Ordovician and Silurian

4

Graptolite Succession in the

Trail Creek Area, Central Idaho 

A Graptolite Zone Reference Section

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 4

-t
Ordovician and Silurian 

Graptolite Succession in the 

Trail Creek Area, Central Idaho 

A Graptolite Zone Reference Section

By CLAIRE CARTER and MICHAEL CHURKIN, JR.

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020

UNITED STATES GOVERNMENT PRINTING OFF ICE, WASHINGTON: 1977
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Carter, Claire.

Ordovician and Silurian graptolite succession in the Trail Creek area, central Idaho-a graptolite zone 

reference section.

(Geological Survey Professional Paper 1020) 

Bibliography: p. 32-33. 

Supt. of Docs. No.: I 19.16:1020

1. Graptolites. 2. Paleontology--Ordovician. 3. Paleontology-Silurian. 4. Paleontology-IdahoCuster Co. 5. Paleontology-Idaho-Blaine Co. I. Churkin, Michael, 1932- joint author. 

III. Title. III. Series: United States Geological Survey Professional Paper 1020.

QE840.5.C37 566 76-608341

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

Washington, D.C. 20402

Stock Number 024-001-02982-1
CONTENTS

Page

Abstract.................................................................................................... 1

Introduction ............................................................................................ 1

Geologic setting...................................................................................... 3

Lithology and structure ...................................................................... 3

Graptolite zones and their correlation .......................................... 5

Lower Ordovician Series ............................................................ 5

Middle Ordovician Series .......................................................... 10

Upper Ordovician Series ............................................................ 12

Silurian System.............................................................................. 13

Systematic descriptions...................................................................... 13

Class Graptolithina...................................................................... 13

Order Graptoloidea .............................................................. 13

Family Dichograptidae .............................................. 13

Genus Loganograptus.......................................... 13

Genus Goniograptus ............................................ 13

Genus Tetragraptus.............................................. 14

Genus Phyllograptus............................................ 14

Genus Didymograptus ........................................ 15

Genus Isograptus .................................................. 15

Genus Maeandrograptus .................................... 16

Family Corynoididae .................................................. 16

Genus Cornyoides ................................................ 16

Family Nemagraptidae .............................................. 16

Genus Leptograptus ............................................ 16

Genus Pleurograptus............................................ 17

Page

Systematic descriptions Continued 

Class Graptolithina Continued 

Order Graptoloidea Continued

Family Dicranograptidae .......................................... 17

Genus Dicranograptus ........................................ 17

Genus Dicellograptus .......................................... 18

Family Glossograptidae.............................................. 21

Genus Glossograptus .......................................... 21

Family Cryptograptidae ............................................ 21

Genus Cryptograptus .......................................... 21

Family Diplograptidae............................................... 22

Genus Dip ograptus ............................................ 22

Genus Climacograptus ........................................ 22

Genus Glyptograptus .......................................... 24

Genus Orthograptus ............................................ 25

Genus Petalograptus ............................................ 27

Genus Pseudoclimacograptus .......................... 27

Family Lasiograptidae................................................ 28

Genus Neurograptus ............................................ 28

Family Retiolitidae ..................................................... 28

Genus Orthoretioiites .......................................... 28

Family Monograptidae................................................ 28

Genus Monograptus ............................................ 28

Family Cyrtograptidae... .......................................... 30

Genus Cyrtograptus ............................................ 30

References cited...................................................................................... 32

Index ...... .............................................................................................. 35

ILLUSTRATIONS

[Plates follow index] Page

PLATE

FIGURE 1. 

2.

Loganograptus, Phyllograptus, Didymograptus, Isograptus, and Tetragraptus.

Leptograptus, Dicellograptus, Pleurograptus, Dicranograptus, Isograptus, and Corynoides.

Dicellograptus, Glossograptus, Cryptograptus, Pseudoclimacograptus, Diplograptus, Neurograptus, and Petalograptus.

Climacograptus, Orthograptus, and Orthoretioiites.

Glyptograptus, Monograptus, and Cyrtograptus.

Cyrtograptus, Dicellograptus, and Gonioeraptus

Sketch of Maeandrograptus, Leptograptus, Dicranograptus, Climacograptus, and Cyrtograptus.

Map showing location of measured sections .......................................................................... .......................................................... 2

Stratigraphic column of the upper plate of the Park Creek thrust in the Trail Creek section, showing

zonal sequence and location of graptolite collections......................................................................................................... . .. 4

Chart showing correlation of graptolite sequences in western North America, Great Britain, Australia

and the U.S.S.R. ............................................................................... 6

Stratigraphic column of the Little Fall Creek section, showing zonal sequence and

location of graptolite collections..................................... ..... .. .... .. ...... .......... . . .. ...... ........................... 9

in
IV CONTENTS

TABLES

Page

TABLE 1. Distribution and zonal ranges of Ordovician graptolite genera and species in the lower part of the Phi Kappa

Formation, Trail Creek section ........................................................................................................................................................... 8

2. Distribution and zonal ranges of Ordovician graptolite genera and species in the Phi Kappa Formation,

Little Fall Creek section......................................................................................................................................................................... 9

3. Distribution and zonal ranges of Ordovician graptolite genera and species in the upper part of the Phi Kappa

Formation, Trail Creek section ............................................................................................................................................................ 10

4. Distribution and zonal ranges of Silurian graptolite genera and species in the Phi Kappa Formation,

Trail Creek section.................................................................................................................................................................................. 13
ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION

IN THE TRAIL CREEK AREA, CENTRAL IDAHO 

A GRAPTOLITE ZONE REFERENCE SECTION

By CLAIRE CARTER and MICHAEL CHLRKIX, JR.

ABSTRACT

The graptolite-bearing sequence in the vicinity of Trail Creek, 

Idaho, consists of an unusually large number of zones virtually 

continuously exposed in a homoclinal section of siliceous shale. 

Eight Ordovician zones have been distinguished in the Phi Kappa 

Formation. These include the Early Ordovician Zones of Didymograptus protobifidus and Isograptus, the Middle Ordovician zones 

of Glossograptus hincksii, Nemagraptus, Climacograptus bicornis, and Climacograptus tubuliferus, and the Late Ordovician 

Zones of Pleurograptus linearis and Dicellograptus ornatus. The 

Early and Middle Silurian Zones of Monograptus convolutus and 

Cyrtograptus overlie this Ordovician succession. The relative 

completeness of the graptolite succession from late Early Ordovician through Late Ordovician becomes apparent when it is 

compared to other known graptolitic sequences of western North 

America. Thus it is a potentially useful reference section for at 

least the southern part of the North American Cordillera. The 

species Leptograptus demissus and the subspecies Phyllograptus 

anna prolatus are new. The species Cyrtograptus kirki Ruedemann is revised.

INTRODUCTION

Graptolites from western North America have 

been collected for over a century. Most of these 

collections have been from isolated outcrops of argillaceous rocks and chert within the Cordilleran geosyncline, particularly in the Basin and Range province, where the graptolitic rocks are assigned to the 

"western" or eugeosynclinal facies (Ross, 1961; 

Churkin, 1974). Until 30 years ago only graptolite 

lists accompanied reconnaissance geologic reports 

of the region. In his monograph of graptolites of 

North America, Ruedemann (1947) first illustrated 

many of these Cordilleran faunas and described 

some new species from the Phi Kappa Formation of 

Idaho. A summary of the older collections, together 

with systematic descriptions and illustrations of 

Ordovician graptolites in the Basin and Range 

province, was published by Ross and Berry (1963). 

This report provides useful documentation of what 

had been identified over the years and also provides, 

in many cases for the first time, systematic descriptions of Cordilleran graptolites. From a biostratigraphic viewpoint, however, most of the graptolite

faunas described prior to 1963 were not fitted into a 

local stratigraphic succession of graptolite faunas. 

Ross and Berry (1963) had to use the graptolite 

succession of the Marathon region, Texas (Berry, 

1960), as a standard to compare and correlate the 

isolated graptolite faunas of the Basin and Range 

province "because *** no readily zonable succession 

has yet been found in the Great Basin" (Ross and 

Berry, 1963, p. 68).

Later, in the vicinity of Trail Creek, Custer and 

Blaine Counties, central Idaho (fig. 1), an unusually 

continuous stratigraphic section of graptolitic shale 

was discovered (Churkin, 1963), and a preliminary 

correlation of the Idaho graptolite succession was 

made with the British graptolite zones of Elles and 

Wood (1901-18). At about the same time, a number of 

incomplete graptolite successions were discovered in 

Nevada (Kay and Crawford, 1964; Roberts, 1964; 

Gilluly and Gates, 1965; Churkin and Kay, 1967; 

Riva, 1970; Carter, 1972). These incomplete faunal 

successions from widely separated localities, when 

pieced together, form a composite succession of 

graptolite zones that closely resembles the continuously exposed Trail Creek, Idaho, succession, and 

individual faunas can be readily correlated with it 

(Churkin, 1974).

In the Cordillera to the north of Idaho, graptolite 

successions similar to that at Trail Creek have been 

described from British Columbia (Larson and Jackson, 1966; Jackson and others, 1965), the Yukon 

Territory (Jackson and Lenz, 1962; Lenz and Perry, 

1972), and Alaska (Churkin and Brabb, 1965; Churkin and others, 1971). The graptolite succession of 

the Road River Formation in Yukon Territory and 

Alaska is more nearly complete than that at Trail 

Creek because it extends with only a few paleonto: 

logical breaks from the Early Ordovician through 

the Silurian and into the Early Devonian. However, 

the succession of graptolite zones in the Road River 

Formation has been established on the basis of
ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

— 43° 50'

FIGURE 1. Location of measured sections in the vicinity of Trail Creek, central Idaho. Base from U. S. Geological 

Survey, Rock Roll Canyon and Phi Kappa Mountain 7W quadrangles.
LITHOLOGY AND STRUCTURE

several separate sections rather than from one continuously exposed homoclinal section as in the Phi 

Kappa Formation.

When the stratigraphic continuity of the Idaho 

graptolitic succession is compared to the best known 

Ordovician graptolitic successions not only in the 

Cordillera but elsewhere in North America for example, the Marathon region, Texas (Berry, 1960); 

Appalachian Mountains (Ruedemann, 1947; Riva, 

1972); and the Canadian Arctic Islands (Trettin, 

1971) the relative incompleteness of individual 

stratigraphic sections in these other areas becomes 

apparent. The Marathon succession, which has been 

repeatedly cited as the standard for correlation of 

North American Ordovician graptolite zones, is, in 

fact, a composite section of several structurally 

complicated sections separated by large covered 

areas (King, 1937; Berry, 1960). Furthermore, the 

Marathon section has at least two important stratigraphic breaks within the Ordovician, each marked 

by coarse conglomerate (King, 1937, p. 30, 32, 36; P. 

B. King, 1974, oral commun.), which may help 

explain missing graptolite zones and some of the 

controversy regarding the correlation of its faunas 

(Kay, 1962, p. 1426; Riva, 1972, 1974b). Graptolite 

provincialism, particularly in the Ordovician, has 

now become well known, and it is necessary to 

establish a set of graptolite zones that typify each 

major geologic province.

A search of the world literature and discussions 

with graptolite specialists working in other regions 

(A. M. Obut, T. N. Koren, and R. F. Sobolevskaya in 

the U.S.S.R.; Peter Toghill in the British Isles; G. H. 

Packham in Australia; R. A. Cooper in New Zealand; 

Bedrich Boucek in Czechoslovakia; Hermann Jaeger 

in Germany and elsewhere) have corroborated the 

fact that the Trail Creek section has an unusually 

continuous sequence of Ordovician graptolite 

faunas. Another important feature is that it appears 

to have only a small covered interval on top of the 

Dicellograptus ornatus Zone that may conceal the 

Ordovician-Silurian boundary. This boundary is 

visible in only a few places in western North America 

(Churkin and others, 1971). When these facts are 

considered, together with its accessibility, the upper 

Lower through Upper Ordovician part of the Phi 

Kappa Formation appears to be a potentially useful 

reference section for at least the southern part of the 

North American Cordillera.

Acknowledgments.—The authors are grateful to 

R. B. Rickards and T. N. Koren' for reading the 

manuscript. We are especially indebted to John Riva 

and R. J. Ross, Jr., for reviewing the manuscript and 

giving us many helpful comments. We also wish to

thank Kenji Sakamoto for photographing the graptolites in plates 1 through 5.

GEOLOGIC SETTING

The graptolite succession in the vicinity of Trail 

Creek, Idaho, described in this paper occurs in the 

Phi Kappa and Trail Creek Formations (Umpleby 

and others, 1930), a part of the shale and chert belt 

extending along the axis of the Cordilleran fold belt 

from southern California and Nevada to Alaska 

(Churkin, 1974, fig. 1). The shale and chert belt, 

which in places contains pillow basalts, originally 

separated the carbonate and quartzite belt (miogeosyncline) from the volcanic and graywacke belt 

(outer part of eugeosyncline). At many localities, 

however, the predominantly argillaceous rocks of 

this central belt have been thrust eastward onto the 

carbonate and quartzite belt.

At Trail Creek the shale and chert belt attains a 

width of 3-8 km (2-5 mi) along the crest of the Pioneer 

Mountains, which separate the Wood River and Big 

Lost River drainages northeast of Ketchum, Idaho 

(Umpleby and others, 1930; Dover, 1969, pi. 1, fig. 32).

LITHOLOGY AND STRUCTURE

The area of the Phi Kappa Formation is complicated by thrust faults and some granitic intrusions, 

as shown by Umpleby, Westgate, and Ross (1930, p. 

64-66, pi. 1) and by Dover (1969, fig. 32, pi. 1). The 

stratigraphic succession within some of the thrust 

plates is relatively undeformed.

East of Trail Creek gorge the Phi Kappa Formation forms much of the upper plate of the Park Creek 

thrust and consists of about 200 m (650 ft) of black 

shale that in its lower half has thin interbeds of gray 

quartzite (fig. 2). The base of the Phi Kappa lying 

above the Park Creek thrust is marked by a massive 

quartzite that has several thin interbeds of shale 

very rich in graptolites. The Phi Kappa appears to be 

thicker in the lower plate of the Park Creek thrust 

than in the upper plate and has conspicuous quartzite that is characterized by distinctive banding.

The argillaceous parts of the Phi Kappa consist of 

dark-gray to black shale, slate, and argillite. Many of 

these beds have yielded Ordovician graptolites. 

Much of the shale is silty, and some thin discrete 

beds of cherty shale alternate rhythmically with 

partings of more fissile shale, particularly in the 

upper part of the section. The Phi Kappa contains 

almost no limestone, except for several thin and 

slabby beds of dark-gray fine-grained limestone.

Small folds in about a 6-m (20-ft) interval in the 

upper part of the section that includes localities 

69ICt 42 and 69ICt 41 (fig. 2) suggest minor displace-
ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

|S 

o

a

II81

Elevation approximately 8,600 ft

Calcareous siltstone. Thinly laminated and nonfossiliferous, 

more than 100 ft thick. Massive, forms cliffs

 Slack siliceous shale with rare shale partings. Nonfossiliferou

69ICt 21 Dark-gray silty shala

Dark-gray to black thin-bedded siliceous shale, nearly chert. 

Thin interbeds of calc-silicate hornfels with rosettes of 

wollastonite. Unit weathers yellow to orange brown. 

Forms resistant knob

69ICt 31 Hard gray silty shale. Uncleaved. Bed 7 in. thick

ith rare shale

Calc-silicate hornfels. Forms ledge 

69ICt 32 Black siliceous shale 

- Marble

Covered interval

Resistant black siliceous shale, nearly chert,

partings 

Siliceous shale with abundant shale partings. Mineralized,

punky, and full of holes where iron pyrite(?) leached out 

ark-gray siliceous shale, nearly chert. Mineralized and unfossiliferous. Forms prominent rib near top of hill 

overed interval 

Marble

69ICt 41 Poorly exposed dark-gray siliceous shale with abundant shale 

Fault partings. Minor folding. Graptolites tectonically stretched 

Dark-gray siliceous shale with abundant shale partings. Forms 

prominent rib with steep folds. Beds 4-6 in. thick

> shale, nearly chert

69ICt 42 

69ICt 43 

69ICt 44, 69ICt 45

— Black siliceo 

691 Ct 51

69ICt 52

69ICt 54 Dark-gray limestone, weathering medium gray. Slabby and

69IC1 55 fine grained

69ICt 56, 69IC1 57

Covered interval

Silty shale with shale partings

Covered interval

Silty shale inter-bedded with shale. Contains abundant poorly

preserved biserial graptolites 

69lCt 64 Almost black silty shale, weathering light gray. Cleaved.

Forms 3-ft-high ledge 

69ICt 65

69ICt 63

Light-gray siliceous shale

691 Ct 66 

69ICt 71

Mostly shale. Minor siliceous shale interbeds

Dark-gray shale, weethering light gray. Fractures into large 

slabs up to 6 in. across. Forms slab-covered slope

69ICt 74, 69ICt 75

69ICt 77 Slaty shale. Iron oxide stained and cleaved

IllCt 79j" ln bold outcr°P

69ICt 81 Bold outcrop 2 ft thick

Iron-oxide-rich silty shale. Forms soft slope

69ICt 82 Slaty shale in bold outcrop

Covered interval,forms narrow ravine

Slaty shale, nearly argillite. Probably slightly baked

69ICI 83 

69ICt 84 

69ICt 86

Dark-gray slaty shale with argillitic sheen. Poorly exposed

69ICt 88 

69IC1 91

Terminology of Umpleby and others, 1930

II

62ICn 53*5

Shale irrterbedded with sandstone in 2-6- 

in.-thick beds. Somewhat hornfelsed. 

Graptolites scarce: Unit is approximately half shale, half sandstone

62ICn 533, 62ICn 472

Quartzite, medium to thinly interbedded 

with dark-gray argillite

Laminated siltstone and argillite

Dark-gray argillite

Glossograptus (float) 

Quartzite

FEET METERS 

20-i

- S

Fine-grained quartzite 

62ICn 511 Slate with limestone lenses

Recrystallized quartz arenite. Fine-grained, 

medium gray,and massive

Tetragraptus, Phyllograptus, Didymograptus 

<-Park Creek thrust 

^_ _ .^y Dicellograptus, Orthograptus, Dicranograptus

^ Elevation approximately B.400 ft

FIGURE 2. Stratigraphic column of .the upper plate of the Park Creek thrust in the Trail Creek section, showing zonal sequence and

location of graptolite collections. See figure 1 for location.
GRAPTOLITE ZONES AND THEIR CORRELATION

ment along a bedding plane fault. The marble lying 

approximately 3 m (10 ft) above 69ICt 41 may thus be 

a structural repetition of the same limestone lying 

directly above locality 69ICt 55. This fault would also 

help explain the presence of Pleurograptus linearis 

Zone graptolites in locality 69ICt 41, structurally 

above the Zone of Dicellograptus ornatus.

Overlying the Ordovician part of the Phi Kappa 

Formation is a section about 16 m (50 ft) thick of 

dark-gray shale that includes several thin beds of 

calc-silicate marble. These beds have yielded Silurian graptolites and were elsewhere assigned to the 

Trail Creek Formation (Umpleby and others, 1930). 

This 16-m thick shale is included in the Phi Kappa 

Formation (J. H. Dover and R. J. Ross, Jr., oral 

commun.). The contact between Ordovician and 

Silurian parts of the Phi Kappa Formation is concealed in a small saddle on the west side of the peak 

(elevation 8832 ft) separating Summit Creek from 

Park Creek (fig. 1). Discontinuous outcrops in the 

saddle (fig. 2, locality 69ICt 32) have yielded early 

but not earliest Silurian graptolites. There is no 

evidence of a stratigraphic break, but folding in the 

uppermost Ordovician beds suggests faulting along 

the contact with the Silurian part of the Phi Kappa. 

Also, the presence of wollastonite-bearing calcsilicate hornfels and marble in the lower part of the 

Silurian beds indicates that thermal metamorphism 

may have locally obscured any earliest Silurian 

graptolite faunas. This metamorphism is probably 

related to emplacement of a quartz monzonite pluton 

or associated dikes centered along Summit Creek. At 

the contact with these intrusive rocks, the Phi Kappa 

is a flinty argillite commonly spotted with incipient 

growth of porphyroblasts.

The uppermost unit within the measured section is 

marked by a massive cliff-forming unit of mediumgray thinly laminated nonfossiliferous siltstone. 

This siltstone, unlike the quartzitic rocks lower in the 

section, is readily distinguished in the field by its 

calcareous cement and in thin section by its high 

proportion (15-20 percent) of angular feldspar 

grains. The base of this siltstone, at least within our 

measured section, is a logical place to draw the upper 

contact of the Phi Kappa Formation.

Locally, especially in the Upper Ordovician part of 

the Phi Kappa Formation, the beds are fairly strongly cleaved and folded. A microscopic lineation in 

these beds has developed where bedding is intersected by cleavage. Graptolites in these beds are 

technically deformed, and thus rhabdosomes lying 

parallel to the lineation on the average are thinner 

than those lying at right angles to the lineation. 

Thecal counts are lowest for specimens of a particular species lying parallel to the lineation and greatest 

for those lying at right angles to the lineation. 

Rhabdosomes making angles between 0° and 90° 

with the lineation have intermediate thecal counts. 

Tectonic deformation of the graptolites, where recognized, has been taken into account in their 

descriptions.

The Phi Kappa Formation in a section only 200-m 

(650 ft) thick appears to represent an unbroken succession of sedimentation ranging from late Early 

Ordovician through latest Ordovician. Similarly 

thin graptolite shale successions occur in other parts 

of the Cordillera as well as in other mobile belts. The 

condensed nature of the graptolitic shales and their 

lithologic similarity to modern deep-sea siliceous 

sediments suggest that they are pelagic sediments 

deposited mainly below the carbonate-compensation 

depth (Churkin, 1974).

