa from the Montoya Dolomite of New Mexico, 

Flower (1961, p. 77-87) emphasized a close genetic relationship of Cyathophylloides to Favistina, pointing up 

the survival of Cyathophylloides into the Silurian, where 

its species differ more widely from those of the shorter 

ranging Favistina. 

Cyathophylloides similar to fergusoni occurs in rocks of 

probable Silurian age in northern Eureka County, Nev. 

Float specimens which may represent either the Late 

Ordovician Hanson Creek Formation or the lower part of 

the Silurian Roberts Mountains Formation were collected by the writer at Section Ridge, Roberts Mountains 

(Duncan, 1956, explanation of pl. 24). Another float 

specimen from the same locality represents a seemingly 

undescribed genus with some features of 

Cyathophylloides but having an aulas and a single 

column of large peripheral dissepiments. 

Cyathophylloides fergusoni, new species 

Plate 5, figures 9, 10 

Type material.-Holotype USNM 159393; Early 

Silurian, Toquima Range, Nev. 

Diagnosis.-Massive cerioid Cyathophylloides forming 

large colonies. Wall thick for the genus, major septa 

meeting axially, minor septa very short; tabulae widely 

spaced, horizontal to arched. 

External features.-Coralla developed as large 

lenticular masses more than 1 foot in diameter; weathered 

dist~l surfaces showing the thick-walled character and 

fairly uniform size of corallites. 

Transverse sections.-Major septa 12-14, fairly straight 

to axial part, smooth and of nearly uniform width without 

taper; some septa wavy toward the axis. In some 

individuais, two or more septa merge laterally, others 

terminate against the side of a contiguous longer septum. 

In a few individuals, median dark line of a septum continues across the axis into that of an opposite septum. No 

axially twisted intertwining of septal terminations as in 

some columellate Rugosa. 

Longitudinal sections.-Wall much thicker than 

tabulae and septa. Septa continuous lamellae, smooth and 

fairly even periaxially. Tabulae in part domed distally, in 

part nearly horizontal. No crenulation or pronounced 

downward bend of the periphery as in the genus 

Crenulites. Tabulae for the greater part widely spaced. 

Microstructure.-Major septa show well-defined 

medial dark line. Trabecular wall structure indistinct in 

longitudinal section. 

Comparison with related forms.-Bassler's figures 

(1950, pl. 17, figs. 10, 11) of the type species, C. 

kassariensis, show more closely set tabulae with decided 

peripheral depression of tabulae not shown by fergusoni. 

Major septa of kassariensis are more numerous and taper 

toward the axis. Cyathophylloides gothlandicus (Edwards 

and Haime) as figured by Bassler (1950, pl. 18, figs.l0,-11) 

shows close-set tabulae and major septa which are thinner 

and do not reach the axis as, by definition, they would be 

expected to do in this genus. C. burksae Flower (1961, p: 

83, pl. 43, figs. 1-10, pl. 44, figs. 1-5) of the Middle and 

Late Ordovician Montoya Group appears to be the closest 

to fergusoni, differing in its somewhat longer minor septa 

and in its distinctly arched, 1nore closely spaced tabulae. 

Occurrence.-Lower Silurian, coral zone A, Masket 

Shale of Kay and Crawford (1964). IkesCanyon, Toquima 

Range, Nev., locality Ml088. Study material consists of 

one very large, nearly complete corallum, two partial 

coralla, and fragments of coralla. 

Genus PALAEOPHYLLUM Billings, 1858 

1858. Palaeophyllum Billings, p. 168. 

1956. Palaeophyllum. Duncan, pl. 25, figs. 1a, lb. 

1959. Palaeophyllum Billings. Hill, p. 4. 

1961. Palaeophyllum Billings, Flower, p. 88. 

1963. Palaeophyllum Billings. Oliver, p. G4. 

Type species.-Palaeophyllum rugosum Billings. Ordovician, Black River or Trenton, Quebec, Canada. 

Diagnosis.-Phaceloid Stauriidae with narrow 

peripheral stereozone and no dissepiments. Major septa 

long and simple, minor septa short; tabulae complete, 

commonly arched with axial depression. Forms very large 

colonies by lateral increase. 

Remarks.-All aspects of the morphology, taxonomy, 

and genetic relationships of Palaeophyllum have in recent years been dealt with by Flower, Hill, and Oliver. 

This phaceloid genus is probably closely related to the 

cerioid Favistina or Favistella and to Cyathophylloides. 

These nondissepimented colonial Rugosa are especially 

important in the higher Ordovician. In the Silurian, forms 

which appear to fit best in Palaeophyllum and 

Cyathophylloides are common in the Cordilleran belt; 
34 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

these occur with other nondissepirnented species having 

complete tabulae and similar growth habit, but having 

partly acanthine septa and therefore probably unrelated. 

Palaeophyllum sp. b 

Plate 3, figures 4, 5 

A large silicified colony of this coral was collected by H. 

R. Cornwall and F. J. Kleinhampl from the lower part of 

the Silurian section at Bare Mountain near Beatty, Nev., in 

beds above the Ely Springs Dolomite. 

Palaeophyllum sp. b has 20 major septa, most of which 

extend more than half the distance to the axis; minor septa are short. The tabulae are straight to slightly arched and 

lack axial sag. 

Palaeophyllum sp. blacks the well-arched tabulae with 

axial sag of thomi (Hall), multicaule (Hall), and 

margaretae Flower; it has more major septa than the 

Silurian multicaule (Oliver, 1963, pl. 4, figs. I, 2). 

Occurrence.-Lower part of the Silurian carbonate 

section on the east side of Bare Mountain, Nev., between 

Tarantula Canyon and Chuckwalla Canyon, locality 

Ml085. The Great Basin Silurian coral zone of this 

occurrence has not been established; it probably represents coral zone A. 

Palaeophyllum? sp. c 

Plate 2, figures 5, 6 

Coral collections from the lower part of the Vaughn 

Gulch Limestone of the Owens Valley region, California, 

include a phaceloid species provisionally assigned to 

Palaeophyllum. Major septa number about 22; minor 

septa commonly exceed half the length of major septa. 

Major septa of most corallites are amplexoid and extend 

less than half the distance to the axis. Tabulae are straight 

or slightly arched. 

Occurrence.-Lower 300 feet of Vaughn Gulch Limestone, 125 feet stratigraphically above beds with Dalmanophyllum sp. A. Associated with Heliolites and small indeterminate horn corals either near top of Silurian coral 

zone A or base of coral zone B. Northern Inyo Mountains, 

east of Kearsarge, at mouth of Mazourka Canyon, locality 

M1086. 

Family PYCNOSTYLIDAE Stumm, 1953 

Reference genus and species.-Pycnostylus guelphensis Whiteaves, 1884. Silurian, Guelph Dolomite; 

Ontario, Canada. 

Fasciculate rugose corals with subcylindrical mature 

corallites; septa low, continuous longitudinal ridges 

arising from narrow stereozone without acanthine spines. 

Tabulae complete, straight, unarched; no dissepiments. 

Reproduction by multiple wall (peripheral) offsets from 

calice interior. Trumpet-shaped flaring calices are 

characteristic. 

Long lamellar septa and arched tabulae of the 

Stauriidae and acanthine septa of the Tryplasmatidae are 

absent in this family, which otherwise presents homeomorphic features. The slender fasciculate tryplasmids are 

externally similar and may, as with Tryplasma 

fascicularia Oliver, 1960, have fivefold axial increase (W. 

A. Oliver, written commun., 1969). Multiple calice offsets 

are probably less characterist{c of the tryplasmids. The 

Zelophyllum group with sporadic acanthine spines are 

also homeomorphic; they are not known with multiple 

calice offsets as in the pycnostylids and seemingly do not 

produce the markedly flaring calices. 

The problematic Fletcheria is poorly understqod. This 

Silurian pycnostylid has some cystose tabulae, and a rather 

thick wall with structure suggesting that of Syringopora 

(Duncan, 1956, pl. 25, figs. 6a, 6b ). According to Duncan, 

Fletcheria lacks septa and does not have the inwardprojecting free trabecular spines of tryplasmids. On the 

basis of Duncan's evaluation and the original figure of 

Edwards and Haime (1851, pl. 14, fig. 5), it appears somewhat doubtful that the type species of Fletcheria is congeneric with Pycnostylus, as implied by Lang, Smith, and 

Thomas (1940, p. 112). 

Genera assigned to the Pycnostylidae are as follows: 

Pycnostylus Whiteaves, 1884 

Fletcheria Edwards and Haime, 1851 

Stylopleura, new genus 

(?)Cyathopaedium Schluter, 1889 

(?)Fletcherina Lang, Smith, and Thomas, 1955 

(?)Maikottia Lavrusevich, 1967 

Genus STYLOPLEURA, new genus 

Type species.-Stylopleura berthiaumi, n. sp., here 

designated. Silurian, Roberts Mountains Formation; 

Roberts Creek Mountain, Nev. 

Diagnosis.-Facsiculate rugose corals with subcylindrical mature corallites joined by long, in some instances hollow, connecting processes. Septa low, 

longitudinal ridges, not differentiated into major and 

minor. Tabulae complete, straight, horizontal, and 

generally rather widely spaced. Septal stereozone narrow. 

No dissepiments. Multiple reproductive offsets, as rnany 

as 11, developed peripherally from the calice wall. Mature 

calice flaring. 

Remarks.-Stylopleura differs from Tryplasma and 

Zelophyllum in its lack of acanthine septa and in possessing the connecting pillars. Fletcheria is believed to 

lack septal ridges and connecting processes. 

Among well-characterized pycnos ty lid genera, 

Pycnostylus is closest to Stylopleura; but insofar as 

known, it does not have the connecting pillars and is, by 

definition, reported to produce only four calicinal offsets; 

this quadripartite offset pattern may not be a valid generic 

character. It is not unlikely the number of offsets is subject 

to considerable variation, as in Stylopleura and probably 

also in Fletcheria. 

Probably a pycnostylid related t.o Stylopleura is the 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 35 

Asiatic genus Maikottia Lavrusevich, 1967, with type 

species M. turkestanica Lavrusevich from Upper Silurian 

rocks of the Turkestan Range. As figured by Lavrusevich 

(1967, pl. 3, figs. 4-6), Maikottia has a compact cerioid 

growth habit, whereas Stylopleura reveals both phaceloid 

and cerioid features, with partly open phaceloid 

characteristics predominant in some species. Maikottia is 

not known to possess lateral connecting pillars like those 

of Stylopleura. 

Maikottia resembling Asiatic M. turkestanica 

Lavrusevich (pl. 2, figs. 13, 14) has been collected by 

Michael Churkin, Jr., of the U.S. Geological Survey from 

Upper Silurian or Lower Devonian beds on the Porcupine 

River, half a mile upstream from the mouth of the 

Salmontrout River, Alaska. 

Stylopleura berthiaumi, new species 

Plate 3, figures 6-20 

Type material.-Holotype USNM 159382; paratypes 

159381, 159383, 159384; figured specimen USNM 159385. 

Diagnosis.-Stylopleura forming loose phaceloid 

colonies with some mature cylindrical corallites of large 

size. Exterior with rugae and long, partly tubular connecting processes which are fairly straight and join corallites at all angles. Peripheral calice offsets variable, 

numbering as many as 11. 

External jeatures.-Son1e itnmature corallites ceratoid 

in lower part of colony, becoming cylindrical upward. 

Longitudinal grooves well defined; where wall is thin, 

these are true septal grooves. Within the loose colonies, 

generation of multiple calicinal offsets oblique becoming 

more nearly erect upward. Interspaces and corallite surfaces occupied in places by attached C ladopora and 

Aulopora. External rugae, rather obtuse folds, reflected internally as circular grooves. Large nonreproductive corallites flaring outward in a trumpetlike calice without 

offsets. 

Transverse sections.-Septal ridges within corallites 

fron1 44 to about 60 in mature corallites, some ridges with 

very minute surficial spines. Narrow stereozone showing 

no internal trabeculae in the silicified material available. 

No differentiation of septal ridges as major and minor. 

Septal ridges broadly rounded on the reflected calice platform. 

Longitudinal sections.-Tabulae complete, rather 

widely spaced. No trabeculae or spines visible in narrow 

stereozone of silicified specimens. Some tubular connecting processes conlmtmicating with interiors of 

attached corallites through open pores. 

Reproductive offsets.-Offsets growing inward and upward from the calice wall, numbering from five to 11. 

Offsets stand erect or axially inclined if the calice is flared; 

where vertical, offsets occupying most of the cal ice. Size of 

offsets fairly uniform within the calice. 

Comparison with related forms.-No other described 

pycnostylid corals having long tubular connecting processes are known. The closest morphologically is 

Pycnostylus guelphensis Whiteaves of the Middle Silurian 

Niagara Series, reported to have quadripartite arrangement of interior calice offsets, not multiple as in 

Stylopleura; it is not known to have the connecting 

stolonal processes of Stylopleura. 

Occurrence.-Upper part of unit 3 of type section of the 

Roberts Mountains Formation (fig. 4), Silurian coral zone 

D; locality M1100 on upper Pete Hanson Creek, west side 

of Roberts Creek Mountain. Simpson Park Mountains 

near mouth of Coal Canyon, Silurian coral zone E; locality 

Mll06, in upper coral-bearing limestone breccia. 

Toquima Range, at Ikes Canyon, Masket Shale of Kay and 

Crawford (1964); locality Mll03 in Silurian coral zoneD 

associated with large Verticillopora. 

Similar Stylopleura occurs in Silurian limestone at Bare 

Mountain near Beatty, Nev. In Chuckwalla Canyon (loc. 

Ml099), dark-gray litnestones containing Stylopleura lie 

in the lower part of the Silurian sequence (Cornwall and 

Kleinhampl, 1960) and are probably correlative with some 

part of the Roberts Mountains Formation. The Bare 

Mountain Stylopleura shows numerous lateral connecting pillars, but available specimens do not reveal the 

multiple calice offsets of berthiaumi. 

Study material of Stylopleura berthiaumi consists of 

about 175 corallites from several coralla (loc. MllOO), three 

corallites (loc. Mll03), and one corallite (loc. Mll06). 

Stylopleura nevadensis, new species 

Plate 2, figures 11, 12, 15, 16; plate 15, figures 1-4 

Type r,naterial.-Holotype USNM 159431; paratypes 

USNM 159379, 159440, l59440a. 

Diagnosis.-Wide, subcylindrical, somewhat meandering corallites loosely to tightly appressed in large 

fasciculate coralla with few connecting pillars. Tabulae 

not distantly spaces. 

External features.-Holotype a large unsilicified 

lenticular head 10 inches in greatest diameter, having 

nonuniform corallites which vary considerably in size at 

distal surface. Corallum with cerioid tendency where 

closely appressed. Flaring calices not observed. 

Transverse sections.-At maturity, about 56 short undifferentiated septa, forming longitudinally continuous 

bladelike internal ridges. Septal stereozone medium to 

narrow, vaguely lamellar; epitheca discrete. 

Longitudinal sections.-Most tabulae straight to slightly wavy, terminating at inner stereozone margin. 

Trabeculae vague, nearly horizontal. 

The single observed lateral connecting pillar (pl. 15, fig. 

4) is stereoplasm filled. Longitudinal sections prepared 

thus far show corallites in parts of the corallum, where 

they are tightly appressed and would not, therefore, be 

expected to reveal connecting processes. 
36 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Reproductive offsets.-Three to five offsets, possibly 

more, filling most of calice. 

Comparison with related forms.-Stylopleura 

berthiaumi has narrower corallites, some of which have 

more widely spaced tabulae and more numerous offsets 

than nevadensis. Stylopleura nevadensis reveals fewer 

lateral connecting pillars, having more closely appressed 

corallites. Markedly flaring calice margins like those of 

sorne corallites of the type species have not been observed 

in nevadensis. 

Remarks.-The types of S. berthiaumi are silicified and 

were prepared by etching, such that connecting pillars are 

evident. The holotype of nevadensis is unsilicified and was 

studied internally by thin sections which show few of these 

lateral processes. It is possible that nevadensis is no more 

than a subspecies of berthiaumi. 

Occurrence.-Late Silurian, coral zone E in upper 

limestone beds of the Roberts Mountains Formation. Coal 

Canyon, northern Simpson Park Mountains, Nev., 

localities Mll07, MilOS, Ml317. Late Silurian coral zone 

D, Ikes Canyon, Toquima Range, Nev., in association 

with large Verticillopora and Tonkinaria;locality Mll03. 

Study material consists of the large co~plete corallum 

which is the holotypc (USNM 159431, loc. Mll07), two 

large coralla (locs. Mll 05, M 1317 ), and one large corallum 

(loc. Mll03). Stylopleura? sp. T. 

Plate 2, figures 7-10 

This loosely appressed phaceloid-cerioid coral with unusually large corallites is provisionally assigned to 

Stylopleura. The wall is much thickened stereoplasmically, and its tabulae straight, 1nostly complete, and 

very closely spaced, in places being essentially in contact 

one upon another. Wall trabeculae are nearly horizontal; 

none extend internally as acanthine spines. 

Stylopleura? sp. T is not known to have the lateral 

connecting pillars of Stylopleura berthiaumi, n. sp., or S. 

nevadensis, n. sp. Its wall is thicker and its tabulae more 

even, much more closely spaced, and more nearly complete than in the Asiatic and Alaskan Maikottia, which 

also differs in having big arched tabellae and a uniformly 

cerioid growth habit. 

Occurrence.-Silurian or Lower Devonian limestone; 

Toquima Range, Nevada, Ikes Canyon vicinity, locality 

Mll04. Collected by Kay and Crawford (1964). 

Family TRYPLASMATIDAE Etheridge, 1907 

Reference genus and species.-Tryplasma aequabile 

Lonsdale, 1845. Silurian, Ural Mountains, Russia. 

Solitary and colonial rugose corals with acanthine septa 

composed of vertical columns of trabecular spines protruding from a peripheral stereozone. Tabulae complete 

or partial; no dissepiments. 

In some species of Tryplasmatidae the trabecular septal 

spines are mostly buried in peripheral stereoplasm with 

only tips exposed; in others, they project obliquely inward and upward as long free spines where the stereozone 

is narrowed. Trabecular spines may develop also in radial 

rows on upper tabular surfaces to produce longer 

acanthine septa (Hill, 1936). 

Genera of the Tryplasn1atidae recognized in the Great 

Basin Silurian are as follows: 

Tryplasma Lonsdale, 1845 

Rhabdocyclus Lang and Smith, 1939 

Palaeocyclus· Edwards and Haime, 1849 

Zelophyllum Wedekind, 1927 

The true Cystiphyllidae of the Silurian c::ommonly have 

trabecular septal spines and, on this basis, have from time 

to time been considered as genetically related to this 

family. However, the pervasively dissepimented character 

of the Cystiphyllidae does not add support to this 

conclusion. 

Genus TRYPLASMA Lonsdale, 1845 

1845. Tryplasma Lonsdale, p. 613. 

1871. Pholidophyllum Lindstrom, p. 125. 

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. Schoupp~. p. 80-84. 

1952. Tryplasma Lonsdale. Stumm, p. 841-843. 

1956. Tryplasma Lonsdale. Hill, p. F312. 

1960. Tryplasma Lonsdale. Oliver, p. 96. 

1962a. Tryplasma Lonsdale. Oliver, p. 13. 

Type species.-Tryplasma 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 which 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, and, as 

noted by Duncan (1956, p. 226-227; pl. 23, figs. 3a, 3b), 

they are among the common fossils in the Silurian of 

western North America. Oliver (1960, p. 96) noted that the 

range of Tryplasma extends into the Lower Devonian of 

Europe, Australia, and eastern North America. 

The genus Tryplasma, as understood at present, includes species with considerably different growth habits, 

ranging from solitary forms with elongate coralla 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 37 

showing repeated rejuvenescence rims to bushy phaceloid 

colonies of slender, relatively sn1ooth branches. 

The genus Tryplasma may be further subdivided 

taxonomically, on the basis of external form and growth 

habit, into units which may eventually be considered subgenera. Two such form groups are recognized in the Great 

Basin Silurian: 

1. Solitary-rugate Tryplasma with numerous rejuvenescence rims like those of the Gotland T. 

hedstromi (Wedekind) and the Great Basin T. 

duncanae, n. sp. 

2. Fasciculate cylindrical Tryplasma with l.:>osely 

arranged slender subcylindrical, nearly smooth 

corallites like those of the Australian T. lonsdalei Etheridge and the Great Basin T. newfarmeri, n. sp. 

Rugate Tryplasma of group 1 conceivably began with a 

form like the nontabulate Rhabdocyclus. Fasciculate 

members of group 2 may include species transitional to the 

colonial Zelophyllum, with less obviously acanthine 

septa. A third tryplasmid group has the growth habit of 

Polyorophe Lindstrom, 1882 (1882a), of the Gotland 

Silurian, which shows excessive lateral outgrowths of 

attachment. Certain rugose corals of the Lone Mountain 

Dolomite have the external appearance ofPolyorophe, but 

internally reveal the nonacanthine structure of Entelophyllum. (See pl. 10, fig. 10.) 

Tryplasma of group 1 (solitary-rugate) 

Tryplasma duncanae, new species 

Plate 1, figures 26-28 

1956. (?)Tryplasma Duncan, pl. 23, fig. 3a. 

Type material.-Holotype USNM 159374; paratypes 

USNM 159375, 159376. Silurian, Roberts Mountains 

Formation, Nevada. 

Diagnosis.-Small solitary Tryplasma with elongate 

subcylindrical n1ature corallum having repeated rejuvenescence rims and prominent septal grooves. Calice 

deep and flat-bottomed with near vertical sides and septa 

which are vertical rows of short trabecular spines. Lateral 

attachment processes developed in nepionic and neanic 

growth stages. 

External jeatures.-Attachment processes and talons 

present on the ceratoid early growth stages, after which the 

corallum becomes more nearly cylindrical with irregularly spaced and very prominent rejuvenescence rims and local changes in growth direction at rejuvenescence. 

Transverse section.-Outer wall a moderately thick 

stereozone in which the trabecular spines are largely 

buried. About 22 short acanthine septa. 

Longitudinal section.-Some widely spaced tabulae 

straight and complete; others slightly bowed, incomplete, 

and inclined at 45° or less. 

Comparison with relatedjorms.-Tryplasma duncanae 

has much more numerous and prominent rejuvenescence 

rims, stronger septal grooves, and shorter septal spines 

than Tryplasma nordica Stumm from the Silurian of 

Maine and Quebec. T. duncanae resembles externally both 

T. prava (Hall) Stumm of the Louisville Limestone, Ky., 

and T. hedstromi (Wedekind) of the Gotland Silurian, 

which have numerous rejuvenescence rims. The similarity 

to hedstromi seems particularly close, but the septal spines 

of duncanae are shorter, and the tabulae are more widely 

spaced. 

Occurrence.-Upper beds of unit 3, Roberts Mountains 

Formation; Late Silurian, coral zone D. Northwest side of 

Roberts Creek Mountain, Nev., upper Hanson Creek 

drainage basin, locality MllOO. Study material consists of 

14 corallites. 

Tryplasma of group 2 (fasciculate-cylindrical) 

Tryplasma newfarmeri, new species 

Plate 2, figures 1-4 

Type material.-Holotype USNM 159377; Silurian, 

Roberts Mountains Formation. 

Diagnosis.-Con1pound Try plasma with slender small, 

very elongate, loosely phaceloid cylindrical corallites reproducing by calicinal offsets at the periphery. Wall 

moderately thick with no prominent rejuvenescence rims, 

lateral connections, or attachments. Tabulae mostly complete and widely spaced. 

External features.-Fairly straight cylindrical corallites; abundant annular incremental striations, but no 

conspicuous rejuvenescence rims, and no septal grooves. 

No calice features on available specimens. 

Transverse sections.-About 40 acanthine septa; septal 

spines short, set in a moderately wide stereozone. 

Longitudinal sections.-Short septal spines projecting 

axially and distally within and beyond stereozone. Most 

tabulae widely spaced and complete or nearly complete; 

many nearly straight, others slightly bowed. Well-defined 

columns of spine bases within the stereozone seen in 

tangential sections. 

Reproductive offsets.-Calicinal offsets observed in 

longitudinal section arise at stages where the calice is of 

greater than average width; several offsets developed concurrently within some individual calices. 

Comparison with related forms.-Tryplasma 

newfarmeri, n. sp., is a more slender form than T. nordica 

Stumm, which is solitary (Oliver, 1962a, p. 13). T. 

lonsdalei Etheridge is an Australian Silurian colonial 

species (Hill, 1940, p. 406) similar to newjarmeri, butT. 

lonsdalei appears to differ by having more closely spaced 

tabulae, and according to Hill, its corallites may be 

connected by processes. 

Occurrence.-Lower beds of unit 3, Roberts Mountains 

Formation; Middle Silurian, coral zone C. Northwest side 

of Roberts Creek Mountain, Nev., upper Hanson Creek 
38 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

drainage basin, locality Mll02. Study material consists of 

one very large corallum and fragments of other coralla. 

Tryplasma sp. R 

Plate 1, figures 29, 30 

This subcylindrical species, known only as isolated 

corallites, has especially long and robust trabecular 

spines; rows of more slender spines occur on upper surfaces of slightly undulant tabulae. In transverse thin section the septal spines lack uniformity of length and 

weight. 

Occurrence.-Unit 3 of Roberts Mountains Formation. 

Roberts Creek Mountain, Nev., locality MllOl. 