GRAPTOLITE ZONES 

AND THEIR CORRELATION

Ten named graptolite zones have been recognized 

in the Trail Creek section (figs. 1, 2). These zones 

have been established on the basis of diagnostic 

assemblages of graptolite species as they occur in the 

Trail Creek section; we have not merely applied the 

zonal schemes worked out elsewhere. The reader 

probably will recognize the names of some of our 

zones (Climacograptus bicornis, Dicellograptus 

ornatus) as being the same as those of nearly 

equivalent zones in other sections and provinces. 

This was done where the zones were nearly equivalent and the appropriate name-giver was present 

at Trail Creek. The Trail Creek zones with unfamiliar names did not contain the name-giver of 

any corresponding "equivalent" zone.

A description of each zone and its correlation with 

some of the better known graptolite successions of 

the Pacific faunal province, as well as with the 

British sequence, follows in ascending order (see also 

fig. 3). The correlations in figure 3 were made by 

directly comparing the faunal assemblages from 

Trail Creek with the faunal assemblages listed by 

other authors. There was no consideration of how 

each author correlated his own section with the 

others. Therefore there are differences in correlation 

between the scheme in figure 3 and the correlation 

schemes of other authors.

LOWER ORDOVICIAN SERIES

Zone of Didymograptus protobifidus.—This zone 

contains the oldest fauna in the Trial Creek section 

(figs. 1, 2). It is characterized by several species of 

Tetragraptus, abundant Phyllograptus anna, P. ilic-
ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

SYSTEM

SILURIAN

 1

<5 w

0>

 a 

 a

i

o

European stage

Wenlockian

Llandoverian

Great Britain

Elles and Wood, 1901-18; 

Bulman, 1970; Toghill, 1970

Cyrtograptus ellesae

Cyrtograptus 

linnarsoni

Cyrtograptus rigidus

Monograptus 

riccartonensis

Cyrtograptus 

murchisoni

Cyrtograptus 

centrifugus

Monoclimacis 

crenulata

Monoclimacis 

griestoniensis

Monograptus crispus

Monograptus 

turriculatus

Rastrites maximus

Monograptus 

sedgwickii

Monograptus 

convolutus

Monograptus 

gregarius

Monograptus 

cyphus to 

Glyptograptus 

persculptus

Trail Creek, 

Idaho

7

Cyrtograptus 

•p

Monograptus 

convolutus

Western Canada

Jackson and Lenz, 1962 

Jackson, 1964

Cyrtograptus 

cf.C. 

murchisoni

Monograptus 

spiralis

Monograptus 

turriculatus

Monograptus 

sedgwickii 

and 

Monograptus 

convolutus

Monograptus 

millepeda

Monograptus 

cyphus and 

Diplograptus 

modestus

Marathon 

region. 

Texas

Berry, 1960

Australia

Thomas, 1960

Northeastern 

U.S.S.R.

Obut and Sobolavskaya, 

1973

Australian stege

c 

.5

o •v

LJJ

C 

0}

_O'55 

^

FIGURE 3. Correlation of graptolite sequences in western North America, Great Britain, Australia, arid the U.S.S.R. The correlations 

on this chart were made by directly comparing individual faunal assemblages from Trail Creek with the faunal assemblages listed 

by the respective authors.

ifolius, P. ilicifolius major, Didymograptus protobifidus, and D. extensus. Isograptus is rare, as are the 

multibranched Goniograptus and Loganograptus 

(table 1). 

This zone is only represented by one collection

from a 7-ft (2.1-m) thick bed that was not searched so 

meticulously as the rest of the section. Thus, it is 

possible that two or more distinguishable horizons 

are lumped together in this collection. 

The association of Tetragraptus amii, T. quadri-
GRAPTOLITE ZONES AND THEIR CORRELATION

SYSTEM

ORDOVICIAN

.£ 

1

<o Q. 

a

D

9)

 o 

 o'•s

9) 

|

European stage

c 

.2

en

-C

<

Caradocian

 o c

C 03 CD ~ 

_i 'v

Llanvirnian

Arenigian

Great Britain

E lies and Wood, 1901-18; 

Bulman, 1970; Toghill, 1970

Dicellograptus 

anceps

Dicellograptus 

complanatus

Pleurograptus 

linearis

Dicranograptus 

clingani

Diplograptus 

multidens

Nemagraptus 

gracilis

Glyptograptus 

teretiusculus

Didymograptus 

murchisoni

Didymograptus 

bifidus

Didymograptus 

hirundo

' Isograptus 

gibberulus

i

s <u

«

V

3 Didymograptus 

a, nitidus

I 

1 

Q

Didymograptus 

deflexus

Trail Creek, 

Idaho

Dicellograptus 

ornatus

Pleurograptus 

linearis

Climacograptus 

tubuliferus

Passage beds -

Climacograptus 

bicornis

Nemagraptus

Glossograptus 

hincksii

Isograptus

Didymograptus 

protobifidus

Western Canada

Jackson and Lenz, 1962 

Jackson, 1964

Dicellograptus 

ornatus

Orthograptus 

quadrimucronatus

7

Dicranograptus 

clingani 

f

Nemagraptus 

gracilis

Glyptograptus 

euglyphus

Cardiograptus 

crawfordi 

Cryptograptus 

schaferi 

Tylograptus 

geniculiformis 

flexilis

Isograptus 

caduceus

Pseudotrigonograptus 

ensiformis

Skiagraptus 

gnomonicus 

Isograptus 

caduceus var.

Didymograptus 

protobifidus

Didymograptus 

extensus

Marathon 

region. 

Texas

Berry, 1960

Dicellograptus 

ornatus

Orthograptus 

quadrimucronatus

Orthograptus 

amplexicaulis

Climacograptus 

bicornis and 

Nemagraptus 

gracilis

Glyptograptus cf . 

G. teretiusculus

Paraglossograptus 

tentaculatus

Isograptus 

caduceus

Didymograptus 

bifidus

Didymograptus 

protobifidus

Tetragraptus 

fruticosus 

3 to 4 branched

Tetragraptus 

fruticosus 

4 branched

Australia

Thomas, 1960

D4

03

D2

D1

Ya2

Yal

Ca3

Ca2

Ca 1

Ch2

Ch 1

Be 4

Be 3

Be 2

Be1

Northeastern 

U.S.S.R.

Obut and Sobolevskaya, 

1973

Dicellograptus 

ornatus and 

Climacograptus 

supernus

Orthograptus 

quadrimucronatus

Diplograptus 

ingens 

wellingtonensis 

and 

Dicranograptus 

clingani

Climacograptus 

peltifer

Nemagraptus 

gracilis

Glyptograptus 

teretiusculus

Paraglossograptus 

tentaculatus 

and 

Cardiograptus 

crawfordi

Cardiograptus 

morsus

Australian stage

Bolindian

Eastonian

Gisbornian

Darriwilian

Yapeenian

Castlemanian

Chewtonian

Bendigonian

FIGURE 3. Continued.
ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

TABLE 1. Distribution and zonal ranges of Ordovician graptolite genera and species in the lower part of the Phi Kappa Formation,

Trail Creek section

[ x, present, in unknown abundance; r, rare; f, frequent; c, common; a, abundant]

Series 

Zone

Collection

No.

Loganograptus logani pertenuis Ruedemann 

Tetragraptus amii Elles and Wood .. ... .. ...... . . . ....

T. quadribrachiatus (Hall) . . . ... 

Phyllograptus anna Hall . . .... . .. .. 

P. anna ? Hall ...... ... .... . 

P. anna prolatus n. subsp ... ..... . . ... . .. 

P. ilicifolius Hall .. ... .. .. .. ... . 

P. ilicifolius major Ruedemann . . ...... 

Didymograptus extensus (Hall) ..... . . .... ...

D. cf. D. gemmmus (Hisinger) 

D. protobifidus Elles . . ..... ...

Isograptus aff. /. caduceus caduceus (Salter) . . .... 

1. cf. /. caduceus imitatus Harris ... 

/. aff. /. victoriae Harris 

/. cf. /. victoriae lunatus (Harris) ....... 

/. aff. /. victorias lunatus (Harris) ....

7. sp

Nemagraptus cf N. gracilis remotus Elles and Wood 

,V. sp . ... 

Dicranograptus cf. D. brevicaulis Elles and Wood .. 

D. contortut- Ruedemann 

D. cf. D. kirki Ruedemann 

D nicholsoni nicholsoni Hopkinson . . ...... 

1) cf D nicholsuni nicholsoni Hopkinson 

D. cf D spimfer Elles and Wood 

Dicdlograptus ditaricatus bicurvatus Ruedemann 

D sextant, exilm Elles and Wood 

D sp ... . ..... 

GluHsograptus hmcksii hincksii (Hopkinson) 

Cr\pttjgraptus trienrrus (Carruthers) 

C sp 

Diplngraptub sp 

Amplt'x.(>graptui> perexcavatus (Lapworth) 

A B p 

Climacugraptui, himrnis bicornis (J. Hall) 

(. bicornis tridenintuis Lapworth . . 

(' brei if, Elles and Wood 

( cf riilddlt'nsi* Harris 

( sp 

(.jlyptagraptu-: ci G. euglyphus euglyphus (Lapworth) 

(/ ci (1 i uai\rth us pygmaeus (Ruedemann) 

(i ti rt I'/U.M uiu - 'Hisinger) 

C, " M) 

1, -[' - - < In . i# rap; a,- amplexicaulis (Hall) 

(> ,\\i <> c (hi-aratus calcaratus (Lapworth) 

O C'U/KI.'U '.t.s acutus Elles and Wood 

t > all i. I'dui cf. subsp acutus Elles and Wood 

' ;>ag> 'i <us pageanus Elles and Wood 

( "f. a tshitfteldi (Hall) 

.' -.me"' imacugraptus cf P. rnodvstuf (Ruedemann) 

/ M 'wrenbergi sc/iarc/?hcr^i (Lapworth) 

P. sp 

/* utiingraptuti harkneimi (Nicholson) 

/. i ' sp 

/,< 'I'Ograptus gemitzianuy Hall

/-; ,n

Lower Ordovician

Didymograptus 

protobifidus

1C

O

S3 ^

r 

r

r 

f 

f 

a

f 

f 

c 

f 

r 

r 

a 

f

r

r 

r

Isograptus

62ICn 485

a

f

r 

c

62ICn 521

K

A

Middle Ordovician

Nemagraptus

(M 

(Nm 

C 

O

S3 to

""x "

x

";-

62ICn 531

a

$1C

d

S3 to

<

"^

>

a

S3 to

--;-

K

62ICn 472

r

r

r 

c

r

 *

COm 

O

(Nto

~\

62ICn 535

X

69ICt 93

r

f

f 

c

a

f

r

r

r

f

Climacograptus 

bicornis

69ICt 92

r

f

c

r

r

f

c

69ICt 91

a

c

f

f

f

r

69ICt 88

f

r

a

r

c

r 

r

r

c

r

69ICt 87

r

a

c

c

69ICt 856, 

r 

r

r

r

f

f

f

c

r 

r

f

r

brachiatus, Didymograptus extensus, D.gracilis, D. 

protobifidus and Phyllograptus anna suggests correlation with the Arenigian Zone of Didymograptus 

extensus in Great Britain (Elles and Wood, 1901-18).

The presence of T. amii, T. quadribrachiatus, Phyllograptus ilicifolius, P. anna, D. extensus, D.protobifidus and Isograptus cf. /. victoriae lunatus also 

indicates correlation with the Early Ordovician
GRAPTOLITE ZONES AND THEIR CORRELATION

Zones of Didymograptus protobifidus and Didymograptus bifidus of Texas (Berry, 1960).

Zone of Isograptus.—This interval is poorly represented in the Trail Creek and Little Fall Creek 

sections (tables 1, 2). It is distinguished mainly by 

the presence of isograptids that occur at higher 

horizons than the D. protobifidus Zone in other areas 

(Australia, Texas). The fauna of this zone is sparse 

and includes abundant Didymograptus extensus 

and rare, small phyllograptids.

About 50 ft (15.2 m) of shale in the Trail Creek 

section is assigned to this zone (collections 62ICn 485 

and 62ICn 521 in table 1; fig. 2). Two collections 

(69ICn 491 and 62ICn 492) from a 125-ft (38.1-m) 

shale interval in the Little Fall Creek section (table 2; 

fig. 4) are also believed to belong to this zone.

This interval is difficult to correlate with sequences 

elsewhere because of the unusual association of D. 

extensus, T. amii, Isograptus victoriae maximodivergens, Isograptus caduceus imitatus, Pseudisograptus dumosus, and Maeandrograptus tau. If only 

the isograptid species are considered, the zone can be 

correlated with the upper Castlemanian to lower 

Yapeenian horizons of Australia (Thomas, 1960).

TABLE 2. Distribution and zonal ranges of Ordoviciangraptolite 

genera and species in the Phi Kappa Formation, Little Fall 

Creek section

[ x , present in unknown abundance; r, rare; f, frequent; c, common; a, abundant; 

questioned where identification uncertain]

Zone .. .. ...... .... .. ..... . ...

Collection 

No. ..... . ... .... . ..... .... . .

D. sp - .. ......... . ................ ..................... . ... . .....

Isograptus caduceus imitatus Harris .......... . 

I. victoriae maximodiuergens (Harris) .. 

/. sp . .... ... ... ... .

Nemagraptus sp

Dicranograptus cf. D. brevicaulis Elles 

and Wood ... .. ... ...... ........... ....... .. .... . . .

Dicellograptus sextans sextans (Hall) . ... ...

Glossograptus hincksii hincksii (Hopkinson)

Glyptograptus euglyphus (Lapworth) ..... 

G. sp ...... ....... .. .. . ...... ..... . ..... ... .

Reteoeraotus eeinitzianus Hall . .. . .....

Lower 

Ordovician

Isograptus

O5

0

oqto

f

f 

r

f

IN

0)

G 

O 

oato

X

*

Middle Ordovician

Glossograptus 

hincksii

TO 

O5

0

ato

r?

c

r

f 

r'

3

a 

o

oqto

f

f

IO 

O5

o

C-J

to

:

X

X

X

Nemagraptus

%

O 

S to

r

f 

r

f

r 

a 

f

r

2 81

I III

t I I I L

Fault

Elevation approximately 9,500 ft

Dark-gray argillite

62ICn 496 

62ICn 495"

Silty shale and siltstone. 

Medium dark grey, 

weathering light gray

62ICn494*

'Collection not precisely 

located within interval

62ICn 493*

Limestone

Isograptus, Didymograptus, Tetragraptus 

(not collected)

Shale FEET METERS 

50 -.-15

62ICn 492

62ICn 491

Elevation approximately 9,120 ft

Covered interval

FIGURE 4. Stratigraphic column of the Little Fall Creek section, 

showing zonal sequence and location of graptolite collections. 

See figure 1 for location.
10 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

MIDDLE ORDOVICIAN SERIES

Zone of Glossograptus hincksii.—This zone is 

characterized by a very sparse fauna of biserial scandent genera and marks the first appearance of the 

long-ranging species Glossograptus hincksii and 

Cryptograptus tricornis. It also marks the first 

appearance of Climacograptus and Glyptograptus 

(table 2).

The zone is represented by three collections (62ICn 

493, 62ICn 494, and 62ICn 495) from 200 ft (61 m) of 

siltstone in the Little Fall Creek section (fig. 4). The 

Isograptus Zone occurs stratigraphically below this 

interval, and the Nemagraptus Zone above it.

The Trail Creek section (fig. 2) contains about 50ft 

(15.2 m) of nearly barren siltstone and silty shale 

between the Zones of Isograptus and Nemagraptus.

Because the sparse fauna of this zone consists only 

of Glossograptus hincksii, Cryptograptus tricornis, 

Climacograptus sp., and Glyptograptus sp., correlation with other sequences is difficult. It seems to be 

about the same age as the Glyptograptus teretiusculus Zone of Great Britain and the upper part of the 

Darriwilian of Australia.

Zone of Nemagraptus.—The fauna of this zone is 

more varied and abundant than that of the preceding 

zone. It is characterized by Nemagraptus and the 

first appearance of Dicranograptus and Dicellograptus in association with biserial scandent genera 

(tables 1, 2).

At least 220 ft (67 m) of interbedded quartzite and 

argillite in the Trail Creek section is assigned to this 

zone (collections 62ICn 552, 62ICn 531-535, 62ICn 

472, and 69ICt 93 (table 1; fig. 2)). One collection 

(62ICn 496) from the Little Fall Creek section is also 

assigned to this zone (fig. 4).

The association of Nemagraptus, Dicellograptus 

sextans exilis, Cryptograptus tricornis, Climacograptus bicornis, Glyptograptus teretiusculus, Orthograptus calcaratus acutus, and Reteograptus geinitzianus (table 1, 2) indicates correlation with the 

Zone of Nemagraptus gracilis in Great Britain (Elles 

and Wood, 1901-18), the Zone of N. gracilis in the 

northern Yukon, Canada (Jackson and Lenz, 1962), 

and the Zone of N. gracilis in Texas (Berry, 1960).

Zone of Climacograptus bicornis.—This zone 

marks the last appearance of Cryptograptus tricornis and Glossograptus hincksii in the Trail Creek 

section (fig. 1). Dicranograptus contortus and Dicranograptus nicholsoni are common, as is Orthograptus calcaratus cf. subsp. acutus. C. bicornis 

bicornis and C. bicornis tridentatus are present in 

small numbers, and there are scattered occurrences 

of Dicellograptus throughout the zone (table 1). 

About 40 ft (12.2 m) of slaty shale with six collections 

in the Trail Creek section is included in this zone.

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12 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

The presence of Corynoides calicularis, Cryptograptus tricornis, Glossograptus hincksii, Dicranograptus nicholsoni nicholsoni, Climacograptus bicornis bicornis, C. bicornis tridentatus, Pseudoclimacograptus scharenbergi scharenbergi, Glyptograptus cf. G. euglyphus euglyphus, and Lasiograptus harknessi suggests a correlation with the 

British Caradocian Zone of Diplograptus multidens. 

The D. multidens Zone differs from the underlying JV. 

gracilis Zone in having D. nicholsoni and abundant 

Corynoides, as well as D. multidens (Riva, 1972). The 

association of Corynoides, Cryptograptus tricornis, 

G. hincksii, D. nicholsoni, C. bicornis, Amplexograptus perexcavatus, and G. cf. G. euglyphus euglyphus indicates a correlation with the Gisbornian 

stage of Australia (Thomas, 1960).

Passage beds.—This interval has yielded eight 

collections from 90 ft (27.4 m) of shale (fig. 2) but with 

only scattered occurrences of any one species (table 

3). The fauna consists mainly of a few dicellograptids, the last of the dicranograptids, and a few new 

species of Orthograptus (particularly the spined 

species). Orthograptus amplexicaulis is present in 

some horizons, but it does not occur throughout the 

interval and is not restricted to this interval.

Zone of Climacograptus tubuliferus.—This zone is 

characterized by the presence of Dicellograptus alector, Climacograptus caudatus, and C. tubuliferus. 

Orthograptus amplexicaulis is abundant in certain 

horizons, and Orthoretiolites is restricted to this zone 

(table 3). It is represented by ten collections from 82 ft 

(25 m) of shale in the Trail Creek section (fig. 2).

The association of Climacograptus caudatus, C. 

tubuliferus, Orthograptus amplexicaulis, and O. amplexicaulis pauperatus allows only a tentative correlation with the British Zone of Dicranograptus 

clingani (Elles and Wood, 1901-18) because the C. 

tubuliferus Zone lacks dicranograptids. Both the 

Orthograptus quadrimucronatus Zone and the O. 

amplexicaulis Zone of the Marathon, Tex., succession (Berry, 1960) contain species found in the C. 

tubuliferus Zone at Trail Creek. Common species 

include C. caudatus, C. tubuliferus, O. quadrimucronatus quadrimucronatus, and Reteograptus pulcherrimus for the O. quadrimucronatus Zone, and C. 

caudatus, P. scharenbergi, O. amplexicaulis, and R. 

pulcherrimus for the O. amplexicaulis Zone. The 

presence of C. caudatus, C. tubuliferus, O. amplexicaulis, O. amplexicaulis pauperatus, O. calcaratus 

acutus, and O. quadrimucronatus suggests a correlation with the upper Eastonian of Australia 

(Thomas, 1960).

UPPER ORDOVICIAN SERIES

Zone of Pleurograptus linearis.—Only 8 ft (2.4 m) 

of siliceous shale is included in this very distinctive 

zone (fig. 2). Its characteristic species include Leptograptus demissus n.sp., Climacograptus cf. C. mohawkensis, Climacograptus tubuliferus, and Climacograptus uncinatus. C. uncinatus is an excellent 

indicator of this zone. P. linearis occurs in only one 

horizon in the middle of the zone (table 3).

The association of P. linearis, Climacograptus 

tubuliferus, Leptograptus cf. L. flaccidus arcuatus, 

and Orthograptus amplexicaulis cf. subsp. socialis 

suggests correlation with the P. linearis Zone of the 

Hartfell Shales in Great Britain (Elles and Wood, 

1901-18; Toghill, 1970). In the Marathon, Tex., succession, the Orthograptus quadrimucronatus Zone 

contains the following species in common with the 

Trail Creek P. linearis Zone: C. minimus, C. tubuliferus, Orthograptus cf. O. calcaratus basilicus, and 

Leptograptus (Berry, 1960). The Trail Creek zone can 

be correlated with the lower and middle Bolindian 

Stage of Australia (Thomas, 1960) on the basis of the 

presence of P. linearis, C. uncinatus, Orthograptus 

amplexicaulis, O. amplexicaulis abbreviatus, and O. 

calcaratus basilicus. O. quadrimucronatus, a species 

common to this interval in Great Britain, Texas, 

Australia, and the northern Yukon, is not present in 

the P. linearis Zone at Trail Creek. Here it is restricted to the underlying C. tubuliferus Zone and the 

passage beds.