Genus RHABDOCYCLUS Lang and Smith, 1939 

1850-54. Palaeocyclus fletcheri Edwards and Haime, p. 248; pl. LVII, 

figs. 3-3£. 

1851. Palaeocyclus fletcheri Edwards and Haime, p. 205. 

l873a. Acanthocyclus Dybowski, p. 333, 359; pl. l, figs. 

10, lOa, lOb [not Lucas, 3 1843-44]. 

1927. Acanthocyclus fletcheri (Edwards and Haime). Lang and 

Smith, p. 450, figs. l, 2. 

1927. Acanthocyclus porpitoides Lang and Smith, p. 486, fig. 

16. 

1936. Acanthocyclus porpitoides Lang and Smith. Hill, p. 

196; figs. 9, 12, 15, 19; pl. 29, fig. 37. 

1936. Acanthocyclus fletcheri. Hill, p. 199, fig. 21. 

1939. Rhabdocyclus Lang and Smith, p. 152. 

1940. Rhabdocyclus. Lang, Smith, and Thomas, p. 113. 

1956. Rhabdocyclus Lang and Smith. Hill, p. F3ll, fig. 213. 

Ia, lb. 

Type species.-Palaeocyclus fletcheri Edwards and 

Haime, by author's designation (Lang and Smith, 1927, p. 

450; Lang, Smith, and Thomas, 1940, p. 113 ). Silurian, 

Wenlock Limestone, Dudley, England. 

Diagnosis.-Turbinate or curved trochoid solitary rugose corals with acanthine septa and lacking tabulae and 

dissepiments. Deep calice extending to nepionic tip. 

Remarks.-Rhabdocyclus is morphologically intermediate between Palaeocyclus and Tryplasma. There is, 

however, no evidence of evolutionary lineage. In 

Rhabdocyclus the initial cone is usually excentric, 

whereas in Palaeocyclus it is commonly near the center. 

Some individuals of typical porpita do show an excentric 

initial cone and patellate convexity of the basal disk. 

Tryplasma is distinguished from Rhabdocyclus by 

development of complete tabulae and could be derived 

from the Ia tter. 

The type species of Rhabdocyclus is reported to come 

from the Wenlock Limestone of Dudley, England. The 

Hidden Valley specimens here dealt with occur in the 

lower part of that formation in coral zone A and are believed to be Lower Silurian (Llandoverian). 

3ln Edwards and Lucas, 1843-44. 

Rhabdocyclus sp. B 

Plate 1, figures 24, 25 

Large silicified trochoid individuals of this form collected at Bare Mountain, Nev., have about 74 acanthine 

septa in which the trabecular spines are especially coarse. 

There is an incipient differentiation into major and minor 

septa. The exterior is longitudinally grooved and has welldeveloped rugae. 

This species resembles R. sp. d but is much larger, and 

its trabecular spines are coarser. 

Occurrence.-In dark-gray Silurian limestone about 

150 feet stratigraphically below contact with light-gray 

dolomite. Study material of sp. B consists of four silicified 

coralla. Bare Mountain quadrangle, Nevada, near 1nouth 

of Chuckwalla Canyon, locality M1099. 

Rhabdocyclus sp. d 

Plate 1, figures 22, 23 

Small silicified specimens assigned to this genus were 

collected by ]. F. McAllister from the lower unit of the 

Hidden Valley Dolon1ite at Whitetop Mountain, northern Panamint Range. 

Rhabdocyclus sp. dis curved trochoid and has about 26 

major septa with coarse trabecular spines; minor septa are 

short and comprise rather widely spaced columns of 

spines. The septal stereozone is medium wide to narrow. 

Lateral projections are present on the exterior. 

Edwards and Haime's figures of R. fletcheri show more 

numerous primary septa and a reflected calice rim not 

present in sp. d. 

Large individuals of Rhabdocyclus sp. B from the 

Silurian of Chuckwalla Canyon, Bare Mountain, Nev., 

reveal more numerous acanthine septa and a trochoid 

corallum. 

Occurrence.-Lower part of the Hidden Valley 

Dolomite; Early Silurian, coral zone A. Whitetop 

Mountain, northern Panamint Range, locality M1096. 

Study material of sp. d consists of two silicified coralla 

and fragmentary coralla. 

Rhabdocyclus sp. K 

Plate 15, figures 5-9 

A curved-turbinate to near-patellate Rhabdocyclus representative of this Silurian tryplasmid genus was collected from the Laketown Dolomite of the Confusion 

Range, Utah, by A.]. Boucot. Its acanthine septa are differentiated as major and minor, with 26 major septa. 

Columns of trabecular nodes form minor septa. This 

species possesses un excentric apex, the apical cone flaring abruptly in the neanic growth stage, followed by 

abrupt curvature in some individuals. Weak obtuse longitudinal ribs are crossed by fine incremental lines and 

rugae on the exterior. 

Rhabdocyclus sp. K resembles the British type species 

fletcheri more closely than either of the other two Great 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 39 

Basin forms. Rhabdocyclus sp. K differs from fletcheri in 

having fewer septa but is very similar in its septal character 

and exterior ornamentation. 

Occurrence.-Laketown Dolomite. Confusion Range, 

Utah; Kings Canyon, Conger Mountain quadrangle, 

locality Mll37. Study material consists of six silicified 

coralla. 

1767. 

1849. 

Genus PALAEOCYCLUS Edwards and Haime, 1849 

Madrepora porpita Linnaeus, p. 1272 (in part). 

Palaeocyclus Edwards and Haime, p. 71. 

1850-54. Palaeocyclus Edwards and Haime, p. xlvi, p. 246-248. 

1851. 

1927. 

1936. 

1936. 

1937. 

1940. 

Palaeocyclus Edwards and Haime, p. 203-206. 

Palaeocyclus porpita. Lang and Smith, p. 485. 

Palaeocyclus Edwards and Haime. Hill, p. 193. 

Not Porpites Schlotheim (in part). Wells, p. 127. 

Paleocyclus Edwards and Haime. Bassler, p. 190, pl. 30, 

figs. l-4. 

Palaeocyclus Edwards and Haime. Lang, Smith, and Thomas, 

p. 94. 

1940. Porpites Schlotheim. Lang, Smith, and Thomas, p. 103. 

1956. Porpites Schlotheim. Hill, p. F312. 

Type species.-Madrepora porpita Linnaeus, 1767 (by 

monotypy). Silurian, Gotland. Uncertainty has long existed regarded validity of the name Palaeocyclus as opposed to Porpites Schlotheim, involving the status of 

Schlotheim's syntypes (Wells, 1936, p. 127; Lang, Smith, 

and Thomas, 1940, p. 103-104). W. A. Oliver, Jr. (written 

commun., 1969), has pointed out that unless there was an 

earlier selection of a genolectotype for Porpites, Wells 

fixed the genus by selecting P. globulatus in 1936. 

Accordingly, the selecting of another species by Lang, 

Smith, and Thomas in 1940 is invalid. Porpites globulatus 

is a scleractinian, and, thus, Porpites is not available as a 

name for a Paleozoic coral. 

Diagnosis.-Small discoid tryplasmid rugose corals 

with flat to slightly patellate epithecal base having a small 

central cone and concentric incremental rings. Thick 

beaded septa with free, broadly convex peripheral edges; 

distal margins of major septa gradually sloping toward 

bottom of deep calicular pit. Minor septa commonly more 

than one-half the length of major septa. No fossula, 

tabulae, or dissepiments. Septal pattern distinctly radial. 

Remarks.-The septal beads or nodes are distal ends of 

large trabeculae. As seen on lateral surfaces of major septa, 

these trabeculae rise obliquely from the base as external 

ridges and slope toward the axis with increasing steepness. 

(See Hill, 1936, figs. 14-17.) The nodes may be very 

I?rominent or even spinose, and toward the periphery they 

become transverse, like yardarm carinae of other Rugosa. 

In some species the basal disk extends laterally as a 

flange beyond the exposed septa. Generally, most of the 

central cone has been removed by abrasion. 

Palaeocyclus porpita, the type species, occurs in the 

Lower Visby Marl of Gotland, regarded as late 

Llandoverian Lower Silurian. At Gotland Palaeocyclus is 

not known to range higher. In England this genus is reported in the Wenlockian (Hill, 1936, p. 193 ). Reported occurrences of the genus in North America (Bassler, 1937, p. 

190) range from the Silurian Clinton Group and 

Manistique Dolomite to the Devonian of the Porcupine 

River, Alaska. Except for the Great Basin forms here dealt 

with these American forms differ considerably from 

porpita, Devonian assignment of the Alaskan form is 

certainly in need of review. 

Palaeocyclus porpita subsp. mcallisteri, n. subsp. 

Plate 1, figures 12-15, 17 

1952. Porpites porpita. McAllister, p. 16. 

Type material.-Holotype USNM 159365; paratypes 

USNM 159364, 159366, 159367. Early Silurian, coral zone 

A; Ubehebe district, California. 

Diagnosis.-Septa thick, with coarse noding for the 

species porpita; septal thickness slightly exceeding length 

of radial interspaces between nodes. 

Transverse features.-Thick major septa, numbering 

20-22, tapering gradually toward axis, where some of the 

attenuated projections meet. (This feature 1nay be 

observed through the transparent basal disk of worn individuals of Gotland porpita.) Minor septa Y2- 2/3 the 

length of major septa. Trabecular nodes on upper edges of 

the major septa number 10 to 12. Central pit reaching 

basal plate. 

Longitudinal features.-Coralla broken in two radially, 

with a radial profile of septa with curve inflection of 

distally convex n1ajor septa usually closer to periphery 

than to axis. Individuals with evenly rounded septal profile and steep-sided axial calice pit predominate. Sides of 

major septa show 10-12 slightly curved, thick trabecular 

spines standing almost vertical near axis, but toward the 

corallite periphery rising in a gentle arc inclined axially 

30°-40°. 

Fine sl'ructure.-Available silicified material lacks fine 

structure. Hill's classic studies of well-preserved Gotland 

porpita material (1936, p. 193-196) deal with minute 

details of trabeculae and are basic to understanding of 

acanthine septal structures among Rugosa. 

Comparison with other species.-As noted above, the 

Hidden Valley form is regarded as conspecific with the 

Gotland porpita but is sufficiently different 

morphologically to warrant its classification as a 

geographic subspecies. Of described American species 

(Bassler, 1937, p. 190, pl. 30 figs. 5 -12), all are too poorly 

known for meaningful comparison. P. M ichiganensis 

Bassler of the Manistique Dolomite appears to have more 

slender, wider spaced septa,IP. rotuloides (Hall) of the 

Clinton Group has fewer septa, and P. kirbyi Meek of 

supposedly Devonian strata at the Porcupine River, 

Alaska, is a larger form with more numerous and more 

closely spaced, seemingly unbeaded septa. The last may represent a different genus and requires restudy. 
40 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

The undescribed Confusion Range, U tab Palaeocyclus 

resembles typical porpita but is, on the whole, smaller. 

Several of the individuals are slightly patellate, like 

variants of the Gotland porpita. Some have a peripheral 

flange on the basal disk. 

Occurrence.-Lower Silurian, Great Basin coral zone A. 

Basal beds of unit I in the lower part of Hidden Valley 

Dolomite. Whitetop Mountain, Northern Panamint 

Range, locality M1096. Southern Andy Hills, northern 

Panamint Range. 

Similar Palaeocyclus occurs in the Confusion Range, 

Utah, locality M1129, and in the Ruby Mountains, Nev. 

(pl. 15, fig. 10), 3 miles northeast of Mitchell Ranch, 

Sherman Mountain quadrangle, locality M1336. 

Study material is as follows: Whitetop Mountain 

(M1096), 25 coralla; Andy Hills, two coralla; Confusion 

Range (M1129), six coralla; Ruby Mountains (M1336), 

two coralla. 

Genus ZELOPHYLLUM Wedekind, 1927 

1927. Zelophyllum Wedekind, p. 34-35, pl. 5, figs. 1-5; 

pl. 6, figs. 11-13. 

1956. Zelophyllum Wedekind. Hill, p. F312, fig. 213.7. 

Type species.-Zelophyllum intermedium Wedekind, 

by author designation. Silurian, Hogklint, Gotland, 

Sweden. 

Diagnosis.-Solitary and colonial nondissepimented 

rugose corals with cylindrical corallites of large and 

medium size. Wall moderately thick, tabulae straight to 

undulant and unarched. Septa short or stubby, usually 

tapering abruptly from wall; in places, walls thinned and 

studded with acanthine trabecular spines. Outer surface 

fairly even, with longitudinal grooves and no pronounced rugae. 

Remarks.-Silurian species from Alaska show 

especially well the acanthine septal spines and possible 

tryplasmid relationships of this coral. In some individuals the large trabeculae are buried in the wall 

stereome and do not project inward as free spines. Differentiation of septa as major and minor may be unrecognizable in those forms with stout abruptly tapering 

very short uniform septa. Other cylindrical Silurian 

genera with which Zelophyllum may be confused are 

Palaeophyllum and Stylopleura. Palaeophyllum is more 

slender, has lamellar septa of greater length, and usually 

possesses well-arched tabulae, whereas tabulae of 

Zelophyllum are normally straight. Stylopleura has a 

trumpetlike calice, has lateral connections between corallites, and is not known to have acanthine septal spines. 

Zelophyllum is common in the Silurian of the Pacific 

Border province, as in southeastern Alaska and the 

Klamath Mountains of northern California. In the Great 

Basin most of the larger nondissepimented rugose corals 

of this general construction are assigned to the new genus 

Stylopleura. 

Occurrence.-Nondissepimented corals possibly representing Zelophyllum occur in the Great Basin, but the 

wall structure is generally not well enough known to confirm this generic assignment. Corals with abundant 

acanthine septa and cylindrical corallites are placed in 

Tryplasma. Possible Zelophyllum occurs at Dry Canyon, 

Toyabe Range, 8 miles south of Austin, Nev., in the 

Thomas Range, Utah, and in the east Tin tic Mountains of 

U tab· Famiiy KODONOPHYLLIDAE Wedekind, 1927 

Representative genus and species.-Kodonophyllum 

milne-edwardsi (Dybowski). Silurian; Gotland, Sweden. 

Solitary and colonial rugose corals with long septa, a 

very wide stereozone, no dissepiments, and a tabularium of 

flat tabulae or arched tabellae which may combine with 

septal ends to produce an axial structure. 

Two subfamilies are recognized: Kodonophyllinae and 

Mycophyllinae. 

Subfamily KODONOPHYLLINAE Wedekind 

Fasciculate colonial and platelike solitary rugose corals 

with the farnily characteristics and arched tabulae and 

tabellae which combine to form an axial structure. 

Genera included in this subfamily are Kodonophyllum 

Wedekind and Schlotheimophyllum Smith. 

Genus KODONOPHYLLUM Wedekind, 1927 

1758. Madrepora truncata Linnaeus (in part), p. 795. 

1873b. Streptelasma milne-edwardsi Dybowski, p. 409-410, pl. xiii, 

figs. 5-12. 

1927. Kodonophyllum Wedekind, p. 9-10, 35-36, pl. 5, figs. 5-11. 

1927. Patrophontes Lang and Smith, p. 456-457, figs. 8-9. 

1929. Kodonophyllum Wedekind; Smith and Tremberth, p. 367-

370, pl. viii, figs. 5-7. 

1937. Kodonophyllum Wedekind; Soshkina, p. 52-55 (in part), 

pl. ix, figs. 4, 5; pl. x, figs. 3-6; pl. xxi, 

figs. 1, 2. 

1940. Codonophyllum Lang, Smith, and Thomas, p. 39. 

1956. Kodonophyllum Wedekind; Hill, p. F27l, fig. 184,la, lb. 

1962b. Kodonophyllum Wedekind; Oliver, p. 23-26, pls. 9-13. 

1964. Kodonophyllum Wedekind; Stumm, p. 26, pl. 25, figs. 9-14. 

Type species.-Streptelasma milne-edwardsi 

Dybowski, 1873; Silurian, Gotland. 

Diagnosis.-Solitary and compound rugose corals with 

trochoid to ceratoid and turbinate corallites. Septa 

thickened peripherally to fm;m a wide sterozone. Major 

septa extending to axis, where they are involved with 

tabulae to form an axial structure thickened by stereoplasm. Tabulae sloping downward from axis. No 

dissepimen ts. 

Remarks.-According to Smith and Tremberth (1929, 

p. 368, 369), Dybowski's Streptelasma milne-edwardsi is a 

synonym of Madrepora truncata Linnaeus, 1758, which 

occurs at Hall, Lilla Karlso, Gotland, and other localities, 

in beds of Wenlockian and Ludlovian age, principally the 

last. In England this species is reported by Smith and 

Tremberth from the Wenlock only. 

The relationship of Kodonophyllum to Schlotheimo-
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 41 

phyllum requires clarification; they appear to be distinct 

genera with quite different growth habits, and they occur 

in different parts of the Gotland section. 

The Great Basin Kodonophyllum mulleri has a large 

columellar boss projecting up in the calice and is more 

nearly ceratoid than trochoid. 

Kodonophyllum mulleri, n. sp. 

Plate 4, figures 3-7 

Type material.-Holotype USNM 159386, 159386a-b; 

paratype USNM 159389. 

Diagnosis.-Medium to large solitary Kodonophyllum 

with trochoid to ceratoid corallum and deep calice with 

columellar boss. 

Transverse sections.-Major septa numbering about 48, 

smooth and fairly straight except as they approach the 

axis; septa thickened somewhat throughout but 

excessively in the wide septal stereozone and within the 

axial structure. Minor septa less than half the length of 

major; in some individuals projecting axially beyond 

stereozone. No fossula. Transverse interseptal traces are 

downward-inclined tabulae, not dissepiments. 

Longitudinal sections.-Tabularium more than half 

the corallite diameter. Stereozone width about one-fifth 

the corallite diameter. Tabulae close-spaced, discontinuous, arched steeply to axial structure, where they 

are obscured by intersection with stereoplasm and septal 

ends. Marginal tabellae flat or axially inclined. 

Trabeculae in septal stereozone inclined peripherally. 

Large calice boss with axial depression. 

Comparison with related forms.-Kodonophyllum 

truncatum of the Gotland Silurian is a colonial species 

and has a narrower tabularium with a less robust axial 

structure and wider septal stereozone. K. richteri 

Wedekind, also of the Gotland Silurian, has fewer major 

septa and more widely spaced, more nearly complete, 

arched tabulae. An undescribed species from the uppermost Gazelle Formation of the Klamath Mountains, 

Calif., differs in having somewhat nodose or spiny septa. 

Occurrence.-ln lin1estone breccia near the top of the 

Silurian section; coral zone E. Coal Canyon, northern 

Simpson Park Mountains, Nev., locality Mll07. Study 

material consists of three partial coralla. 

Subfamily MYCOPHYLLINAE Hill, 1940 

Large solitary platelike and subcylindrical rugose corals 

with the family characteristics and having straight, 

usually unarched, and complete tabulae with no axial 

structure. 

Genera included in this subfamily are as follows: 

Mucophyllum Etheridge, 1894 

Chlamydophyllum Po'tta, 1902 

Pseudamplexus Weissermel, 1897 

(?)Briantia Barrois, 1889 

Other Rugosa, having similar growth habit but differing in details of internal structure, have been considered in connection with the Kodonophyllidae. Among 

these are Naos (Lang, 1926) and Craterophyllum (Foerste, 

1909), which are dissepimented. The name 

Chonophyllum has been applied erroneously to corals 

now classified as Schlotheimophyllum (Smith, 1945, p. 

18). 

Genus MUCOPHYLLUM Etheridge, 1894 

1894. Mucophyllum Etheridge, p. 11-18, pls. iii, iv. 

1926. Mucophyllum. Lang, p. 431, 433; pl. xxx, figs. 7, 8. 

1940. Mycophyllum. Lang, Smith, and Thomas, p. 87. 

1940. Mucophyllum crateroides Etheridge. Hill, p. 400; pl. 12, 

figs. 1, 2. 

1940. Not Mycophyllum liliiforme (Etheridge). Hill, p. 401, pl. 12, 

figs. 3-6. 

1945. Mucophyllum crateroides Etheridge. Smith, p. 19. 

1949. Mycophyllum Etheridge. Stumm, p. 49, pl. 23, figs. 9, 10. 

1956. Mucophyllum Etheridge. Hill, p. F277, fig. 189.3a. 

Type species.-Mucophyllum crateroides Etheridge, 

1894, by monotypy. Silurian, Hatton's Corner, Yass River, 

New South Wales, Australia. 

Diagnosis.-Large discoid or patellate to turbinate, 

usually solitary, rugose corals with broad calice platform, 

reflexed margin, and flat-bottomed central pit. Numerous 

thick septa in contact laterally to form a wide stereozone, 

some longer septa reaching the axis. Tabulae medium 

wide or narrow, complete, and straight to undulant. No 

dissepiments. Longitudinal section showing fine, nearhorizontal incremental layering of thick stereozone transected by near-vertical trabecular pillars. Radial grooves of 

cal ice platform overlying sutures between thickened septa. 

Remarks.-The layered and usually thick stereoplasmic peripheral disk of Mucophyllum is the most distinctive feature of this genus. Schlotheimophyllum, with 

similar growth habit, has a comparable, though possibly 

less dense, stereozone and differs in possessing a more complex axial structure like that of Kodonophyllum. Naos 

Lang, 1926 (possibly a synonym of Craterophyllum 

Foerste, 1909), differs in having well-defined dissepiments and zigzag septa which break up peripherally in 

naotic fashion. Chonophyllum Edwards and Haime, 

1850, has been confused with all of these genera; as here interpreted, this coral has separate generic status. Other 

forms which might be confused externally with 

Mucophyllum or Chonophyllum having a trumpetshaped calice are longer stemmed corals, some of which 

are referrable to the new genus Stylopleura. 

The longest septa of Mucophyllum extend in part beyond the stereozone and become involved with tabulae in 

an incipient axial structure, as in M. oliveri, n. sp.; this 

structure does not become complex like that of 

Schlotheimophyllum. 

Occurrence.-The type species from Yass River, 

Australia, occurs in beds of high Wenlockian or 

Ludlovian age (Hill, 1940, p. 388). The Klamath Moun-
42 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

tains representatives are of equivalent age; those from the 

Great Basin are believed to be Ludlovian. 

Mucophyllum oliverl, n. sp. 

Plate 5, figures 1-6 

Type material.-Holotype USNM 159390; paratype 

USNM 159391. 

Diagnosis.-Mucophyllum with multiple, fine 

horizontal layering of massive stereozone and close-spaced 

fine trabecular pillars normal to layers. Tabulae narrow, 

nearly horizontal, and undulant; thickened where involved with long septa. 

Traverse1 sections.-About 76 septa, most of which extend to the tabularium; a few attenuated and very irregular twisted extensions reaching or curving around the 

axis. Septa straight and even within the wide stereozone; 

prominent dark radial bands are sutures between 

thickened septa. Enlargement of transverse section reveals 

a closely spaced pattern of trabecular rods in septa disposed normal to the section. Ends of these trabecular rods 

number about 30 per square millimeter. Ends of rods commonly revealing clear calcite interior and shadowy dark 

peripheral zone, suggesting initially tubular construction. 

Longitudinal sections.-Horizontal laminae of massive 

stereozone reflecting curvature of calice platform, bending 

as they approach the tabularium to a steep axial in., 

clination. Laminae alternating light and dark, varying 

considerably in thickness, and averaging about six per 

millimeter. Trabecular rods normal to laminae, becoming 

inclined peripherally near the tabularium. Tabulae 

numbering about 16 per centimeter, wavy and only in part 

complete, some terminating against other complete 

tabulae. Some tabulae thickened throughout, with excessive swelling close to the axis, where septa intersect. 

Comparison with related forms.-Mucophyllum 

oliveri resembles an undescribed species in the Gazelle 

Formation of the Klamath Mountains, Calif. The Gazelle 

form possesses a similar calice platform, but layering of 

the massive stereozone is more widely spaced. The Gazelle 

species has thickened horizontal tabulae but lacks the 

tabular undulation and thickened septal intersections, 

being in this regard more typical of Mucophyllum. 

Mucophyllum crateroides, the type species, has a wider 

tabularium and straight tabulae with seemingly less closely spaced horizontal stereozone laminae. 

Certain features of the tabularium and axis of M. oliveri 

are in a sense more suggestive of the genus Schlotheimophyllum than of typical Mucophyllum because of the 

development of an incipient axial structure. Compared in 

detail with a longitudinal section of S. patellatum, the 

type species figured by Lang ( 1926, pl. xxx, fig. 5 ), there is 

little close similarity. In Schlotheimophyllum the marginal parts of the tabulae are peripherally inclined, and 

these tabulae are strongly arched. A fairly complex wide 

axial structure is formed in Schlotheimophyllum by the 

meeting of the numerous major septa and their twisted involvement with arched tabulae. In S. patellatum the 

stereozone trabecular rods show steep axial inclination 

over a large part of the peripheral disk; this is not a feature 

of Mucophyllum. 

Occurrence.-Limestone breccia zone near the top of 

the Silurian section coral zone E. Coal Canyon, northern 

Sin1pson Park Mountains; locality MilOS. Study material 

consists of two nearly con1plete cm-alla and three partial 

coralla. 

Famlly ARACBNOPHYIJJDAE Dybowskl, 1873 a 

Reference genus.-Arachnophyllum Dana, 1846. 

These Early and Middle Silurian astraeoid and 

thamnostraeoid rugose corals rese1nble in growth habit 

certain Devonian Disphyllidae and Phillipsastraeidae, 

among which are Billingsastraea andPachyphyllum. The 

superficial similarity is one of gross morphologic convergence and is not indicative of genetic relationship. 

Dybowski (l873a, p. 339), in naming the family, 

erroneously included Devonian homeomorphs and 

strangely enough, assigned his Darwinia, a homonym and 

synonym of Arachnophyllum, to the Ptychophyllidae. 

It appears doubtful that among described corals there 

are other genera sufficiently close morphologically to 

warrant their inclusion in the Arachnophyllidae. 

However, the single genus as it stands is highly diverse 

(Stumm, 1964) and may lend itself, on detailed study, to at 

least subgeneric division. 

1839. 

1846. 

1848. 

1850-'54. 

1873a. 

1927. 

1937. 

1940. 

1949. 

1956. 

1964. 

Genus ARACBNOPBYLLUM Dana, 1846 

Acervulana baltica Schweigger (in part). Lonsdale, 4pl. XVI, 

figs. 8b-e. 

Arachnophyllum Dana, p. 186, text fig. 1. 

Arachnophyllum Dana, p. 360. 

Strombodes typus (McCoy). Edwards and Haime, p. 293, 

pl. 71, figs. 1, 1a, 1b, 2a. 

Darwinia Dybowski, p. 404, pl. II, figs. 8, Sa. 

Arachnophyllum typus (McCoy). Lang and Smith, p. 452, 

figs. 5, 6, 7. 

Darwinia Dybowski. Soshkina, p. 57, pl. XVI, fig. 5. 

Arachniophyllum; Lang, Smith, and Thomas, p. 19. 

Arachnophyllum pentagonum (Goldfuss). Amsden, p. 104, 

pl. XXVI, figs. 1-6. 

Arachnophyllum Hill, p. F274, fig. 187.3a, 3b. 

Arachnophyllum Dana. Stumm, p. 30, pis. 20, 21. 

Type species.-Acervularia baltica Schweigger (in 

part), Lonsdale, 5 1839, pl. XVI, figs. 8b-e, according to 

Lang, Smith, and Thomas (1940). Lang and Smith (1927, 

p. 452) and Lang, Smith, and Thomas (1940, p. 19) gave 

localities for ·the type species at Wenlock and Dudley, 

England, Silurian Wenlock limestone. 

Dzagnosis.-Astraeoid or thamnastraeoid rugose corals 

building horizonta1ly layered colonies in which individual corallites lack a discrete wall but on the distal surface are defined by elevated rim and axial pit. with or with4ln Murchison (1839). 5ln Murchison (1839). 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 43 

out crateriform margin. Septa thin, commonly with abundant angulation carinae; longer tnajor septa reaching the 

axis. Dissepiments very numerous, largely with nearhorizontal bases in a wide dissepimentarium. with 

tabellae arched distally or rather flat. Longitudinal sections showing groups of vertical trabecular thickenings 

commonly defining septal traces. 

Remarks.-These corals with shallow platform calice 

and axial pit have frequently been classified as 

"Strombodes," the presently accepted type of which is a 

phaceloid species (Strombodes stellaris Linnaeus) differing in many other structural details. Described 

Arachnophyllum species show a considerable diversity 

with respect to size range of the flat dissepiments, continuity and carination of septa, prominence of cal ice rims, 

and arching of tabellae. In some species the tabularium is 

weakly defined and the arching much less distinct than 

that shown in Dybowski's (1873a, pl. 2, fig. 8) drawing of 

speciosa. Peripheral discontinuity of septa and development of outer zones of irregular lonsdaleioid dissepiments is a characteristic of some species. 

As at present understood, Arachnophyllum is mainly a 

Lower and Middle Silurian coraL The genus was reported 

from the Llandoverian red marls below the Gotland Vis by 

Marl by Lindstrom (1884, p. 7), and in North America it 

ranges up-ward to the Brownsport and the Louisville Formations. In the Great Basin, Arachnophyllum has been 

found thus far only in Silurian coral zone A, which is considered Early Silurian Llandoverian. 

Arachnophyllum kayi, n. sp. 

Plate 5, figures 7, 8 

Type material.-Holotype USNM 159392; lower part of 

the Silurian section, Ikes Canyon, Toquima Range, Nev. 

Diagnosis.-~orallites small for the genus, with no 

lonsdaleioid dissepiments; septa thin, continuous into adjacent corallites, with numerous angulation carinae increasing in complexity toward the axis. Dissepiments 

mostly small; tabularium poorly differentiated. 

External features.-Upper surface of colony with 

medial crateriform rims; no elevated rims observed 

between corallites. 

Transverse section.-Ten major septa, most extending 

to axis; minor septa long, terminating just within 

tabularium margin. Angulation or zigzag carinae 

numerous, especially pronounced toward inner edge of 

dissepimentarium. Septal extensions wavy or twisted, but 

noncarinate in tabularium. Dissepiment traces vaguely 

defined, none are lonsdaleioid. 

Longitudinal section.-Multiple columns of small, low 

dissepiments with more or less horizontal bases; larger 

globose dissepin1ents uncommon, and pattern more 

uniform than in most other described species. No arching 

of tabellae or indication of arching at rims between 

corallites. Septal traces showing carinal spurs. Shado"':'y 

near-vertical trabeculae defining septal traces; shadowy 

trabec"!.llae present elsewhere in larger groups. 

Comparison with related forms.-The upper surface of 

Arachnophyllum speciosa (Dybowski) from Kattentak, 

Estonia, resembles that of kayi, but Dybowski's figure does 

not show the minutely zigzag septa. Soshkina's (1937, pl. 

16, fig. 5) figure of a similar form also referred tb 

Dybowski's speciosa con1es from the Ural Mountains in 

strata reported to be Wenlockian. 

Arachnophyllum typus (McCoy) of the British 

Wenlock, as figured by Edwards and Haime (1850-54, p. 

293, pl. 71, figs. 1-1b), differs in having wall rims on the 

upper surface and sporadic larger globose dissepiments. 

Of American species, the Brownsport pentagonum of 

Amsden (1949, p. 104, pl. 26, figs. 1-6) also differs in 

having wall rims and sporadic large globose dissepiments. Of the six species described from the Louisville 

Limestone (Stumm, 1964, p. 30, pls. 20,21 ), most have wall 

rims, discontinuous septa, and large globose or 

lonsdaleioid dissepiments in a wide peripheral zone. 

Occurrence.-Lower part of the· Silurian limestone 

section, in Masket Shale of Kay .and Crawford (1964); 

Silurian coral zone A. Ikes Canyon, Toquima Range, 

Nev., locality M1088. 

Study material consists of two partial coralla and fragments of other coralla from Ikes Canyon (M1088) and a 

partial corallun1 from Whitetop Mountain, northern 

Panamint Range (M1096). 

Family LYKOPHYLLIDAE Wedekind, 1927 

Representative genus and species.-Phaulactis 

cyathophylloides Ryder, 1926. Silurian, Wenlockian, 

Slite Group, Vastergarn, Gotland, Sweden. 

Diagnosis.-Medium and large solitary rugose corals 

with multiple columns of small to medium dissepin1ents, 

a tabularium which may not be abruptly differentiated at 

margin from dissepimentarimn, with septa commonly 

thickened and laterally in contact into or beyond neanic 

growth stage, and with no well-defined fossula in 

advanced growth stages. 

Remarks.-These well-dissepimented Silurian corals 

have some features of the Devonian Halliidae, but in the 

advanced growth stages they do not, like the Halliidae, 

have a well-defined fossula, and they lack the lonsdaleioid 

dissepiments of the Papiliophyllum subgroup. The 

Devonian Bethanyphyllidae are also very similar to these 

Silurian genera and n1ay ·be difficult to distinguish; in 

general, the Bethanyphyllidae of the Great Basin province have more irregular, wavy, thin mature septa, a more 

distinct though not always sharp fossula, and more 

numerous straight tabulae; among Bethanyphyllidae, the 

early septal thickening does riot persist in-growth beyond 

fairly early neanic stages. 

Genera classified under the Lykophyllidae are as 

follows: 
44 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Phaulactis Ryder, 1926 

Pycnactis Ryder, 1926 

Holophragma Lindstrom, 1896 

Desmophyllum Wedekind, 1927 

Cyathactis Soshkina, 1955 

Ryderophyllum Tcherepnina, 1965 

Neocystiphyllum Wedekind, 1927, may also belong 

here. Too little is known of the structure of 

Lamprophyllum Wedekind, 1927, towarrantplacingit, at 

present, in this family. Genera otherwise qualifying for 

assignment to the Lykophyllidae are doubtless synonyms, 

such as Mesactis Ryder, 1926, and Lykophyllum 

Wedekind, 1927. 

Genus RYDEROPHRLUM Tcberepnlna, 1965 

1965. Ryderophyllum Tcherepnina, p. 31, pl. 2, figs. la, lb. 

Type species.-Ryderophyllum kasandiensis 

Tcherepnina; by author designation. Ludlovian, Altai 

Mountains, Siberia. 

Diagnosis.-Small and medium-sized ceratoid to trochoid rugose corals with numerous long, usually thin, 

smooth major septa; no septal stereozone or fossula. 

Dissepimentarium wide, with several columns of small to 

medium globose dissepiments. Tabularium wide, with 

close-spaced, mostly incmnplete, axially flattened tabulae. 

Remarks.-Ryderophyllum is not known to pass 

through a Pycnactis-like neanic growth sequence with 

septa thickened and laterally in contact, differing thus 

from Phaulactis, in which thickened septa may persist in 

cardinal quadrants well into mature growth (Ryder, 1926; 

Smith, 1930; Minato, 1961). Ryderophyllum may be a 

junior synonym of Cyathactis Soshkina, 1955. An 

anguloconcentric pattern of chevron dissepiments 

develops in Cyathactis tenuiseptatus Soshkina and 

lonsdaleioid dissepiments in C. social is Soshkina, neither 

feature appearing in the type species (C. typus Soshkina) 

or in Ryderophyllum. Other lycophyllids assigned to 

Cyathactis reveal, in longitudinal section, a depressed 

zone at the outer tabularium margin; among these are 

Cyathactis pegramense (Foerste) and Cyathactis catilla 

(Sutherland). As in the genus Phaulactis, species of 

Ryderophyllum may have adult major septa thickened 

axially within the tabularium but attenuated in the 

dissepimen tari urn. 

The type species, kasandiensis, was reported by 

Tcherepnina (1965) to occur in beds of Ludlovian age at 

Kasandi, Altai Mountains, U.S.S.R. Great Basin representatives are in coral zone B, which is early 

Wenlockian in age. The probably related Phaulactis of 

Gotland is abundant in the Wenlock (Wedekind, 1927; 

Minato, 1961) and ranges elsewhere from Llandoverian to 

upper Ludlovian (Smith, 1930; Bulvanker, 1952; Hill, 

1956; Oliver, 1962a). Cyathactis is known in beds of 

Middle and Late Silurian age. 

Ryderopbyllum ubebebensls, n. sp. 

Plate 6, figures 1-7 

Type material.-Holotype USNM 159396; paratypes 

USNM 159394, 159395, 159397, 159398, 159399. Hidden 

Valley Dolomite, Ubehebe district, California; locality 

Ml094. 

Diagnosis.-Medium-sized ceratoid and trochoid 

Ryderophyllum with wide tabularium in which some of 

the axially flattened tabulae are nearly complete. Peripheral dissepiments steeply inclined. Calice deep and 

acutely conical. 

External features.-Available material is silicified and 

weathered such that external details are poorly shown. 

Exteriors appear to have been rather even and smooth, 

with few rugae. Rejuvenescence rims 1nay be developed in 

mature growth stages. Longitudinal grooves of weathered 

specimens interseptal, not true septal grooves. Outer wall 

probably very thin and without a septal stereozone. 

Transverse sections.-Long major septa numbering 

about 46 in larger adult individuals; some septa extending to axis in early ephebic stage. Minor septa long, 

commonly more than half the length of major septa. In 

ephebic stages, all septa usually rather uniformly thinned, unbroken, and only slightly wavy. Close-set 

dissepiment traces of outer zone making the anguloconcentric chevron pattern of this genus and some species 

of Phaulactis. 

N eanic stages well enough preserved for sectioning are 

not available. The possibility that this species passes 

through a Pycnactis stage with thickened septa cannot be 

entirely eliminated. 

One mature specimen shows thickening of major septa 

within the tabularium only. 

Longitudinal sections.-Eight or 10 dissepiment 

columns on each side; most of these steeply inclined 

axially, ind uding those near the periphery. Wide 

tabularium sharply set off from dissepimedtarium in most 

places; some tabulae nearly complete. Wider tabulae 

nearly straight or with slight axial sag, bending down 

peripherally at the depression which lies between the 

tabularium and dissepimentarium. In parts of the 

tabularium wide tabellae combined with the more 

continuous tabulae. 

Comparison with related forms.-Ryderophyllum 

ubehebensis has a slightly narrower tabularium than 

kasandiensis, the type species. Cyathactis of the Gazelle 

Formation in the Klamath Mountains has a narrower 

tabularium and a crowded chevron dissepiment pattern 

not present in ubehebensis. Cyathactis pegramense of the 

Brownsport Formation in Tennessee differs in having 

laterally depressed tabulae as in the Gazelle species. The 

northern British Columbia Ptycophyllum sp. (Norford, 

1962, pl. XIV, figs. 5-8), from the Silurian Sandpile 

Group, is probably very similar to ubehebensis. Material 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 45 

showing early growth stages is needed to compare R. 

ubehebensis with Phaulactis, the adult stages of which 

commonly resemble this new species. 

Occurrence.-Hidden Valley Dolomite; Silurian coral 

zone B. Ubehebe Peak area, northern Panamint Range, 

locality Ml094. Andy Hills, northern Panamint Range, 

localities Ml095, Mll09. Funeral Mountains, locality 

Ml098. Study material of this species consists of 14 coralla 

(Ml094), five coralla (Ml095), one corallum (Mll09), and 

two coralla (Ml098). 

1820. 

1850-54. 

1926. 

1927. 

1937. 

1940. 

1956. 

Genus PYCNACTIS Ryder, 1926 

Hyppurites mitratus Sch1otheim, p. 352 (in part). 

Aulacophyllum mitratum. Edwards and Haime p. 280, 

pl. 1xvi, figs. 1, 1 a, 1 b. ' 

Pycnactis Ryder, p. 386-390; pl. ix, figs. 1-8. 

Aulacophyllum angelini Wedekind, pl. 24, figs. 3-5. 

Pycnactis Ryder. Butler, p. 93-95. 

Pycnactis Ryder. Lang, Smith and Thomas, p. 112. 

Pycnactis Ryder. Hill, p. F272, fig. 185.5. 

Type species.-Hyppurites mitratus Schlotheim, 1820; 

by original designation (Ryder, 1926). Silurian, Gotland, 

Sweden. 

Diagnosis.-Solitary trochoid rugose corals with long 

thickened major septa laterally in contact and pinnately 

arranged; cardinal septum long, minor septa very short or 

suppressed. Tabulae and dissepiments suppressed. 

Remarks.-The ontogeny of Pycnactis mitratus was 

elucidated by Ryder (1926, p. 389), and the supposed 

genetic relationships of Pycnactis, Mesactis, andPhaulactis were further examined by Butler ( 1937). Phaulactis and 

other lykophyllids are believed to pass through early 

growth stages, such as Pycnactis (Minato, 1961); however, 

the Pycnactis stages are not known inRyderophyllum and 

Cyathactis. 

Occurrence.-According to Ryder (1926, p. 389), the 

Gotland and British Pycnactis mitratus is from beds of 

Wenlockian age. Hede (in Regnell and Hede, 1960, p. 70, 

73, 77) listed this species from the Slite Group, which is 

higher Wenlockian. Great Basin Pycnactis occurs in coral 

zone B, considered early Wenlockian. 

Pycnactis sp. k 

Plate 6, figures 10-12 

Silicified corals assigned to Pycnactis occur in 

association with Ryderophyllum ubehebensis. Because of 

their large size, they are probably not immature growth 

stages of this lykophyllid. 

From 36 to 48 septa, arranged pinnately with reference 

to cardinal plane. Minor septa not distinguishable in 

transverse section. Epitheca or outer wall absent in available specimens, which externally show pinnate pattern of 

thickened septa. 

Occurrence.-Hidden Valley Dolomite; early Middle 

Silurian, coral zone B. Andy Hills, northern Panamint 

504-634 0- 73 - 4 

Range, locality Mll09. Funeral Mountains, locality 

Ml098. Study material consists of two coralla (Mll09) and 

one corallum (Ml098). 

Family CYSTIPHYLLIDAE Edwards and Hatme, 1850 

Reference form.-Cystiphyllum siluriense Lonsdale,6 

1839; Silurian, Wenlock Limestone, Dudley, England. 

Remarks.-Silurian cystiphylloid corals include species 

which reveal trabec_ular septal spines in transverse thin 

section; some, however, lack these spines interally. In 

some individuals septal traces have been observed only on 

the calice floor, where they show as weak, radiating, spiny 

septal ridg~s or striations (Po(:'ta, 1902). Edwards and 

Haime's (1850-54, p. 298, pl. 72, fig. la) description and 

figure of the trochoid Cystiphyllum siluriense suggest that 

the type species has faint calicular septal ridges. However, 

the internal features of siluriense from the type area 

remain to be elucidated. Cystiphyllum cylindricum 

Lonsdale (Lang and Smith, 1927, p. 4 77, pl. 36, figs. 1-5; 

Hill, 1956, fig. 214.la, lb), another British Silurian 

species, shows numerous trabecular septal spines more or 

less radially alined. Wedekind's figures of Gotland corals 

referred to Lonsdale's C. siluriense also reveal abundant 

short trabecular septal spines. In the Gotland 

Holmophyllum Wedekind and Hedstromophyllum 

Wedekind the trabecular spines are much longer and 

heavier than in the genus Cystiphyllum. 

Cystiphyl.loids thus far studied by the writer from the 

Silurian of western North America reveal few or no trabecular spines. However, Cystiphyllum c£. C. tubijorme 

Poulson figured by Norford (1962, pl. 13, figs. 8-11) from 

the Silurian of British Columbia clearly shows such 

features. Cystiphyllum? henryhousense Sutherland (1965, 

p. 24, pls. 13-16) shows sporadic trabecular spines in some 

individuals, but, otherwise, it may be generically distinct 

from Cystiphyllum. 

Cystiphylloids of the Devonian undoubtedly represent 

many homoeomorphic lineages not closely related to the 

Silurian Cystiphyllum and are placed in other families, 

such as the Cystiphylloidae and Digonophyllidae, the last 

with strong septal crests and discrete septa. 

Microplasma Dybowski of the western North American 

Silurian shows trabecular septal spines only in the wall 

and is, with reservation, assigned to this family. 

Forms here provisionally assigned to the family Cystiphyllidae are as follows: 

Cystiphyllum Lonsdale/ 1839 

Hedstromophyllum Wedekind, 1927 

Holmophyllum Wedekind, 1927 

Group of Cystiphyllum? henryhousensis Sutherland, 

1965 

(?)Microplasma Dybowski, 1873 

6ln Murchison (1839, p. 675-699, 5. pls.). 

7In Murchison (1839, p. 675-699, 5 pls.). 
46 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Genus MICROPLASMA Dybowskl, 1873 

Type species.-!vlicroplasma gotlandicum Dybowski; 

by subsequent designation, Wedekind (1927, p. 64). Silurian, Gotland, Sweden. 

Diagnosis.-Slender cylindrical corallites; in longitudinal thin section, interior occupied by two to four columns 

of large globose dissepiments or tabellae which are not 

readily distinguishable. Wall a stereozone in which septal 

trabeculae are embedded and from which very short septal 

ridges project inward. No trabecular septal spines on dissepiments or tabellae as in Cystiphyllum. 

Remarks.-Microplasnw may be a fasciculate colonial 

genus, but ordinarily only isolated corallites are found. 

Microplasma? sp. R 

Plate 7, figures 10,11 

Small and presumably solitary cystiphylloid corals occurring in the Silurian Roberts Mountains Formation of 

the type section are known only from fragmentary 

material referred provisionally to this genus. 

A transverse thin section ll mm in diameter shows an 

outer ring of large lonsdaleioid dissepimental traces with 

two larger tabellar traces occupying the interior. In 

longitudinal thin section, all these chambers are defined 

by axially inclined, usually continuous tabulae or 

tabellae, disposed in such manner that the term "dissepiment'' may not be entirely appropriate. 

The wall is laminar stereome in which are embedded 

septal trabeculae, spaced about four per millimeter; these 

trabeculae support very short abruptly tapering septa 

which cannot be distinguished as major and minor. 

Occurrence.-Top of unit 2, just above limestones with 

abundant Conchidium-like pentameroid brachiopods, 

and at base of Silurian coral zone C, type section of Roberts 

Mountains Formation. Ridge between south and middle 

forks of Pete Hanson Creek, locality Ml089. 

Family GONIOPHYLLIDAE Dybowskl, 1873 

Representative genus and species.-Goniophyllum pyramidalis (Hisinger); Silurian, Gotland, Sweden. 

These extraordinary operculate rugose corals have a 

worldwide distribution in the Silurian and Devonian 

(Lindstrom, 1883). Most of the American forms initially 

assigned to Calceola have, on careful study, been 

recognized as the genus Rhizophyllum, which is largely 

Silurian but ranges upward into strata of Devonian age. 

Oliver (1964) restudied several of the American species and 

described new species of Rhizophyllum. 

The following genera are included in this family: 

Goniophyllum Edwards and Hain1e, 1850 

Rhizophyllum Lindstrom, 1866 

Teratophyllum Lang, Smith, and Thomas, 1940 

Rhytidophyllum Lindstrom, 1883 

Calceola Lamarck, 1799 

Of these genera, only Rhizophyllum has been found in 

the Great Basin and in western North An1erica generally. 

Genus RHIZOPHYLLUM Lindstrom, 1866 

1866. Rhizophyllum Lindstrom, p. 287. 

1940. Rhizophyllum Lindstrom. Hill, p. 39cl. 

1956. Rhizophyllum Lindstrom. Hill, p. F3lcl. 

1964. Rhizophyllum Lindstrom. Oliver, p. DH9-D158. 

Type species.-Calceola gotlandica Roemer, 1856; by 

monotypy. Silurian, Gotland, Sweden. 

Diagnosis.-Calceoloid rugose corals with operculum; 

interior occupied by cystiphylloid dissepiments and 

tabellae. Septa short and limited to flat side; counter 

septum commonly longer and more prominent. 

Radicifonn processes occasionally present. 

Remarks.-Calceola differs in having a stereoplasmfilled interior and is, insofar as known, confined to 

Devonian rocks. 

Rbizopbyllum sp. D, Oliver 

Plate 7, figures 12-14 

1930. Calceola sandalina Lamarck. Stauffer, p. 107, pl. 12, figs. 2, 3. 

1964. Rhizophyllum sp. D, Oliver, p. D155. 

This somewhat compressed species has its greatest diameter of about 35 mm at the calice rim and a cardinalcounter diameter of about 15 mm; the length is about 43 

mm. The flat thick septate wall projects as a tongue 16 mm 

above the calice rim; this wall is notched medially to accomodate the counter septum. The position of the medial 

counter septum is evident on the flat exterior where it lacks 

the strong longitudinal fold of R. gotlandicum; there are 

no indications of radiciform processes. 

In mature transverse section this form resembles Rhizophyllum sp. A of Oliver (1964, p. D153, fig. 153.1) in 

general features of size, proportions, and distribution of 

dissepiments and tabellae. This southeastern Alaska 

species comes from the higher Silurian of Kosciusko 

Island. Rhizophyllum sp. d. R. enorme of Oliver from 

Late Silurian coral facies of the Roberts Mountains 

Formation at Coal Canyon, Simpson Park Mountains, 

Nev., appears to be a somewhat less compressed form than 

sp. D. 

Occurrence.-Middle part of the Vaughn Gulch Limestone about 800 feet above its base. Mazourka Canyon, 

northern Inyo Mountains, Calif., near locality M1092. 

The float specimen is probably from a horizon near the 

bottom of coral zone E. 

Family KYPHOPHYLLIDAE Wedekind, 1927 

Reference genus and species.-Kyphophyllum 

lindstromi Wedekind. Silurian, Gotland, Sweden. 

The Kyphophyllidae are mostly colonial, phaceloid and 

cerioid forms among which the fasciculate species with 

long subcylindrical corallites predominate.Long lamellar 

septa are characteristic, with one to several dissepiment 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 47 

colun1ns, the outer of which are lonsdaleioid in some 

genera. Tabulae are fairly wide and arched in some of the 

genera, and in a few a flaring calice rin1 is known. 

Genera provisionally included in this family are as 

follows: 

Kyphophyllum Wedekind, 1927 

Strombodes Schweigger, 1819 

Petrozium Smith, 1930 

Entelophyllum Wedekind, 1927 

Entelophylloides Rukhin, 1938 (as a subgenus) 

Entelophylloides (Prohexagonaria), n. subgen. 

Neomphyma Soshkina, 1937 

(?)Tonkinaria, n. gen. 

Genus KYPHOPHYLLUM Wedekind, 1927 

1927. Kyphophyllum Wedekind, p. 18-22. 

1940. Cyplzophyllwn, Lang, Smith, and Thomas, p. -!7. 

1956. Kyphophyllum Wedekind. Hill, p. F276. 

Type species.-Kyphophyllum lindstromi Wedekind 

( 1927, explanation pl. 2); by original desegnation. 

Silurian, Gotland, Sweden. 