Zone of Dicellograptus ornatus.—The characteristic species of this zone are Dicellograptus cf. D. ornatus minor, Climacograptus longispinus hualross, C. 

hastatus, and in the upper part of the zone, C. pacificus pacificus and-D. ornatus ornatus. Orthograptus 

amplexicaulis abbreviatus and O. a. cf. subsp. abbreviatus occur in the lower part and the upper part of 

the zone, respectively (table 3). It is difficult to determine the true thickness of this zone because a P. 

linearis Zone fauna was either infolded or faulted 

into the middle of it (table 3; fig. 2).

This zone can be correlated with the Dicellograptus anceps Zone of the Hartfell Shales in Great 

Britain (Toghill, 1970) because of the presence in 

both of D. ornatus, O. amplexicaulis abbreviatus, 

and local subspecies of Climacograptus longispinus. 

The presence of D. ornatus and O. amplexicaulis 

abbreviatus indicates correlation with the D. ornatus Zone in the northern Yukon, Canada (Jackson 

and Lenz, 1962), the D. ornatus Zone in Texas (Berry, 

1960), and the Bolindian of Australia (Thomas, 

1960).
SYSTEMATIC DESCRIPTIONS 13

SILURIAN SYSTEM

Zone of Monograptus convolutus.—Most of the 

lower Llandoverian is missing in the Trail Creek 

section, and the middle Llandoverian monograptids 

occur directly above the Upper Ordovician D. ornatus Zone. These include Monograptus convolutus, 

Monograptus lobiferus, Monograptus sedgwickii, 

and M. cf. Monograptus decipiens decipiens. 

Climacograptus cf. C. scalaris is also present (table 

4). This zone is represented by two collections (69ICt 

32 and 69ICt 31) from a 12-ft (3.7-m) interval of 

siliceous shale (fig. 2).

The association of M. convolutus, M. lobiferus, M. 

sedgwickii, M. cf. M. decipiens, Monograptus cf. M. 

argutus argutus, Monograptus cf. M. leptotheca, 

and Petalograptus minor suggests a correlation with 

the British Llandoverian Zone of M. convolutus 

(Elles and Wood, 1901-18) and the Zone of M sedgwickii and M. convolutus in the northern Yukon 

(Jackson and Lenz, 1962).

Zone of Cyrtograptus.—This zone, containing the 

youngest fauna in the section (collection 69ICt 21), 

includes such upper Llandoverian and lower Wenlockian species as Cyrtograptus laqueus and Cyrtograptus cf. C. grayae, and the middle Wenlockian 

species Cyrtograptus rigidus rigidus and Monograptus cf. M. flemingii flemingii (table 4). In the 

northern Yukon, cyrtograptids occur mainly in the 

Cyrtograptus cf. C. murchisoni zone, (Jackson and 

Lenz, 1962) although the range of C. laqueus extends 

down into the M. spiralis Zone (Jackson and Etherington, 1969). In Australia, Cyrtograptus indicates 

an Eildonian age, as does M. flemingii.

SYSTEMATIC DESCRIPTIONS 1

Class GRAPTOLITHINA

Order GRAPTOLOIDEA

Suborder DIDYMOGRAPTINA

Family DICHOGRAPTIDAE

Genus Loganograptus Hall, 1868

Loganograptus logani pertenuis Ruedemann

Plate 1, figure 1

Loganograptus logani mut. pertenuis Ruedemann,

1904, New York State Mus. Mem. 7, p. 633, pi. 9,

fig. 5. 

Loganograptus logani mut. pertenuis Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 287, pi. 45,

fig. 14 (not figs. 15, 16). 

Loganograptus logani mut. pertenuis Ruedemann.

'Bulman's (1970) terminology and classification have been used in the following 

descriptions.

TABLE 4.—Distribution and zonal ranges of Silurian graptolite 

genera and species in the Phi Kappa Formation, Trail Creek 

section

[r, rare; f, frequent; a, abundant]

Series ..... ..... .. . ......... ..... .. .....

Collection 

No. .............................. .................. ......................

Climacograptus cf. C. scalaris (Hisinger) ............ 

C.sp ....................................................................................

Glyptograptus cf. G. tamariscus (Nicholson) ......

Msp ..................................................................................

C. rieidus rieidus TullberK ..........................................

_.. . Middle Lower Silunan si,urian

Monograptus 

convolutus

69ICt 32

f 

f 

r

f

f 

f

69ICt 31

f

f

a 

f

f 

f

Cyrtograptus

69ICt 21

a

f 

f 

r 

r 

f

Berry, 1960, Texas Univ. Pub. 6005, p. 50, pi. 12,

fig. 5. 

Loganograptus logani (Hall). Churkin, 1963, Am.

Assoc. Petroleum Geologists Bull., v. 47, p. 1617,

pi. 1, fig. 18.

Diagnosis: According to Berry (1960, p. 50) this subspecies is like the typical form of L. logani except that 

it is much thinner (0.2-0.3 mm wide) and has thecae 

that are more closely spaced (10-12 thecae per centimeter).

Discussion: This subspecies greatly resembles 

Brachiograptus etaformis Harris and Keble but can 

be distinguished from it by the presence of fourth 

order branches, which do not occur in Brachiograptus.

Figured specimen: USNM 189095.

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail 

Creek, Idaho. Zone of Paraglossograptus tentaculatus (Hallograptus etheridgei) (Fort Pena Formation) in the Marathon region, west Texas (Berry, 

1960). Deepkill Shale in New York (Ruedemann, 

1947). Lower member of Valder Formation, HD 

Range, Nevada (Riva, 1970).

Genus Goniograptus M'Coy, 1876 

Goniograptus geometricus Ruedemann

Plate 6, figure 5 

Goniograptus geometricus Ruedemann, 1904, N.Y.
14 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

State Mus. Mem. 7, p. 627-630, text-figs. 43-45,

pi. 7, figs. 5, 10-20. 

Goniograptus geometricus Ruedemann, 1947, Geol.

Soc. America Mem. 19, p. 296-297, pi. 48, figs.

16-21.

Diagnosis: According to Ruedemann (1947, p. 297), 

the sicula is long and narrow, averaging 3.5 mm in 

length, and the first two thecae grow from it near its 

apex. These two thecae are about 2 mm long, as are 

the next four thecae, which form the four secondorder branches diverging at angles of 120°-150°. The 

four zigzagging main stipes bear branches at nearly 

right angles to their general direction of growth. The 

thecae are tubular and narrow, three times as long as 

wide, and number eight per centimeter.

Discussion: This species resembles Goniograptus 

perflexilis Ruedemann but differs from it by the 

shorter length of its sicula and thecae and the more 

compact arrangement of its branches. G. perflexilis 

has a sicula 4 mm long and six to seven thecae per 

centimeter.

Figured specimen: USNM 189114.

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail 

Creek, Idaho. Didymograptus bifidus Zone, Deepkill 

Shale, New York (Ruedemann, 1947).

Genus Tetragraptus Salter, 1863 

Tetragraptus pseudobigsbyi Skevington

Plate 1, figure 7 

Graptolithus bigsbyi J. Hall, 1865, Canada Geol.

Survey, Canadian Organic Remains, Dec. 2, pi. 16,

figs. 22-24, 27, 28. 

Tetragraptus pseudobigsbyi Skevington, 1965, Bull.

Geol. Instn. Univ. Uppsala, v. 43, p. 8-9, fig. 2.

Diagnosis: According to Skevington (1965, p. 9), 

the second order stipes are highly reclined and 

straight or slightly flexed. They have a mature dorsoventral width of 2.9-3.2 mm (including the apertural 

denticles) and 12-13 thecae per centimeter.

T. pseudobigsbyi differs from Tetragraptus bigsbyi (Hall) in having a less scandentrhabdosome, less 

strongly overlapping thecae with more prominent 

denticles, and generally straight, parallel-sided 

stipes.

Discussion: Most of the Idaho specimens have 

somewhat narrower stipes (2.5 mm wide) and slightly more thecae per centimeter (12-14) than Skevington's type specimen. The figured specimen (pi. 1, fig. 

7) is more reclined than the others; it has wider stipes 

(2.7 mm) and fewer thecae (11 per centimeter).

Figured specimen: USNM 189134.

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail

Creek, Idaho. Levis Shale in Quebec (Hall, 1865). 

Zone of Didymograptus hirundo (Ontikan limestone) 

in Oland, Sweden (Skevington, 1965).

Genus Phyllograptus Hall, 1858

Phyllograptus anna prolatus n. subsp.

Plate 1, figures 2, 3

Description; The rhabdosome is small, relatively 

long, and measures 4.5-5.4 mm wide at its widest 

point near the level of th 101 , gradually decreasing in 

width thereafter. The maximum observed length is 

16.5 mm. The thecae are curved and number 12-14 

per centimeter. The thecal apertures are concave and 

mucronate.

Discussion: This subspecies closely resembles P. 

anna Hall except for the length of the rhabdosome. 

Hall (1865, p. 124) stated that the rhabdosome of P. 

anna is up to 7/16 inch (11 mm) long, whereas this 

subspecies is as much as 16.5 mm long. P. anna 

longus Ruedemann is about 10-14 mm long but much 

narrower (3.5 mm wide) than this subspecies. P. 

anna ultimus Ruedemann is only 3.6 mm long and 

has 22 thecae per centimeter. P. annaprolatus can be 

distinguished from all other phyllograptids by its 

small size and closely spaced thecae.

Holotype: USNM 189143.

Figured specimens: USNM 189143, USNM 189144.

Occurrence: Zones of Didymograptus protobifidus 

and Isograptus (Phi Kappa Formation; collections 

62ICn 511,62ICn 491,62ICn 492), Trail Creek, Idaho.

Phyllograptus ilicifolius major Ruedemann

Plate 1, figure 4 

Phyllograptus ilicifolius var. major Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 318-319,

pi. 53, fig. 21. 

Phyllograptus ilicifolius Hall. Churkin, 1963, Am.

Assoc. Petroleum Geologists Bull., v. 47, p. 1617,

pi. 1, fig. 14. 

Phyllograptus ilicifolius var. major Ruedemann.

Ross and Berry, 1963, U.S. Geol. Survey Bull. 1134,

p. 83, pi. 3, fig. 17.

Diagnosis: According to the original description, 

this form resembles P. ilicifolius ilicifolius Hall in 

general outline and the characters of its thecae but is 

larger in size and has more closely spaced thecae. 

The rhabdosome is 18.5 mm long and 8.5 mm wide, 

with 14-12 thecae per centimeter. Ross and Berry 

(1963) described specimens of P. ilicifolius major 

from the Phi Kappa Formation as being about 25 mm 

long and 10 mm wide, with 18-10 thecae per centimeter and narrowly pointed proximal portions. Our 

specimens are as much as 32 mm long, 12-14 mm 

wide, and have 18-12 thecae per centimeter.
SYSTEMATIC DESCRIPTIONS 15

Discussion: P. ilicifolius grandis Elles is similar to 

our specimens in size but has much more widely 

spaced thecae (11-13 per cm). P. typus Hall is narrower and has only 9-10 thecae per centimeter. P. 

griggsi Ross and Berry is only 9-6 mm wide and has 

13-11 thecae per centimeter. 

Figured specimen: USNM 189145. 

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail 

Creek, Idaho. Sarbach Formation, western Canada 

(Ruedemann, 1947).

Genus Didymograptus M'Coy 1851

Didymograptus cf. D. geminus (Hisinger)

Plate 1, figure 9

Prionotus geminus Hisinger, 1840, Lethaea Suecica,

Supplementus Secundum.

Didymograptus murchisoni var. geminus (Hisinger). Elles and Wood, 1901-18, Palaeontographical 

Soc., Mon. British Graptolites, p. 40-41, text-figs. 

25a-d, pi. 3, figs. 2a-j.

Diagnosis: According to Elles and Wood (1901-18, 

p. 40-41), this species has stipes which widen more 

rapidly than those of D. murchisoni (Beck) and has a 

more slender and more rounded proximal region. The 

stipes are generally divergent throughout most of 

their length, diverging initially at angles of about 

90° and then curving so as to form an angle of 20°- 

30°. They widen abruptly from about 0.9 mm to 2.5 

mm. The sicula is about 2.6 mm long. Thecae number 

12 per centimeter, and they curve so that their angle 

of inclination increases from 45° initially to 55° at 

the aperture.

Discussion: The Idaho specimens are only about 

0.6 mm wide proximally and have shorter siculae 

(about 1.0 mm long) than those described above. 

They resemble D. bifidus (Hall) in general appearance, but bifidus has 15-13 thecae per centimeter and 

stipes with straight dorsal margins. Ruedemann's 

(1947, pi. 54, figs. 33-35) figured specimens of D. 

murchisoni geminus are considerably wider than 

those from Trail Creek. 

Figured specimen: USNM 189146. 

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail 

Creek, Idaho. Zone of Didymograptus murchisoniin 

Great Britain (Elles and Wood, 1901-18).

Jjidymograptus protobifidus Elles 

Plate 1, figures 5, 8

Didymograptus protobifidus Elles, 1933, Great Britain Geol. Survey Summary of Progress for 1932, 

p. 98, figs. 1-4.

Didymograptus protobifidus Elles. Ripper, 1937,

Proc. Royal Soc. Victoria, v. 49 (N.S.), pt. 2, p. 154-

156, figs. 1A-C, 2A,B, 3. 

Didymograptus protobifidus Elles. Berry, 1960,

Texas Univ. Pub. 6005, p. 63-64, pi. 8, figs. 5-9. 

Didymograptus protobifidus Elles. Churkin, 1963,

Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1617, pi. 1, fig. 12. 

Didymograptus protobifidus Elles. Ross and Berry,

1963, U.S. Geol. Survey Bull. 1134, p. 90, pi. 4,

figs. 6, 12.

Diagnosis: According to the original description, 

the pendant stipes of this species are 10-20 mm long, 

narrow proximally, and widen to 1.3 mm distally. 

The stipes diverge at angles of about 20°-25° or are 

subparallel. Thecae number 13 per centimeter and 

they overlap one-half and are inclined at a low but 

variable angle to the stipe axis.

Discussion: The Idaho specimens closely resemble 

Elles' holotype (1933, fig. 1) but appear to be slightly 

narrower (0.5-1.2 mm wide) than specimens figured 

by Berry (1960, pi. 8, figs. 5-9) and Ross and Berry 

(1963, pi. 4, figs. 6, 12), and they have 14 thecae per 

centimeter. D. protobifidus strongly resembles Didymograptus artus Elles and Wood, which has 18-19 

thecae per centimeter.

Figured specimens: USNM 189147, USNM 189148.

Occurrence: Zone of D. protobifidus (Phi Kappa 

Formation, collection 62ICn 511), Trail Creek, Idaho. 

Zone of D. protobifidus (Marathon Limestone) in the 

Marathon region of west Texas and the Deepkill 

Shale in New York (Berry, 1960). Bendigonian and 

Chewtonian Stages (Lower Ordovician) in Australia 

(Thomas, 1960). Zones of Didymograptus extensus 

and Didymograptus hirundo (Skiddaw Slates) in 

Great Britain (Elles, 1933).

Genus Isograptus Moberg, 1892

Isograptus aff. I. victoriae Harris

Plate 2, figure 9

Isograptus victoriae Harris. Cooper, 1973, Palaeontology, v. 16, pt. 1, p. 59.

Diagnosis: The rhabdosome is V-shaped, with 

nearly straight stipes about 10 mm long and a 

conspicuous nema 10 mm long. The sicula is 3.7 mm 

long, 0.7 mm wide at its aperture, and its supradorsal length is 1.9 mm. There are 14 thecae per 

centimeter, with slightly concave, denticulate apertural margins, and 5 pendent thecae in the proximal 

region. The stipes are 2.0 mm wide proximally and 

attain a maximum width of 2.5 mm at about theca 7. 

Discussion: There is only one mature specimen of 

this form in our collections, and it is not completely 

preserved. It has the general characters of I. victoriae but does not match any of its subspecies
16 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

(Cooper, 1973) in details. It appears to be about the 

same size as I. victoriae victoriae Harris, which 

differs in being U-shaped and having only 11 thecae 

per centimeter.

Figured specimen: USNM 189111.

Occurrence: Zone of Didymograptus protobifidus 

(Phi Kappa Formation, collection 62ICn 511), Trail 

Creek, Idaho. I. victoriae ranges from Castlemanian 

to Daniwilian in Australasia (Cooper, 1973).

Isograptus sp. 

Plate 1, figure 6

Discussion: The illustrated specimen (pi. 1, fig. 6) is 

the only one of its kind in the collection and is 

probably an immature form. Its sicula is 5.0 mm long 

and 0.8 mm wide at the aperture and extends 2.0 mm 

above the dorsal edge of the stipes. The stipes are 2.0 

mm wide proximally, narrowing to 1.5 mm distally, 

and are about 3.5 mm long.

Figured specimen: USNM 219001.

Occurrence: Zone of Isograptus (Phi Kappa Formation, collection 62ICn 521), Trail Creek, Idaho.

Genus Maeandrograptus Moberg, 1892 

Maeandfograptus tau Harris

Plate 7, figure 1 

Maeandrograptus tau Harris, 1933, Proc. Royal Soc.

Victoria, v. 46, pt. I, p. 107, pi. 6, figs. 5A-D,

text-figs. 47-49.

Maeandrograptus tau Harris. Cooper, 1973, Palaeontology, v. 16, pt. 1, p. 89-90, text-figs. 24a, b, d. 

Maeandrograptus tau Harris. Beavis and Beavis,

1974, Proc. Royal Soc. Victoria, v. 86, pt. 2, p. 212,

figs. 20a-b.

Diagnosis: According to the original description, 

the rhabdosome is usually small (less than 1 cm long) 

and consists of two short stipes diverging at an angle 

of 180° or slightly more. The long sicula measures 5- 

6 mm in length. The thecae overlap one-half to onethird and have sigmoidally curved ventral margins 

and concave apertures.

Figured specimen: USNM 164425.

Occurrence: Zone of Isograptus (Phi Kappa Formation; collection 62ICn 491), Trail Creek, Idaho. 

Castlemanian Ca 3 to Yapeenian Ya 1 in Victoria, 

Australia (Beavis and Beavis, 1974).

Family CORYNOIDIDAE 

Genus Corynoides Nicholson, 1867 

Corynoides calicularis Nicholson

Plate 2, figure 12 

Corynoides calicularis Nicholson, 1867a, Geol.

Mag., v. 4., p. 108, pi. 7, figs. 9-11. 

Corynoides gracilis Ruedemann, 1947, Geol. Soc.

America Mem. 19, p. 361, pi. 58, figs. 34-37a. 

Corynoides gracilis mut. perungulatus Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 361, pi. 58,

figs. 38-46. 

Corynoides calicularis Nicholson. Strachan, 1949,

Geol. Mag., v. 86, p. 156-157, text fig. 1. 

Corynoides calicularis Nicholson. Berry, 1960,

Texas Univ. Pub. 6005, p. 68-69, pi. 15, fig. 5 

Corynoides calicularis Nicholson. Ross and Berry,

1963, U.S. Geol. Survey Bull. 1134, p. 95-96, pi. 5,

figs. 32-33.

Discussion: The figured specimen from collection 

69ICt 88 fits the description of Cornyoides calicularis given by Strachan (1949, p. 156). Several other 

specimens from the same collection, though morphologically identical, are smaller than the figured 

specimen, measuring only 6.0-7.5 mm long and 0.4- 

0.5 mm wide. Riva (1974b, p. 36) has suggested that 

such smaller forms should be included in the species 

C. calicularis.

Figured specimen: USNM 189084.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collection 69ICt 88), Trail Creek, 

Idaho. C. bicornis Zone (Vinini Formation), Simpson 

Park Range, Nevada (Ross and Berry, 1963). Zones 

of Nemagraptus gracilis and C. bicornis (Woods 

Hollow Shale), Marathon region, west Texas (Berry, 

1960). Normanskill Shale in New York,Glenogle 

Shale in British Columbia (Ruedemann, 1947). Zones 

of Climacograptus wilsoni and Dicranograptus 

clingani (Moffat Shales), Great Britain (Strachan, 

1949). The Beauceville (Magog) Slates and the Quebec City Formation of Quebec and the lower Snake 

Hill Formation of New York (Riva, 1974b).

Family NEMAGRAPTIDAE 

Genus Leptograptus Lapworth, 1873

Leptograptus demissus n. sp. 

Plate 2, figure 1; plate 7, figures 2, 3 

Description: The stipes are long, narrow, and 

broadly curved, diverging from the sicula at angles 

of less than 180° (slightly declined) initially. The 

stipes are as much as 11 cm long but commonly are 

much shorter (about 2 cm or less). The width of the 

stipes at the first thecal aperture is 0.2 mm, at the 

fifth thecal aperture 0.3 mm, increasing gradually to 

a maximum of 0.8 mm. The thecae are of characteristic leptograptid type, numbering 8V2-10 per centimeter initially and 10-11 per centimeter distally. The 

sicula is prominent, 1.2-1.7 mm long.

Discussion: The most distinguishing feature of 

this species is the angle of divergence of the stipes. 