Diagnosis.-Phaceloid and solitary rugose corals with 

elongate subcylindrical corallites; three or more columns 

of dissepiments, the outer of which are in part 

lonsdaleioid; n1oderately wide, partly continuous tabulae, 

and a rather narrow septal stereozone. 

Remarks.-Lang, Smith, and Thomas (1940, p. 47) and 

Smith (1945, p. 57) noted the sitnilarity of internal structure between Wedekind's Kyphophyllum lindstromi and 

the phaceloid Strombodes stellaris, type species of 

Strombodes Schweigger, 1819. That the two are actually 

congeneric is somewhat doubtful at present, and suppression of Kyphophyllum as a synonym on this basis 

should await comparison of adequate Gotland topotype 

material. 

In Kyphophyllum the septa are long, major septa 

approaching the axis, and are peripherally discontinuous 

as septal crests in the lonsdaleioid areas. The tabulae are 

typically arched but may be flat or even sagging. 

Entelophyllum differs by lacking the lonsdaleioid dissepiments, having a narrower septal stereozone, and 

having fairly numerous lateral radiciform connections 

between corallites. Pilophyllum Wedekind, with 

lonsdaleioid tnarginarium, has a heavier septal stereozone and a n1uch wider tabularium comprising many 

overlapping tabellae and few complete tabulae. 

Wedekind's type speciesK. lindstromi is reported from a 

locality north of Stenkyrke huk, Gotland, in the "untere 

Mergel"; this map occurrence suggests Visby Marl, probably the lower part, and therefore late Llandoverian age. 

Undescribed Kyphophyllum from the Gazelle Formation, 

Klatnath Mountains, Calif., occurs in strata believed to be 

high in that formation and is therefore either Ludlovian or 

very early Devonian. The Great Basin occurrences are also 

high in the Silurian (Ludlovian). 

--J 1 ... ophyllum nevadensis, n. sp. 

Plate 13, figures 1-4 

Type material.-Holotype USNM 159425; Upper 

Silurian, Ikes Canyon, Toquima Range, Nev. 

Diagnosis.-Kyphophyllum forming large phaceloid 

or bushy colonies; corallites with narrow stereozone, 

medium-wide closely spaced tabulae, and irregular, wide 

peripheral segments of lonsdaleioid dissepitnents. 

Transverse sections.-About 22 major septa, most of 

which reach the axis, where they may be somewhat 

twisted; septa smooth and straight to wavy, in places 

having sharp zigzag carinae. Minor septa nonuniform and 

discontinuous, varying from short projections at the 

stereozone to broken septa more than half as long as major 

septa. All septa discontinuous in the lonsdaleioid areas. 

Dissepiment trace pattern very irregular. Septal stereozone 

narrow. 

Longitudinal sections.-Tabulae closely spaced, partly 

complete with downward sag and averaging about onequarter width of corallite. Dissepimentarium with three to 

five columns of nonuniform dissepiments ranging from 

small and globose to large and elongate, the outer ones 

being partly lonsdaleioid; most dissepiments steeply 

inclined, the inner ones near vertical. No discrete axial 

structure. 

Reproductive offsets.-Probably develop laterally from 

calice rim. 

Microstructure.-Trabeculae not clearly shown in walls 

and stereozone of well-preserved specimens. 

Comparison with related forms.-A similar undescribed Kyphophyllum from Late Silurian or Early 

Devonian strata of the Gazelle area, northeast Klamath 

Mountains, Calif., has a narrower tabularimn and more 

extensive development of large lonsdaleioid dissepiments; 

some of the Klamath specimens have a wider stereozone. 

Kyphophyllum lindstromi of the Gotland Silurian shows 

a narrower dissepimentarium, and its wider tabulae are 

arched with median sag and marginal depression not 

present in either nevadensis or the Klamath species. The 

Gotland form is reported to be a solitary coral. 

Occurrence.-In lower part of McMonnigal Limestone 

of Kay and Crawford (1964); coral zone E. Northwest side 

of Copper Mountain, Ikes Canyon, Toquima Range, 

locality M 1114. Study material consists of one large, nearly 

complete corallum and fragments of other coralla. 

Genus PETROZIUM Smith, 1930 

Type species.-Petrozium dewari Smith (1930, p. 307, 

pl. XXVI, figs. 20-28) by original designation. Lower 

Silurian, Valentian, Shropshire, England. 

Diagnosis.-Phaceloid rugose corals having long 

slender cylindrical corallites without connecting 

processes. Long axially thin major septa, some of which 

meet at the center, where they may be involved in an 

incipient axial structure. Dissepiments 1n several 
48 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

colu1nns, small, globose, steeply inclined toward axis. 

Tabularium wide, comprising arched tabellae mostly inclined toward the periphery. Septal stereozone thin or 

absent. 

Remarks.-True carinae, though mentioned in Smith's 

generic diagnosis, are not present in the American species; 

however, the septa may possess zigzag features. An 

Alaskan species of Petrozium from Kuiu Island, southeastern Alaska, has a discrete axial structure reinforced by 

stereoplasm to form a small bladelike columella. 

Petrozium probably ranges through most of the 

Silurian System; the type species is Valentian 

(Llandoverian) Early Silurian. P. mcallisteri, n. sp., of the 

Great Basin occurs in coral zone B, which is Wenlockian. 

An undescribed Petrozium in the Gazelle Formation of the 

Klamath Mountains in California is high Wenlockian or 

Ludlovian. As Petrozium is a rather specialized genus, 

such a long range is surprising. 

Petrozium mcallisteri, n. sp. 

Plate 9, figures 6-10 

Type material.-Holotype USNM 159411. 

Diagnosis.-Petrozium with major septa slightly 

thickened peripherally, tapering to very thin where 

meeting axially. Septa have minute zigzag features. 

Transverse sections.-About 20 major septa, some of 

which reach the axis; septa mostly wavy and commonly 

zigzag peripherally. Major septa slightly thickened peripherally, attenuated axially. Minor septa rather long, 

some exceeding half the length of major septa. Septal 

stereozone weakly developed or absent. Symmetry entirely 

radial; no suggestion of a fossula. 

Longitudinal sections-Tabularium about half the 

width of corallum, con1prising arched tabellae without 

complete tabulae. Tips of major septa intersect, 

suggesting an inCipient axial structure, but no 

development of true columella. 

Comparison with related forms.-Petrozium 

mcallisteri has fewer septa than dewari, the type species, 

but it is otherwise very similar, especially in longitudinal 

section. An undescribed Petrozium in the Silurian Gazelle 

Formation of the Klamath Mountains has more even, less 

tapering septa without zigzag features; some corallites of 

the Gazelle species have a suggestion of a fossula not recognized in mcallisteri. 

Occurrence.-Lower part of the Hidden Valley 

Dolomite; 1~ miles north of Ubehebe Peak, Northern 

Panamint Range, locality Mllll. The large silicified head 

of the coral here described was collected as float below the 

main in situ locality (Ml094), but it is believed to have 

come from the bed of silicified corals which is the type 

occurrence of Great Basin coral zone B. Study material 

consists of a single large corallum. 

Genus ENTELOPHYLLUM Wedekind, 1927 

1927. Entelophyllum Wedekind, p. 22-24; pl. 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. 

1940 Entelophyllum Wedekind. Lang, Smith, and Thomas, p. 

57-58. 

1940. Entelophyllum Wedekind. Hill, p. 4ll. 

1956. Entelophyllum. Duncan, pl. 23, figs. 5c, 5d. 

1956. Entelophyllum Wedekind. Hill, p. F275, fig. 187,2a-c. 

1962. Entelophyllum Wedekind. Stumm, p. 2, 3. 

1962a. Entelophyllum Wedekind. Oliver, p. 15. 

1964. Entelophyllum Wedekind. Stumm, p. 32. 

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 at several 

localities in strata of Wenlockian and Ludlovian age on 

Gotland; it is recorded in England from Wenlock 

Limestone. 

Diagnosis.-Phaceloid or solitary rugose corals with 

elongate subcylindrical mature corallites. Major septa 

thin or slightly thickened only near outer wall, approaching or slightly withdrawn from axis. Tabularium 

wide, typically with closely spaced flat tabulae and 

tabellae and a narrow peripheral, proximally depressed 

zone bordering the dissepimentarium. Dissepimentarium 

having from a few to many columns of small steeply inclined globose dissepiments. Outer wall thin and without 

stereozone. No fossula or indication of bilateral symmetry 

in mature stages. Septa slightly to moderately wavy, but 

well-developed angle-carinae not present in typical form. 

Lateral attachment outgrowths from wall characteristic of 

some species. Five or six reproductive offsets developed 

marginal to the calice. 

Remarks.-Not all species placed in Entelophyllum 

have the strongly depressed peripheral zone of the tabularium shown by the type species. The English Wenlock 

representatives of E. pseudodianthus (Weissermel) have 

zigzag, thickened, highly carinate septa and less elongated cylindrical corallites (Smith and Tremberth, 

1929, p. 361-362; Lang and Smith, 1927, p. 475, textfig.l5). 

Disphyllum of the Middle Devonian is similar to 

Entelophyllum. However, it is usually very slender, lacks 

the numerous coarse or thick attachment outgrowths of 

some species of Entelophyllum, has more even septa 

without carinae, and commonly has a somewhat wider 

tabularium. The transverse sections of Disphyllum show a 

more uniformly even concentric distribution of axially 

concave dissepiment traces. Some forms of Entelophyllum 

have several reproductive offsets marginal to the calice, a 

condition not known in Disphyllum. 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 49 

Entelophyllum eurekaensls, n. sp. 

Plate 10, figures 1, 2, 14, 15 

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, with 

longer major septa approaching axis. Small- to mediumsized dissepiments appearing in transverse sections as 

axially concave and chevron traces. 

External features.-Known only from isolated pieces 

but assumed to be phaceloid, like the related species E. 

engelmanni of the same interval in the Lone Mountain 

Dolomite. Available specimens ceratoid rather than subcylindrical. 

Transverse sections.-About 30 major septa, most of 

which are withdrawn, but a few approach the axis; minor 

septa from short wedge like stu1nps to about half the length 

of major septa. Septa not as thin as in most species of 

Entelophyllum and only slightly wavy. No carinae recognized. Dissepiments include herringbone and chevron 

traces as well as those that are concentric and axially concave. Septa wedge out markedly at outer wall, but no 

thickened stereozone; epitheca rather thin. 

Longitudinal sections.-Tabularium width nearly twothirds the diameter. Tabulae, in part, nearly continuous, 

axially and periaxially flat, peripherally depressed. Flat 

peripheral tabellae also present. Small to fairly large, 

steeply inclined dissepiments. 

Comparison with related forms.-This species has a 

wider tabularium than engelmanni of the upper Lone 

Mountain Dolomite; the tabulae are medially flat with 

peripheral sag, conditions less characteristic of 

engelmanni. Elongate cylindrical corallites with lateral 

growths and the bushy growth habit of engelmanni are 

unknown in eurekaensis. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; t,~pper Lone Mountain-Laketown 

biofacies containing Howellella pauciplicata. Southern 

Fish Creek Range, Nev. locality Mlll3; associated with a 

silicified brachiopod assemblage including Howellella 

pauciplicata, Protathyris hesperalis, and Camerotoechia 

pahranagatensis. Study material of this species consists of 

22 disassociated corallites. 

Entelophyllum engelmanni, n. sp. 

Plate 10, figures 5-13 

Type material.-Holotype USNM 159413; paratypes 

USNM 159414, 159415, 159416, 159417; figured specimen 

USNM 159418. 

Diagnosis.-Phaceloid Entelophyllum forming large 

bushy colonies of nearly straight subcylindrical corallites 

joined by lateral outgrowths. Tabularium wide, tabulae 

mostly complete and subparallel, not always with peripheral sag as in typical Entelophyllum; some tabulae 

with axial and periaxial sag or with slight distal arching. 

Tabellae not com1non. Major septa withdrawn from ax1s, 

slightly wavy, and with no carinae. Minor septa short, usually less than half the length of major septa. Septa thin 

internally but with wedge thickening at wall. No stereozone. 

External features.-Elongate mature corallites large for 

this genus, with well defined septal grooves crossed by 

annular incremental striations but without coarse annular 

folds or rugae. Some corallites with thick irregular lateral 

attachment outgrowths along one side with vertical 

distribution. 

Transverse sections.-About 28 major septa, thin internally and slightly withdrawn from the axis. Minor 

septa short, less than half the length of major septa. All 

septa wedges thickening at very thin outer wall. Septa 

slightly wavy and lacking carinae. Dissepiments not 

numerous, rather irregular as chevrons, forks, and simple 

traces which are either almost straight or slightly concave 

axially. 

Longitudinal sections.-Tabularium wide, about twothirds of the diameter. Tabulae mostly complete, varying 

from straight or slightly arched axially and periaxially 

with or without peripheral depression to those with axialperiaxial sag and no peripheral depression. Dissepiments 

globose in one to three columns, steep and of small, 

medium, and large size. A few broad flat tabellae peripherally. 

Comparison with related forms.-Entelophyllum 

engelmanni differs from eurekaensis in the unevenness of 

its tabulae, which commonly lack the peripheral depression; its very elongate cylindrical corallites have 

lateral processes not observed in eurekaensis. 

Occurrence.-Late Silurian, upper part of the Lone 

Mountain Dolomite; upper Lone Mountain-Laketown 

biofacies. Southern Mahogany Hills, Nev.locality Mlll2. 

Southern Fish Creek Range, Nev., locality Ml087. A 

similar form occurs in Silurian dolomite of the Ruby 

Mountains, Nev. (pl. 15, figs. 12-16). 

Study material of this species consists of several hundred 

corallites from numerous coralla (lacs. Ml087, Mlll2). 

Genus ENTELOPHYLLOIDES Rukhin, 1938 (as subgenus of ENTELOPBYLLUM) 

1938. Entelophyllum (Entelophylloides) inequalum (Hall). Rukhin, 

p. 23. 

Type species.-Columnaria inequalis Hall (in part), 

1852, p. 323, pl. 72, figs. 3, 4; by author designation. 

Silurian, Cobleskill Limestone, New York. 

Diagnosis.-Cerioid rugose corals with long, even 

septa, several columns of small and medium dis-
50 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

sepiments, and tabulae of medium width. Lonsdaleioid 

dissepiments inconspicuous or lacking. No axial structure. 

Remarks.-Carinae were not observed in transverse thin 

sections of the type species, but longitudinal thin sections 

reveal numerous delicate spinose bars or spurs extending 

laterally from the tabularium septal extensions. In the 

type species the number of major septa, being about 12, is 

small for the compound Rugosa. Some major septa reach 

the axis; minor septa are only a little shorter. The outer 

dissepiments are more irregular and nonuniform than the 

more concentric inner ones and may be sporadically sublonsdaleioid in the largest corallites. 

Entelophylloides, erected by Rukhin as a subgenus 

under Entelophyllum, is here considered an independent 

genus. 

The genus is Late Silurian. Specimens collected by Jean 

Berdan from the Silurian Cobleskill Limestone in the 

vicinity of Shutters Corners, Schoharie quadrangle, New 

York, are considered topotype material of Hall's inequalis. 

Similar corals from the Keyser Limestone of the Evitts 

Creek area, Maryland, collected by Jean Berdan and Helen 

Duncan, appear to be a distinct species with thicker septa 

and fewer sental spines within the tabularium. 

Subgenus ENTELOPHYLLOIDES, sensu stricto 

Type species.--Entelophylloides (Entelophylloides) 

inequalis (Hall). 

This subgenus has the characters of the genus Entelophylloides in the strict sense. Its members include species 

with small corallites, a small average number of major 

septa (about 12), straight unarched tabulae, and numerous 

lateral spines or spurs on major septa within the 

tabularium. 

Subgenus PROHEXAGONARIA, new subgenus 

Type species.-Entelophylloides (Prohexagonaria) occidentalis, n. sp.; here designated. Silurian, bottom of unit 

3 of the Roberts Mountains Formation; Roberts Creek 

Mountain, Nev. 

Diagnosis.-Cerioid rugose corals with numerous long 

thin septa, some reaching the axis; minor septa threefourths the length of major septa. Tabularium less than 

one-third the corallite diameter; tabulae close spaced, 

some complete and straight, some arched as tabellae. Dissepimentarium wide, with eight or more columns of 

small- and medium-sized dissepiments which are nearly 

flat peripherally. Elbow or zigzag carinae inconspicuous. 

Septa with no lateral spines. 

Remarks.-This subgenus has about 18 major septa, 

averaging 12 in typical Entelophylloides. Another 

significant distinction is absence of septal spines or spurs, 

which show well in longitudinal thin sections of the type 

speoes. 

Hexagonaria of the Devonian has more evenly and 

uniformly globose dissepiments, a more uniform pattern 

of concentric dissepimental traces in transverse section, 

and a broader tabularium. The typical H exagonaria is 

characterized by yardarm carinae not present in Entelophylloides. The septal spines or spurs of the latter are 

absent in H exagonaria. 

Prohexagonaria resembles the Silurian cerioid T enuiphyllum Soshkina; the latter has an arched axial development more like Petrozium. Somewhat closer 

morphologically are Silurian cerioid forms heretofore 

classified as cerioid "Xylodes" or cerioid Entelophyllum. 

Undescribed cerioid Silurian Rugosa of the Gazelle 

Formation, Klamath Mountains, Calif., superfically 

resemble Entelophylloides, sensu stricto, but the 

tabularium is narrower, tabulae are weakly developed, the 

septa are thickened toward the wall, and larger 

lonsdaleioid dissepiments are sporadically developed. 

Entelophylloides (Prohexagonaria) occidentalis, n. sp. 

Plate 9, figures 1-4 

1940. Strombodes. Merriam, p. 12, 92. 

1963b. Strombodes. Merriam, p. 38. 

Type material.-Holotype, USNM 159410; Silurian, 

unit 3 of the Roberts Mountains Formation. Roberts Creek 

Mountain, Nev. 

Diagnosis.-Prohexagonaria with numerous, somewhat wavy, unthickened septa. In transverse thin section, 

the dissepiment pattern includes many peripheral anguloconcentric and nearly straight traces. Tabulae close spaced 

and arched or flat. Corllite wall fairly straight. 

External features.-Occurs in compact cerioid heads 

exceeding a diameter of l 0 inches. 

Transverse sections.-Major septa 18-20, unthickened 

throughout, with waviness increasing peripherally. Some 

incipient angulation carinae developed, but none 

showing in depth as true carinae in longitudinal thin 

sections. Pattern of dissepiment traces mostly ,concentric,, 

but peripherally these traces changing to irregularly 

anguloconcentric or nearly straight with increasing septal 

waviness. A slight tendency to develop scattered small 

sublonsdaleioid dissepiments near walls. 

Longitudinal sections.-Mostly small globose 

dissepiments developed in eight or more columns. 

Combinations of close-spaced complete tabulae and 

tabellae which are more commonly uparched than flat in 

the tabularium. 

Reproductive offsets.-Small interstitial reproductive 

offsets developed from the calice margin (seen in 

transverse sections). 

Comparison with related forms.-Entelophylloides 

(Prohexagonaria) sp. from Visby, Gotland, figured by 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 51 

Smith and Tremberth (1929, pl. 8,fig. 1) as "Xylodes sp." 

resembles occidentalis in transverse section. (See pl. 9, fig. 

5.) The cerioid "Acervularia mixta" Lindstrom (1882b) 

from reported Silurian rocks of the central Siberian 

uplands differs in having a zigzag wall, and in 

longitudinal section it shows an axial structure more like 

that of Petrozium. Other than this species, American Late 

Silurian forms assigned to Entelophylloides for the most 

part have the subgeneric features of inequalis (Hall), as 

outlined above. A species from the New Jersey Decker 

Ferry Formation assigned by Weller (1903, p. 219, pl. 17, 

figs. 12, 13) to Hall's species is similar to occidentallis in 

transverse section, but, as illustrated in longitudinal 

section, it lacks straight or complete tabulae. 

Entelophylloides from the Keyser Limestone of 

Maryland assigned by Swartz (1913, pl. 20, figs. 1-4) to 

Hall's inequalis presumably falls in the subgenus Entelophylloides, sensu stricto; this species differs from 

occidentalis in its peripherally wedge-thickened septa and 

in its scattered large peripheral dissepiments. 

Occurrence.-Lower beds of unit 3 in the Roberts 

Mountains Formation; Middle Silurian coral zone C. 

Northwest side of Roberts Creek Mountain, Nev., locality 

Mll02. Study material consists of two large coralla and 

pieces of other coralla from same coral bed. 

Genus NEOMPHYMA Sosbkina, 1937 

1937. Neomphyma Soshkina, p. 76, 98; pl. XV, figs. 3, 4. 

1940. Neomphyma Soshkina. Lang, Smith, and Thomas, p. 88. 

1956. Neomphyma Soshkina. Hill, p. F298, fig. 203.4a-b. 

Type species.-Neomphyma originata Soshkina, 1937; 

by original designation. Silurian, Petropavlovsky region, 

east slope Ural Mountains. Reported as "Upper Ludlow.'' 

Diagnosis.-Solitary and fasciculate rugose corals with 

slender cylindrical mature corallites having a narrow 

peripheral stereozone, large irregular peripheral 

lonsdaleioid dissepiments, and a few thin nonuniform discontinuous septa, which may extend to the axis. 

Tabularium usually narrow; tabulae very unevenly 

developed, either widely spaced or closely set. 

Remarks.-Some corallites show almost no septa except for short spinose projections from the stereozone. 

The type species is reported by Soshkina to occur in beds 

of upper Ludlovian age. Neomphyma crawfordi, n. sp., 

from the Toquima Range, Nev., is associated with 

Arachnophyllum and Cyathophylloides fergusoni in 

strata which probably represent Great Basin coral zone A 

of Early Silurian (Llandoverian) age. 

Neomphyma crawfordi, n. sp. 

Plate 13, figures 5-8 

Type material.-Holotype USNM 159426. 

Diagnosis.-Phaceloid, cylindrical Neomphyma with a 

few very large and irregular lonsdaleioid dissepiments in 

mature stages. Septal lamellae smooth. Primary septa 

highly irregular, nonuniform and wavy, most not 

reaching axis, commonly few or lacking medially, but 

always appearing at wall as crests. Outer wall a moderately 

thick stereozone. Dissepiments near vertical; tabulae 

mostly narrow, widely spaced, and nearly flat. 

External features.-Bushy phaceloid colonies 8 or more 

inches in diameter comprising close-set cylindrical, fairly 

straight corallites. No connecting processes observed. Surface marked by septal grooves and not very pronounced 

transverse rugae. Numerous small offsets originate from 

parental calice, especially at outer wall; one calice may 

have as many as four of these marginal offsets. 

Transverse section.-Neanic stages with about 16. 

smooth simple wavy major septa, most of which do not 

reach the axis; minor septa very short. In ephebic stages, 

with appearance of the large lonsdaleioid dissepiments, 

the major septa increasing to 20 or more but commonly 

suppressed medially, showing only as the peripheral crests 

in some cystiform individuals. Peripheral stereozone 

about 1110 or 1

{ 2 thediameteroftheephebiccorallite. With 

some individuals, major septa discontinuous, appearing 

as short radial crests. 

Longitudinal section.-Large, steeply inclined to vertical nonuniform dissepiments arranged in one or two 

columns and occupying most of the corallite width. Few 

tabulae, widely spaced, more or less straight, and usually 

narrow. Walls of contiguous corallites commonly 

coalescing. 

Reproductive offs.ets.-(See external features.) 

Microstructure.-Trabecular structure poorly defined 

in stereozone, inclined peripherally a few degrees from 

horizontal. 

Comparison with related forms.-Neomphyma 

originata Soshkina (1937, p. 98, pl. XV, figs. 3, 4) differs 

from crawfordi in having longer, more continuous major 

septa and a more irregular pattern of dissepiments, as observed in longitudinal section. The Russian species is reported from beds of Ludlovian age in the Urals and may 

accordingly be considerably younger than crawfordi of 

coral zone A. 

Occurrence.-Lower Silurian, coral zone A; in the 

Masket Shale of Kay and Crawford (1964). Ikes Canyon, 

Toquima Range, Nev., locality Ml088. In association 

with Arachnophyllum kayi, n. sp., and Cyathophylloides 

fergusoni, n. sp. Study material consists of one nearly complete corallum and pieces of other coralla. 

Genus TONKINARIA, new genus 

1956. (?)Entelophylluf!l. Duncan, pl. 23, figs. Sa, Sb. 

Type species.-Tonkinaria szmpsoni, n. gen., n. sp.; 

here designated. Silurian; unit 3 of the Roberts Mountains Formation. 

Diagnosis.-Solitary and loosely phaceloid rugose 

corals with flaring trumpet-shaped calice, ceratoid to tur- · 

binate corallites, and narrow tabularium. Wall a narrow 
52 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

stereozone; septa thin, major septa reaching or slightly 

withdrawn from axis. Some dissepiments large, elongate, 

and steeply inclined. Multiplication by three or more 

peripheral calice offsets. 

Remarks.-Unlike Entelophyllum, the new genus Tonkinaria does not have a cylindrical growth habit. The 

tabularium also differs from that of typical Entelophyllum, which commonly has several columns of smaller dissepiments. The internal structure of Tonkinaria resembles that ofNeomphyma Soshkina (1937, p. 98), which 

differs in its cylindrical shape and larger dissepiments. 

Tonkinaria simpsoni is associated at its type occurrence with phaceloid Rugosa of comparable exterior 

growth form but is otherwise unrelated. Placed in the new 

genus Stylopleura, these externally similar colonial corals 

are nondissepimented and possess cylindrical mature 

coral lites. 

Tonkinarla simpsoni, n. sp. 

Plate 7, figures 1-8 

Type material.-Holotype USNM 159403; paratypes 

USNM 159402, 159404; figured specimen USNM 159405. 

Diagnosis.-Small Tonkinaria with ceratoid or 

trochoid corallites and usually a flaring calice; reproductive offsets developed at the calice rim. Attachment by 

talons. 

External features.-The calice deeply conical to very 

widely flaring with peripheral platform and central pit. 

Broadly flaring or reflected types with a thin rim to which 

reproductive offsets are attached; septa extending to rim as 

broad slightly rounded to nearly flat ribs separated by 

sharp grooves. Septal grooves not strongly defined 

externally. 

Transverse sections.-Septa thin, somewhat wavy, and 

numbering about 8; most extending more than half the 

radius, and some reaching the axis. Short minor septa 

commonly present. Septa thickened peripherally toward 

the narrow septal stereozone. Dissepimental traces rather 

irregularly concentric and axially concave to straight. 

Longitudinal sections.-Tabularium narrow, less than 

one-third of diameter. Tabulae poorly defined in available specimens but, where shown, very narrow, irregularly concave distally, and rather closely spaced. Dissepiments in three or more columns, steeply inclined, many of 

them relatively large and elongate. 

Reproductive offsets.-Offsets characteristically 

growing laterally or vertically from the calice rim, as illustrated on plate 7, figures l and 2. Asexual progeny commonly attached to successive parents, resulting in complex colonial growth (pl. 7, fig. 9). 

Occurrence.-Late Silurian, coral zoneD; unit 3 of the 

Roberts Mountains Formation. Roberts Creek Mountain, 

Nev., locality MllOO. Ikes Canyon reference section, 

Toquima Range, Nev., locality Mll03. Provisionally assigned to Tonkinaria is the Hidden Valley specimen (pl. 7, 

fig. 9) from locality Ml097, Funeral Mountains (Ryan 

quadrangle). 

Study material consists of 21 coralla (loc. MllOO), one 

corallum (loc. Mll03), and one compound corallum (loc. 

Ml097). 

Family CHONOPHYLLIDAE Holmes. 1887 

Refererrce genus.-Chonophyllum Edwards and 

Haime, 1850. 

These <;:orals are cmnmonly very rugate externally, be-

:ause of their numerous rejuvenescence flanges and conein-cone growth habit. They have been frequently confused with theplatelike nondissepimented Mycophyllinae 

because of taxonomic complications involving the 

identity of the type species of Chonophyllum (Smith, 

1945, p. 19). As interpreted at present, the Chonophyllidae include only solitary species with a strong dissepimentarium comprising medium and large elongate 

lonsdaleioid dissepiments; most of the septa are discontinuous. Tabulae are flat medially, and most are 

continuous. 

Only the two genera Chonophyllum Edwards and 

Haime, 1850, and Ketophyllum Wedekind, 1927, are with 

assurance included in this family. 

Genus CHONOPHYLLUM Edwards and Haime 1850 

1826. Cyathophyllum plicatum Go1dfuss, p. 59, pl. xviii, fig. 5. 

1850. Chonophyllum Edwards and Haime, pl. lxix. 

1851. Chonophyllum perfoliatum (Goldfuss manuscript). Edwards 

and Haime, p. 405. 

1902. Chonophyllum pseudohelianthoides Sherzer. Po"tta, pl. 109, figs. 

3-6. 

1926. Not Chonophyllum Lang, p. 428-434, pl. xxx, figs. 4-6. 

1927. Not Chonophyllum Lang and Smith, p. 454. 

1927. Not Chonophyllum patellatum Schlotheim. Wedekind, pl. 7, 

fig. 1. 

1927. Not Chonophyllum planum Wedekind, pl. 7, figs. 2, 3. 

1927. Omphyma flabellata Wedekind, p. 59; pl. 17, figs. 3, 4; pL 18, 

figs. 10, 11. 

1940. Chonophyllum Edwards and Haime. Lang, Smith, and Thomas, 

p. 36. 

1945. Chonophyllum Edwards and Haime. Smith, p. 19; pl. 30, fig. 3. 

1949. Chonophyllum Edwards and Haime. Stumm, p. 48 (in part); 

pl. 23, fig. 4, ?fig. 3, not figs. 5, 6. 

1956. Chonophyllum Edwards and Haime. Hill, p. F300; fig. 204.3a, 

3b. 

Type species.-Cyathophyllum perfoliatum Goldfuss; 

Edwards and Haime, 1850; by original designation. 

Silurian, Gotland. Cyathophyllum perfoliatum Goldfuss 

is C. plica~ urn Goldfuss ( 1826, p. 59; pl. xviii, fig. 5 ), not C. 

plicatum Goldfuss (1826, p. 54, pl. xv, fig. 12). 

Diagnosis.-Large solitary trochoid, ceratoid, and turbinate rugose corals with poorly defined wall and rough, 

uneven outer surface showing distally repeated edges of 

superposed growth cones. Septa numerous, long, somewhat thickened; some major septa reaching axis. 

Tabularium narrow (14- 1 /s mature corallite diameter); dissepimentarium wide, with nonuniform large and small 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 53 

dissepiments, most of which are elongate. Peripheral dissepiments nearly flat, commonly very elongate, and in 

part lonsdaleioid. Calice shallow with broad, commonly 

reflected rim and central pit. 

Remarks.-Identity of the Chonophyllum type species 

has long remained in doubt. According to Lang, Smith, 

and Thomas (1940, p. 36) and Smith (1945, p. 19), the 

species name perfoliatum was personally substituted by 

Goldfuss for the name plicatum on the label of the 

Gotland type specin1en in question, the name plicatum 

having been used also by him for another coral under the 

genus Cyathophyllum (Edwards and Haime, 1851, p. 405). 

Usage of Chonophyllum perfoliatum as set forth by Edwards and Haime (1850, pl. lxix; 1851, p. 405) is accordingly adopted here. 

A transverse section of the type specimen of Chonophyllum perfoliatum (Goldfuss manuscript) in the 

Goldfuss collection at the University of Bonn was figured 

by Smith (1945, p. 19-20, pl. 30, fig. 3), but the 

longitudinal section of this species remains unknown, 

leaving some uncertainty about the status of Chonophyllum. Hill (1956, p. F300) noted, however, that the 

longitudinal section of perfoliatum has not been figured, 

but that the transverse section illustrated by Smith ( 1945, 

pl. 30, fig. 3) is very similar to that of the Gotland 

Omphyma flabellata Wedekind (1927, pl. 17, figs. 3, 4), 

which is known and illustrated in vertical section. 

Longitudinal sections of the Great Basin Chonophyllum 

simpsoni are very much like the section of Wedekind's 

flabellata, which was erroneously placed by him in 

Omphyma. 

Chonophyllum is probably related to Ketophyllum 

Wedekind, 1927, but has a narrower tabularium and septa 

that are more dilated. Ketophyllum usually has large 

lonsdaleioid dissepiments; these are less common or less 

conspicuous in Chonophyllum but are strongly developed 

in certain of the Great Basin corals assigned provisionally 

to this genus. 

Chonophyllum as used here is distinct from the large 

turbinate to patelloid nondissepimented Silurian corals 

with which it has been confused and which are now correctly placed in Mucophyllum or in Schlotheimophyllum. Chonophyllum is copiously dissepimented, has 

septa which are far less dilated and which form a wide 

stereozone in these two genera, and lacks the axial structure of Schlotheimophyllum. Corals belonging in Chonophyllum or Ketophyllum have in the past been erroneously assigned to Omphyma, the type of which, as 

noted by Hill (1956, p. F300), is unknown. 

Occurrence.-The range of Chonophyllum in the Gotland Silurian is poorly known. Wedekind's (1927, pl. 17, 

figs. 3, 4) record of Chonophyllum flabellata at "Othem, 

Solklint" suggests the Slite Group of Wenlockian age. 

Smith (1945, p. 19) recorded an occurrence of C. 

perfoliatum at Kraklingbo, Gotland, which may well be 

from strata of the Klinteberg Limestone, which is considered Ludlovian. 

Great Basin occurrences are in the higher part of the 

Silurian column a'lld are doubtless Ludlovian. 

Chonophyllum simpsoni, n. sp. 

Plate 8, figures 1-4 

Type material.-Holotype USNM 159408; paratype 

USNM 159409. 

Diagnosis.-Large trochoid to ceratoid Chonophyllum with major septa reaching axis, irregular lonsdaleioid peripheral dissepiments, and narrow tabularium 

with dose-spaced undulant incomplete tabulae and marginal tabellae. Inner dissepiments commonly anguloconcentric in transverse section. 

External features.-This form possibly ceratoid in later 

mature stages of growth. Uneven projecting rims of closely spaced superposed rejuvenescence growth cones typical 

of the genus. 

Transverse sections.-About 32 major septa; minor septa generally more than half the length of major septa. Septa slightly thickened, sn1ooth, straight to slightly wavy, 

not extending to periphery as spines in lonsdaleioid parts. 

Indications of stereoplasmic thickening of axial ends of 

septa, but no discrete axial structure. Some inner dissepiment traces with anguloconcentric chevron pattern. Lonsdaleioid pattern highly irregular, occupying most of dissepimentarium or narrow. 

Longitudinal sections.-Tabularium sharply set off 

from dissepimentarium. Undulant tabulae spaced three to 

seven per millimeter; all tabulae incomplete and combined marginally with tabellae. Most of the peripheral dissepiments very elongate and either nearly horizontal or inclined axially at a low angle. Stereoplasmic thickenings 

on upper surfaces of dissepiments. 

Reproductive offsets.-Chonophyllum simpsoni probably a solitary species, as none of the study specimens 

show offsets. 

Comparison with related forms.-Chonophyllum 

simpsoni has smoother, more even septa than appear in 

Smith's (1945, pl. 30, fig. 3) transverse figure of the type 

species, perfoliatum, which may also have broken septa 

and septal spines in the lonsdaleioid parts. C. flabellata 

(Wedekind) shows discontinuous septa in lonsdaleioid 

patches throughout the wide dissepimentarium; the 

longitudinal section of this form is, however, very similar 

to that of C. simpsoni, although the tabulae are more nearly complete and less undulant in flabellata. C. pseudohelianthoides Sherzer of Po'C:ta (1902, pl. l 09, figs. 3-6) is 

similar but has less undulant tabulae and has lonsdaleioid dissepin1ents throughout the wide dissepimentarium. This Bohemian form is reported from Barrandian 

Stage For f of the Koneprus, which is presumably Early 

Devonian. 

Occurrence.-Upper part of the Roberts Mountains 
54 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Formation; Upper Silurian, coral zone E. Coal Canyon, 

northern Simpson Park Mountains, Nev., locality M1108. 

The study material from this locality consists of two incomplete mature cm·alla and unsec~ioned fragmentary 

specimens probably representing this species. 

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 with some large lonsdaleioid dissepiments, and a narrow to very wide tabularium comprising closely spaced tabulae (Jones, 1929). No axial 

structure. 

Genera provisionally assigned to the Endophyllidae are 

as follows: 

Endophyllum Edwards and Haime, 1851 

Y assia Jones, 1930 

Australophyllum Stumm, 1949 

Australophyllum (Toquimaphyllum), n. subgen. 

An undescribed cerioid genus similar to Toquimaphyllum in the Silurian Gazelle Formation of the Klamath Mountains, Calif., also belongs in the Endophyllidae.Pilophyllum Wedekind of the Gotland Silurian, a 

solitary or phaceloid genus, may likewise be a member, 

but it differs from the others in having a wider septal sterozone and a noncompact subcylindrical growth habit. 

Some corals here placed in the Endophyllidae have 

previously been assigned to Spongophyllum. Spongophyllum is typified by S. sedgwicki Edwards and Haime; 

this genus is not included in the Endophyllidae as here redefined by reason of its slender corallites, rather narrow 

tabularium, and narrower, simpler, and possibly only 

sparingly lonsdaleioid dissepimentarium. It is proposed 

that the generic name Spongophyllum be confined to 

species 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). These 

illustrations show a thickened wall and little suggestion of 

lonsdaleioid dissepiments in four of the five transverse 

views. A single figure (2d) of Edwards and Haime's plate 

56 shows a lonsdaleioid pattern. There is no assurance that 

the specimen so illustrated (2d) is conspecific. (See also 

Stumm, 1949, p. 3I, pl. 14, figs.IO, II; Birenheide, I962,p. 

68-74, pl. 9, fig. 8, and pl. 10, fig. 10). 

Lonsdaleioid dissepiments occur in several rugose coral 

families and by themselves are not regarded as indicative of 

genetic relationships. In the Silurian rocks, dissepiment 

patterns of this kind characterize the Endophyllidae and 

genera of other families, such as Strombodes, Kyphophyllum, Pilophyllum, Spongophylloides, and Ketophyllum. Of the various Devonian rugose coral groups so 

characterized, several of cerioid growth habit have rather 

indiscriminately been classified as Spongophyllum. Some 

of these, may more appropriately be assigned to Australophyllum, whereas others are perhaps allied to Hexagonaria. The rather abundant Late Paleozoic columellate 

corals of Lonsdaleioid habit are typified by Lonsdaleia. 

Abbreviation and loss of septa is a tendency manifested 

by the later Silurian Endophyllidae; among these are 

Y assia, which lacks septa, A ustralophy llum 

(Toquimaphyllum), with septa reduced or lost in some 

corallites, and the undescribed Klamath Mountains genus 

with similarly reduced or obsolete septa. 

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. l, 2. 

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

fig. 207. 4a, 4b. 

Type species.-Spongophyllum cyathophylloides 

Etheridge; by author designation. "Lower Middle 

Devonian: Douglas Creek, Clermont, Queensland, 

Australia.'' 

Diagnosis.-Cerioid endophyllid corals with mediumwide to narrow, closely spaced, proximally sagging 

tabulae, and a wide to very wide dissepimentarium with 

scattered to wholly lonsdaleioid dissepiments, some of 

which are large. 

Remarks.-Australophyllum differs from 

Spongophyllum in possessing multiple columns of lonsdaleioid dissepiments and more closely spaced sagging 

tabulae which lack a peripheral depression. Stumm's 

diagnosis of Australophyllum includes carinate septa, although his figures of the type species do not show these 

features convincingly. The wall of typical 

Australophyllum is somewhat thickened stereoplasmically. Septal crests do not appear to be characteristic of Australophyllum sensu stricto, as they are of the 

new subgenus Toquimaphyllum. 

Subgenus TOQUIMAPHYLLUM, new subgenus 

1888. Endophyllum (spongophylloides?) Foerste, p. 131, pl. 13, 

figs. 16, 17. 

1940. Spongophyllum spongophylloides (Foerste). Hill, p. 408, 

pl. xiii, figs. 3-5. 

1956. Spongophyllum. Hill, p. F298 (in part). 

Type species.-Australophyllum (Toquimaphyllum) 

johnsoni, n. sp.; here designated. Late Silurian coral zone 

E, Toquima Range, Nev. 

Diagnosis. -Cerioid rugose corals possessing mature 

corallites with wide, almost wholly lonsdaieioid dissepimentarium, predominantly large dissepiments, and 

moderately wide to rather narrow, closely spaced, sagging 

tabulae without peripheral depression. Septa usually 

smooth, discontinuous peripherally as septal crests. In 

some mature corallites, septa greatly shortened or 

obsolete. 

Remarks.-Australophyllum (Toquimaphyllum) differs from Australophyllum sensu stricto in the greater 
SYSTEMATIC AND DESCRIPTIVE PALEONTOLOGY 55 

development of large lonsdaleioid dissepiments, in having 

an almost wholly lonsdaleioid mature dissepimentarium, 

in the presence of septal crests peripherally, and in the tendency to abbreviate and to lose septa in some corallites. 

Septa of Toquimaphyllum lack true carinae. Endophyllum differs in having a much wider tabulariun1, the 

tabulae being nearly flat to slightly arched medially with a 

peripheral sag not found in other described genera of this 

family (Jones, 1929). The type species of Endophyllum 

shows a tendency to lose the outer wall, thus becoming 

aphroid or partly aphroid. Insofar as known, 

Endophyllum does not have the tendency to shorten and 

lose septa, as do Toquimaphyllum and other members of 

this family. 

Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

Plate 11, figures 1, 2, 5-7; plate 15, figure 17 

Type material.-Holotype USNM 159420, Toquima 

Range, Nev.; paratype USNM 159422, Simpson Park 

Mountains, Nev. Late Silurian, coral zone E. 

Diagnosis.-Toquimaphyllum with major septa extending to axis of nonnal corallites, breaking up peripherally as septal crests. Mature corallites with widest dissepimentaria having correspondingly narrow tabularia. 

Partially aseptate corallites retain only short inner-tip 

segments of tnajor septa. 

Exterior.-Mature coralla compact globular heads with 

diameter commonly exceeding I foot. Individual corallites 

ranging from small to large at distal surface; calices 

moderately deep with no fossula and with raised rims 

formed by the thickened wall. A few corallites with a single 

peripheral calice offset bounded externally by a wall 

angulation. Corallite wall prominently grooved 

longitudinally. 

Transverse sections.-About 38 septa in large normal 

corallites; in those with suppressed septa, number reduced to 24 or fewer. Only axial tips of major septa 

retained in some reduced corallites. All septa discontinuous peripherally, appearing only as crests in the 

lonsdaleioid band. Minor septa less continuous than 

major septa and commonly exceeding half the length of 

major septa. All septa more wavy and irregular toward 

axis; may be slightly thickened in tabularium. Wall 

moderately thickened stereoplasmically, forming obtuse 

wall crests. No true carinae. Symmetry entirely radial. 

Large and very large lonsdaleioid dissepiments predominate. 

Longitudinal sections.-In widest corallites, eight or 

more lonsdaleioid dissepiment columns on each side. 

Outer dissepiments of large mature corallites nearly flat; 

innermost three smaller and steeply inclined. In wide 

corallites with narrow tabularium, tabulae from 1/s to~ 

the diameter. Tabulae delicate, crowded, complete or incomplete; proximal sag may be pronounced. No flat 

tabulae with peripheral sag. Tabularium sharply set off 

from dissepimentariun1. Son1e axial parts of septa with 

small lateral spines. Some longitudinal sections with 

numerous septal crests rising vertically from upper surfaces of large nearly flat dissepiments. 

Fine structure.-Trabeculae nearly normal to wall in 

stereoplasmic thickening; internal trabecular projections 

present but uncon1mon. 

Reproductive offsets.-A single offset in some calices. 

Small interstitial corallites common, in various stages of 

lonsdaleioid development and septal suppression; most 

interstitial corallites with septa continuous to wall 

Comparzson with related forms.-Closely related 

Toquimaphyllum occurs in the upper part of the middle 

unit of the Vaughn Gulch Limestone of the northern Inyo 

Mountains. Australophyllum (Toquimaphyllum) 

spongophylloides (Foerste) of the Yass-Bowning area, 

Australia (Hill, 1940, p. 408, pl. xiii, figs. 3-5 ), has wider 

tabulae but is otherwise very similar to johnsoni. 

Australophyllum (Toquimaphyllum) fritschi (Novak) of 

the Czechoslovakian Late Silurian as figured by Po~ta 

( 1902, pl. 1 02) does not reveal septal crests except for the 

wall crests and has a somewhat thicker wall and wider tabularium. The more distantly related endophyllids of the 

Silurian in the Klamath Mountains, Calif., have much 

wider, flat tabulae with peripheral sag and are viewed as a 

distinct genus. Australophyllum of the Early Devonian 

Rabbit Hill Limestone is not classified in this subgenus. 

Occurrence and age.-Late Silurian, coral zone E. 

Uppermost 200 feet of the Silurian, Coal Canyon, 

northern Simpson Park Mountains, Nev., localities 

Ml026, Mll06, Mll08, M1335; Ikes Canyon, Toquima 

Range, Nev., locality M1114. Upper part of middle unit of 

Vaughn Gulch Limestone, Mazourka Canyon, Inyo 

Mountains, Calif.; locality M1115; these differ slightly 

from typical johnsoni. A ustralophyllum possibly belonging in this species occurs in the Antelope Peak section 12 miles north of Wells, Elko County, Nev. 

Study material of this new form consists of 14 nearly 

complete and partial coralla, as follows: Locality Mll14 

(six), locality M1106 (three), locality MilOS (three), 

locality M1026 (one), locality M1335 (one). Five partial 

coralla were collected in the vicinity of locality M1115. 

Family ACERVULARIIDAE Lecompte, 1952 

Reference genus and species.-Acervularia ananas 

(Linnaeus); Silurian, Wenlock, England. 

This family includes phaceloid and cerioid forms which 

have a fairly discrete iune1 wall dividing thedissepimentarium from the tabularium; the inner wall is formed by 

stereoplasmic addition near ends of minor septa. Major 

septa may continue to axis. Tabulae either are complete 

and slightly arched or comprise tabellae with overall sag. 

The genera included in this family are Acervularia 

Schweigger, 1819, and Dzplophyllum Hall, 1852. In the 

past, several Devonian species now classified as 
56 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Hexagonaria were erroneously placed in Acervularia. 

Gotland Silurian species placed in Rhabdophyllum 

Wedekind, 1927, also belong here as synonyms of 

Acervularia and possibly of Diplophyllum (Oliver, 1963, 

p. G2). 

Genus DIPLOPHYLLUM Hall, 1852 

1956. Diplophyllum Hall. Hill, p. F277, fig. l88.6a, 6b. 

1963 Diplophyllum Hall. Oliver, p. Gl; pls. l-3. 

Type species.-Diplophyllum caespitosum Hall, by 

monotypy. Silurian, Lockport Dolomite, New York. 

Diagnosis.-"Compound rugose corals with a distinct 

inner wall of septal origin, separating the tabularium 

from a narrow peripheral dissepimentarium. The tabulae 

are mostly complete; dissepiments are flat to gently 

arched, forming a single series in each space bounded by 

the inner and outer walls and two adjacent septa." 

Remarks.-The diagnosis here given is that of Oliver 

(1963, p. G1), who has reviewed the systematics of this 

genus in the light of restudy of the type species and Hall's 

original material. 

Oiplophyllum? sp. m 

Plate 4, figures 10-14 

Slender cylindrical corallites of a probable colonial 

form provisionally assigned to Diplophyllum? occur in 

the topmost beds of the Vaughn Gulch Limestone at 

Mazourka Canyon, northern In yo Mountains. Some corallites of this weakly dissepimented species have more the 

character of Palaeophyllum than of Diplophyllum in 

lacking the false inner wall and peripheral column of dissepiments. 

A normal corallite in longitudinal thin section shows 

an outer column of rather flatdissepiments between a thin 

discontinuous false inner wall and the outer stereozone. 

Tabulae are straight or slightly arched and may bend 

sharply toward the periphery. In transverse thin section, 

the minor septa of a norn1al corallite may terminate 

against the thin false inner wall or may bend abruptly to 

meet an adjacent major septum near the false inner wall. 

As pointed out by Oliver (written commun., 1969), the 

false inner wall of sp. m appears to be of tabular origin and 

is not actually a true inner wall. 

As in some forms of D. caespitosum (Hall), the major 

septa of sp. m are continuous toward the axis of some 

corallites. However, the stereoplasmic swellings near tips 

of minor septa in caespitosum were not recognized in the 

Vaughn Gulch species. (See Oliver, 1963, pl. 2, fig. 1.) The 

Palaeophyllum-like corallites of this western form in 

transverse thin section resemble those of P. margaretae 

Flower (1961, pl. 48) but have much less arching of 

tabulae. 

Occurrence.-Northern Inyo Mountains, west side at 

mouth of Mazourka Canyon; locality M1090, within 20 

feet of top of Vaughn Gulch Limestone. These beds are 

here considered to be either Late Silurian or Early 

Devonian. 

Genera with no family designation 

Genus SALAIROPHYLLUM Besprozvannlkh, 1968 

Salairophyllum? sp. 

Plate 12, figures 6-8 

A solitary coral referred provisionally to the Russian 

genus is characterized by wide, more or less complete, 

close-s paced tabulae, a rela ti vel y narrow 

dissepimentarium and fairly wide septal stereozone. Septa 

of mature growth stages number about 56; some of the 

greatly thinned major septa reach the axis, longer minor 

septa are half the length of major septa. Septa are 

thickened stereoplasmically to a point beyond the stereozone, thinning markedly thence toward the axis. Some 

septa are minutely wavy with well-developed lateral 

spines which are not true carinae. 

Observed in longitudinal thin section, some of the wide 

close-set tabulae are nearly flat. Peripherally inclined 

trabeculae are especially well shown in the stereozone; 

some of these extend into the dissepimentarium as long 

spines like those of Tryplasmatidae. The small dissepiments are steeply inclined in two or three columns. 

The fully mature calice of the figured specimen shows 

four peripheral offsets. 

This coral is most closely related to undescribed 

Salairophyllum? from Kuiu Island, southeastern Alaska 

(Joe. M1186), where it occurs with Conchidium alaskense. 

Septa are more numerous in the Alaskan species. The 

RussianS. angus tum (Zheltonogova) has fewer septa and a 

wider stereozone. It occurs in strata reported by Shurygina 

(1968, p. 123) as Early Devonian; however, the SilurianDevonian boundary fauna listed in association has a 

distinctly Gotlandian Silurian aspect. 