The curvature of the stipes gives the rhabdosome the 

gross appearance of 180° of divergence, but actually
SYSTEMATIC DESCRIPTIONS 17

the initial mode of growth is slightly declined. The 

stipes of the figured specimen (pi. 2, fig. 1) diverge at 

an angle of 135°. Although Bulman (1970, p. V121) 

listed one of the generic characters of Leptograptus 

as "slightly reclined" stipes, this species is certainly a Leptograptus. It differs from L. flaccidus 

flaccidus (Hall) in having thinner stipes and a 

different angle of divergence. L. flaccidus macer 

Elles and Wood has more widely spaced thecae (8-6 

per centimeter). L. capillaris (Carruthers) is similar 

in appearance to this species but differs in having a 

maximum width of only 0.5 mm and more strongly 

curved stipes.

Holotype: USNM 189085.

Figured specimens: USNM 189085, USNM 164427.

Occurrence: Zone of Pleurograptus linearis (Phi 

Kappa Formation, collections 69ICt 61, 69ICt 59, 

69ICt 58, 69ICt 57, 69ICt 56), Trail Creek Idaho.

Leptograptus n. sp.? 

Plate 2, figure 3

Description: The stipes are straight after their 

initial flexure near the sicula. They are 0.5 mm wide 

and bear about 12 thecae per centimeter. The sicula is 

2.5 mm long.

Discussion: The Idaho specimens have more thecae per centimeter, a longer sicula, and straighter 

stipes than Leptograptus flaccidus flaccidus (Hall). 

They have narrower stipes, a longer sicula, and more 

thecae per centimeter than Leptograptus validus 

validus Elles and Wood. However, only a few specimens were collected and they are not well enough 

preserved to merit a new name.

Figured specimen: USNM 189086.

Occurrence: Zone of Climacograptus tubuliferus 

(Phi Kappa Formation, collection 69ICt 71), Trail 

Creek, Idaho.

Genus Pleurograptus Nicholson, 1867

Pleurograptus linearis linearis (Carruthers)

Plate 2, figure 4

Cladograpsus linearis Carruthers, 1858, Proc. Royal

Phys. Soc. Edinburgh, v. 1, p. 467, fig. 1. 

Pleurograpsus linearis (Carruthers). Nicholson,

1867b, Geol. Mag., v. 4, p. 258, pi. XI, figs. 1-5. 

Pleurograptus linearis (Carruthers). Elles and Wood,

1901-18, Palaeontographical Soc., Mon. British

Graptolites, p. 119-121, pi. 16, fig. 7, pi. 17, fig. 1. 

Pleurograptus linearis (Carruthers). Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 375, pi. 61,

figs. 29-30. 

Pleurograptus linearis (Carruthers). Strachan, 1969,

Bull. British Mus. (Nat. Hist.) Geology, v. 17, no. 4,

p. 186-187, text figs la-c, pi. 2. 

Pleurograptus linearis (Carruthers). Toghill, 1970,

Bull. British Mus. (Nat. Hist.) Geology, p. 20, pi. 10,

figs. 2, 4.

Discussion: The Idaho specimens are fragmentary 

but still exhibit the characteristic branching pattern 

of P. linearis. The stipes are 0.5-0.7 mm wide and 

have 9-10 thecae per centimeter. Elles and Wood 

(1901-18, p. 120) gave the count as 7-8 thecae per 

centimeter.

Figured specimen: USNM 189087.

Occurrence: Zone of Pleurograptus linearis (Phi 

Kappa Formation, collection 69ICt 59), Trail Creek, 

Idaho. Upper part of Utica Shale, New York State 

(Ruedemann, 1908). The Exploits Group of Newfoundland (Bergstrom and others, 1974). Zone of P. 

linearis (Hartfell Shales), Scotland (Toghill, 1970).

Family DICRANOGRAPTIDAE

Genus Dicranograptus Hall, 1865

Dicranograptus contortus Ruedemann

Plate 2, figure 6; plate 7, figure 4 

Dicranograptus contortus Ruedemann, 1908, N.Y.

State Mus. Mem. 11, p. 337-338, pi. 23, fig. 9,

text-figs. 275-278. 

Dicranograptus contortus Ruedemann, 1947, Geol.

Soc. America Mem. 19, p. 389, pi. 65, figs. 14-36. 

Dicranograptus contortus Ruedemann. Churkin,

1963, Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1617, pi. 1, fig. 4. 

Dicranograptus contortus Ruedemann. Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 109,

pi. 7, figs. 9, 14.

Diagnosis: According to Ruedemann (1908), the 

rhabdosome is very small and consists of a short 

biserial portion, which is 3 mm long and 0.8 mm 

wide, and two relatively thick uniserial, uniformly 

wide (0.7 mm) branches which in compressed specimens are intricately contorted. The biserial portion 

contains 5 thecae on either side, and the uniserial 

branches have 18-20 thecae per centimeter. The 

proximal end has a long virgella and conspicuous 

lateral spines.

Discussion: The Idaho specimens have biserial 

portions measuring 2.0-2.8 mm long and 0.7-1.2 mm 

wide. The stipes are commonly 0.6 mm wide. Ruedemann (1947, pi. 65, figs. 19-25) illustrates several 

specimens from Fall Creek, Hailey quadrangle, 

Idaho, which appear to be closely similar to those 

illustrated here.

Figured specimens: USNM 189088a, b, USNM

219006.

Occurrence: Zones of Nemagraptus and Climacograptus bicornis (Phi Kappa Formation, collections 

69ICt 93, 69ICt 92, 69ICt 91, and 69ICt 88), Trail 

Creek, Idaho. Normanskill Shale in New York and
18 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

correlative units in Quebec and Newfoundland (Ruedemann, 1947). Zone of Nemagraptus gracilis 

(Woods Hollow Shale), Marathon region, Texas 

(Berry, 1960). Upper member of Valder Formation, 

HD Range, Nevada (Riva, 1970).

Dicranograptus cf. D. kirki Ruedemann

Plate 2, figure 7 

Dicranograptus kirki Ruedemann, 1947, Geol. Soc.

America Mem. 19, p. 391, pi. 66, figs. 1-4. 

Dicranograptus kirki Ruedemann. Ross and Berry,

1963, U.S. Geol. Survey Bull. 1134, p. 109-110,

pi. 7, figs. 1-4, 6, 21.

Diagnosis: According to Ross and Berry (1963, p. 

109), who re-examined Ruedemann's type material, 

the biserial part of the rhabdosome is approximately 

3.5 mm long and 0.8-1.0 mm wide and is composed of 

three to five thecae on each side. The uniserial stipes 

diverge initially and then bend distally with the 

convex side ventral, so that they become subparallel 

or approach each other slightly. Thecae number 

eight to nine per centimeter.

Discussion: Our specimens are difficult to identify 

positively because they do not have a sufficient 

length of uniserial stipe preserved. The biserial 

portions are 3.0 mm long and about 0.8 mm wide.

Figured specimen: USNM 189089.

Occurrence: Zone of Climacograptus bicornis and 

passage beds (Phi Kappa Formation, collections 

69ICt 86, 69ICt 83), Trail Creek, Idaho. Zone of 

Orthograptus amplexicaulis (Saturday Mountain 

Formation), Bruno Creek, Bayhorse quadrangle, 

Idaho (Ross and Berry, 1963). Tiser Limestone and 

Agort Chert, HD Range, Nevada'(Riva, 1970).

Dicranograptus nicholsoni nicholsoni Hopkinson 

Plate 2, figures 10, 11

Dicranograptus nicholsoni Hopkinson, 1870, Geol.

Mag., v. 7, p. 357, pi. 16, fig. 3. 

Dicranograptus nicholsoni Hopkinson. Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 171-173, pi. 25, figs, la-h,

text-figs. 108a-e. 

Dicranograptus nicholsoni Hopkinson. Bulman,

1944-47, Palaeontographical Soc. Mon., Caradoc

Graptolites in Laggan Burn, p. 36-40, text-figs.

18-20, pi. 3, figs. 1-11. 

Dicranograptus nicholsoni Hopkinson, Harris and

Thomas, 1955, Mining Geol. Jour. (Victoria), v. 5,

no. 6, p. 43, figs. 22, 23. 

Dicranograptus nicholsoni Hopkinson. Berry, 1960,

Texas Univ. Pub. 6005, p. 78, pi. 17, fig. 6. 

Dicranograptus nicholsoni Hopkinson. Churkin,

1963, Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1617, pi. 1, fig. 3 (in part).

Dicranograptus nicholsoni Hopkinson. Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 110-

111, pi. 7, fig. 5.

Discussion: There is much variation in the dimensions of this species from one locality to another 

(see Ross and Berry, 1963, p. 110, for summary). The 

Idaho specimens agree most closely with the description given by Bulman (1944-47, p. 36-37). They have 

biserial portions 6.2-9.5 mm long and widening from 

0.8-1.0 mm wide proximally to 2.0-3.0 mm wide near 

the point of bifurcation. The uniserial stipes are 

about 1.0-1.5 mm wide and have 9-10 thecae per 

centimeter.

Figures specimens: USNM 189090, USNM 189091.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collections 69ICt 92, 69ICt 91, 

69ICt 88,69ICt 87, and 69ICt 86), Trail Creek, Idaho. 

Zone of Orthograptus amplexicaulis (Maravillas 

Chert), Marathon region, Texas (Berry, 1960). Sams 

Spring Formation (Caradocian), Toquima Range, 

Nevada (Kay, 1962). Zones of Nemagraptus gracilis 

to Dicranograptus clingani (Glenkiln Shales, Hartfell Shales) in Great Britain (Elles and Wood, 1901- 

18). Upper Ordovician from near the Wellington 

River, Victoria, Australia (Harris and Thomas, 

1955).

Genus Dicellograptus Hopkinson, 1871 

Dicellograptus alector Carter

Plate 3, figures 8, 12, 13, 17 

Dicellograptus morrisi Hopkinson. Churkin, 1963,

Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1619, pi. 2, fig. 24.

Dicellograptus alector Carter, 1972, Jour. Paleontology, v. 46, no. 1, p. 46-47, text-figs. 2A,G, PI. 1,

figs. 9, 11, 12, 15.

Diagnosis: According to the original description, 

the stipes are as long as 2.5 cm, somewhat flexed, 

increasing gradually from a width of 0.3-0.4 mm at 

their origin to a maximum width of 1.5 mm, and they 

form an axial angle of 70°-90°. The sicula is 2.0 mm 

long, and short, slender lateral spines and virgella 

are present. The thecae have introverted apertural 

margins opening within excavations and number 8- 

11 per centimeter. The axil is square.

Discussion: The Idaho specimens generally have 

an axial angle of around 45°, but this may be due to 

tectonic distortion. D. alector is distinguished from 

other species of Dicellograptus by the squareness of 

its axil and its well-defined thecae.

Figured specimens: USNM 189092, USNM 189093 

a, b, USNM 189094.

Occurrence: Zones of Climacograptus tubuliferus 

and Pleurograptus linearis (Phi Kapa Formation, 

collections 69ICt 75, 69ICt 74, 69ICt 73, 69ICt 71,
SYSTEMATIC DESCRIPTIONS 19

69ICt 66, 69ICt 61), Trail Creek, Idaho, Zone of Dicranograptus clingani (Jacks Peak Formation of 

Churkin and Kay, 1967), Independence Range, 

Nevada (Carter, 1972).

Dicellograptus cf. D. angulatus Elles and Wood

Plate 3, figure 1 

Dicellograptus angulatus Elles and Wood, 1901-18,

Palaeontographical Soc., Mon. British Graptolites, p. 149-150, text-fig. 93a-c, pi. 21, fig. 4.

Diagnosis: According to the original description, 

the stipes of D. angulatus are 1-2 cm long, very 

slender (0.4 mm wide, maximum), and straight, 

diverging at about 270°-300° from a conspicuous 

sicula (1.5 mm long). The virgella and lateral spines 

are slender but conspicuous, and the axil is square. 

The thecae number 10-8 per centimeter and have 

slightly introverted apertures and gently curving 

free ventral walls.

Discussion: The figured specimen (pi. 3, fig. 1) is 

the only whole rhabdosome of this species in the 

Idaho collections. The remainder are proximal fragments consisting of a sicula and the first four to six 

thecae. The poor state of preservation of the specimens does not allow determination of the thecal 

characteristics and, therefore, more precise identification. However, they do closely resemble D. 

angulatus in the extreme narrowness and straightness of the stipes, the angle of divergence, the square 

axil, and the length of the sicula.

Figured specimen: USNM 189105.

Occurrence: Zone of Climacograptus tubuliferus 

(Phi Kappa Formation, collections 691 Ct 63-65), 

Trail Creek, Idaho. Zones of Climacograptus peltifer 

and Climacograptus wilsoni (Glenkiln and Hartfell 

shales) Scotland (Elles and Wood, 1901-18). Zone of 

Orthograptus quadrimucronatus (Road River Formation) in Yukon Territory, Canada (Jackson and 

Lenz, 1962).

Dicellograptus divaricatus bicurvatus Ruedemann 

Plate 2, figure 5

Dicellograptus divaricatus var. bicurvatus Ruedemann, 1908, N.Y. State Mus. Mem. 11, p. 300, 

text-fig. 216, pi. 18, fig. 8.

Dicellograptus divaricatus var. bicurvatus Ruedemann, 1947, Geol. Soc. America Mem. 19, p. 379, 

pi. 62, figs. 31-35, pi. 63, fig. 4.

Dicellograptus divaricatus var. bicurvatus Ruedemann. Ross and Berry, 1963, U.S. Geol. Survey 

Bull. 1134, p. 104, pi. 6, figs. 5, 9. 

Diagnosis: According to Ross and Berry (1963), the

stipes are 0.75 mm wide proximally, widening to 1

mm distally, and have 12-10 thecae per centimeter.

The stipes diverge at an angle greater than 270°, and

2-5 mm from the sicula they bend abruptly, so that 

their subsequent divergence is lessened.

Discussion: The distinguishing feature of this subspecies is the shape of its rhabdosome—the acutely 

rounded axil and the abrupt bend in the stipes. It 

differs from Dicellograptus elegans elegans (Carruthers) in having straight free ventral walls, whereas those of D. e. elegans are" strongly curved. The 

Idaho specimens agree with the above description in 

all respects except for being slightly narrower proximally (0.5 mm).

Figured specimen: USNM 189096.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collections 69ICt 92, 69ICt 88), 

Trail Creek, Idaho. Normanskill Shale, New York, 

and Womble Shale, Arkansas (Ruedemann, 1947).

Dicellograptus cf. D. elegans elegans (Carruthers)

Plate 2, figure 2 

Didymograpsus elegans Carruthers, 1868, Geol.

Mag., v. 5, p. 129, pi. 5, figs. 8a,d. 

Dicellograpsus elegans (Carruthers). Hopkinson,

1871, Geol Mag., v. 8, p. 24-25, pi. 1, fig. 3a-e. 

Dicellograptus elegans (Carruthers). Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 159-160, text-figs. lOOa-d,

pi. 23, figs. 2a-e. 

Dicellograptus elegans (Carruthers). Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 380-381,

pi. 63, fig. 1. 

Dicellograptus elegans (Carruthers). Strachan, 1969,

Bull. British Mus. (Nat. Hist.) Geology, v. 17, no. 4,

p. 187-188, text-figs. 2a,b, pi. 3, fig. 1.

Diagnosis: According to Elles and Wood (1901-18, 

p. 159), the stipes are 7-10 cm or more in length, with 

pronounced curvature and an approximately uniform width of 0.8-1.0 mm. The sicula is long (2-3 

mm), and the virgella and lateral spines are always 

well developed. The thecae number 10-8 per centimeter and have strongly curved free ventral walls. 

Thecal apertures are strongly introverted, opening 

in a deep excavation which occupies about one-half 

the width of the stipe. In the proximal region, the 

stipes grow nearly parallel to each other, forming a 

square axil, then make an abrupt bend, lessening 

their subsequent divergence.

Discussion: Dicellograptus elegans elegans 

resembles Dicellograptus divaricatus bicurvatus 

Ruedemann in its curving stipes but differs by 

having a square axil and more abrupt curvature of 

the stipes. D. divaricatus bicurvatus has a more 

V-shaped axil and more gently curved stipes. The 

Idaho specimen (pi. 2, fig. 2) has even more contorted stipes (possibly due to tectonic deformation) 

than a normal D. e. elegans. It also does not have the
20 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

characteristic prominent virgella and lateral spines; 

this could be due to an accident of preservation.

Figured specimen: USNM 189097.

Occurrence: Passage beds (Phi Kappa Formation, 

collection 69ICt 79), Trail Creek, Idaho. Sams Spring 

Formation (Caradocian) of Kay (1962), Toquima 

Range, Nevada (Kay,^1962). Zones of Dicranograptus clingani and Pleurograptus linearis (Hartfell 

Shales), Great Britain (Elles and Wood, 1901-18).

Dicellograptus cf. D. elegans rigens Elles and Wood 

Plate 2, figure 8

Dicellograptus elegans var. rigens (Lapworth MS)

Elles and Wood, 1901-18, Palaeontographical Soc.,

Mon. British Graptolites, p. 161, text-fig. 101a,b,

pi. 23, fig. 3.

Diagnosis: According to Elles and Wood (1901-18, 

p. 161), this subspecies has the same characteristics 

as D. elegans elegans but differs in having almost no 

curvature in the stipes. They are characteristically 

straight and rigid.

Discussion: The Idaho specimen has straight 

stipes measuring 0.5 mm wide proximally and 

widening to 1.0 mm distally. The thecae are typical 

for D. e. elegans—strongly introverted, with very 

curved free ventral walls—and they number six in 5 

mm (12 per cm). The lateral spines are 0.8 mm long. 

What appears to be a membrane is present within the 

axil extending up to the level of the second thecal 

apertures. Elles and Wood (1901-18, p. 160) mentioned a similar membrane occurring in D. e. 

elegans.

Figured specimen: USNM 189098.

Occurrence: Zone of Climacograptus tubuliferus 

(Phi Kappa Formation, collection 69ICt 74), Trail 

Creek, Idaho. Zone of Pleurograptus linearis in Great 

Britain (Elles and Wood, 1901-18).

Dicellograptus cf. D. ornatus minor Toghill 

Plate 3, figures 11, 14, 15, 16

Dicellograptus complanatus ornatus Elles and 

Wood, 1901-18, Palaeontographical Soc., Mon. 

British Graptolites, p. 140-141, pi. 20, fig. 2c. 

Dicellograptus ornatus minor Toghill, 1970, Bull. 

British Mus. (Nat. Hist.) Geology, p. 16-17, textfigs. 3c-g, pi. 6, figs. 5-7.

Diagnosis: According to Toghill (1970, p. 16), this 

very slender dicellograptid has introverted thecae 

numbering 11-12 per centimeter. The stipes are 

straight, 0.2 mm wide proximally widening to a 

maximum of 0.5 mm, and enclosing a square axial 

region with an axial angle of 100°-120°. The sicula 

and virgella are conspicuous, and the first two thecae 

bear very short apertural spines.

Discussion: The Idaho specimens are similar in 

size and appearance to D. ornatus minor but differ in 

having a smaller axial angle (45°-70°) and a less 

prominent sicula. There is a certain amount of 

tectonic distortion involved in these measurements, 

but it is doubtful that undistorted specimens would 

have axial angles of 100°-120°.

Figured specimens: USNM 189099, USNM 189100, 

USNM 189101, and USNM 189102.

Occurrence: Zones of Pleurograptus linearis and 

Dicellograptus ornatus (Phi Kappa Formation, collections 69ICt 59, 69ICt 58, 69ICt 55,69ICt 54,69ICt 

45, 69ICt 44, 69ICt 43), Trail Creek, Idaho. Zone of 

Dicellograptus anceps (Hartfell Shales), Scotland 

(Toghill, 1970).

Dicellograptus n.sp.(?) 

Plate 3, figures 2, 3; plate 6, figure 2

Description: The sicula, though not commonly 

preserved, has been measured as 2.2 mm long. The 

stipes are long, curving, and cross each other once 

and possibly twice. They diverge initially and then 

curve inward, so that they cross each other approximately 1 cm above the level of the first thecae. They 

are 0.5 mm wide proximally, increasing to a maximum width of 1.0 mm, and have 11-12 thecae per 

centimeter. The thecal apertures are extremely introverted and probably introtorted. The free ventral 

walls of the thecae are curved and the proximal 

thecae often bear small mesial spines. The axil is 

square and the axial angle is approximately 70°- 

80°.

Discussion: Dicellograptus n.sp.(?) resembles Dicellograptus intortus Lapworth in the crossing habit 

of its stipes (as illustrated by Elles and Wood, 1901- 

18, pi. 20, fig. 4b) but differs in the characters of its 

thecae and axial region. D. intortus has thecae with 

straight free ventral walls and only slightly introverted apertures; its axial angle is very small, and 

the axil is V-shaped. D. affinis T. S. Hall, D. gurleyi 

Lapworth, and D. caduceus Lapworth are similar to 

Dicellograptus n.sp.(?) in having crossing branches. 

D. affinis differs from Dicellograptus n.sp.(?) in 

having long and stout lateral spines similar to those 

of D. ornatus ornatus Elles and Wood (in fact, Ross 

and Berry (1963, p. 104) included one of T. S. Hall's 

original illustrated specimens in their synonomy of 

D. ornatus); D. gurleyi differs in having a greater 

maximum width (1.25 mm), a rounded axil, and a 

prominent, thickened virgella (see Lapworth's original manuscript figure in Ruedemann, 1908, textfig. 223); and D. caduceus differs in having a much 

more acute axial angle (20° or more),thecae that are 

more closely spaced (14-12), and the first crossing of
SYSTEMATIC DESCRIPTIONS 21

the stipes less than 5 mm above the level of the first 

thecae.