Occurrence.-Probably from upper Silurian coral zone 

E, upper beds of the Roberts Mountains Formation. Coal 

Canyon, northern Simpson Park Mountains, Nev. Float 

material, locality Mil 17, collected by R. J. Roberts. 

Genus DENAYPHYLLUM, new genus 

Type species.-Denayphyllum denayensis, n. gen, n. sp. 

Here designated. Silurian, type section of the Roberts 

Mountains Formation, Roberts Creek Mountain, Nev., 

upper 600 feet. 

Diagnosis.-Slender phaceloid rugose corals with 

about 12 fairly thin major septa which are slightly withdrawn from the axis; a wall which is thin to only moderately thickened; a single column of large, partly horizontal 

and fairly uniform dissepiments; and rather widely 

spaced, complete tabulae which are straight or have an 

axial sag. 

Remarks.-Denayphyllum resembles Battersbyia 

Edwards and Haime, 1851, the type species of which-B. 

inaequalis Edwards and Haime-is reported from the 

Devonian of Teignmouth, Devonshije, England. The 

figures of Edwards and Haime (1853, pl. 47, figs. 2-2b, 

transverse sections only) represent·B. inaequalis to have a 
LOCALITY REGISTER 57 

thicker wall. Glinski (1957, p. 91-106) has reviewed in 

detail the classification and structure of Devonian corals of 

this kind from the Rhine River valley, Germany, pointing 

out that Fasciphyllum Schluter, 1885, is a subjective 

synonym of Battersbyia. Glinski's longitudinal sections of 

Battersbyia show a thick wall and a more irregular 

arrangement of large elongate and small steeply inclined 

dissepiments which double here and there to form two 

columns, though in other places dissepiments are absent, 

as in Dendrostella Glinski, 1957. Denayphyllum differs 

from Columnaria Goldfuss in having much larger and 

more uniform, nearly horizontal dissepiments in a single 

column, and narrower tabulae. 

Denayphyllum denayensls, n. sp. 

Plate 7, figures 15-18 

Type material.-Holotype USNM 159407. 

Diagnosis.-Denayphyllum with few or no minor septa 

and fairly straight corallites without connecting processes. Nearly horizontal dissepiments about one-third the 

diameter, or about same as width of tabulae. 

Transverse sections.-Average of 12 septa, but ranging 

from 10 to about 15, most slightly withdrawn from the 

axis, but some reaching the axis. Short minor septa uncommon. Wall normally thickened slightly as a narrow 

stereozone. Septa usually thickened moderately and progressively toward the periphery and somewhat wavy. Few 

dissepiments, only at the border of the tabularium. 

Longitudinal sections.-Characteristically, a single 

column of large dissepiments which are either almost 

horizontal or inclined axially; no specimens with 

doubling of dissepiments or places where these structures 

are lacking, as in Columnaria. Tabulae complete, widely 

spaced, most with a slight sag. In longitudinal section, 

corallite is divided into three columns, each one-third of 

the diameter, the tabulae being the middle third. 

Reproductive offsets.-None observed. 

Comparison with related forms.-No similar rugose 

corals are known from the American Silurian or 

Devonian. Only European species of the Middle Devonian 

assigned to Battersbyia are structurally comparable; the 

generic differences have been dealt with above. 

Occurrence.-Unit 3 in type section of the Roberts 

Mountains Formation, Middle Silurian, coral zone C. 

Roberts Creek Mountain, Nev. locality Mll02. At locality 

Ml102 this coral occurs in large tabular colonies. The 

study material consists of six pieces broken from one large 

colony collected in place. 

LOCALITY REGISTER 

North-central Great Basin 

Tuscarora Mountains, northern Eureka County, Nev.: 

Locality M287.-Near Elko·Eureka County line on east side 

of road between Dunphy and Tuscarora. Talus slope at base 

of hill. Limestone with abundant silicified fossils of Silurian 

age, including Coelospira. Collected by R. J. Roberts, 1954. 

Locality Mll20.-Tuscarora Mountains, at north end of Eureka County, Nev.; "Round Mountain," southwest end. Probably the "Lynn Window" vicinity of R. J. Roberts. Silurian 

limestone with rugose corals. Collected by R. J. Roberts, 

June 1958. 

Southern Ruby Mountains, Nev.: 

Locality M1124.-Sherman Mountain quadrangle, Nevada. North 

of Sherman Mountain, 3 miles southeast of Mitchell Ranch 

on northeast side of Sherman Creek; altitude 8,400 feet. Silicified corals collected by Ronald Will den and R. W. Kistler, 196 7. 

Northern Simpson Park Mountains, Nev.: 

Coal Canyon area; Horse Creek Valley quadrangle: 

Locality MI026.-East side of Coal Canyon near its mouth, 

SB4 sec. 17, T. 25 N., R. 49 E.; altitude 6,320 feet. Coarse 

limestone breccia in upper part of the Silurian section, 

about 100 feet stratigraphically below the contact with the 

Lower Devonian (Helderberg) Rabbit Hill Limestone. 

Locality Mll05.-Bottom of Coal Canyon, four-tenths of a 

mile south of its mouth; float material from upper part 

of the Silurian limestone on east side of canyon. 

Locality Mll06.-Near mouth of Coal Canyon on east side; 

altitude 6,300 feet. Silurian coral-rich limestone breccia. 

Locality Ml107.-About one-quarter of a mile south of mouth 

of Coal Canyon on east side; 200 feet above canyon bottom. 

Silurian coral-rich limestone breccia below Rabbit Hill 

Limestone. 

Locality MllOB.-Near mouth of Coal Canyon, on east side; 

float material below Silurian limestone breccia. 

Locality MJllO.-Vicinity of locality Ml026. Collections made 

by A. J. Boucot, 1964. 

Locality Mlll7.-NElf4 sec. 20, T. 25 N., R. 49 E.; probably 

about six-tenths of a mile south of Coal Canyon mouth 

on east side of canyon. Collections made by R. J. Roberts, 

1954. 

Central Great Basin 

Roberts Creek Mountain, Nev.; Roberts Creek Mountain quadrangle: 

Locality M1089.-Northwest side of Roberts Creek Mountain; 

measured section on top spur between south and middle 

forks of Pete Hanson Creek, 2,500 feet N. 79° W. of summit 

9219; altitude 8,500 feet. Base of unit 3 of type section of 

Roberts Mountains Formation. 

Locality MllOJ.-Same horizon and locality as locality Ml089. 

Locality Mll02.-Same measured section as locality Ml089, 

about 100 feet stratigraphically above locality Ml089. Lower 

beds of unit 3 with rugose coral fauna. 

Locality MllOO. -Same measured section as locality M1089. 

1,800 feet N. 79° W. of summit 9219; altitude 8,680 feet. 

Upper beds of unit 3 of Roberts Mountains Formation. 

Southern Sulphur Spring Range, Nev.; Garden Valley quadrangle: 

Locality Mll21.-Dolomite hills 2 miles south-southwest of 

Romano Ranch, at east edge of range; eight-tenths of a mile 

S. 60° W .. of bench mark 5825, on top of easternmost ridge; 

altitude 6,440 feet. Lone Mountain Dolomite, lower part 

with silicified fossils. 

Lone Mountain, Eureka County, Nev.; Whistler Mountain quadrangle: 

Locality MI122.-South side of Lone Mountain. Lone Mountain Dolomite with fragmentary rugose corals, four-tenths 

of a mile due south of summit 7360; altitude 6,840 feet. 

Southern Mahogany Hills, Nev.; Bellevue Peak quadrangle: 

Locality M1112.-About 1~ miles due north of top of Wood 

Cone Peak, half a mile north-northwest of bench mark 7201 

in lower foothills; altitude 7,350 feet. Upper part of Silurian 

Lone Mountain Dolomite with rugose coral fauna in darkgray dolomite facies. 
58 SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 

Southern Fish Creek Range, Nev.; Bellevue Peak quadrangle: 

Locality M1087.-West side of range at south boundary of quadrangle, about 2,000 feet due south of summit 7232; altitude 

7,000 feet. Lone Mountain Dolomite, upper part with silicified rugose coral fauna. 

Locality Ml113.-At south boundary of quadrangle, four-tenths 

of a mile south-southeast of hill 7232; altitude 7,080 feet. 

Lone Mountain Dolomite, upper part with silicified coral 

and brachiopod fauna. 

West-central Great Basin 

Toquima Range, Ikes Canyon, Nev.; Dianas Punch Bowl quadrangle: 

Locality M1088.-About 1 mile up Ikes Canyon from mouth; 

north side of canyon, 150 feet above bottom; altitude 7,840 

feet. Silurian Masket Shale of Kay and Crawford (1964). 

Locality M1103.-Same locality and section as locality Ml088, 

about 250 feet above canyon bottom; altitude 7,900 feet. 

Silurian Masket Shale of Kay and Crawford (1964). 

Locality M1104.-Collections made by Kay and Crawford (1964) 

from their McMonnigal Limestone Ikes Canyon area. Probably 

from beds north of Ikes Cabin, north side Ikes Canyon, l\4 miles 

northwest of mouth of this canyon. 

Locality Mll14.-Ikes Canyon area, one-eighth of a mile northwest of summit 8474 (Copper Mountain); altitude 8,300 feet. 

Probably in McMonnigal Limestone of Kay and Crawford 

(1964). Coral fauna of Silurian coral zone E. 

South-central Great Basin 

Monitor Range, Dobbin Summit area, Nye County, Nev.: 

Locality M1123.-About I mile southeast of East Dobbin Summit Spring, on east side of canyon. Silurian beds below Rabbit Hill Limestone. 

Hot Creek Range, Tybo area, Nye County, Nev.: 

Locality Ml125.-Ridge north of town of Tybo; probably about 

2,000 feet north of Cunningham prospect. Silurian dolomite 

above Eureka Quartzite. 

Southwestern Great Basin 

Northern Inyo Mountains, Calif.; Independence quadrangle: 

Locality M1086.-Mouth of Mazourka Canyon; foothills on 

north side Vaughn Gulch, in NE\4 sec. 8, T. 13 S., R. 36 

E. Northeast-southwest measured section. Lower unit of Silurian Vaughn Gulch Limestone, 550 feet stratigraphically above 

top of quartzite of Ordovician Johnson Spring Formation. 

(See fig. 3.) 

Locality M1090.-Same measured section as locality Ml086; 

beds of Late Silurian or Early Devonian age within 20 feet 

of top of Vaughn Gulch Limestone. 

Locality M1091.-Same measured section as locality Ml086; 

near east line of sec. 8, T. 13 S., R. 36 E.; altitude 4,840 

feet. About 150 feet stratigraphically above chert unit at base 

of Vaughn Gulch Limestone. 

Locality MI092.-Same measured section as locality Ml086; 

west of east line of section 8; altitude 4,880 feet. Middle 

unit of Vaughn Gulch Limestone, about 1,000 feet stratigraphically above Barrel Spring Formation. 

Locality MI093.-Same measured section as locality Ml086; 

upper unit of Vaughn Gulch Limestone between localities 

Ml090 and Ml092, about 1,350 feet stratigraphically above 

Barrel Spring Formation, 450 feet stratigraphically below 

top of Vaughn Gulch Limestone. 

Locality Mll15.-Same measured section as locality Ml086; 

about 110 feet stratigraphically below horizon of locality 

Ml093. 

Locality M1116.-Same measured section as locality Ml086; 

coral bed 30 feet stratigraphically below locality Ml093. 

Locality M1118.-Same measured section as locality Ml086; 

fossil collections made between localities Ml092 and Ml093. 

Upper part of middle unit of Vaughn Gulch Limestone. 

Locality M1119.-Same measured section as locality Ml086; 

middle unit of Vaughn Gulch Limestone, below locality 

Ml092. 

Southern Inyo l\lountains: 

Locality Mll26.-New York Butte quadrangle, California; 

13,000 feet due north ol Cn1o Conlo mine, south side of 

Bonham Canyon; altitude 7.~00 lt'l't. Silurian dolomite with 

fossils. 

Northern Panamint Range: 

Locality M1094.-Ubehebe Peak quadrangle, California; 1~ miles 

north of top of llbehebe Peak, eight-tenths ot a mile west· 

of bench mark 3765. About 200 feet stratigrpcally above base 

of Hidden Valley Dolomite in Silurian coral zone B. 

Locality M1095.-Quartz Spring area of ]. F. McAllister; 22,600 

feet S. 15° W. of Rest Spring, south side At'ldy Hills, in 

lower part of Hidden Valley Dolomite. Silurian coral fauna. 

Locality M1096.-Quartz Spring area of ]. F. McAllister; 9,600 

feet N. 86° E. of Rest Spring at Whitetop Mountain. Silurian corals in lower part of Hidden Valley Dolomite. 

Locality M1109.-Quartz Spring area of ]. F. McAllister; 22,500 

feet S. Hl0 \V. from Rest Spring, south side of Andy Hills. 

Lower part of Hidden Valley Dolomite with Silurian corals. 

Locality Mllll.-llbbehebe Peak quadrangle, California; about I \1 miles north of llbehebe Peak, at east foot of range 

and two-tenths of a mile east of locality Ml094. Silurian 

coral float from lower beds of Hidden Valley Dolomite. 

Funeral Mountains: 

Locality Ml097.-Ryan quadrangle, California; 1.95 miles N. 

51° W. of Pyramid Peak. Lower part of Hidden Valley Dolomite with Silurian corals. 

Locality M1098.-Ryan quadrangle, California; 3 miles S. 22° 

E. of Schwaub Peak. Silurian corals, lowest fossil collections 

in Hidden Valley Dolomite. 

Localitv M1127.-Ryan quadrangle, California; 1.9 miles N. 

59° E. from Pyramid Peak. Silicified Silurian fossils from 

cherty dolomite 100-150 feet above base of Hidden Valley 

Dolomite. 

Bare Mountain, Nevada: 

Locality M1085.-Bare Mountain quadrangle, Nevada; northeast side of Bare Mountain; south side of Tarantula Canyon 

near its head; near north edge sec. 36, T. 12 S., R. 47 E.; 

altitude 5,000 feet. Corals in lower part of Silurian section. 

Locality M1099.-Bare Mountain quadrangle, Nevada; Chuckwalla Canyon near m6uth, on north side; altitude about 

4,300 feet. Dark-gray Silurian limestone with corals, about 

150 feet stratigraphically below contact with light-gray dolomite. 

Eastern Great Basin 

Confusion Range, Utah: 

Locality Mll29.-Southern part of Confusion Range; NW\4 sec. 

23, T. 18 S., R. 16 W. /Isolated dolomite exposure containing 

Palaeocyclus and other Silurian Fossils. Collected by R. K. 

Hose. 

Locality Mll37.-Kings Canyon on U.S. Highway 6 and 50, 

near top of Confusion Range; Conger Mountain quadrangle. 

South side of road about I, 700 feet east of bench mark 5949; 

altitude 6,200 feet. Upper dark-gray Laketown Dolomite with 

Rhabdocyclus. Collected by A. J. Boucot. 
SILURIAN RUGOSE CORALS OF THE CENTRAL AND SOUTHWEST GREAT BASIN 59 

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A 

adbitum, Endophyllum --------------

Acanthocyclus -------------------

fletcheri-------------------

porpitoides-----------------

Acervularia---------------------

ananas---------------------------

baltica ---------------------------

mixta-----------------------------

Acervulariidae ----------------------

Acknowledgments-----------------------

aequabile, Tryplasma------------------

Age conclusions, based on Silurian Rugosa, 

Great Basin Silurian section>------

Page 

54 

38 

38 

38 

55, 56 

55 

42 

51 

30, 55 

4 

36 

26 

Alaska, zone A correlation------------ 22 

southeastern, zone E correlation------- 24 

alaskense, Conchidium -------------16, 24, 56 

Alveolites--------------------16, 20, 21 

ananas, Acervularia ------------------- 55 

angelini, Aulocophyllum------------- 45 

angustum, Salairophyllum--------------- 56 

annulata, Verticillopora--------------29; pl. 16 

Antelope Peak, zone E fauna----------- 22 

Arachnophyllidae---------------------- 30, 42 

Arachnophyllum -------------20, 26, 30, 42, 51 

kayi--------14, 20, 23, 30, 43, 51; pl. 5 

pentagonum ----------------------- 42, 43 

speciosa---------------------- 43 

typus------------------- 22, 23, 42, 43 

articulatum, Entelophyllum --------------- 25, 48 

articulatus, Madreporites---------------- 48 

astreiformis, Stauria--------------------- 32 

Atrypa--------------------14, 15, 17, 20, 21 

sp -------------------------- 16 

Atrypina ------------------------------ 20, 21 

Aulacophyllum angelini------------------- 45 

mitratum------------------------ 45 

Aulopora --------------------------- 21, 35 

Australia, eastern, zone C correlation------ 24 

Australophyllum ----------------22, 30, 54 

(Toquimaphyllum)------------22, 54; pl. 11 

fritschi ----------------------- 25, 55 

giganteum ---------------- 25 

johnsoni---14, 16, 21, 22, 25, 26, 30; 54, 55; 

pls. 11, 12, 15 

originalis ------------------ 22, 25 

spongophylloides ---------------- 25, 55 

sp------------------22; pls. 12, 14 

B 

baltica, Acervularia ------------------- 42 

Bare Mountain, localities-------------- 58 

Barrandella sp------------------- 16 

Battersbyia-------------------- 56, 57 

inaequalis------------------ 56 

berthiaumi, Stylopleura ... 14, 15, 21, 30, 34, 35, 36; pl. 3 

Bethanyphyllidae ·----------------------------- 43 

Bighomia --------------------------------- 32 

Billingsastraea ---------------- 42 

Bootstrap mine, zone E fauna---------- 21 

bowerbanki, Endophyllum ------------- 54 

Brachiopods, Camarotoechia-like----------- 20 

Conchidium-like ---------------- 10 

pentameroid------------- 4 

INDEX 

[Italic page numbers indicate major references] 

Page 

Brachyelasma------------------ 29, 31 

prima---------------------- 31 

sp. B-----------14, 29, 31; pls. 1, 16 

sp -------------------------20; pl. 1 

(Breviphrentis), Siphonophrentis---------------- 31 

Briantia--------------------- 41 

brownsportensis, Tryplasma---------- 24 

burksae, Cyathophylloides ------------- 33 

c 

caespitosum, Diplophyllum---------- 56 

Calceola --------------------- 46 

gotlandica------------------------ 46 

sandalina--------------------- 46 

Camarotoechia------------------- 14, 20 

pahranagatensis ------------------ 17 

Canada, Northwest, zone A correlation----- 22 

Northwest, zone B correlation-------- 23 

Carlin mine area, zone E fauna---------- 21 

Carlin mining district, zone A fauna------ 20 

Catenipora-------------------------- 32 

catilla, Cyathactis----------------- 44 

Cerro Gordo mining district----------- 2, 8 

Chlamydophyllum ----------------- 41 

Chonophyllidae------------------ ,30, 52 

Chonophyllum-----------------22, 30, 41, 52 

flabellata --------------------- 24 

patellatum ------------------------------ 52 

perfoliatum------------------- 52, 53 

planum----------------------------------------------- 52 

pseudohelianthoides ------------- 52, 53 

simpsoni---------------14, 16, 24, 30, 53; pl. 8 

sp ------------------------22; pl. 8 

Cladopora-------------------14, 20, 21, 35 

Classification of Silurian Rugosa ----------- 29 

Coal Canyon reference section---------- 10 

Codonophyllum ----------------------- 40 

Coelospira------------------------- 20, 21 

Columnaria ---------------------- 57 

inequalis------------------------ 24, 49 

gothlandica ----------------------- 32 

Comparison with Pacific Border Silurian rugose corals ------------------------ 2 

Conchidium--------------------4, 26, 46 

alaskense--------------------16, 24, 56 

munsteri------------------------------------- 21 

Confusion Range, fossil localities---------- 58 

zone A fauna---------------------- 20 

zoneD fauna------------------------- 21 

Conocardium sp---------------------- 16 

conulus, Zaphrentis ------------------- 31 

Copper Mountain, fossil collections---------- 10 

Coral, depositional environments------------ 28 

Coral-bearing rocks, Silurian, distribution---- 5 

Coral zone A----------------------------------------- 14, 20 

age---------------------------- 26 

correlation-------------------------- 22 

Coral zone B------------------------- 14 

age---------------------------- 26 

correlation--------------------------- 23 

northern Panamint Range reference section 

Roberts Creek Mountain reference sectionCoral zone C-------------------------

age-------------------------------

12 

21 

15 

26 

correlation-------------------------- 24 

Roberts Creek Mountain reference section 10, 21 

Page 

Coral zone D ----------------- 15 

age------------------------- 26 

correlation---------------------- 24 

lkes Canyon reference section---------------- 21 

Mazourka Canyon reference section-- 21 

Roberts Creek Mountain·-------------------- 10 

Verticillopora--------------------------------------- 9 

Coral zone E---------------------- 15 

age--------------------------------- 26 

Coal Canyon-------------------- 11 

correlation---------------------------- 24 

Ikes Canyon reference section------------- 21 

Coralline rocks, Great Basin, compared with 

those of other regions---------------

Gl-eat Basin Silurian, depositional features 

in relation to the reef problem-----

Corals, rugose, geologic correlation in 

basin ,----------------------------------

21 

27 

28 

17 

Cordilleran belt, Silurian faunas------- 4 

corniculum, Streptelasma ------------- 30 

Correlation, coral zone A------------- 22 

coral zone B --------------------- 23 

coral zone C ------------------ 24 

coral zone D--------------------- 24 

coral zone E ---------------------- 24 

geologic, rugose corals in the basin------- 17 

Laketown and Lone Mountain Dolomite- 25 

Crassilasma sp--------------22; pls. 4, 6 

crateroides, Mucophyllum-------------- 41, 42 

Craterophyllum ------------------ 41 

crawfordi, Neomphyma-----14, 20, 30, 51; pl. 13 

Cyathactis ----------------23, 24, 30, 44 

catilla --------------------- 44 

pegramense---------------------------------- 44 

socialis---------------------- 44 

tenuiseptatus----------------------- 44 

typus---------------------- 44 

sp -------------------------16, 30; pl. 8 

Cyathaxonia dalmani ------------------ 32 

Cyathopaedium ----------------------- 34 

Cyathophylloides ------------------- 29, 32 

burksae ------------------------------ 33 

fergusoni------------14, 20, 29, 33, 51; pl. 5 

gothlandicus ------------------------ 33 

kassariensis ------------------------ ,32, 33 

cyathophylloides, Phaulactis ------------ 23, 43 

Spongophyllum ---------------------- 54 

Cyathophyllum perfoliatum---------- 52 

plicatum------------------------- 52 

cylindricum, Cystiphyllum------------------------ 45 

Cymostrophia sp ------------------ 16 

Cyphophyllum------------------------ 47 

(Cystihalysites) magnitubus, Halysites --- 15 

Cystiphyllida&----------------------- 30, 45 

Cystiphyllum cylindricum--------------- 45 

henryhousense----------------- 45 

siluriense ---------------------------------- 45 

tubiforme---------------------- 45 

Czechoslovakia, Toquimaphyllum ---------- 26 

zone E correlation------------------ 25 

D 

Dalmanella------------------------------------------------- 14 

dalmani, Cyathaxonia ------------------- 32 

Dalmanophyllum-----------------23, 26; pl. 1 

63 
64 

Page 

Dalmanophyllum ---------9, 20, 26, 29, 32 

dalmani---------------23, 26; pl. 1 

sp. A------14, 20, 23, 26, 29, 32, 34; pl. 1 

Darwinia-------------------- 42 

Dasycladaceae------------------29; pl. 16 

Delmanophyllum----------------- 31 

denayensis, Denayphyllum-14, 15, 30, 56, 57; pl. 7 

Denayphyllum-------------- 30, 56 

denayensis--------14, 15, 30, 56, 57; pl. 7 

Dendrostella------------------ 57 

Depositional facies, coral-bearing rocks---- 5 

Depositional features, Great Basin Silurian 

coralline rocks in relation to the reef 

problem--------------------- 28 

Desmophyllum------------------- 44 

dewari, Petrozium------------------24, 26, 47 

Dicaelosia---------------------14, 15, 20 

Dinophyllum ------------------- 32 

Diplophyllum-----------------21, 30, 55,56 

caespitosum-------------------- 56 

sp. m--------------------------30, 56; pl. 4 

Disphyllidae------------------------- 42 

Disphyllum---------------------------- 48 

Distribution, Silurian coral-bearing rocks---· 5 

Dolomite belt, eastern--------------------· 5, 6, 7 

duncanae, Tryplasma--~14, 15, 24, 26, 30, 37; pl. 1 

Dybowskia------------------------------ 31 

prima------------------------------------ 31 

E 

Eastern dolomite belt------------------ 5, 6 

Eatonia ---------------------------------- 20 

Encrinurus--------------------------------- 20 

Endophyllidae-------------------------------30, 54 

Endophyllum ----------------------------------- 54 

abditum-------------------------------- 54 

bowerbanki----------------------------- 54 

(spongophylloides) ---------------------- 54 

engelmanni, Entelophyllum--17, 25, 30, 49; pls. 10, 

15 

enorme, Rhizophyllum --------------14, 16, 24, 46 

Entelophylloides-----------4, 24, 26, 30, 47, 49, 50 

(Entelophylloides) inequalis------------------- 50 

(Prohexagonaria) ----------------------- 24, 47 

occidentalis---14, 15, 24, 26, 30, 50; pl. 9 

sp----------------------50; pl. 9 

(Entelophylloides) inequalis, Entelophylloides 50 

inequalum, Entelophyllum------------ 49 

Entelophyllum-16, 22, 24, 25, 26, 29, 30, 37, 47, 48, 

50, 51, 52; pl. 15 

articulatum------------------------ 25, 48 

engelmanni ----------17, 25, 30, 49; pis. 10, 15 

eurekaensis-------------17, 25, 30, 49; pl. 10 

fasciculatum---------------------------- 25 

Lone Mountain Dolomite------------- 13 

pseudodianthus --------------------- 48 

(Entelophylloides) inequalum----------- 49 

Eospirifer (Striispirifer)------------------- 21 

eurekaensis, Entelophyllum---17, 25, 30, 49; pl. 10 

Evenkiella-------------------------- 24 

F 

Facies, depositional and faunal, coral-bearing 

rocks ------------------------ 5, 13 

Entelophyllum--------------------------- 7 

Fardenia --------------------------- 20, 21 

fascicularia, Try plasma------------------- 34 

fasciculatum, Entelophyllum --------------- 25 

Fasciphyllum ---------------------------- 57 

Faunal facies, coral-bearing rocks-------- 5, 13 

Favistella----------------------- 32 

Favistina ------------------------- 32 

Favosites------------------------------- 16 

fergusoni, Cyathophylloides-14, 20, 29, 33, 51; pl. 5 

Fish Creek Range, southern, localities------ 57 

flabellata, Chonophyllum--------------- 24 

Omphyma-------------------------- 52, 53 

fletcheri, Acanthocyclus----------------- 38 

Palaeocyclus ----------------------- 38 

Rhabdocyclu.'l---------------- 38 

INDEX 

Fletcheria---------------------------

Fletcherina --------------------------

{ritschi, Australophyllum (Toquimaphyllum)-

Funeral Mountains, localities-------------

zone B fauna-----------------------

G 

giganteum, Australophyllum (ToquimaphylPage 

34 

34 

25, 55 

58 

20 

lum ) ------------------------------- 25 

globulatus, Porpites ----------------------- 39 

Goniophyllidae --------------------------- 30, 46 

Goniophyllum ------------------------ 46 

pyramidalis------------------------- 46 

gothlandica, Columnaria------------------ 32 

gothlandicus, Cyathophylloides ------------ 33 

Gotland, Sweden. See Sweden, Gotland. 