According to J. Riva (personal commun., 1975), 

dicellograptid stipes are not rigid and can twist in 

many different directions. Therefore, because crossing stipes may not be a diagnostic feature, and 

because the specimens are few in number and not 

especially well preserved, they have not been named.

Holotype: USNM 189106.

Figured specimens: USNM 189103, USNM 189104, 

USNM 189106.

Occurrence: Passage beds (Phi Kappa Formation, 

collections 69ICt 76-77), Trail Creek, Idaho.

Suborder GLOSSOGRAPTINA

Family GLOSSOGRAPTIDAE

Genus Glossograptus Emmons, 1855

Glossograptus hincksii hincksii (Hopkinson)

Plate 3, figure 4

Diplograptus hincksii Hopkinson, 1872, Geol. Mag.,

vol. 9, p. 507-508, pi. 12, fig. 9. 

Glossograptus hincksii (Hopkinson). Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 309-312, text-figs. 205 a-f,

pi. 33, figs. 2a-j. 

Glossograptus hincksii (Hopkinson). Berry, 1960,

Texas Univ. Pub. 6005, p. 71, pi. 12, fig. 9a. 

Glossograptus hincksii (Hopkinson). Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 99,

pi. 5, figs. 25, 26.

Discussion: The Idaho specimens closely fit the 

description given by Elles and Wood (1901-18, p. 309- 

10). G. h. hincksii is distinguished from other glossograptids by the spacing of its thecae (16-10 per cm), 

the shape and size of its rhabdosome (2-4 cm long 

with rounded proximal end, 3 mm wide), and the 

appearance of its spines.

Figured specimen: USNM 189107.

Occurrence: Zones of Glossograptus hincksii and 

Climacograptus bicornis (Phi Kappa Formation, 

collections 62ICn 493-496, 69ICt 92, 69ICt 91, and 

69ICt 88), Trail Creek, Idaho. Zones of Paraglossograptus tentaculatus (P. etheridgei) to C. bicornis 

(Vinini Formation, Valmy Formation, Palmetto 

Formation), Nevada (Ross and Berry, 1963). Zones of 

Paraglossograptus tentaculatus (P. etheridgei) (Fort 

Pefia Formation) and Nemagraptus gracilis (Woods 

Hollow Shale), in the Marathon region, Texas (Berry, 

1960). Petes Summit Formation and Sams Spring 

Formation, Toquima Range, Nevada (Kay, 1962). 

Valder Formation and Agort Chert, HD Range, 

Nevada (Riva, 1970). Zones of N. gracilis to Climacograptus wilsoni (Glenkiln and Hartfell Shales)

Great Britain (Elles and Wood, 1901-18). Zone of N. 

gracilis (Road River Formation) in Yukon Territory, 

Canada (Jackson and Lenz, 1962). Road River Formation in east-central Alaska (Churkin and Brabb, 

1965).

Family CRYPTOGRAPTIDAE 

Genus Cryptograptus Lapworth, 1880 

Cryptograptus tricornis (Carruthers)

Plate 3, figure 5

Diplograpsus tricornis Carruthers, 1858, Proc. Royal Phys. Soc. Edinburgh, v. 1, p. 468, fig. 2. 

Cryptograptus tricornis (Carruthers). Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 296-298, text-figs. 200a-j,

pi. 32, figs. 12a-d. 

Cryptograptus tricornis (Carruthers). Ruedemann,

1908, N.Y. State Mus., Mem. 11, p. 443-448, pi. 28,

figs. 1-3. 

Cryptograptus tricornis (Carruthers). Bulman,

1944-47, Palaeontographical Soc. Mon., Caradoc

Graptolites in Laggan Burn, p. 29-36, pi. II, figs. 1-

8, text-figs. 14-17. 

Cryptograptus tricornis (Carruthers). Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 446, pi. 76,

figs. 23-33. 

Cryptograptus tricornis (Carruthers). Berry, 1960,

Texas Univ. Pub. 6005, p. 70, pi. 15, fig. 9. 

Cryptograptus tricornis (Carruthers). Churkin, 1963,

Am. Assoc. Petroleum Geologists Bull., v. 47, p.

1617, pi. 1, fig. 9. 

Cryptograptus tricornis (Carruthers). Ross and

Berry, 1963, U.S. Geol. Surv. Bull. 1134, p. 97-98,

pi. 5, fig. 27. 

Cryptograptus tricornis (Carruthers). Strachan,

1969, Bull. British Mus. (Nat. Hist.) Geology, p.

194-195, text-fig. 3c, pi. 4, figs. 4-6.

Discussion: This well known and easily recognized 

graptolite is distinguished by the three proximal 

spines present in scalariform view.

Figured specimen: USNM 189108.

Occurrence: Zones of Nemagraptus and Climacograptus bicornis (Phi Kappa Formation, collections 

69ICt 86-88, and 69ICt 91-93), Trail Creek, Idaho. 

Zones of Glyptograptus teretiusculus to C. bicornis 

(Vinini Formation, Valmy Formation, Toquima 

Formation), Nevada (Ross and Berry, 1963). McAfee 

Quartzite (Middle Ordovician), northern Independence Range, Nevada (Churkin and Kay, 1967). 

Petes Summit Formation and Sams Spring Formation of Kay (1962), Toquima Range, Nevada. Upper 

member, Valder Formation of Riva (1970), HD 

Range. Zones of Nemagraptus gracilis and C. bicornis (Woods Hollow Shale), Marathon region, Texas
22 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

(Berry, 1960). Normanskill Shale in New York, 

Womble Shale in Arkansas, Womble Shale in Oklahoma, and Glenogle Shale in British Columbia 

(Ruedemann, 1947). Lower Caradoc Zones 9-10 (Road 

River Formation) in east-central Alaska (Churkin 

and Brabb, 1965). Zone of Didymograptus extensus 

and zones of Didymograptus bifidus through Dicranograptus clingani in Great Britain (Elles and Wood, 

1901-18).

SuborderDIPLOGRAPTINA

Family DIPLOGRAPTIDAE

Genus Diplograptus M'Coy, 1850

Diplograptus sp.

Plate 3, figure 7

Description: The rhabdosome is about 15 mm long 

and widens gradually from a width of 1 mm proximally through 1.7 mm at the fifth thecal pair to a 

maximum width of 3.0 mm, which is attained about 

12 mm from the proximal end and thereafter maintained. The virgella is short (about 0.5 mm long) and 

two equally short, straight lateral spines are present 

on the proximal end. There are 6 thecae in 5 mm proximally and 10 thecae per centimeter distally. Climacograptus-like thecae are present for about the first 3 

mm, followed by Orthograptus-like thecae.

Discussion: Only one good specimen of this form is 

present in the collection. 

Figured specimen: USNM 189109. 

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collection 69ICt 86), Trail Creek, 

Idaho.

Genus Climacograptus Hall, 1865

Climacograptus bicornis tridentatus Lapworth

Plate 4, figure 14

Climacograptus bicornis var. tridentatus Lapworth,

1876, Cat. Western Scottish Fossils, p. 6, pi. 2,

fig. 52. 

Climacograptus bicornis var. tridentatus Lapworth.

Elles and Wood, 1901-18, Palaeontographical Soc.,

Mon. British Graptolites, p. 195-196, pi. 26, figs.

9a-c. 

Climacograptus bicornis var. tridentatus Lapworth.

Ruedemann, 1908, N.Y. State Mus. Mem. 11, p. 83,

pi. A, figs. 32-38. 

Climacograptus bicornis (Hall) var. tridentatusLapworth. Ruedemann, 1947, Geol. Soc. America Mem.

19, p. 426, pi. 72, fig. 56.

Discussion: The figured specimen (pi. 4, fig. 14) 

shows the three proximal spines characteristic of 

this subspecies and a triangular membrane developed between the spines and the rhabdosome. In 

addition, one of the Idaho specimens has wide spines

covered by membrane and another has very slender 

spines.

Figured specimen: USNM 189110.

Occurrence: Zone of Climacograptus bicornis and 

passage beds(?) (Phi Kappa Formation, collections 

69ICt 88 and 69ICt 84), Trail Creek, Idaho. Zone of C. 

bicornis, Cresent Valley quadrangle, Nevada (Ross 

and Berry, 1963). Sams Spring Formation, Toquima 

Range, Nevada (Kay, 1962). Valder Formation, HD 

Range, Nevada (Riva, 1970). Normanskill Shale in 

New York and Womble Shale (Stringtown Shale of 

Ruedemann, 1947) in Oklahoma. Zones of Climacograptus peltifer and Climacograptus wilsoni 

(Glenkiln Shales and Hartfell Shales) in Great 

Britain (Elles and Wood, 1901-18).

Climacograptus hastatus T. S. Hall 

Plate 4, figure 7

Climacograptus hastata T. S. Hall, 1902, New South

Wales Geol. Survey Rec., v. 7, pt. 2, p. 54-55,

pi. 14, figs. 1-3. 

Climacograptus hastatus T. S. Hall. Harris and

Thomas, 1955, Victoria Dept. Mines, Mining and

Geology Jour., vol. 5, no. 6, p. 39, figs. 8, 9. 

Climacograptus hastatus T. S. Hall. Ross and Berry,

1963, U.S. Geol. Survey Bull. 1134, p. 121, pi. 8,

figs. 8, 10. 

Climacograptus hastatus var. angustus Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 122-

123. pi. 9, fig. 22.

Climacograptus hastatus var. martini Ross and 

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 123-

124. pi. 9, figs. 4, 6, 7, 10, 11, 16. 

Climacograptus n. sp. (not described) Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, pi. 9,

fig. 19.

Discussion: The figured specimen (pi. 4, fig. 7) 

resembles Climacograptus n. sp. Ross and Berry 

(1963, pi. 9, fig. 19) with its rounded proximal end and 

slender lateral spines. Most probably it is an immature specimen of Climacograptus hastatus, as it is 

always associated with well developed examples of 

C. hastatus in the Idaho collections.

Figured specimen: USNM 189118.

Occurrence: Zone of Dicellograptus ornatus (Phi 

Kappa Formation, collections 69ICt 33, 69ICt 42, 

69ICt 44, 69ICt 45, 69ICt 54, 69ICt 55), Trail Creek, 

Idaho. Also reported from Phi Kappa Formation, 

Idaho, by Ross and Berry (1963). Eastonian series 

(Upper Ordovician) in Victoria, Australia (Harris 

and Thomas, 1955).

Climacograptus longispinus hvalross Ross and Berry 

Plate 4, figures 12, 13

Climacograptus hvalross Ross and Berry. 1963, U.S.
SYSTEMATIC DESCRIPTIONS 23

Geol. Survey Bull. 1134, p. 124-125, pi. 8, figs. 19,

26, 27. 

Climacograptus supernus Elles and Wood. Churkin,

1963, Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1621, pi. 3, fig. 38. 

Climacograptus hvalross Ross and Berry. Toghill,

1970, Bull. British Mus. (Nat. Hist.) Geology, p. 22,

pi. 2, figs. 1-4, 7. 

Climacograptus longispinus hvalross Ross and

Berry. Riva, 1974a, Spec. Paper Palaeont., no. 13,

p. 114-119, text-figs. 5, 6, 7.

Description: The rhabdosome widens from 0.5-0.7 

mm proximally to about 2.0 mm (and as much as 2.6 

mm in specimens compressed perpendicularly to 

their length) in a distance of approximately 9 mm 

and is parallel sided thereafter. Thecae number 12-8 

per centimeter in specimens compressed perpendicular to the rhabdosome length and 15-12 per centimeter in specimens compressed parallel to their 

length. Thecal excavations occupy about one-third 

the width of the rhabdosome. The proximal end 

bears conspicuous stout spines that are as much as 

1.1 cm long and are thickened by membranes on their 

undersides for about one-fourth to one-half or more of 

their length.

Discussion: Climacograptus longispinus hvalross 

resembles Climacograptus longispinus longispinus 

T. S. Hall, from which it differs by having shorter 

and usually thinner spines with only one set of 

membranes on their undersides. C. /. longispinushas 

one or more sets of membranes along the upper sides 

of the spines. (See Riva, 1974c.) There are numerous 

specimens present in our collections (69ICt 44; 69ICt 

43; 69ICt 42), however, that have much shorter basal 

spines and membranes (see pi. 4, fig. 13). These 

specimens may represent a new subspecies evolving 

from C. /. hvalross, as they are found in association 

with C. /. hvalross in collections 69ICt 44 and 69ICt 

43 but without it in collection 69ICt 42.

Figured specimens: USNM164466, USNM189112.

Occurrence: Zone of Dicellograptus ornatus (Phi 

Kappa Formation, collections 69ICt 55, 69ICt 45, 

69ICt 44, 69ICt 43, 69ICt42, 69ICt33), Trail Creek, 

Idaho. Top of the Agort Chert in the HD Range and 

the Perkins Canyon Formation in the Toquima 

Range in Nevada (Riva, 1974c).

Climacograptus pacificus pacificus Ruedemann

Plate 4, figures 8, 9

Climacograptus innotatus Nicholson var. pacificus 

Ruedemann, 1947, Geol. Soc. America Mem. 19, 

p. 429, pi. 73, fig. 29.

Climacograptus innotatus var. pacificus Ruedemann. Ross and Berry, 1963, U.S. Geol. Survey 

Bull. 1134, p. 125, pi. 8, fig. 21.

Climacograptus pacificus Ruedemann. Riva, 1974a,

Canadian Jour. Earth Sci., vol. 11, p. 1457-1459,

figs. 2a-h.

Diagnosis: According to Riva (1974a, p. 1457-59), 

the rhabdosome is small, with an average length of 7- 

8 mm, exclusive of virgella and nema, and a width 

that gradually increases from 1.1-1.2 mm at the first 

thecal pair to a maximum of 1.6-2.0 mm distally. 

Thecae number 7 in the first 5 mm in relatively undeformed specimens in Nevada and as many as 9-10 

per 5 mm in the Idaho specimens. Thecal excavations are shallow, occupying only about one-eighth 

to one-fifth the width of the rhabdosome. One or two 

spines, about 0.8-0.9 mm long, project from each 

geniculum.

Discussion: This species differs from Climacograptus innotatus and its subspecies in its stubby 

shape and double genicular spines.

Figured specimens: USNM 189113, USNM 189115.

Occurrence: Zone of Dicellograptus ornatus (Phi 

Kappa Formation, collections 69ICt 43, 69ICt 42, 

69ICt 33), Trail Creek, Idaho. First described from 

Trail Creek by Ruedemann (1947) and also reported 

by Ross and Berry (1963). Perkins Canyon Formation (Marshall Kay collection), Toquima Range, 

Nevada (Riva, 1974a).

Climacograptus tubuliferus Lapworth 

Plate 7, figure 5

Climacograptus tubuliferus Lapworth, 1876, Cat.

Western Scottish Fossils, pi. 2, fig. 49. 

Climacograptus tubuliferus Lapworth. Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 203-204, text figs. 134a-c,

pi. 27, figs. 8a-d. 

Climacograptus tubuliferus Lapworth. Ruedemann,

1947, Geol. Soc. America Mem. 19, p. 440, pi. 75,

figs. 54-56. 

Climacograptus tubuliferus Lapworth. Harris and

Thomas, 1955, Mining Geol. Jour. (Victoria), v. 5,

no. 6, p. 40, figs. 10-12. 

Climacograptus tubuliferus Lapworth. Berry, 1960,

Texas Univ. Pub. 6005, p. 85, pi. 19, fig. 5. 

Climacograptus tubuliferus Lapworth. Churkin,

1963, Am. Assoc. Petroleum Geologists Bull., v. 47,

p. 1619, pi. 2, fig. 29. 

Climacograptus tubuliferus Lapworth. Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 132,

pi. 10, figs. 1, 2.

Discussion: According to Elles and Wood (1901-18, 

p. 203), the virgella of Climacograptus tubuliferus is 

well developed and as much as 4 mm long. Harris 

and Thomas (1955, p. 40) noted that the rodlike 

virgella of C. tubuliferus is "sometimes surrounded 

by a membranous body as in C. caudatus" but that
24 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

the membrane "is longer in C. caudatus and the 

virgella projects considerably beyond its extremity." There are specimens of C. tubuliferus in our 

collections with virgellas 3.0-3.3 mm long and virgellar membranes 1.3-2.8 mm long. There are also specimens (for example, pi. 7, fig. 5) with virgulas of the C. 

tubuliferus type, virgellas up to 11 mm long and 

virgellar memfiranes up to 5.3 mm long, which are 

within the limits cited by Elles and Wood (1901-18, p. 

202) for C. caudatus. Whether these specimens are C. 

caudatus with abnormal virgulas or C. tubuliferus 

with abnormally elongated virgellas remains a matter of conjecture.

Figured specimen: USNM 164424.

Occurrence: Zones of Climacograptus tubuliferus 

and Pleurograptus linearis (Phi Kappa Formation, 

collections 69ICt 71-75, 69ICt61-65, and 69ICt 56- 

59), Trail Creek, Idaho. Zone of Orthograptus quadrimucronatus (Hanson Creek Formation) in Nevada 

(Ross and Berry, 1963). Jacks Peak Formation (upper 

Caradocian), northern Independence Range, Nevada (Churkin and Kay, 1967). Zone of O. quadrimucronatus (Maravillas Chert) in the Marathon 

region, Texas (Berry, 1960). Polk Creek Shale of 

Oklahoma (Ruedemann, 1947). Upper Ordovician 

from near the Wellington River, Victoria, Australia 

(Harris and Thomas, 1955). Zones of Dicranograptus 

clingani and P. linearis (Hartfell Shales) in Great 

Britain.

Climacograptus? uncinatus Keble and Harris

Plate 4, figures 1, 2

Climacograptus uncinatus Keble and Harris, 1934, 

Nat. Mus. Melborne, Mem. 8, p. 173-174, pi. 20, figs. 

5a-c.

Climacograptus uncinatus Keble and Harris. Harris 

and Thomas, 1955, Mining Geol. Jour. (Victoria), 

v. 5, no. 6, p. 40, fig. 13.

Climacograptus uncinatus Keble and Harris. Churkin, 1963, Am. Assoc. Petroleum Geologists Bull., 

v. 47, p. 1619, pi. 2, fig. 21.

Climacograptus? uncinatus Keble and Harris. Carter, 1972, Jour. Paleontology, v. 46, no. 1, p. 48, 

text-figs. 2J, L-O, pi. 1, figs. 2-7, 10. 

Diagnosis: According to the original description, 

the rhabdosome widens from a pointed proximal end 

to 2.5 mm in 3 mm and thereafter maintains that 

width. Thecae number 12-14 per centimeter. Two 

fairly stout curved spines, about 2 mm long, arise 

approximately 2.0 mm from the proximal end.

Discussion: The Idaho specimens are all considerably narrower (1.0-1.5 mm maximum) than the 2.5- 

mm width cited by Keble and Harris (1934, p. 173). 

However, measurement of their figures (1934, pi. 20,

figs. 5a-c) indicates a width of 1.0 mm or less. Its 

small size and septal spines distinguish C.I uncinatus from other species of Climacograptus.

Figured specimens: USNM 189116, USNM 189117.

Occurrence: Zone of Pleurograptus linearis (Phi 

Kappa Formation, collections 69ICt 61, 69ICt59, 

69ICt 57, 69ICt 56, 69ICt 41), Trail Creek, Idaho. 

Upper Ordovician Bolindian Stage in Victoria, Australia (Keble and Harris, 1934; Harris and Thomas, 

1938 and 1955).

Genus Glyptograptus Lapworth, 1873 

Glyptograptus cf. G. euglyphus euglyphus (Lapworth)

Plate 5, figure 1 

Diplograptus (Glyptograptus) euglyphus Lapworth,

1880, Ann. Mag. Nat. Hist. Ser. 5, no. 5, p. 166, pi. 4,

figs. 14a-e.

Diplograptus (Glyptograptus) teretiusculus var. euglyphus Lapworth. Elles and Wood, 1901-18, Palaeontological Soc., Mon. British Graptolites, p.

252, text-fig. 172, pi. 31, figs. 2a-d. 

Diplograptus (Glyptograptus) euglyphus Lapworth.

Ruedemann, 1908, N.Y. State Mus. Mem. 11, p.

369-370, text-figs. 315-316, pi. 25, figs. 22, 23. 

Diplograptus (Glyptograptus) euglyphus Lapworth.

Ruedemann, 1947, Geol. Soc. America Mem. 19,

p. 405-406, pi. 69, figs. 46-50, 55-59. 

Glyptograptus teretiusculus var. euglyphus (Lapworth). Berry, 1960, Texas Univ. Pub. 6005, p. 88,

pi. 15, fig. 8. 

Glyptograptus euglyphus (Lapworth). Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 140,

pi. 10, figs. 27, 28; pi. 11, figs. 3, 4.

Discussion: Some of the Idaho specimens are 

slightly wider (up to 2.5 mm) than G. euglyphus 

euglyphus (2.1 mm wide), and some have 14-12 

thecae per centimeter instead of the 7-10 thecae per 

centimeter of G. e. euglyphus. In other respects, 

however, they fit the description of G. e. euglyphus, 

which is distinguished by its long, slender rhabdosome and widely spaced thecae.

Figured specimen: USNM 189119.

Occurrence: Zone of Climacograptus bicornis and 

passage beds (Phi Kappa Formation, collections 

69ICt 92, 69ICt 86, 69ICt 81,69ICt 79, and 69ICt 78), 

Trail Creek, Idaho. Zones of Paraglossograptus tentaculatus (Hallograptus etheridgei) to Orthograptus 

amplexicaulis (Vinini Formation), Nevada and in 

California (Ross and Berry, 1963). Zones of Nemagraptus gracilis and C. bicornis (Woods Hollow 

Shale) in the Marathon region, Texas (Berry, 1960), 

Nonnanskill Shale of New York, the Womble Shale 

of Oklahoma (Stringtown Shale of Ruedemann, 

1947), and Arkansas. 7-ones of Glyptograptus tere-
SYSTEMATIC DESCRIPTIONS

tiusculus to Climacograptus wilsoni in Great Britain 

(Elles and Wood, 1901-18). Zones of Glyptograptus 

euglyphus to N. gracilis (Road River Formation) in 

Yukon Territory, Canada (Jackson and Lenz, 1962).