gotlandica, Calceola ------------------- 46 

gotlandicum, Micro plasma-------------- 45 

Rhizophyllum ----------------------- 46 

Graywacke belt, western (Pacific Border)---- 5 

Great Basin Silurian section, age conclusions 

based on Silurian Rugosa-------- 26 

guelphensis, Pycnostylus--------------- 34, 35 

H 

Halliidae --------------------------- 43 

Halysites---------------------14, 15, 17, 20, 21 

(Cystihalysites) magnitubus-------------- 15 

hedstroini, Tryplasma -------------------- 20, 24 

Hedstro'mophyllum ---------------------------- 45 

Heliolites---------------------9, 14, 15, 20, 21, 34 

henryhousense, Cystiphyllum--------------- 45 

hercynicus, Monograptus------------------ 12 

hesperalis, Protathyris----_;_________________ 17 

Hesperorthis--------------------------- 20, 32 

Hexagonaria ---------------------------- 54, 56 

Hindella -------------------------------- 17 

Holmophyllum------------------------ 25, 45 

Holophragma-------------------------- 44 

Homoeospira ----------------------------- 15 

Hot Creek Range, locality---------------- 58 

Howellella pauciplicata-------------- 16, 17, 21, 25 

smithi----------------------------- 17 

sp -------------------------------- 16 

Huromella------------------------------- 20 

Huronia---------------------------- 20 

Hyattidina--------------------------- 17 

Hyppurites mitratus ----------------------- 45 

Ikes Canyon reference section------------

zone A fauna------------------------

zone D fauna------------------------

zone E fauna------------------------

inaequalis, Battersbyia ---------------

inequalis, Columnaria-------------------

Entelophylloides (Entelophylloides) ----

inequalum, Entelophyllum (Entelophylloides) 

Intermediate limestone belt-------------

intermedium, Zelophyllum-------------

Investigation, purpose, scope, and history---

lnyo Mountains, localities---------

J,K 

9 

20 

21 

21 

56 

24, 49 

50 

49 

5, 7 

40 

1 

58 

johnsoni, Australophyllum (Toquimaphyllum) 14, 16 

21. 22, 25, 26, 30, 54, 55; pis. 11, 12, 15 

Toquimaphyllum----------------- 25 

kasandiensis, Ryderophyllum----------- 44 

kassariensis, Cyathophylloides --------- 32, 33 

kayi, Arachnophyllum--14, 20, 23, 30, 43, 51; pl. 5 

Kentucky, zoneD correlation--------- 24 

Ketophyllum--------------------52, 53, 54 

kirbyi, Palaeocyclus---------------- 22, 39 

Klamath Mountains, zone B correlation--- 23 

zone E correlation---------------- 24 

Kodonophyllidae --------------- 30, 40 

Page 

Kodonophyllinae------------------ 30, 40 

Kodonophyllum ---------------24, 25, 30, 40, 41 

milne-edwardsi ------------------- 40 

mulleri-------------14, 16, 24, 30, 41; pl. 4 

richteri ---------------------- 24, 41 

truncatum---------------------- 41; pl. 4 

sp. a--------------------------- pl. 4 

Kozlowskiellina ------------------------- 15 

sp ------------------------- 16 

Kyphophyllidae------------------------ 30, 46 

Kyphophyllum-16, 21, 22, 24, 25, 30, 47, 54; pl. 14 

lindstro"mi----------------------- 46, 4 7 

nevadensis----------14, 22, 30, 47; pls. 13, 14 

L 

Laketown Dolomite------------------ 16, 25 

Leonaspis sp ------------------------------- 16 

Leperditia sp---------------------- 16 

Leptaena--------------------------- 21 

liliiforme, Mycophyllum------------------ 41 

Limestone belt, intermediate----------------· 5, 7 

lindstri/mi, Kyphophyllum ---------------- 46, 4 7 

Locality register----------------------- 57 

Lone Mountain, locality----------------- 57 

Lone Mountain Dolomite------------------ 10 

correlation with Laketown Dolomite----- 25 

fossils-------------------------- 13 

rugose corals-------------------------- 16 

stratigraphy------------------------ 16 

Lone Mountain reference section----------- 12 

lonsdalei, Tryplasma----------- 24, 25, 26, 37 

Lonsdaleia------------------- 54 

Lykophyllidae------------------------ 30, 43 

Gotland, Sweden---------------------- 26 

M 

mcallisteri, Palaeocyclus porpita-----14, 30, 39; pl. 1 

Petrozium ------------ 14, 24, 30, 48; pl. 9 

Madrepora porpita ------------------- 39 

truncata --------------------- 40 

Madreporites articulatus---------------- 48 

magnitubus, Halysites (Cystihalysites)----- 15 

Mahogany Hills, southern, locality -------- 57 

Maikottia----------------------- 34 

turkestanica ----------------------35; pl. 2 

sp ---------------------- pl. 2 

margaretae, Palaeophyllum --------------- 34 

Mazourka Canyon reference section----------- 8 

zone A fauna----------------------- 20 

zone D fauna----------------------- 21 

Merista------------------------ 20 

Meristella sp------------------------ 16 

Mesactis--------------------------- 45 

michiganensis, Palaeocyclus-------------- 39 

Microplasma ----------------- 21, 30, 45, 46 

gotlandicum ------------------------- 45 

sp. R-------------------30, 46; pl. 7 

milne-edwardsi, Kodonophyllum----------- 40 

Streptelasma--------------------- 40 

mitratum, Aulacophyllum --------------------- 45 

mitratus, Hyppurites --------------------- 45 

Pycnactis---------------------- 45 

mixta, Acervularia-------------------------- 51 

Monitor Range, locality--------------- 58 

Monograptus--------------- 20 

hercynicus ---------------------- 12 

nilssoni ----------------------- 25 

praehercynicus --------------------- 12 

riccartonensis -------------------- 20 

Mucophyllum----------------------25, 30, 41, 53 

crateroides---------------------- 41, 42 

oliveri-------------14, 16, 24, 30, 42; pl. 5 

mulleri, Kodonophyllum ----14, 16, 24, 30, 41; pl. 4 

multicaule, Palaeophyllum------------- 34 

milnsteri, Conchidium-------------- 21 

Mycophyllidae --------------- 26 

Mycophyllinae----------------- 30, 41 

Mycophyllum liliiforme-------------- 41 
N 

Page 

Naos ----------------------- 41 

Neocystiphyllum --------------------- 44 

Neomphyma--------------25, 30, 47, 51, 52 

crawfordi ------------14, 20, 30, 51; pl. 13 

originata---------------------- 51 

nevadensis, Kyphophyllum -- 22, 30, 47; pls. 13, 14 

Stylopleura-------14, 15, 30, 35; pls. 2, 15 

New York State, zone A correlation------- 22 

zone C correlation--------------- 24 

newfarmeri, Tryplasma-14, 15, 24, 26, 30, 37; pl. 2 

nilssoni, Monograptus--------------- 25 

nordica, Tryplasma----------------- 37 

0 

occidentalis, Entelophylloides (Prohexagonaria) 14, 

15, 24, 26, 30, 50; pl. 9 

oliveri, Mucophyllum------14, 16, 24, 30, 42; pl. 5 

Omphyma flabellata ---------------- 52, 53 

originalis, Australophyllum (Toquimaphyllum)22, 25 

originata, Neomphyma -------------------- 51 

Orthoceras-like cephalopod------------- 16 

Orthophyllum ---------------------- 20, 31 

Orthostrophia sp ---------------------- 16 

p 

Pachyphyllum------------------- 42 

Pacific Border (Western) graywacke belt-------- 5, 27 

pahranagatensis, Camarotoechia·------ 17 

Palaeocyclus--17, 20, 22, 23, 25, 26, 30, 31, 36, 39; 

pl. 15 

fletcheri -------------------- 38 

kirbyi------------------------ 22, 39 

michiganensis---------------- 39 

porpita---------------20, 26, 39; pls. I, 15 

mcallisteri----------- 14, 23, 30, 39; pl. I 

rotuloides----------------------- 39 

Palaeofavosites-------------------- 32 

Palaeophyllum----------21, 22, 30, 33, 40, 56 

margaretae-------------------- 34 

multicaule--------------------- 34 

rugosum----------------- 33 

thomi-------------------- 34 

sp. b---------------------30, 34; pl. 3 

sp. c-------------------30, 34; pl. 2 

Panamint Range, northern, localities----- 58 

northern, reference section----------- 12 

Papiliophyllum-------------------- 43 

patellatum, Chonophyllum------------ 52 

Schlotheimophyllum--------- 24, 42 

pauciplicata, Howellella-----------------------16, 21, 25 

pegramense, Cyathactis- 44 

pentagonum, Arachnophyllum------ 42, 43 

Pentamerida, Conchidium-like----- 20, 21, 26 

perfoliatum, Chonophyllum- 52, 53 

Cyathophyllum 52 

Petrozium-------21, 23, 24, 26, 30, 47, 51 

dewari-------------24, 26,47 

mcalliste · 14, 24, 30, 48; pl. 9 

Phaulactis------------ 23, 24, 44, 45 

cyathophylloides- 23, 43 

Phillipsastraeidae 42 

Pholidophyllum------------ 36 

Pilophyllum--------------- 47, 54 

planum, Chonophyllum -------------- 52 

Plectatrypa 22, 24 

~ w 

plicatum, Cyathophyllum---------- 52 

Polyorophe-------------- 37 

porpita mcallisteri, Palaeocyclus-14, 23, 30, 39; pl. I 

Madrepora----------------- 39 

Palaeocyclus --------20, 26; pls. 1, 15 

Porpites-------------- 39 

Porpites---------------- 39 

globulatus ----- 39 

porpita---------------- 39 

porpitoides, Acanthocyclus-------- 38 

INDEX 

Page 

praehercynicus, Monograptus--------- 12 

prava, Tryplasma-------------- 24 

Pytchopleurella-------------------- 21 

prima, Brachyelasma--------------- 31 

Dybowskia------------------ 31 

Prohexagonaria----------------- 30,50 

(Prohexagonciria), Entelophylloides-------- 24, 47 

occidentalis, Entelophylloides -14, 15, 24, 26, 30, 

50; pl. 9 

sp., Entelophylloides -----------50; pl. 9 

Protathyris hesperalis------------- 17 

Pseudamplexus------------------ 41 

pseudodianthus, Entelophyllum---------- 48 

pseudohelianthoides, Chonophyllum------- 52 

Ptychophyllidae---------------- 42 

Ptycophyllum sp------------------- 44 

Ptychopleurella------------------ 20 

Purpose of investigation------------ 1 

Pycnactis----------20, 21, 23, 26, 30, 44, 45 

mitratus------------------ 45 

sp. k--------------14, 30, 45; pl. 6 

Pycnostylidae------------------- 30, 34 

Pycnostylus-------------------- 34 

guelphensis -------------------- 34, 35 

sp ----------------------- pl. 15 

pyramidalis, Goniophyllum-------------- 46 

Q,R 

Quadrithyris zone, coral zone E ----------

Ra{inesquina sp---------------------

rectiseptatum, Spongophyllum -----------

Reference sections, Coal Canyon---------

Great Basin Silurian --------------------------

Ikes Canyon-------------------

zone A fauna-----------------

zone D fauna-----------------

zone E fauna------------------

Lone Mountain----------------

Mazourka Canyon----------------

zone A fauna---------------

zone D fauna-------------

nortlulm Panamint Range----------

Roberts Creek Mountain------------

zone A fauna---------------

zone B fauna----------------

12 

16 

24, 26 

10 

8 

9 

20 

21 

21 

12 

8 

20 

21 

12 

10 

20 

21 

zone C fauna-------------- 21 

zone E fauna---------------- 21 

Rhabdocyclus------------- 30, 36, 37, 38 

fletcheri------------------- 38 

sp. B ------------------30, 38; pl. 1 

sp. d------------.---14, 30, 38; pl. 1 

sp. K----------------30, 38; pl. 15 

Rhabdophyllum--------------- 56 

Rhegmaphyllum------------------- 29, 31 

turbinatum --------------------- 31 

sp. h---------------14, 29, 31; pl. 1 

Rhegmatophyllum--------------- 31 

Rhipidium----------------- 21 

Rhizophyllum-----------24, 25, 26, 27, 30, 46 

,enorme------------------14, 16, 24, 46 

gotlandicum ---------------- 46 

sp. A----------------------- 46 

sp. D------------14, 22, 30, 46; pl. 7 

Rhynchospirina sp---------------- 16 

Rhytidophyllum------------------------------------- 46 

riccartonensis, Monograptus----------- 20 

richteri, Kodonophyllum--------------- 24, 41 

Roberts Creek Mountain, localities------- 57 

Roberts Creek Mountain reference section, 

zone A fauna-------------- 20 

zone B fauna--------------- 21 

zone C fauna--------------- 21 

zone E fauna---------------- 21 

Romingerella------------- 21 

rotuloides, Palaeocyclus----------- 39 

Ruby Mountains, southern, locality----- 57 

zone A fauna------------- 20 

Rugosa, Silurian, age determinations---- 26 

65 

Rugosa-Continued Page 

Silurian, basis of characterization ---- 4 

characteristic, by zones ---------- 14 

classification------------ 29 

correlation with distant Silurian rocks 22 

correlation within Great Basin---- 17 

rugosum, Palaeophyllum ---------- 33 

Ryderophyllum----20, 21, 23, 24, 26, 30, 44, 45 

kasandiensis -------------- 44 

ubehebensis------------14, 30, 44, 45; pl. 6 

sp ---------------------16, 22; pl. 6 

s 

Salairophyllum-----------'--- 16, 24, 30, 56 

angustum--------------------- 56 

sp-----------------14, 30, 56; pl. 12 

Salopina--------------------- 17 

sandalina, Calceola ----------------- 46 

Schellwienella sp------------------ 16 

Schlotheimophyllum----23, 25, 26, 40, 41, 42, 53 

patellatum ------------------- 24, 42 

Scope of investigation-------------- 1 

sedgwicki, Spongophyllum---------- 54 

Sharopshire, England, zone B correlation---· 24 

Siberia, zone C correlation---------- 24 

Sicorhyncha----------:------- 16 

Silurian coralline rocks, Great Basin, compared with those of other regions-- 27 

Silurian Rugosa, age determinations----- 26 

correlation with distant rocks------ 22 

correlation within Great Basin------ 17 

Silurian System, identification in Great Basin 4 

siluriense, Cystiphyllum -------------- 45 

Simpson Park Mountains, northern, localities- 57 

simpsoni, Chonophyllum--14, 16, 24, 30, 53; pl. 8 

Tonkinaria --------14, 15, 30, 51, 52; pl. 7 

Siphonophrentis (Breviphrentis) --------- 31 

smithi, Howellella---------------- 17 

socialis, Cyathactis------------- 44 

Solenoporaceae----------------- 29 

speciosa, Arachnophyllum ------------ 43 

Spiniferina------------------ 36 

Spongophylloides--------------- 25, 54 

(Spongophylloides), Endophyllum------ 54 

spongophylloides. Australophyllum (Toqui- maphlJJllum. _____________ 25, 55 

Spongophyllum ------------------ 54 

Spongophyllum------------------ 54 

cyathophylloides-------------- 54 

rectiseptatum -------------------- 24, 26 

sedgwicki------------------- 54 

spongophylloides-------------- 54 

Stauria astreiformis------------- 32 

Stauriidae------------------29, 32, 33 

stellaris, Strombodes------------- 43, 47 

Stortophyllum--------------- 36 

Stratigraphy, Laketown and Lone Mountain 

Dolomite -----------·------------·-----·-- 16 

Streptelasma---------------- 31 

corniculum--------------··-- 30 

milne-edwardsi -------------- 40 

Streptelasmatidae ------------------ 29, 30 

Streptelasmidae-----·------------- 29, 30 

(Striispirifer), E08pirifer------------- 21 

Strombodes-------------------47, 50, 54 

stellaris---------------- 43, 47 

typus-------------------- 42 

Study methods------------------ 2 

Stylopleura--------21, 22, 26, 30, 34, 40; pl. 3 

berthiaumi-----14, 15, 21, 30, 34, 35, 36; pl. 3 

nevadensis-------14, 15, 30, 35; pls. 2, 15 

sp. T-------------- 36; pl. 2 

sp --------------------- pl. 16 

Sulphur Spring Range, southern, locality-- 57 

Swe .ten, Gotland---------------- 22 

· rotland, Lykophyllidae---------- 26 

thickness of Silurian System----- 28 

zone A correlation----------· 22 

zone B correlation-------- 23 

zone C correlation-------- 24 
66 

Sweden-Continued Page 

Gotland-Continued 

zone D correlation--------- 24 

zone E correlation--------------- 24 

Syringopora---------------------- 15, 34 

T 

Tennessee, zone D correlation------------ 24 

Tenuiphyllum------------------- 50 

tenuiseptatus, Cyathactiff----------------- 44 

Teratophyllum------------------ 46 

thomi, Palaeophyllum ------------------ 34 

Tonkinaria--------------21, 30, 47, 51; pL 7 

simpsoni -------------14, 15, 30, 51, 52; pL 7 

Toquima Range, localities-------------------- 58 

Toquimaphyllum------16, 22, 23, 24, 25, 26, 30, 54 

johnsoni------------------------- 25 

(Toquimaphyllum), Australophyllum --22, 54; pL 11 

{ritschi, Australophyllum ---------- 25, 55 

giganteum, Australophyllum------- 25 

johnsoni, Australophyllum----14, 16, 21, 22, 25, 

26, 30, 54, 55; pls. 11, 12, 15 

originalis, Australophyllum--------- 22, 25 

spongophylloides, Australophyllum----- 25, 55 

truncata, Madrepora------------------ 40 

INDEX 

Page 

truncatum, Kodonophyllum --------- 41; pl. 4 

Tryplasma----------21, 25, 30, 31, 36, 37 

aequabile --------------------- 36 

brownsportensis-------------- 24 

duncanae------14, 15, 24, 26, 30, 37; pl. 1 

fascicularia---------------- 34 

hedstromi------------------ 20, 24 

lonsdalei ---------------24, 25, 26, 37 

newfarmeri------14, 15, 24, 26, 30, 37; pl. 2 

nordica------------------------ 37 

prava------------------------- 24 

sp. R ----------------------30, 38; pl. 1 

sp --------------------------- pL 10 

Tryplasmatidae ------------------------- 30, 36 

tubiforme, Cystiphyllum------------------- 45 

turbinata, Turbinolia--------------------- 31 

turbinatum, Rhegmaphyllum-------------- 31 

Turbinolia turbinata------------------ 31 

turkestanica, Maikottia-----------------35; pL 2 

Tuscarora Mountains, localities------- 57 

zone A fauna-------------------- 20 

typus, Arachnophyllum ---------- 22, 23, 42, 43 

Cyathactis---------------------- 44 

Strombodes--------------------- 42 

Page 

Tyria------------------------- 32 

u,v,w 

ubehebensis, Ryderophyllum ---14, 30, 44, 45; pL 6 

Ural Mountains, zone C correlation------- 24 

Verticillopora-----------9, 15, 20, 21, 22, 25, 26 

annulata ---------------------29; pl. 16 

Virgiana----------------------- 4 

Western (Pacific Border) graywacke belt------ 5, 27 

X,Y,Z 

Xylodes----------------------- 48 

sp ------------------------------- 51 

Yassia---------------------------- 54 

Zaphrentis conulus ------------------- 31 

Zelophyllum ------------------30, 36, 37, 40 

intermedium--------------------- 40 

Zonation, Rugosa, Great Basin Silurian---- 13 
PLATES 1-16 

[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. Dalmanophyllum sp. A. 

1, 2. Lateral and calice views (x 2); USNM 159360. Lower Silurian, coral zone 

A, lower unit of Vaughn Gulch Limestone; locality M1091, Mazourka Canyon, 

northern lnyo Mountains, Calif. 

3. Calice view (x 2); USNM 159361. Lower Silurian, coral zone A, lower member 

of Hidden Valley Dolomite; locality M1096, Whitetop Mountain, Ubehebe district, California. 

4. Dalmanophyllum dalmani (Edwards and Haime). 

Lateral view (x 2); Flint Ridge, Ohio. Copy of Edwards and Haime holotype figure 

(1851, pl. 1, fig. 6). 

5, 6. Brachyelasma sp. 

Transverse and longitudinal thin sections of same individual (x 2), USNM 165355. 

Middle Silurian, coral zone B, lower part of Hidden Valley Dolomite; locality 

M1098, Ryan quadrangle, Funeral Mountains, Calif. 

7, 8. Rhegmaphyllum sp. h. 

Calice and lateral views (x 2); USNM 159362. Lower Silurian, coral zone A, lower 

member of Hidden Valley Dolomite; locality M1096, Whitetop Mountain, Ubehebe 

district, California. 

9-11. Brachyelasina sp. B. 

9, 10. Transverse and longitudinal thin sections of same individual (x 2); USNM 

159363. Middle Silurian, coral zone B, lower part of Hidden Valley Dolomite; 

locality M1094, Ubehebe district, California. 

11. Longitudinal thin section (x 2), USNM 165352. Coral zone B, lower part of 

Hidden Valley Dolom~te; locality M1097, Ryan quadrangle, Funeral Mountains, 

Calif. 

12-15, 17. Palaeocyclus porpita subsp. mcallisteri, n. subsp. 

12. Edge view of paratypes (x 3); USNM 159364. 

13, 14. Bottom and calice views of holotype (x 3); USNM 159365. 

15. Calice view of paratype (x 2); USNM 159366. 

17. Calice view of paratype (x 2); USNM 159367. 

Lower Silurian, cbral zone A, lower member of Hidden Valley Dolomite; locality 

M1096, Whitetop Mountain, Ubehebe district, California. 

16. Palaeocyclus porpita cf. subsp. mcallisteri, n. subsp. 

Calice view (x 21

/2); USNM 159368. Lower Silurian, coral zone A; locality M1129, 

Confusion Range, Utah. 

18-21. Palaeocyclus porpita (Linnaeus). 

18, 21. Calice and edge views, same individual (x 2); USNM 159369. 

19. Edge view (x 2); USNM 159370. 

20. Edge view of broken individual (x 3), showing calice and trabeculae; USNM 

159371. Lower Silurian, Visby, Gotland, Sweden. 

22, 23. Rhabdocyclus sp. d. 

22. Calice view (x 4), showing trabecular spines; USNM 159372. 

23. Lateral view of broken individual (x 2), showing calice and trabecular spines; 

USNM 159373. 

Lower Silurian, coral zone A; locality M1096, Whitetop Mountain, Ubehebe district, 

California. 

24, 25. Rhabdocyclus sp. B. 

Calice views of two large individuals (x 1 V2); USNM 165353a, 165353b. Silurian; 

locality M1099, Chuckwalla Canyon, Bare Mountain quadrangle, Nevada. 

26-28. Tryplasma duncanae, n. sp. 

26. Lateral view ofholotype(x 2)~ USNM 159374. 

27. Calice view of paratype (x 5); USNM 159375. 

28. Longitudinal thin section (x 21;2); USNM 159376. 

Middle Silurian, coral zone D, unit 3 of Roberts Mountains Formation; localitv MllOO, 

Roberts Creek Mountain, Nev. 

29, 30. Tryplasma sp. R. 