Glyptograptus(?) sp. 

Plate 5, figures 2, 3

Description: The rhabdosome is short (about 2 cm) 

and very wide, increasing throughout its length from 

a width of about 1.0 mm proximally to 3.4 mm 

distally. The thecae are of the Glyptograptus type 

and number 11-8 per centimeter, with marked sigmoid curvature and slightly convex apertural margins perpendicular to the axis of the rhabdosome. 

The apertural excavations are deep, giving a very 

serrate appearance to the rhabdosome margins similar to Glyptograptus sinuatus sinuatus Nicholson 

(see Elles and Wood, 1901-18, p. 256, text-fig. 175b).

Discussion: Only 3 specimens of this species are in 

the collection and none of them have the proximal 

end preserved. For this reason, the species has not 

been named. However, its great width is distinctive. 

Glyptograptus serratus serratus Elles and Wood is 

also very wide (as much as 3.5 mm) but is of Silurian 

age.

Figured specimens: USNM189120, USNM189121.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collection 69ICt 86), Trail Creek 

Idaho.

Genus Orthograptus Lapworth, 1873 

Orthograptus aff. O. calcaratus calcaratus (Lapworth)

Plate 4, figure 10 

Diplograptus foliaceus var. calcaratus Lapworth,

1876, Cat. Western Scottish Fossils, p. 6, pi. 1,

fig. 30. 

Diplograptus (Orthograptus} calcaratus Lapworth.

Elles and Wood, 1901-18, Palaeontological Soc.,

Mon. British Graptolites, p. 239-241, text-figs.

159a-c, pi. 30, figs. la-c. 

Diplograptus (Orthograptus} calcaratus Lapworth.

Ruedemann, 1947, Geol. Soc. America Mem. 19,

p. 398-399, pi. 68, figs. 21-23. 

Orthograptus calcaratus (Lapworth). Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 144-

145, pi. 11, fig. 14.

Description: The rhabdosome is 18 mm long and 

widens from 1.0 mm wide initially to a maximum of 

3.0 mm, which is attained 11 mm from the proximal 

end and maintained thereafter. The thecae are of the 

O. calcaratus type, numbering 14 per centimeter. The 

virgella is tiny, and two inconspicuous lateral spines 

are present on the initial thecae.

Discussion: This form differs from O. calcaratus

calcaratus in two respects: it has more thecae per 

centimeter (O. c. calcaratus has 10-8 per centimeter), 

and it lacks the prominent lateral spines and virgella 

of O. c. calcaratus. It fits the description of O. calcaratus vulgatus Elles and Wood (1901-18, p. 241) 

except for the number of thecae per centimeter 

(approximately 10-8 per centimeter in O. c. vulgatus}, and it does not appear to widen as abruptly as 

their illustrated specimens (1901-18, pi. 30, figs. 5ad). It differs from the remaining subspecies of O. 

calcaratus as described by Elles and Wood (1901-18, 

p. 242-245) in details of rhabdosome size and thecal 

spacing. Perhaps it is a new subspecies of O. calcaratus, but it is not very distinctive in appearance 

and has therefore not been named.

Figured specimen: USNM 189123.

Occurrence: Zones of Nemagraptus and Climacograptus bicornis (Phi Kappa Formation, collections 69ICt 93, 69ICt 86), Trail Creek, Idaho. O. calcaratus has been reported from the C. bicornis Zone 

in Nevada (Ross and Berry, 1963), the Polk Creek 

Shale of Oklahoma (Ruedemann, 1947), and the 

Zones of Climacograptus wilsoni to Pleurograptus 

linearis in Great Britain (Elles and Wood, 1901-18).

Orthograptus calcaratus cf. subsp. tenuicornis 

Elles and Wood

Plate 4, figure 11 

Orthograptus calcaratus var. tenuicornis Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 243, text-fig. 163a, b, pi. 30,

figs. 4a-c. 

Diplograptus (Orthograptus} calcaratus Lapworth,

var. tenuicornis Elles and Wood. Harris and

Thomas, 1955, Mining Geol. Jour. (Victoria), v. 5,

no. 6, p. 36, figs. 33, 34.

Discussion: The Idaho specimens are up to 4.4 cm 

long, 1.0 mm wide initially, and up to 3 mm wide 

distally and have 13-10 thecae per centimeter. One 

specimen (pi. 4, fig. 11) has slender spines about 1.5 

mm long on the basal thecae. This agrees with the 

description and figured specimens given by Elles 

and Wood (1901-18, p. 243) except for the number of 

thecae per centimeter, which was implied to be 10-8 

per centimeter. Also, the lateral spines are more 

curved and not as long as those of O. calcaratus tenuicornis (1 mm). The figured specimen (pi. 4, fig. 11) 

also resembles Ross and Berry's (1963, pi. 11, figs. 15, 

16) figures of Orthograptus cf. O. calcaratus.

Figured specimen: USNM 189122.

Occurrence: Zone of Pleurograptus linearis (Phi 

Kappa Formation, collection 69ICt 59), Trail Creek, 

Idaho. Base of Agort Chert, HD Range, Nevada 

(Riva, 1970). Zone of Dicranograptus clingani (Hart-
20 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

fell Shales), Scotland (Elles and Wood, 1901-18). 

Upper Ordovician from near the Wellington River, 

Victoria, Australia (Harris and Thomas, 1955).

Orthograptus calcaratus cf. subsp. acutus 

Elles and Wood

Plate 4, figures 15-17

Diplograptus (Orthograptus) calcaratus var. acutus [Lapworth Ms] Elles and Wood, 1901-18, 

Paleontographical Soc., Mon. British Graptolites, 

p. 242, pi. 30, figs. 3a-c.

Diplograptus (Orthograptus} calcaratus var. acutus 

Lapworth. Ruedemann, 1947, Geol. Soc. America 

Mem. 19, p. 399, pi. 68, figs. 14-19. 

Orthograptus calcaratus var. acutus (Lapworth). 

Berry, 1960, Texas Univ. Pub. 6005, p. 89, pi. 16, 

figs. 3, 4.

Orthograptus calcaratus var. acutus Elles and Wood. 

Ross and Berry, 1963, U.S. Geol. Survey Bull. 1134, 

p. 145, pi. 11, fig. 18, pi. 12, figs. 1, 17. 

Description: The specimens are as much as 5 cm 

long and increase steadily in width from 1.5 mm wide 

at theca I 1 through 2.9-3.0 mm wide at theca 51 to a 

maximum width of 4.5 mm. The thecae are of the O. 

calcaratus type, numbering 14-9 per centimeter. 

There are two short, slender lateral spines on the 

apertures of the basal thecae. The virgella is stout 

and 1.6-3.5 mm long, sometimes partially surrounded by a membrane 1.0-1.5 mm long, similar to 

the sicular downgrowths observed by Bulman (1944- 

47, p. 69, text-fig. 36) on Pseudoclimacograptus 

scharenbergi. In some specimens, a broad tubelike 

structure runs through the length of the rhabdosome. 

Discussion: According to the original description, 

this subspecies lacks the large basal spines of O. 

calcaratus. It widens rapidly from 1 mm to 4 mm 

within 1.5 cm of the proximal end and has 12-9 

thecae per centimeter.

The Idaho specimens appear to widen more rapidly than do specimens of O. c. acutus illustrated by 

Elles and Wood (1901-18, p. 30, figs. 3a, b). The 

British specimens measure 1.5-1.7 mm wide at the 

level of theca 51 , whereas the specimens in our 

collections are 2.9-3.0 mm wide at theca 51 .

Figured specimens: USNM189124, USNM189125, 

USNM 189126.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collections 69ICt 92, 69ICt 91, 

69ICt 88, and 69ICt 87), Trail Creek, Idaho. Orthograptus calcaratus acutus s.s. occurs in: Zones of 

Nemagraptus and Climacograptus tubuliferus and 

passage beds (Phi Kappa Formation, collections 

62ICn 472, 69ICt 83, 69ICt 77, and 69ICt 62), Trail 

Creek, Idaho; Zones of C. bicornis and Orthograptus 

amplexicaulis (Palmetto and Toquima Formations, 

Nevada, and Saturday Mountain(?) Formation, Idaho) (Ross and Berry, 1963); Agort Chert, HD Range, 

Nevada (Riva, 1970); Zone of C. bicornis (Woods 

Hollow Shale), Marathon region, Texas (Berry, 

1960); Normanskill Shale, New York (Ruedemann, 

1947); Zone of Nemagraptus gracilis (Road River 

Formation) in northern Yukon Terr., Canada (Jackson and Lenz, 1962); Zones of N. gracilis and Diplograptus multidens in Great Britain (Elles and 

Wood, 1901-18).

Orthograptus pageanus pageanus Elles and Wood 

Plate 4, figure 3

Diplograptus pageanus Lapworth, nom. nudum,

1873, Geol. Mag., v. 10, p. 134. 

Diplograptus (Orthograptus} pageanus Lapworth.

Elles and Wood, 1901-18, Palaeontographical

Soc., Mon. British Graptolites, p. 225-226,

text-fig. 147, pi. 28, figs. 3a-c.

Diagnosis: According to Elles and Wood (1901-18, 

p. 225), the rhabdosome is 2.5-4 cm long and 

typically somewhat fusiform in shape. It widens 

from 2 mm initially to a maximum width of 4.5 mm 

within 1 cm of the proximal end but usually 

diminishes distally to about 3 mm wide. The thecae 

number 16-12 per centimeter and are of the 

Orthograptus type, with long, horizontal, somewhat 

flexed spines. The spines on the basal thecae are 

especially long (as much as 4 mm).

Discussion: The Idaho specimens closely fit the 

above description. O. p. pageanus resembles Orthograptus quadrimucronatus (Hall) but differs from it 

in being generally shorter and wider proximally and 

having thecae that are more closely spaced. The long 

basal spines are also a distinctive feature of O. p. 

pageanus. Ruedemann (1947, p. 455) noted the 

similarity of this species to Orthograptus quadrimucronatus cornutus (Ruedemann) in the general 

character of the rhabdosome and the basal spines 

but stated that his species was narrower and had less 

closely spaced thecae than O. p. pageanus. O. quadrimucronatus cornutus has much longer thecal spines 

than O. p. pageanus (John Riva, written commun., 

1973).

Figured specimen: USNM 189127.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collection 69ICt 86), Trail Creek, 

Idaho. Tiser Limestone, HD Range, Nevada (Riva, 

1970). Zone of Dicranograptus clingani (Hartfell 

Shales), Scotland (Elles and Wood, 1901-18).

Orthograptus quadrimucronatus quadrimucronatus 

(J. Hall)

(not figured)

Graptolithus quadrimucronatus J. Hall, 1865, Canada Geol. Survey, Canadian Organic Remains, 

Decade 2, p. 144-146, pi. 13, figs. 1-10.

Diplograptus (Orthograptus} quadrimucronatus (J.
SYSTEMATIC DESCRIPTIONS 27

Hall). Elles and Wood, 1901-18, Palaeontological 

Soc., Mon. British Graptolites, p. 223-224, textfigs. 145a-f, pi. 28, figs. la-d.

Glossograptus (Orthograptus) quadrimucronatus (J. 

Hall). Ruedemann, 1908, N.Y. State Mus. Mem. 11, 

p. 385-392, text-fig. 336.

Glossograptus quadrimucronatus (J. Hall). Ruedemann, 1947, Geol. Soc. America Mem. 19, p. 452- 

454, pi. 78, figs. 1-5. 

Orthograptus quadrimucronatus (J. Hall). Berry,

1960, Texas Univ. Pub. 6005, p. 91, pi. 18, fig. 1. 

Orthograptus quadrimucronatus (J. Hall). Ross and 

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 146- 

147, pi. 12, figs. 4-6.

Diagnosis: According to Elles and Wood (1901-18, 

p. 223), the rhabdosome is 7 cm or more in length and 

widens gradually from an initial width of 1.5 mm to a 

maximum of about 3.0 mm within 2 cm from the 

proximal end. The thecae number 12-8 per centimeter, are rectangular in cross section, and have stiff 

spines projecting from both outer angles of the 

aperture.

Discussion: Some of the Idaho specimens fit the 

above description closely. Others are slightly wider 

(3.5 mm) and have more thecae per centimeter (16- 

12) and have been designated as O. cf. O. quadrimucronatus quadrimucronatus (see pi. 4, fig. 5).

Occurrence: Zone of Climacograptus tubuliferus 

and passage beds (Phi Kappa Formation, collections 69ICt 65, 69ICt 82, and 69ICt 83), Trail Creek, 

Idaho. O. cf. O. q. quadrimucronatus ranges from the 

passage beds to the lower Dicellograptus ornatus 

Zone in Idaho (collections 69ICt 55, 69ICt 66, and 

69ICt 84). O. quadrimucronatus quadrimucronatus 

is also reported from the Zone of O. quadrimucronatus in Nevada (Ross and Berry, 1963); the zone 

of O. quadrimucronatus (Maravillas Chert) in the 

Marathon region, Texas (Berry, 1960); Sams Spring 

Formation, Toquima Range, Nevada (Kay, 1962); top 

of the Agort Chert, HD Range, Nevada (Riva, 1970); 

the Atwater Creek Shale in New York and the 

Glouster Shale in Quebec (Ruedemann, 1947); the 

Zone of Pleurograptus linearis (Hartfell Shales) in 

Scotland (Elles and Wood, 1901-18); the Zone of O. 

quadrimucronatus (Road River Formation) in northern Yukon Terr., Canada (Jackson and Lenz, 1962); 

upper Caradocian (Road River Formation) in eastcentral Alaska (Churkin and Brabb, 1965).

Orthograptus quadrimucronatus inequispinosus 

(Ruedemann)

Plate 4, figure 4

Glossograptus quadrimucronatus mut. inequispinosus Ruedemann, 1925, N.Y. State Mus. Bull. 262, 

p. 66-67, pi. 7 figs. 7-10.

Glossograptus quadrimucronatus var. inequispinosus Ruedemann, 1947, Geol. Soc. America Mem. 19, 

p. 455-456, pi. 79, figs. 16-19. 

Diagnosis: According to the original description, 

this subspecies is similar to O. quadrimucronatus 

quadrimucronatus except for the presence of double 

length spines (2 mm or more) on the sixth or seventh 

and sometimes the fifth pair of thecae. The rhabdosome is as much as 40 mm long, is 2.5 mm wide, 

and has 14-10 thecae per centimeter.

Discussion: The Idaho specimens closely fit the 

above description. Orthograptus quadrimucronatus 

spinigerus Lapworth is similar to this subspecies but 

has longer spines (5 mm or more), and they are on the 

tenth thecal pair. 

Figured specimen: USNM 189130. 

Occurrence: Passage beds (Phi Kappa Formation, 

collections 69ICt 78, 69ICt 76), Trail Creek, Idaho. 

The Utica Shale of New York (Ruedemann, 1925).

Genus Petalograptus Suess, 1851

Petalograptus minor Elles

Plate 3, figure 10

Petalograptus minor Elles, 1897, Quart. Jour. Geol.

Soc. London, v. 53, p. 201, pi. 14, figs. 17-21. 

Petalograptus minor Elles. Elles and Wood, 1901-18, 

Palaeontographical Soc., Mon. British Graptolites, p. 279-281, text-figs. 193a, b, pi. 32, figs. 5a-e. 

Petalograptus minor Elles. Churkin and Carter, 

1970, U.S. Geol. Survey Prof. Paper 653, p. 32, 

text-figs. 13E, F, pi. 3, fig. 5.

Petalograptus minor Elles. Rickards, 1970, Palaeontographical Soc. Mon., Llandovery graptolites 

of Howgill Fells, p. 48, pi. 3, figs. 3, ?6, ?7. 

Discussion: The Idaho specimens are 6.5-10 mm 

long, 2.7-3.5 mm wide, and have 14-12 thecae per 

centimeter, which is in agreement with published 

descriptions of P. minor. The shape and size of its 

rhabdosome and proximal end serve to distinguish 

P. minor from immature specimens of Petalograptus 

palmeus (Barrande). 

Figured specimen: USNM 189131. 

Occurrence: Zone of Monograptus convolutus (Phi 

Kappa Formation, collection 69ICt 31), Trail Creek, 

Idaho. Zone of Monograptus gregarius (Descon 

Formation), Noyes Island, southeast Alaska 

(Churkin and Carter, 1970). Zones of M. gregarius 

and M. convolutus (Birkhill Shales) in Great Britain 

(Elles and Wood, 1901-18).

Genus Pseudoclimaoograptus Pribyl, 1947

Pseudoclimacograptus schaxenbergi schaxenbergi (Lapworth)

Plate 3, figure 6

Climacograptus scharenbergi Lapworth, 1876, Cat. 

Western Scottish Fossils, pL 2, fig. 55.
28 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

Climacograptus scharenbergi Lapworth. Elles and

Wood, 1901-18, Palaeontographical Soc., Mon.

British Graptolites, p. 206-208, text-figs. 139a-c,

pi. 27, figs. 14a-e. 

Climacograptus scharenbergi Lapworth. Ruedemann, 1908, N.Y. State Mus. Mem. 11, p. 428-431,

text-figs. 394-399, pi. 28, fig. 31. 

Climacograptus scharenbergi Lapworth. Bulman,

1944-47, Palaeontographical Soc. Mon., Caradoc

Graptolites in Laggan Burn, p. 65-70, pi. 7, figs.

1-10, pi. 8, figs. 1, 5-7, text-figs. 34-38. 

Climacograptus scharenbergi Lapworth. Ruedemann, 1947, Geol. Soc. America Mem. 19, p. 438-

439, pi. 74, fig. 41-54. 

Climacograptus scharenbergi Lapworth. Ross and

Berry, 1963, U.S. Geol. Survey Bull. 1134, p. 129-

130, pi. 9, figs. 14, 17. 

Climacograptus scharenbergi Lapworth. Berry

1964, Norsk Geol. Tidssk., B. 44, H. 1, p. 137-139,

pi. 13, fig. 8. 

Pseudoclimacograptus scharenbergi (Lapworth).

Riva, 1974b, Palaeont., v. 17, pt. 1, p. 27-29, textfigs. 8c-h, pi. 2, figs. 4, 5.

Discussion: Because the Idaho specimens are compressed, the zigzag septal groove characteristic of P. 

s. scharenbergi is not preserved, but the introversion 

of their thecal apertures, the alternate arrangement 

of their thecae, and the dimensions of their rhabdosomes identify them as P. s. scharenbergi.

Figured specimen: USNM 189132.

Occurrence: Zone of Climacograptus bicornis (Phi 

Kappa Formation, collection 69ICt 91), Trail Creek, 

Idaho. Zone of C. bicornis in Nevada (Ross and 

Berry, 1963). Middle Ordovician McAfee Quartzite, 

Independence Range, Nevada (Churkin and Kay, 

1967). Sams Spring Formation, Toquima Range, 

Nevada (Kay, 1962). Zone of Orthograptus amplexicaulis (Maravillas Chert) in the Marathon region, 

Texas (Berry, 1960). Lower Caradocian (Road River 

Formation) in east-central Alaska (Churkin and 

Brabb, 1965). The Normanskill Shale in New York 

(Ruedemann, 1947). Zone of Diplograptus multidens 

(Quebec City Formation) in Quebec (Riva, 1974b). 

Zones of Didymograptus bifidus(?) to Climacograptus wilsoni in Great Britain (Elles and Wood, 1901- 

18). Zones of Didymograptus murchisoni and Glyptograptus teretiusculus (Ogygiocaris series) in the 

Oslo region, Norway (Berry, 1964).

Family LASIOGRAPTIDAE

Genus Neurograptus Elles and Wood, 1908

Neurograptus margaritatus (Lapworth)

Plate 3, figure 9

Lasiograptus margaritatus Lapworth, 1876, Cat. 

Western Scottish Fossils, pi. 2, fig. 60.

Lasiograptus (Neurograptus) margaritatus (Lapworth). Elles and Wood, 1901-18, Palaeontographical Soc., Mon. British Graptolites, p. 332-333,

text-figs. 219a, b, pi. 34, figs. 6a-e.

Diagnosis: According to Elles and Wood (1901-18, 

p. 332-333), the rhabdosome is about 1.5 cm long, 

with an average uniform width of 1.5 mm (exclusive 

of the lacinia). The thecae are of the Hallograptus 

type, alternate, and number 14-12 per centimeter. 

The lacinia is delicate and continuous.

Discussion: This species is represented in our 

collections by only one specimen. It is somewhat 

wider (about 2.5 mm) than the width reported by 

Elles and Wood (1901-18), but measurement of their 

figures (pi. 34, figs. 6a-e) reveals a width of 2.5-3.0 

mm. Neurograptus fibratus (Lapworth) resembles N. 

margaritatus but is a much larger form and has a 

thinner periderm; consequently, its clathria is much 

more pronounced than that of N. margaritatus.

Figured specimen: USNM 189133.

Occurrence: Passage beds (Phi Kappa Formation, 

collection 69ICt 84), Trail Creek, Idaho. Zone of 

Dicranograptus clingani (Point Leamington Greywacke) in Newfoundland (Bergstrom and others, 

1974). Zone of D. clingani (Hartfell Shales) in Scotland (Elles and Wood, 1901-18).

Family RETIOLJTIDAE

Genus Orthoretiolites Whittington, 1954

Orthoretiolites hami robustus Skevington

Plate 4, figure 6 

Orthoretiolites hami var. robustus Skevington, 1960,

Palaeontology, v. 2, p. 226-235, text-figs. 1-4, pi.

34,35. 

Orthoretiolites hami robustus Skevington. Carter,

1972, Jour. Paleontology, v. 46, p. 49, text-figs. 2 P,

Q, pi. 1, figs, 13,14.

Discussion: The figured specimen (pi. 4, fig. 6) is 

much longer (2.5 cm) than any previously described 

specimen of this form. It is 1.0 mm wide proximally 

and 2.5 mm wide distally, exclusive of spines. There 

are 9 thecae in 5 mm proximally and 12 thecae per 

centimeter distally. The apertural spines measure 

1-1.5 mm long.

Figured specimen: USNM 189129.

Occurrence: Zone of Climacograptus tubuliferus 

(Phi Kappa Formation, collections 69ICt 73 and 

69ICt 72), Trail Creek, Idaho. Jacks Peak Formation, 

northern Independence Range, Nevada (Churkin 

and Kay, 1967; Carter, 1972). Ordovician Viola Limestone in the Criner Hills, Oklahoma (Skevington, 

1960).

Suborder MONOGRAPTINA

Family MONOGRAPTIDAE

Genus Monograptus Geinitz, 1852

Monograptus convolutus (Hisinger)

Plate 5, figure 11

Prionotus convolutus Hisinger, 1837, Lethaea 

Suecica Supp., p. 114, pi. 35, fig. 7.
SYSTEMATIC DESCRIPTIONS 29

Graptolithus convolutus (Hisinger). Carruthers,

1868, Geol. Mag., v. 5, p. 127, pi. 5, fig. 1. 

Monograptus convolutus (Hisinger). Tb'rnquist, 1899, 

Lunds Univ. Arsskr., v. 35, no. 1. p. 21-22, pi. 4, 

figs. 15-22.

Monograptus convolutus (Hisinger). Elles and Wood, 

1901-18, Palaeontographical Soc., Mon. British 

Graptolites, p. 467-469, text-figs. 324a, b, pi. 47, 

figs. la-d.

Dimirastrites convolutus (Hisinger). Pribyl and 

Munch, 1941, Rozpr. Ceske Akad., v. 51, no. 31, 

p. 15-17, pi. 1, figs. 9-10, pi. 3, figs. 7-9. 

Monograptus convolutus (Hisinger). Sudbury, 1958, 

Philos. Trans. Royal Soc. London, Ser. B, no. 685, 

v. 241, p. 511-513, text-fig. 13, pi. 21, figs. 76-78. 

Monograptus convolutus (Hisinger). Churkin, 1963, 

Am. Assoc. Petroleum Geologists Bull., v. 47, 

p. 1621, pi. 3, fig. 36.

Monograptus convolutus (Hisinger). Rickards, 1970, 

Palaeontographical Soc. Mon., Llandovery Graptolites of Howgill Fells, p. 82-83, text-fig. 13, fig. 15. 

Discussion: M. convolutus is distinguished from 

most monograptids by its spirally coiled rhabdosome. Monograptus spiralis (Geinitz) has a spiral 

rhabdosome but differs from M. convolutus in 

having triangular-shaped thecae throughout its 

length. The thecae of M. convolutus are Rastriteslike in the proximal part of the rhabdosome, changing to triangular-shaped distally. 

Figured specimens: USNM 189135. 

Occurrence: Zone of Monograptus convolutus (Phi 

Kappa Formation, collection 69ICt 31), Trail Creek, 

Idaho. Zones of Monograptus gregarius and M. convolutus (Gatecliff Formation), Toiyabe Range, Nevada (Kay and Crawford, 1964). Zone of M. convolutus to Monograptus sedgwickii (Road River Formation), northern Yukon Territory, Canada (Jackson and Lenz, 1962). Zones of M convolutus and M. 

sedgwickii in Great Britain (Sudbury, 1958). Zones 

of M. convolutus to Rastrites maximus (Birkhill 

Shales) in Scotland (Toghill, 1968). Zone of M 

convolutus (Stockdale Shales), Howgill Fells, northern England (Rickards, 1970). Zones of Diplograptus folium and Diplograptus cometa at Tomarp, 

Sweden (Tornquist, 1899).

Monograptus cf. M. decipiens decipiens Tornquist

Plate 5, figures 9, 10 

Monograptus decipiens Tornquist, 1899, Lunds

Univ. Arsskr., v. 35, no. 1, p. 20-21, pi. 4, figs. 9-14. 

Monograptus decipiens Tornquist. Elles and Wood,

1901-18, Palaeontographical Soc., Mon. British

Graptolites, p. 469-470, text-fig. 325a (not b-d),

pi. 47, figs. 3a?, b, e (not 3c, d). 

Demirastrites decipiens decipiens (Tornquist). Pribyl

and Miinch, 1941, Rozpr. Ceske Akad., v. 51, no. 31,

p. 13-14, text-fig. 1, fig. 6 

Monograptus decipiens Tornquist. Sudbury, 1958,

Philos. Trans. Royal Soc. London, Ser. B, no. 685, 

v. 241, p. 510-511, pi. 21, figs. 74, 75. 

Monograptus decipiens Tornquist. Rickards, 1970, 

Palaeontographical Soc. Mon., Lland. Graptolites 

of Howgill Fells, p. 83, text-fig. 13, fig. 16, textfig. 17, fig. 8, text-fig. 18, fig. 3. 

Diagnosis: According to the original description, 

the rhabdosome initially forms a spiral of at most 

two involutions and continues in an arcuate manner 

tending to become straight. It increases in width 

from 1 mm to 1.5 mm. The thecae are located on the 

convex margin of the rhabdosome and number 10 per 

centimeter. Proximally they are tubular and isolate 

as in Rastrites, gradually becoming subtriangular 

distally. All the thecae terminate in a reflexed lobe. 

Discussion: Rickards (1970, p. 83) cited a maximum 

width of 1.4 mm and a thecal spacing of 8-11 per 

centimeter for this species. Sudbury (1958, p. 511) 

stated that the early thecae are about 0.45-1.0 mm 

high and rastritiform until about the eighth or tenth 

theca, after which they become more triangular. 

She also stated that the maximum rhabdosome 

width observed was 1.7 mm and that the thecae 

number 10 per centimeter. The proximal thecae of the 

Idaho specimens are 0.6-1.0 mm high and number 10 

per centimeter. They increase to 1.5 mm high distally 

and exhibit the characteristics of M. decipiens. However, the Idaho specimens are all fragmentary, and it 

is difficult to identify the various spiral monograptids from fragmentary material. They differ from 

Monograptus urceolus Richter sensu Elles and 

Wood, which has 11-12 thecae per centimeter and an 

irregularly coiled rhabdosome. M. convolutus is 

much wider and has as many as five whorls in its 

spiral rhabdosome.

Figured specimens: USNM 189140, USNM 189141. 

Occurrence: Zone of M. convolutus (Phi Kappa 

Formation, collections 69ICt 32, 69ICt 31), Trail 

Creek, Idaho. Zones of Monograptus gregarius to M. 

sedgwickii in Great Britain (Elles and Wood, 1901- 

18). Zone of M convolutus (Stockdale Shales), Howgill Fells, northern England (Rickards, 1970). Zones 

of M. gregarius and M. convolutus in Great Britain 

(Sudbury, 1958). Zone of Diplograptus cometa (Scanian Rastrites beds) at Tomarp, Sweden (Tornquist, 

1899).

Monograptus cf. M. flemingii flemingii (Salter)

Plate 5, figures 6-8 

Graptolithus flemingii Salter, 1852, Quart. Jour.

Geol. Soc. London, v. 8, p. 390, pi. 21, figs. 5a, b,

6, 7a, b. 

Monograptus flemingii (Salter). Elles and Wood,

1901-18, Palaeontographical Soc., Mon. British

Graptolites, p. 425-426, text-figs. 287a-d, pi. 42,

figs. 5a-d.

Diagnosis: According to Elles and Wood (1901-18, 

p. 425), the rhabdosome is straight or slightly flexed,
30 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

reaches a length of 17 cm or more, has a recurved 

proximal portion, and widens gradually to a maximum width of 2.5 mm. The sicula is about 1.6 mm 

long. The thecae number 14-9 per centimeter and 

have abruptly narrowing apertural regions which 

commonly bear a short spine, giving the appearance 

of a beak. The whole beak occupies from one-fifth 

(proximally) to one-third (distally) of the total width 

of the rhabdosome.

Discussion: The Idaho specimens are as much as 7 

cm long, 0.8 mm wide proximally, and 2.2-3.2 mm 

wide distally. They have 12-8 thecae per centimeter 

and siculae measuring 1.2-2.0 mm long. In comparison to Elles and Wood's figured specimens (1901- 

18, pi. 42, figs. 5a-d), they have more slender, slightly 

more recurved proximal ends. They resemble Monograptus priodon (Bronn), but M. priodon has a 

straight, rigid rhabdosome and widens much more 

slowly.

Figured specimens: USNM 189136, USNM189137, 

USNM 189138.

Occurrence: Upper Llandoverian and Wenlockian 

(Phi Kappa Formation, collection 69ICt 21), Trail 

Creek, Idaho. Wenlock Zones of Monograptus flexilis 

belophorus (=Cyrtograptus rigidus) through Cyrtograptus lundgreni in northern England (Rickards, 

1967). Also reported from the Trail Creek area by 

Bassler (1915). Jackson and Lenz (1962) identified M. 

cf. M. flemingii from a horizon between the Zones of 

Cyrtograptus lundgreni and Monograptus riccartonensis (Road River Formation) in Yukon Territory, 

Canada.

Monograptus sedgwickii (Portlock)

Plate 5, figure 4

Graptolithus (Prionotus) Sedgwickii Portlock, 1843, 

Rept. Geology of Londonderry, p. 318, pi. 19, fig. 1. 

Monograptus Sedgwickii (Portlock). Elles and Wood, 

1901-18, Palaeontographical Soc., Mon. British 

Graptolites, p. 441-443, text-figs. 304a-e, pi. 44, 

figs. lOa-f.

Monograptus sedgwickii (Portlock). Rickards, 1970, 

Palaeontographical Soc. Mon., Llandovery Graptolites of Howgill Fells, p. 73-74, text-fig. 14, fig. 34. 

Diagnosis: According to Elles and Wood (1901-18, 

p. 441), the rhabdosome is straight or slightly flexed, 

reaches 20 cm or more in length, and widens gradually to a maximum width of 3 mm exclusive of spines. 

The thecae number 10-6 per centimeter and have 

isolate, retroverted apertural regions that occupy 

about one-half the width of the rhabdosome. The 

apertural margin is spined, with the spine becoming 

more conspicuous distally. 

Discussion: M. sedgwickii may be distinguished

from Monograptus halli (Barrande) by its less rapidly increasing width, its more flexuous rhabdosome, 

and its more strongly retroverted thecal apertures.

Figured specimen: USNM 189139.

Occurrence: Zone of Monograptus convolutus (Phi 

Kappa Formation, collection 69ICt 32), Trail Creek, 

Idaho. Zones of Monograptus sedgwickii and Rastrites maximus (Birkhill Shales), Dobbs linn, Scotland (Toghill, 1968). Zone of M. sedgwickii (Stockdale Shales), Howgill Fells, northern England (Rickards, 1970).

Family CYRTOGRAPTIDAE

Genus Cyrtograptus Carruthers, 1867

Cyrtograptus kirki Ruedemann

Plate 6, figure 1

Cyrtograptus kirki Ruedemann, 1947, Geol. Soc.

America Mem. 19, p. 495, pi. 89, figs. 4, 12 (not

figs. 1-3, 5-11, 13, 14).

Ruedemann (1947, pi. 89, figs. 1-14) included two 

separate species in his orginal description and illustrations of C, kirki from Trail Creek. Since he did not 

designate a holotype, the problem arises as to which 

of the two species should be designated as C. kirki. As 

one of the species (Cyrtograptus laqueus Jackson 

and Etherington) has subsequently been described 

elsewhere, it has been decided to restrict the name C. 

kirki to the species most nearly represented by 

Ruedemann's reconstructions 2 (1947, pi. 89, figs. 13,

14).

Revised description: The rhabdosome measures 

about 10 cm across and has numerous cladia, of one 

or two generations, separated by two to nine thecae. 

The main stipe is coiled in an irregular spiral 

through 2Vz volutions, being more tightly coiled proximally and becoming nearly straight distally. The 

first volution is a loop formed when the stipe crosses 

itself near the sicula. The diameter of the last 

volution is 1.0-1.5 cm. The main stipe is more than 9 

cm long and widens from about 0.5 mm proximally to 

1.0-1.5 mm wide near the point of origin of the first 

cladium, between th23 and th32 . The cladia are 

strongly dorsally curved and measure 1.3-1.5 mm 

wide; they are as much as 8 cm long and have 8-10 

thecae per centimeter. The first thecal segment of 

each cladium is 2.3-3.0 mm long. The thecae on the 

main stipe are triangular, with hooked apertural 

regions and apertural spines. Cladial thecae are less 

strongly hooked and more beaklike but generally are 

seen in profile only near the origin of the cladium.

The maximum number of primary cladia observed 

on a single rhabdosome is eight. One specimen (pi. 6,

2Those reconstructions do, however, misrepresent the nature of the proximal portion 

of C. kirki.
SYSTEMATIC DESCRIPTIONS 31

fig. 1) has three secondary cladia on the third 

primary cladium. The proximal part of the main 

stipe is narrow, and the proximal thecae are smaller 

and more widely spaced than the distal thecae. 

Initially, the main stipe is nearly straight, then 

curves to cross itself near the sicular end, forming a 

loop. It continues to coil for another IVfe volutions, 

becoming nearly straight distally.

Discussion: C. kirki resembles Cyrtograptus canadensis Jackson and Etherington but differs in having more irregular spacing between cladia, shorter 

initial thecal segments in its cladia, narrower stipes, 

and an irregularly coiled main stipe with a smaller 

diameter of the last volution.

Boucek and Pribyl (1952, p. 183-185) described C. 

kirki as a subspecies of Cyrtograptus multiramis 

Tbrnquist and designated as lectotype the specimen 

figured by Ruedemann (1947) in pi. 89, fig. 12. 

However, this was done largely on the basis of the 

long, thin, loop-shaped proximal parts of specimens 

figured by Ruedemann in pi. 89, figs. 3,4,9-11 (1947), 

and further examination has convinced this writer 

that one of those specimens (pi. 89, fig. 11) is actually 

Cyrtograptus laqueus. Boucek and Pribyl's figures of 

C. multiramis multiramis (1952, pi. I, fig. 1, text fig. 

Ib) show that that species has fewer volutions in its 

spiral main stipe than does C. kirki and its cladia are 

not bent back as far. Otherwise, the two species are 

quite similar. However, the form described and 

illustrated by Boucek and Pribyl as C. multiramis 

kirki (1952, p. 183-185, pi. I, fig. 2, text-figs. Ic-d) has 

many more secondary cladia than the Idaho species. 

Only one of Ruedemann's original specimens has 

any secondary cladia, and it has only three, located 

on the third primary cladium. Therefore, C. kirki 

may indeed be a subspecies of C. multiramis, but it is 

not the same form as C. multiramis kirki of Boucek 

and Pribyl.

Figured specimen: USNM 219002.

Occurrence: Upper Llandoverian and Wenlockian 

(Phi Kappa Formation, collection 69ICt 21), Trail 

Creek, Idaho.

Cyrtograptus laqueus Jackson and Etherington 

Plate 6, figure 3

Cyrtograptus kirki Ruedemann, 1947, Geol. Soc.

America Mem. 19, pi. 89, fig. 11. 

Cyrtograptus laqueus Jackson and Etherington,

1969, Jour. Paleontology, v. 43, no. 5, pt. I, p. 1119-

1121, pi. 130, figs. 1-3, text-figs. 4A, B.

Diagnosis: According to the original description, 

the rhabdosome is up to 9 cm across, with usually 

two, but occasionally with as many as five, simple 

cladia. The coiled main stipe is up to 5 cm long, with

the proximal 10 mm almost straight; therefore, the 

stipe crosses itself, forming a loop. The cladia are 

dorsally curved, and the first cladium is given off the 

main stipe between th12 and th15 . Subsequent cladia 

are separated by 3-5 thecae. The first thecal segment 

of each cladium is 2.0-2.5 mm long and 1.1 mm wide 

across the aperture. Cladia attain a maximum width 

of 1.3 mm. Proximal thecae on the main stipe are 

subtriangular with hooked apertural portions. Distal 

thecae on the main stipe and all cladial thecae are 

straight walled, with slightly reflexed distal margins. Width of thecae at the aperture level increases 

from 0.4 mm proximally to a maximum of 1.5 mm. 

Thecae number seven to eight per centimeter.

Discussion: The specimens from Idaho closely fit 

the above description with only minor differences. 

The first cladium is given off the main stipe between 

approximately th21 and th 23 in the Idaho specimens. 

Also, the first cladial thecae are somewhat longer 

(2.5-3.3 mm) and wider (1.2-1.4 mm).

C. laqueus can be distinguished from other cyrtograptids by its loop-shaped main stipe and small 

number of cladia.

Figured specimen: USNM 219003.

Occurrence: Upper Llandoverian and Wenlockian 

(Phi Kappa Formation, collection 69ICt 21), Trail 

Creek, Idaho. Zone of Monograptus spiralis into 

basal Wenlockian at Clearwater Creek, Northwest 

Territories, Canada (Jackson and Etherington, 

1969).

Cyrtograptus rigidus rigidus Tullberg 

Plate 5, figure 5; plate 6, figure 4; plate 7, figure 6

Cyrtograptus rigidus Tullberg, 1883, Skanes Graptoliter II, p. 38, pi. 4, figs. 12-14. 

Cyrtograptus symmetricus Elles. Elles and Wood, 

1901-18, Palaeont. Soc., Mon. British Graptolites, 

p. 509 [parts], pi. 51, figs. 5a, b, text-fig. 355 (not 

pi. 51, fig. 5c).

Cyrtograptus rigidus Tullberg. Gortani, 1922, Palaeont. italica, vol. 28, p. 59-61, pi. 11 [4], figs. 5-11, 

pi. 13 [6], figs. 4D, D', 6A, A'. 

Description: The rhabdosome is small, rarely more 

than 3 cm across, with a single simple cladium. The 

main stipe is coiled proximally into a spiral of onehalf or one volution, becoming nearly straight distally. The thecae occur on the convex side of the stipe 

proximally; usually beyond the cladium the stipe 

twists 90°-180° in such a way that the thecae are 

obscured or lie on the concave side.

The single cladium is straight or gently curved 

dorsally (toward the distal end of the main stipe) and 

is as much as 4.5 cm long. It is given off the main 

stipe between th7 and th9 and measures 1.2-1.5 mm
32 ORDOVICIAN AND SILURIAN GRAPTOLITE SUCCESSION, IDAHO

wide. The first thecal segment of the cladium is 2.1- 

2.8 mm long and 1.2-1.5 mm wide at the level of the 

aperture. There are SVfe-lO thecae per centimeter on 

the cladium.

Proximally, the thecae on the main stipe are triangular, with hooked apertural portions and short 

apertural spines. Distally, the amount of apertural 

hooking decreases, so that the thecae become beaklike to nearly tubular. The thecae on the cladium are 

similar to those on the distal part of the main stipe.

Discussion: The proximal spiral of the main stipe 

must have been somewhat helical (not in a single 

plane) because the compressed specimens from Idaho always have broken or twisted proximal portions, 

and so the sicula and first few thecae are lying at an 

acute angle to the main direction of the stipe.

Figured specimens: USNM189142, USNM 219004, 

USNM 219005.

Occurrence: Upper Llandoverian and Wenlockian 

(Phi Kappa Formation, collection 69ICt 21), Trail 

Creek, Idaho. Middle Wenlock Zone of C. rigidus (-C. 

symmetricus) in Great Britain (Elles and Wood, 

1901-18).

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Bergstrom, S. M., Riva, John and Kay, Marshall, 1974, Significance of conodonts, graptolites, and shelly faunas from the 

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west Texas: Univ. Texas Pub. 6005, 179 p., 20 pis.

———1964, The Middle Ordovician of the Oslo region, Norway: 

Graptolites of the Ogygiocaris series: Norsk Geologisk Tidsskrift, v. 44, p. 61-170, pis. 1-16.