Longitudinal and transverse thin sections (x 4); USNM 165354. Middle Silurian, 

bottom of coral zone C, base of unit 3 of Roberts Mountains Formation; locality 

M1101, Roberts Creek Mountain, Nev. 
GEOLOGICAL SURVEY PROPESSIONAL PAPER 777 PLATE 1 

2 3 5 

10 11 

7 6 

9 

12 

22 

14 15 

8 13 

504- 634 0 - 73 - 6 
PLATE 2 

FIGURES 1- 4. Tryplasma newfarmeri, n. sp. 

1. Longitudinal thin section (x 3); holotype, USNM 

159377. 

2, 3. Longitudinal views of a single thin section (x 4); holotype, USNM 159377 

4. Transverse thin section (x 2); holotype, USNM 159377. 

Silurian, coral zone C, unit 3 of Roberts Mountains 

Formation; locality M1102, Roberts Creek Mountain, Nev. 

5, 6. Palaeophyllum? sp. c. 

Longitudinal and transverse thin sections (x 2). Lower Silurian, lower unit of 

Vaughn Gulch Limestone; locality M1086, northern Mazourka Canyon, lnyo 

Mountains, Calif. 

7-10. Stylopleura? sp. T. 

Transverse and longitudinal sections of USNM 159378. 

7. Smoothed surface photographed in water (x 1). 

8-10. Thin sections (x 1112). 

Silurian or Lower Devonian limestone; locality M1104, Ikes Canyon vicinity, Toquima 

Range, Nev. 

11, 12. Stylopleura nevadensis, n. gen., n. sp. 

Transverse and longitudinal thin sections of paratype (x 4); USNM 159379. Middle 

Silurian, coral zone D, Masket Shale of Kay and Crawford (1964); locality 

M1103, Ikes Canyon, Toquima Range, Nev. 

13, 14. Maikottia sp., cf. M. turkestanica Lavrusevich. 

Transverse and longitudinal thin sections (x 2) of large massive colony. Upper 

Silurian or Lower · Devonian; Porcupine River, half a mile upstream from mouth 

of Salmontrout River, Alaska. 

15, 16. Stylopleura nevadensis, n. gen., n. sp. 

15. Transverse thin section (x 2); paratype, USNM 159440. 

16. Longitudinal section (x 11

12); paratype, USNM 159440a. 

Upper part of the Silurian section; locality M1105, Coal Canyon, northern Simpson 

Park Mountains, Nev. 
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TRYPLASMA, PALAEOPHYLLUM?, STLOPLEURA, AND MAIKOTTIA 
PLATE 3 

FiGURES 1-3. Stylopleura cf. S. berthiaumi. 

1. Lateral view of part of a fasciculate colony (x 1); USNM 165356. 

2, 3. Transverse and longitudinal sections (x 2). 

Silurian; locality M1099, Chuckwalla Canyon, Bare Mountain quadrangle, Nevada. 

4, 5. Palaeophyllum sp. b. 

Transverse and longitudinal sections (x 21/z); USNM 165357. From large phaceloid 

colony. Lower part of Silurian section; locality Ml085, Bare Mountain quadrangle, 

Nevada. 

6-8. Stylopleura berthiaumi, n. gen., n. sp. 

Calice and two lateral views (x 1); USNM 159380. Upper Silurian, coral zone 

D; locality Mll03, lkes Canyon, Toquima Range, Nev. 

9-17. Stylopleura berthiaumi, n. gen., n. sp. 

9, 10. Calice view and longitudinal polished section of paratype (x 1); USNM 

159381. 

11. Partial lateral view of holotype (x 11/z); USNM 159382. 

12. Calice view of paratype (x 2), showing multiple calice budding; USNM 159383. 

13. View of broken calice interior, showing three offsets (x 2). 

14. Partial lateral view of paratype (x 1), showing lateral pillar attached to 

Cladopora branch; USNM 159384. 

15, 16. Longitudinal thin sections (x 2); USNM 165358a, 165358b. 

17. Lateral view of a piece of a large colony (x 1), showing connecting pillars; 

USNM 165359. 

Upper Silurian, coral zone D, unit 3 of Roberts Mountains Formation; locality 

MllOO, Roberts Creek Mountain, Nev. 

18-20. Stylopleura berthiaumi, n. gen., n. sp. 

Partial interior view of calice offsets and lateral view and calice view of same 

individual (x 1), showing multiple calice budding and bases of lateral pillars; 

USNM 159385. Upper Silurian, coral zone E; locality M1106, Coal Canyon, 

northern Simpson Park Mountains, Nev. 
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STYLOPLEURA AND PALAEOPHYLLUM 
PLATE 4 

FIGURES 1, 2. Kodonophyllum truncatum (Linnaeus). 

1. Transverse thin section (x 2). Silurian, Wenlock Limestone; Dudley, England. 

2. Longitudinal thin section (x 3). Silurian; Lilla Karlsb Island (off Gotland), Sweden. 

Both figures copied from plate viii, Smith and Tremberth, 1929. 

3-7. Kodonophyllum mulleri, n. sp. 

3. Longitudinal thin section (x 2) of holotype; USNM 159386. 

4. Longitudinal thin section (x4) of holotype; USNM 159386. Enlargement of part of fig. 3. 

5. Transverse thin section (x 2) of holotype; USNM 159386a. 

6. Transverse thin section (x 4) of holotype; USNM 159386b. 

Upper Silurian, coral zone E; locality M1108, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

7. Transverse thin section (x 1'/z) of paratype; USNM 159389. 

Upper Silurian, coral zone E; locality M1107, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

8, 9. Kodonophyllum sp. a. 

Transverse sections of ephebic stage (x 4). Silurian; Gotland, Sweden. Both figures 

copied from plate X, Minato, 1961. 

10-14. Diplophyllum? sp. m. 

Transverse and longitudinal thin sections (x 31M, USNM 165350. Upper Silurian 

or Lower Devonian, topmost beds of Vaughn Gulch Limestone; Mazourka Canyon, 

Inyo Mountains, Calif. 

15, 16. Crassilasma? sp. 

Longitudinal and transverse thin sections (x 2), USNM 165351. Middle Silurian, 

middle unit of Vaughn Gulch Limestone; Mazourka Canyon, Inyo Mountains, 

Calif. 
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KODONOPHYLLUM, DIPLOPHYLLUM?, AND CRASSILASMA? 
PLATE 5 

FIGURES 1-6. Mucophyllum oliveri, n. sp. 

1. Transverse section of holotype (x 1); smoothed surface photographed m water; 

USNM 159390. 

2. Longitudinal thin section of holotype (x 2); USNM 159390. 

3. Enlargement of part of same thin section as fig. 2 (x 4), showing trabeculae; 

USNM 159390. 

4. Part of transverse thin section of holotype (x 4), showing pattern of trabecula e; 

USNM 159390. 

5. Calice view (x 1) of para type; USNM 165349. 

6. Longitudinal section of paratype (x 1), showing depth of calice pit; photographed 

in water; USNM 159391. 

Upper Silurian, coral zone E; locality Ml108, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

7, 8. Arachnophyllum kayi, n. sp. 

Transverse and longitudinal thin sections of holotype (x 8); USNM 159392. Lower 

Silurian, coral zone A, Masket Shale of Kay and Crawford (1964); locality 

M1088, Ikes Canyon, Toquima Range, Nev. 

9, 10. Cyathophylloides fergusoni, n. sp. 

Transverse and longitudinal sections of holotype (x 8); USNM 159393. Lower Silurian, 

coral zone A, Masket Shale of Kay and Crawford (1964); locality M1088, Ikes 

Canyon, Toquima Range, Nev. 
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MUCOPHYLLUM, ARACHNOPHYLLUM, AND CYATHOPHYLLOJDES 
PLATE 6 

FIGURES 1-7. Ryderophyllum ubehebensis, n. sp. 

1. Transverse thin section of paratype (x 2); USNM 159394. 

2. Longitudinal thin section of paratype (x 3); USNM 159395. 

3. Transverse thin section of holotype (x 2); USNM 159396. 

4. Longitudinal thin section of para type (x 2); USNM 159397. 

5. Longitudinal thin section of paratype (x 1); USNM 159398. 

·6: Lateral view of paratype (x 1); USNM 159441. 

7. Transverse thin section of paratype (x 4); USNM 159399. 

Lower Middle Silurian, coral zone B, lower part of Hidden Valley Dolomite; locality 

M1094, Ubehebe district, California. 

8. Ryderophyllum sp. 

Transverse thin section (x 2). Upper Silurian or Lower Devonia n, upper unit of 

Vaughn Gulch Limestone; locality M1093, Mazourka Canyon, lnyo Mountains, 

Calif. 

9. Crassilasma? sp. 

Transverse thin section (x 2). Same locality as fig. 8. 

10-12. Pycnactis sp. k. 

10, 12. Lateral view (x 1) and transverse thin section (x 2) of same individual; 

USNM 159400. 

11. Transverse thin section (x 2); USNM 150401. 

Lower Middle Silurian, coral zone B, lower part of Hidden Valley Dolomite; locality 

M1109, Andy Hills, Ubehebe district, California. 

13, 14. Ryderophyllum? sp. 

13. Transverse thin section (x 2). Upper Silurian, coral zone E; locality M1106, 

Coal Canyon, northern Simpson Park Mountains, Nev. 

14. Longitudinal thin section (x 4). Upper Silurian, coral zone E; locality MlllO, 

Coal Canyon, northern Simpson Park Mountains, Nev. 
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PLATE 7 

FIGURES 1-8. Tonkinaria simpsoni, n. gen., n. sp. 

1, 2 Lateral view (x 11/2) of para type; USNM 159402. 

3, 4. Calice and lateral views of holotype (x 11/2); USNM 159403. 

5, 6. Transverse thin section (x 4) and longitudinal thin section (x 31/2) of paratype; USNM 159404. 

7. Transverse thin section (x 2); USNM 159405. 

8. Calice view (x 2). 

Upper Silurian, coral zone D, unit 3 of Roberts Mountains Formation; locality 

M1100 Roberts Creek Mountain, Nev. 

9. Tonkinaria cf. T. simpsoni. 

Lateral view of colony showing peripheral calice offsets (x 2); USNM 159406. 

Lower part of Hidden Valley Dolomite; locality M1097, Ryan quadrangle, Funeral 

Mountains, Calif. 

10, 11. Microplasma? sp. R. 

Transverse and longitudinal thin sections (x 2). Middle Silurian, bottom of coral 

zone C, base of unit ~ of Ro berts Mounta ins Forma tion ; locality MI089, Roberts Creek 

Mountain, Nev. 

12-14. Rhizophyllum sp. D. 

Calice view (x 1), view of flat side (x 1), and transverse thin section (x 2) of 

same individual; USNM 121346. Upper Middle Silurian, middle unit of Vaughn 

Gulch Limestone; near locality M1092, Mazourka Canyon, northern Inyo Mountains, Calif. 

15- 18. Denaphyllum denayensis, n. gen., n. sp. 

15. Transverse thin section of holotype (x 71/2); USNM 159407. 

16. Transverse thin section of holotype (x 15); USNM 159407. 

17, 18. Longitudinal thin sections of holotype (x 15); USNM 159407. 

Middle Silurian, coral zone C, unit 3 of Roberts Mountains Formation; locality 

M1102, Roberts Creek Mountain, Nev. 
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TONKINARIA, MICROPLASMA ?, RHJZOPHYLLUM, AND DENAYPHYLLUM 
PLATE 8 

FIGURES 1-4. Chonophyllum simpsoni, n. sp. 

1, 2. Transverse and longitudinal thin sections of holotype (x ll/2); USNM 159408. 

3. Enlargement of part of same longitudinal thin section as fig. 2 (x 4); USNM 

159408. 

4. Longitudinal thin section of paratype (x 2); USNM 159409. 

Upper Silurian, coral zone E; locality Mll08, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

5, 6. Cyathactis? sp. 

5. Transverse thin section (x 4). 

6. Longitudinal thin section (x 4). 

Upper Silurian, coral zone E; locality Mll06, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

7. Chonophyllum sp., cf.C. simpsoni, n. sp. 

Transverse thin section (x 4). Upper Silurian, coral zone E; locality MillO, Coal 

Canyon, northern Simpson Park Mountains, Nev. 

8. Chonophyllum sp. 

Side view of weathered specimen (x 1). Upper Silurian or Lower Devonian, upper 

unit of Vaughn Gulch Limestone; locality M1093, Mazourka Canyon, northern 

Inyo Mountains, Calif. 

9. Chonophyllum? sp. 

Calice view (x 11/z). Middle Silurian, middle unit of Vaughn Gulch Limestone; 

locality M1092, Mazourka Canyon, northern Inyo Mountains, Calif. 

10. Chonophyllum sp. 

Longitudinal thin section (x 4). Upper Silurian or Lower Devonian, upper unit 

of the Vaughn Gulch Limestone; locality M1093, Mazourka Canyon, northern 

Inyo Mountains, Calif. 

11, 12. Chonophyllum? sp. 

Transverse and longitudinal thin sections (x 2). Upper Silurian or Lower Devonian, 

upper unit of the Vaughn Gulch Limestone; locality Ml093, Mazourka Canyon, 

northern Inyo Mountains, Calif. 
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CHONOPHYLLUM AND CYATHACTIS? 

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PLATE 9 

FIGURES 1-4. Entelophylloides (Prohexagonaria) occidentalis, n. subgen., n. sp. 

1. Transverse thin section of holotype (x 3); USNM 159410. 

2. Enlargement of part of transverse thin section of holotype (x 6); USNM 159410. 

3. Longitudinal thin section of holotype (x 81/2); USNM 159410. 

4. Longitudinal thin section of holotype (x 6); USNM 159410. 

Middle Silurian, coral zone C, unit 3 of Roberts Mountains Formation; locality 

M1102, Roberts Creek Mountain, Nev. 

5. Entelophylloides (Prohexagonaria) sp. 

Transverse thin section (x 11/2). Copied from pl. VIII, Smith and Tremberth, 1929. 

Visby, Gotland, Sweden. 

6-10. Petrozium mcallisteri, n. sp. 

6-9. Transverse and longitudinal thin sections of holotype (x 6); USNM 159411. 

10. View of part of fasciculate colony which is the holotype (x 1); USNM 159411. 

Lower Middle Silurian, coral zone B, lower part of Hidden Valley Dolomite; locality 

M1111, Ubehebe district, California. 
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J::NTELOPHYLLO!DES (PROHEXAGONARIA) AND PETROZIUM 

504- 634 0 - 73 - 7 
PLATE 10 

FIGURES 1, 2 . Entelophyllum eurekaensis, n. sp. 

Transverse and longitudinal thin sections (x 4) of holotype; USNM 159412. Upper 

Silurian, upper part of Lone Mountain Dolomite; locality M1113, southern 

Fish Creek Range, Nev. 

3, 4. Tryplasma sp. 

Transverse and longitudinal thin sections (x 2). Upper Silurian, upper part of 

Lone Mountain Dolomite; locality M1087, southern Fish Creek Range, Nev. 

5-8. Entelophyllum engelmanni, n. sp. 

5. Transverse thin section of holotype (x 4); USNM 159413. 

6. Longitudinal thin section of paratype (x 21/2); USNM 159414. 

7. Part of same thin section as fig. 6 enlarged (x 4); USNM 159414. 

8. Longitudinal thin section of para type (x 81/2); USNM 159415. 

Upper Silurian, upper part of Lone Mountain Dolomite; locality M1112, southern 

Mahogany Hills, Eureka County, Nev. 

9-11. Entelophyllum engelmanni, n . sp. 

9. Transverse thin section of paratype (x 2); USNM 159416. 

10. Lateral view of corallite (x 11/2); USNM 159492. 

11. Lateral view of two attached corallites (x 1). 

Shows attached shell ofHowell(!lla: 

Upper Silurian, upper part of Lone Mountain Dolomite; locality Ml087, southern 

Fish Creek Range, Nev. 

12, 13. Entelophyllum engelmanni, n. sp. 

12. Oblique view of three corallites from large paratype colony, slightly reduced; 

USNM 159417. 

13. Transverse thin section (x 2); USNM 159418. 

Upper Silurian, upper part of Lone Mountain Dolomite; locality M1112, southern 

Mahogany Hills, Eureka County, Nev. 

14, 15. Entelophyllum eurekaensis, n. sp. 

Transverse and longitudinal sections of paratype (x 2); USNM 159419. Upper Silurian, 

upper part of Lone Mountain Dolomite; locality Ml113, southern Fish Creek 

Range, Nev. 
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ENTELOPHYLLUM AND TR YPLASMA 
PLATE 11 

FiGURES 1, 2. Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

Transverse and longitudinal thin sections of holotype (x 4); USNM 159420. Upper 

Silurian, coral zone E; locality M1114, Ikes Canyon, Toquima Range, Nev. 

3, 4, Australophyllum (Toquimaphyllum) cf. johnsoni, n. subgen., n. sp. 

Calice view (x 1) and transverse thin section (x 2); USNM 159421. Upper Silurian, 

coral zone E; locality M1108, Coal Canyon, northern Simpson Park Mountains, 

Nev. 

5, 6. Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

5. Longitudinal thin section of para type (x 4); USNM 159422. 

6. Transverse thin section of same para type (x 11/2); USNM 159422. 

Upper Silurian, coral zone E; locality M1106, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

7. Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

Transverse thin section of holotype (x 2); USNM 159420. Same locality as figs. 

1, 2. 
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AUSTRALOPHYLLUM (TOQUIMAPHYLLUM) JOHNSONJ, N. SUBGEN.,N. SP. 
PLATE 12 

FIGURES 1-3. Australophyllum (Toquimaphyllum) cf. johnsoni, n. subgen., n. sp. 

Transverse thin section (x 2), transverse thin-section enlargment (x 31/z), longitudinal 

thin section (x 4); USNM 149423. Upper Silurian, coral zone E, middle unit 

of Vaughn Gulch Limestone; locality M1115, Mazourka Canyon, northern Inyo 

Mountains, Calif. 

4, 5. Australophyllum sp. 

4. Transverse thin section (x 4). Middle unit of Vaughn Gulch Limestone; locality 

M1116, Mazourka Canyon, northern Inyo Mountains, Calif. 

5. Transverse thin section (x 31/z). Upper Silurian or Lower Devonian, upper unit 

of Vaughn Gulch Limestone; locality M1093, Mazourka Canyon, northern Inyo 

Mountains, Calif. 

6-8. Salairophyllum? sp. 

6. Transverse thin section (x 3); USNM 159424. 

7. Longitudinal thin section (x 4); USNM 159424. 

8. Transverse thin section (x 11/z); USNM 159424. 

Note four peripheral calice offsets. Probably from Upper Silurian, coral zone E; 

locality M1117, Coal Canyon, northern Simpson Park Mountains, Nev. 
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A USTRALOPHYLL UM (TOQUIMAPHYLL UM), A USTRALOPHYLL UM, AND SALAIROPHYLL UM? 
PLATE 13 

FIGURES 1-4. Kyphophyllum neuadensis, n. sp. 

1, 2. Transverse and longitudinal thin sections of holotype (x 4); USNM 159425. 

3. Transverse thin section of holotype (x 2); USNM 159425. 

4. Transverse thin section of holotype (x 4); USNM 159425. 

Upper Silurian, coral zone E; locality M1114, Ikes Canyon, Toquima Range, Nev. 

5-8. Neomphyma crawfordi, n. sp. 

5-7. Transverse thin sections of holotype (x 41/2); USNM 159426. 

8. Longitudinal thin section of holotype (x 4); USNM 159426. 

Lower Silurian, coral zone A; locality M1088, Ikes Canyon, Toquima Range, Nev. 
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KYPHOPHYLLUM NF:VADENSIS, N. SP., AND NEMOPHYMA CRA WFORDI,N. SP. 
PLATE 14 

FIGURES 1, 2. Kyphophyllum cf. K. nevadensis, n. sp. 

Transverse and longitudinal thin sections (x 4); USNM 159427. Upper Silurian 

or Lower Devonian, upper unit of the Vaughn Gulch Limestone; locality M1093, 

Mazourka Canyon, northern lnyo Mountains, Calif. 

3, 4. Australophyllum sp. 

Transverse and longitudinal thin sections (x 4); USNM 159428. Middle Silurian, 

middle unit of the Vaughn Gulch Limestone; locality M1119, Mazourka Canyon, 

northern lnyo Mountains, Calif. 

5. Australophyllum sp. 

Longitudinal thin section (x 7). Upper Silurian or Lower Devonian, upper unit 

of the Vaughn Gulch Limestone; locality M1093, Mazourka Canyon, northern 

lnyo Mountains, Calif. 

6. Kyphophyllum cf. K. nevadensis, n. sp. 

Transverse thin section (x 2); USNM 159429. Middle unit of the Vaughn Gulch 

Limestone; locality M1118, Mazourka Canyon, northern lnyo Mountains, Calif. 

7. Kyphophyllum cf. K. nevadensis, n . sp. 

Lateral view (x 1) of colony USNM 159427 from which thin sections shown in 

figs. 1, 2 were cut. Locality M1093. 
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KYPHOPHYLLUM AND A USTRALOPHYLLUM 
PLATE 15 

FiGURES 1-4. Stylopleura nevadensis, n. gen., n. sp. 

1. Upper surface of corallum (x 1/2); holotype USNM 159431. 

2-4. Transverse thin section (x 2), longitudinal thin section (x 2), and longitudinal 

thin section (x 2) showing a connecting pillar; holotype USNM 159431. 

Upper Silurian, coral zone E; locality M1107, Coal Canyon, northern Simpson 

Park Mountains, Nev. 

5-9. Rhabdocyclus sp. K. 

5. 6. Calice and lateral views (x 2112), USNM 159432; note excentric apical cone. 

7, 8. Calice and lateral views (x 4), USNM 159433. 

9. Calice view (x 2), USNM 159434. 

Silurian, Laketown Dolomite; locality M1137, Kings Canyon, Conger Mountain 

quadrangle, Confusion Range, Utah. 

10. Palaeocyclus cf. P. porpita (Linnaeus). 

Calice view (x 2); USNM 159435. Silurian dolomite; locality M1336, 3 miles northeast of Mitchell Ranch, Sherman Mountain quadrangle, Ruby Mountains, Nev. 

11. Pycnostylus sp. 

Longitudinal sections (x 11/2); USNM 159436. Silurian, Lone Mountain Dolomite; 

locality M1148, 3 miles south of Romano Ranch, Garden Valley quadrangle, 

southern Sulphur Spring Range, Nev. 

12-16. Entelophyllum cf. E. engelmanni, n. sp. 

12. Lateral view of large corallite (x 1); USNM 159437. 

13-16. Longitudinal and transverse thin sections (x 2) of corallite; USNM 159438. 

Silurian dolomite; 3 miles southeast of Mitchell Ranch, Sherman Mountain quarangle, southern Ruby Mountains, Nev. 

17. Australophyllum (Toquimaphyllum) johnsoni, n. subgen., n. sp. 

Calice view (x 1/2) of part of colony; paratype USNM 159439. Upper Silurian, 

coral zone E; locality M1026, Coal Canyon, northern Simpson Park Mountains, 

Nev. 
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STYLOPLEURA, RHABDOCYCLUS, PALAEOCYLUS,PYCNOSTYLUS, ENTELOPHYLLUM, AND AUSTRALOPHYLLUM 

(TOQUJMAPHYLL UM) 
PLATE 16 

FIGURES 1, 2. Brachyelasma sp. B . 

. Longitudinal thin section and calice view of same individual (x 2); thin section 

shows incrustation by probable bryozoa on right. Middle Silurian, coral zone 

B, lower part of Hidden Valley Dolomite; locality Ml127, Ryan quadrangle, 

Funeral Mountains, Calif. 

3, 4. Stylopleura? sp. 

Lateral and calice views (x 11/2). Silurian, lower part of the Lone Moun~ain Dolomite; 

locality M112l, southern Sulphur Spring Range, Nev. 

5, 6. Verticillopora annulata Rezak. 

5. Weathered interior (x 11/z) showing ray bases. 

6. Weathered specimen (x 2) showing internal stipe cavity. 

Upper Silurian, coral zone D, unit 3 of Roberts Mountains Formation; locality 

MllOO, Roberts Creek Mountain, Nev. 

7-13, 17. Verticillopora annulata Rezak. 

7, 8. Longitudinal and transverse thin sections of same individual (x 2) showing internal 

stipe cavity and rays. 

9, 10. Lateral and transverse views of same individual (x 11/z). 

11, 12. Lateral views of two large individuals (x 11/2). 

13. Lateral view of fragmentary individual (x 2) showing external pattern of pore 

cycles. 

17. Longitudinal interior (x 3) showing ray pore cycles. 

Upper Silurian, coral zones D and E, upper part of middle unit of Vaughn Gulch 

Limestone; Mazourka Canyon, northern lnyo Mountains, Calif. 

14. Verticillopora annulata Rezak. 

Lateral view (x 1). Upper Silurian, coral zones D and E ', upper part of middle 

unit of Vaughn Gulch Limestone; Mazourka Canyon, northern lnyo Mountains, 

Calif. 

15, 16. Verticillopora a'nnulata Rezak. 

Exterior and transverse views of part of an annular segment (x 2) showing rays 

and ray pores. Upper Silurian or Lower Devonian,· upper unit of Vaughn 

Gulch Limestone· locality M1093, Mazourka Canyon, northern lnyo Mountains, 

Calif. · ' 
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BRACHYELSAMA, STYLOPLEURA? AND VERTICILLOPORA 

U. 5. GOVERNMENT PR INTING OFFICE : 1973 0 -504-634