Boucek, Bedrich, and Pribyl, Alois, 1952, Contribution to our 

knowledge of the cyrtograptids from the Silurian of Bohemia 

and on their stratigraphical importance: Ceska Akad. Ved a 

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INDEX

[Italic page numbers indicate both major references and descriptions]

abbreviatus, Orthograptus amplexicaulis .............. 12

acutus, Diplograptus (Orthograptus) calcaratus .. 26 

Orthograptus calaratus ............................ 10, 12, 26

affinis, Dicellograptus .................................................... 20

alector, Dicellograptus ............................................ 12, 18

amii, Tetragraptus .................................................. 6, 8, 9

amplexicaulis, Orthograptus ............ 12, 18, 24, 26, 28

abbreviatus, Orthograptus .................................... 12

pauperatus, Orthograptus .................................... 12

socialis, Orthograptus ........................................... 12

Ample xograptus perexcavatus ................................... 13

anceps, Dicellograptus .......................................... 12, 20

angulatus, Dicellograptus ............................................ 19

angustus, Climacograptus hastatus .......................... 22

anna, Phyllograptus ........................................... 5, 8, 14

longus, Phyllograptus ............................................ 14

prolatus, Phyllograptus ........................................ 14

arcuatus, Leptograptus flaccidus .............................. 12

argutus, Monograptus argutus .................................... 13

<irgutus, Monograptus ............................................ 13

artus, Didymograptus ................................................... 15

B

basilicus, Orthograptus calcaratus ............................ 12

Basin and Range province ............................................ 1

belophorus, Monograptus flexilis .............................. 30

bicornis, Climacograptus ................... 5, 10, 16, 17, 18,

19, 22, 24, 25, 26, 28 

Climacograptus bicornis ................................ 10, 12

bicomis, Climacograptus .............................. 10, 12

tridentatus, Climacograptus .................. 10, 12, 22

bicurvatus, Dicellograptus divaricatus .................... 19

bifidus, Didymograptus ...................... 9, 14, 15, 22, 28

Big Lost River ................................................................. 3

bigsbyi, Graptolithus ................. ............................... 14

Tetragraptus . ............................................. ....... 14

Brachiograptus .............. ........................................ 13

etaformis .............. .......... ... .............................. 13

caduceus, Dicellograptus .............................................. 20

imitatus, Isograptus ................................................ 9

calcaratus, Diplograptus foliaceus ........ ...... ......... 25

Diplograptus (Orthograptus) ................ ...... 25

Orthograptus .. . .... ...... ............. ..... 25, 26

calcaratus .. .... ...................... ................. 25

acutus, Diplograptus (Orthograptus) .. ..... 26

Orthograptus ..................................... 10, 12, 26

basilicus, Orthograptus .......................................... 12

calcaratus, Orthograptus .................................... 25

tenuicornis, Orthograptus .......... ..... . ...... 25

uulgatus, Orthograptus ... ............. ..... . .25

calicularis, Corynoides ...... ............. . 12, 16

canadensis, Cyrtograptus ...... ...... ......... ... .. 31

capillaris, Leptograptus ..... .... ........... ...... ... 17

caudatus, Climocograptus .............................. 12, 23, 24

Cladograpsus linearis .................................................... 17

Climacograptus .. . .............. ....... 10, 22, 24

bicornis ... . ...... .. .... ... . 10, 12, 22

bicornis .. .. ......... ....... . 10, 12

tridentatus .. ...... .... ... . 10, 12, 22; pi. 4

Zone ... .. ........... ..... ...... 5, 10, 16, 17, 18,

19, 21, 24, 25, 26, 28

Page 

Climacograptus—Continued

caudatus ....................................................... 12, 23, 24

hastatus .................................................. 12, 22; pi. 4

angustus ............................................................ 22

martini ................................................................ 22

hvalross .............................................................. 22, 23

innotatus ................................................................. 23

pacificus ............................................................ 23

longispinus .... ................................................... 12

hvalross ........................................... 12, 22; pi. 4

longispinus ................................................... 23

minimus..... ........................................................... 12

mohawkensis ........... ......................................... 12

pacificus........................................................ 23; pi. 4

pacificus........................................................ 12, 23

peltifer Zone ................................................. .. 19, 22

scalaris.................................................................. 13

scharenbergi................................... ................... 27

supernus...................... .. .................................... 23

tubuliferus............................................ 12, 23; pi. 7

Zone....... .........12, 17, 18, 19, 20, 24, 26, 27, 28

uncinatus....................................... ........ 12, 24; pi. 4

wilsoni Zone .............................. 16, 19, 21, 22, 25, 28

sp ....... .............................................................. . 10, 22

clingani, Dicranograptus............ ... 12, 16, 18, 19, 20,

22, 24, 25, 26, 28 

cometa, Diplograptus .................... . ......... ..... 29

complanatus ornatus, Dicellograptus ... . .... 20

contortus, Dicranograptus...................... .......... 10,17

convolutus, Dimirastrites .................. . ..... .... 29

Graptotithus ................ ... ............ . . 29

Monograptus .................................. 13, 27, 28, 29, 30

Prionotus ...... ........... .. .... ............. 28

Cordilleran geosyncline ....... ..... .......... 1

cornutus, Orthograptus quadrimucronatus .... 26

Correlation .. .. ........ .......... . ... ........ 5

Corynoides ...... ................. .. .... .. .......... 12, 16

calicularis ............. ... ... .. ..... .... 12, 16; pi. 2

gracilis . .......... ....... ...... . . ....... ......... 16

perungulatus ........ ..... ............ 16

Corynoididae ..................................................................... 16

Cryptograptidae .... ....................... . ..... 21

Cryptograptus .......... ... ....... . ........... 21

tricornis ........ ..... .... .................. 10, 12, 21; pi. 3

Cyrtograptidae .. ..... ............. . .... ...... ..... 30

Cyrtograptus ......... .. .. ................... .... 30

canadensis .. . ............. ..... .... .. 31

grayae . ... ....... ....... .. . .... .... 13

kirki...................... ... ..... ... ..... 30; pi. 6

laqueus .. ....... ... .......... . ....... 13, 30, 31; pi. 6

lundgreni Zone .. .................. .. 30

multiramis .... ....... ... ... 31

kirki............. ... . ..... ... . .. 31

multiramis..... . . . ....... . 31

murchisoni Zone ...... ........... . .. 13

rigidus . ........... .. . ..... ... 31

rigidus ............... .. . 13, 31; pis. 5, 6, 7

Zone....... .. .............. ... 30, 32

symmetricus ..... .... . ......... 31, 32

Zone ... ......... .... .. .... 13

D

decipiens, Demirastrites decipiens ..... ... .. 29

Monograptus . ........ .... 13, 29

decipiens .... ............ ...... ... 13, 29

Page

decipiens—Continued

decipiens, Demirastrites................................. 29

Monograptus ............................................... 13, 29

Demirastrites decipiens decipiens ...................... 29

demissus, Leptograptus .......................................... 12, 16

Dicellograptus ........................................................... 10, 18

affinis .................................................................. 20

alector..................................................... 12, 18; pi. 3

anceps Zone - - ----- .....—..... ..—.......— 12, 20

angulatus-.............................. .................. 19; pi. 3

caduceus............. ................. ..... .. ... .......... 20

complanatus ornatus................................... 20

divaricatus bicurvatus ....... ...... .............. 19; pi. 2

elegans elegans.. ............................. .... 19, 20; pi. 2

rigens ............. .............................. ... ....20; pi. 2

gurleyi.................................................. .......... 20

intortus.............................. .. ..... ........... ... 20

morrisi ................. ..... . . ....... .... ........ 18

ornatus................. . ... ... ... .................. 12

minor ...................... ......... ....._ 12, 20; pi. 3

ornatus ............................... .. ..... 12,20

Zone ..................... 3, 5, 12, 13, 20, 22, 23, 27

sextans exilis ... ............... .......... .. 10

sp .. ...... ...... ...... ........... ... .... 20; pi. 6

Dichograptidae . . ....... ..... .......... 13

Dicranograptidae .............. ........ .... 18

Dicranograptus .......... . .... ....... ..... ...... .. 10,77

clingani Zone .... ...... .... ..... 12, 16, 18, 19, 20, 22

24, 25, 26, 28 

contortus .... ... . .. ... .. 10, 17; pis. 2, 7

kirki . . . .... 18; pi. 2

nicholsoni . .... .. ... 10, 12, 18

nicholsoni . . .... 12, 18; pi. 2

Didymograpsus elegans ..... 19

Didymograptina . .... 13

Didymograptus . ... .. . 15

artus .. .. .. ... 15

bifidus ... ..... 15

Zone . ... .. .. 9, 14, 22, 28

extensus 6, 8, 9

Zone . 15, '22

geminus .......................... ............... ........... 15; pi. 1

gracilis ............................................................... 8

hirundo................................................................ 14

Zone.....................—.............................„..— 15

murchisoni ........................................................ 15

geminus ......................... ............................ 15

Zone................................. ........................... 28

protobifidus.....................................................5, 8; pi. 1

Zone ....................................... 5, 9, 13, 14, 15, 16

Dimirastrites convolutus ...................................... 29

Diplograpsus tricornis ......................................... 21

Diplograptidae. ............................................ ......... 22

Diplograptina........................................................ 22

Diplograptus ...... ............................................... 22

cometa ........................................................ 29

foliaceus calcaratus.................................. . 25

folium ....................... ............................ ...... 29

hincksii...................... ........................................... 21

multidens ........... .... ........................... .. ...... 12

Zone ........... ——.—.....................—. 12, 26, 28

pageanus ......................................................... 26

(Glyptograptus) euglyphus ......... .. ............ 24

teretiusculus .......... ... ........................ 24

(Orthograptus) calcaratus............................ . 25

calcaratus acutus ............... ................ 26

35
36 INDEX

Page

Diplograptus—Continued

( Orthograptus)—Continued

pageanus ...................................... ........... 26

quadrimucronatus ..................................... 26

sp . ....................................................... ...........22; pi. 3

divaricatus bicurvatus, Dicellograptus............... 19

dumosus, Pseudisograptus ..................................... 9

E

etegans, Dicellograptus elegans ........................... 19, 20

Didymograpsus .................................................... 19

elegans, Dicellograptus ................................... 19, 20

rigens, Dicellograptus....................................... 20

etaformis, Brachiograptus....................... ............. 13

etheridgei, Hallograptus .......................................... 24

Paraglossograptus ............................................ 21

euglyphus, Diplograptus (Glyptograptus).......... 24

Glyptograptus .................................................. ..24, 25

euglyphus ..................................................... 12, 24

teretiusculus ......................... ...................... 24

euglyphus, Glyptograptus.............................. 12, 24

exilis, Dicellograptus sextans ................................ 10

extensus, Didymograptus .......................... 6, 8, 9, 15, 22

fibratus, Neurograptus. ...................

flaccidus, Leptograptus flaccidus.

arcuatus, Leptograptus.............

flaceidus, Leptograptus ...........

macer, Leptograptus .................

flemingii, Graptolithus.....................

............. 28

17 

12 

............ 17

............. 17

............. 29

Monograptus ....................................................... 13, 29

flemingii ...................................................... 13, 29

flemingii, Monograptus .................................. 13, 29

flexilis belophorus, Monograptus ........................ 30

foliaceus calcaratus, Diplograptus ...................... 25

folium, Diplograptus ............................................. 29

geinitzianus, Reteograptus ..........

geminus, Didymograptus..............

Didymograptus murchisoni 

Prionotus ....................................

Geologic setting................................

geometricus, Goniograptus ..........

................ 10

................ 15

................ 15

................ 15

................ 3

................ 13

Glossograptidae .......................................................... 21

Glossograptina ........................................................... 21

Glossograptus ............................................................. 21

hincksii....................................................................lO, 12

hincksii..................... ................................... 21; pi. 3

Zone.................................................................. 10, 21

quadrimucronatus .............................................. 27

inequispinosus .............................................. 27

(Orthograptus) quadrimucronatus ................ 27

Glyptograptus ...................................................... 10, 24, 25

euglyphus .......................................................... 24; pi. 5

euglyphus ...................................................... 12, 24

Zone.................................................................. 25

serratus serratus .................................................. 25

sinuatus sinuatus ............................................... 25

teretiusculus .......................................................... 10

euglyphus ...................................................... 24

Zone .................................................. 10, 21, 24, 28

sp .................................................................. 10, 25; pi. 5

(Glyptograptus) euglyphus, Diplograptus .......... 24

teretiusculus, Diplograptus .............................. 24

Goniograptus ................................................................ 6, 13

geometricus........................................................ 13; pi. 6

perflexilis................................................................ 14

gracilis, Corynoides .................................................... 16

Didymograptus .................................................... 8

Nemagraptus ......................12, 16, 18, 21, 24, 25, 26

perungulatus, Corynoides ................................ 16

grandis, Phyllograptus ilicifolius .......................... 15

Graptolithus bigsbyi .................................................. * 14

conuolutus.............................................................. 29

flemingii.................................................................. 29

Graptolithus—Continued 

quadrimucronatus ......

(Prionotus) sedgu-ickii

Graptoloidea...................... ...

grayae, Cyrtograptus ... .....

Page

26 

.......................... 30

....................... 13

........................ 13

gregarius, Monograptus . ................................. 27, 29

griggsi, Phyllograptus ........................... ....... ....... 15

gurleyi, Dicellograptus ............................ ............... 20

H

halli, Monograptus . ................................................ 30

Hallograptus ........................................................... 28

etheridgei......... ................................................... 24

hand robustus, Orthoretiolites...... .... ................. 28

harknessi, Lasiograptus.......... .................................. 12

hastatus, Climacograptus ....................................... 12, 22

angustus, Climacograptus... ........................... 22

martini, Climacograptus .......................... ....... 22

hincksii, Diplograptus ............................................. 21

Glossograptus ............................................ 10, 12, 21

hincksii......... ............................ .................... 21

hincksii, Glossograptus . ................................ 21

hirundo, Didymograptus .................................... .... 14, 15

hvalross, Climacograptus ....................................... 22, 23

Climacograptus longispinus............................ 12, 22

ilicifolius, Phyllograptus .......................................... 5, 14

Phyllograptus ilicifolius........ ............... ........ . 14

grandis, Phyllograptus...................................... 15

ilicifolius, Phyllograptus .................................. 14

major, Phyllograptus ........................................ 6, 14

imitatus, Isograptus caduceus ............................... 9

inequispinosus, Glossograptus

quadrimucronatus .............................. 27

Orthograptus quadrimucronatus .................. 27

innotatus, Climacograptus ..................................... 23

pacificus, Climacograptus............................... 23

intortus, Dicellograptus ........................................... 20

Isograptus ..................................................................... 6, 15

caduceus imitatus................................................ 9

victoriae. ........................................... - ----- -- 15; pi. 2

lunatus............................................................ 8

maximodivergens ........................................ 9

victoriae.......................................................... 16

Zone .. . ........ . ......... .... ... 9, 10, 14, 16

sp .............................................................................. 16

K

kirki, Cyrtograptus ..................

Cyrtograptus multiramis. 

Dicranograptus ...................

30

31

18

laqueus, Cyrtograptus..................................—... 13, 30, 31

Lasiograptidae.............................................................. 28

Lasiograptus harknessi............................................ 12

margaritatus ........................................................ 28

(Neurograptus) margaritatus .......................... 28

Leptograptus ................................................................ 12, 17

capillaris ................................................................ 17

demissus .............................................. 12, 16; pis. 2, 7

flaccidus arcuatus .............................................. 12

flaccidus... ....................................................... 17

macer .............................................................. 17

validus validus .................................................... 17

sp .......................................................................... 17; pi. 2

leptotheca, Monograptus .......................................... 13

linearis, Cladograpsus .............................................. 17

Pleurograptus................ 5, 12, 17, 18, 20, 24, 25, 27

linearis............................................................ 17

linearis, Pleurograptus ...................................... 17

lobiferus, Monograptus.......................-..........—......... 13

logani, Loganograptus .............................................. 13

pertenuis, Loganograptus ................................ 73

Page

Loganograptus ............................................................ 6, 73

logani ......... ..................................................... 13

pertenuis ................................................. 73; pi. 1

longispinus, Climacograptus ................................. 12

Climacograptus longispinus... ....................... 23

hvalross, Climacograptus ..... .......................... 12, 22

longispinus, Climacograptus ......................... 23

longus, Phyllograptus anna ........................... ....... 14

lunatus, Isograptus victoriae ................................ 8

lundgreni, Cyrtograptus.... ................................... 30

M

macer, Leptograptua flaccidus ............................. 17

Maeandrograptus ...................................................... 16

tau ....................................................................9, 16; pi. 7

major, Phyllograptus ilicifolius.............................. 6, 74

Marathon region, Texas.......................................... 1, 3

margaritatus, Lasiograptus ................................... 28

Lasiograptus (Neurograptus) ......................... 28

Neurograptus ..... ................................................ 28

martini, Climacograptus hastatus ....................... 22

maximodivergens, Isograptus victoriae. ............ 9

maximus, Rastrites ................................................... 29

Metamorphism .......................................................... 5

minimus, Climacograptus ........................................ 12

minor, Dicellograptus ornatus.... ........................... 12, 20

Petalograptus..... ................................................. 13, 27

mohawkensis, Climacograptus ...... ....................... 12

Monograptidae ........................................................... 28

Monograptina .............................................................. 28

Monograptus .............................................................. 28

argutus argutus.................................................... 13

convolutus .................................................. 13, 28; pi. 5

Zone................................................... 13, 27, 29, 30

decipiens ................................................................ 13, 29

decipiens ........................................... 13, 29; pi. 5

/temmgH.............................................................. 13, 29

flemingii........................................ 13, 29; pi. 5

flexilis belophorus Zone ................................... 30

gregarius Zone..................................................... 27, 29

halli ......................................................................... 30

leptotheca ............................................................. 13

lobiferus ................................................................. 13

priodon ................................................................... 30

riccartonensis Zone ............................................ 30

sedgwickii ............................... .... ...... 13, 30; pi. 5

Zone.......................................................... 13, 29, 30

spiralis .................................................................... 29

Zone.................................................................. 13, 31

urceolus .................................................................. 29

multidens, Diplograptus.................——.-.......—12,26,28

multiramis, Cyrtograptus ........................................ 31

Cyrtograptus multiramis.................................. 31

fa'rAi, Cyrtograptus ............................................ 31

multiramis, Cyrtograptus ................................ 31

morrisi, Dicellograptus .............................................. 18

murchisoni, Cyrtograptus ....................................... 13

Didymograptus .................................................... 15, 28

geminus, Didymograptus...........—.. .................. 15

N

Nemagraptidae............................................................ 16

Nemagraptus................................................................ 10

Zone..........-............-......-...-....--......10, 17, 21, 25, 26

graci/is Zone................................12, 16, 18, 21, 24, 25, 26

Neurograptus ................................................................ 28

/iftrotus.................................................................. 28

margaritatus .................................................... 28; pi. 3

(Neurograptus) margaritatus, Lasiograptus...... 28

nicholosoni, Dicranograptus .................................. 10, 18

Dicranograptus nicholsoni .............................. 12, 78

nicholsoni, Dicranograptus......—.................... 12, 78

O

ornatus, Dicellograptus ........................................ 3, 5, 12,

13, 20. 22, 23, 27
INDEX 37

ornatus—Continued

Page

Dicellograptus complanatus ..... ...... ...... .... 20

ornatus.......................................... ...... 12,20

minor, Dicellograptus ................................... 12, 20

ornatus, Dicellograptus ................ ... ..... .. 12, 20

Orthograptus ................ ...................... 12, 22, 25, 26

amplexicaulis ........ ........ ......... ..... ..... 12

abbreviatus...... .................. ...... ......... 12

pauperatus . ..... ... ... . ... ..... .......... 12

socialis ......... .... .......... .. ........... 12

Zone................................... ... 12, 18, 24, 26

calcaratus ............. ..... . ............... .. 25, 26

acutus ...... ...... .......... ..... . .10, 12, 26; pi. 4

basilicas...... ... ...... .. ...................... 12

calcaratus ............................. .... ..... 25; pi. 4

tenuicornis . .................................... 25; pi. 4

vulgatus..................................... ............. 25

pageanus pageanus.. ........................... ..26; pi. 4

quadrimucronatus ................. ......... 12, 24, 26, 27

cornutus................................ ............... 26

inequispinosus. ..... . .................... 27; pi. 4

quadrimucronatus ............ ....... 12, 26; pi. 4

spinigerus .............................................. . 27

Zone............................................... ...... 12, 19,27

(Orthograptus) calcaratus, Diplograptus........... 25

calcaratus acutus, Diplograptus .................... 26

pageanus, Diplograptus 26 

quadrimucronatus, Diplograptus ................ 26

Glossograptus ......................................... 27

Orthoretiolites ................................. ........................ 12, 28

hami robustus .............................. ............... . 28; pi. 4

pacificus, Climacograptus.................................... 23

Climacograptus innotatus............................ 23

pacificus............................................... ..... 12, 23

pacificus, Climacograptus.................... ......... 12, 23

pageanus, Diplograptus............... ....................... 26

Diplograptus (Orthograptus) ......................... 26

Orthograptus pageanus ......................... ....... 26

pageanus, Orthograptus ................................. 26

palmeus, Petalograptus ........................................... 27

Paraglossograptus etheridgei Zone ........... ........ 21

tentaculatus Zone............................................. 13, 21

Park Creek .................................................................. 5

Park Creek thrust........................ .............................. 3

Passage beds ...........................................12, 20, 22, 27, 28

pauperatus, Orthograptus amplexicaulis............ 12

peltifer, Climacograptus........................................... 19, 22

perexcavatus, Amplexograptus............................. 12

perflexilis, Goniograptus .......................................... 14

pertenuis, Loganograptus logani .......................... 13

perungulatus, Corynoides gracilis ........................ 16

Petalograptus................................................................ 27

minor.......................................................... 13, 27; pi. 3

palmeus ................................................................ 27

Phi Kappa Formation....... ................................... 3, 5

Phyllograptus ... ..... 

anna ..... .....

prolatus .. . ... .. ... .. . . 

griggsi ... ... ... .. 

ilicifolius .... ..... 

grandis .... . . . 

ilicifolius . ...... 

major. . .. ... . ..... ... 

typus .

linearis .. ... .. .... 

linearis ... 

Zone. ...... 5, 12, 17, 18,

priodon, Monograptus ... . . ....

(Prionotus) sedgwickii, Graptolithus 

prolatus, Phyllograptus anna ..... ..... 

protobifidus, Didymograptus ...

Pseudisograptus dumosus . 

Pseudobigsbyi, Tetragraptus .... 

Pseudoclimacograptus . . .... ..

scharenbergi . .. .. 

pulcherrimus, Reteograptus . .

Q

quadribrachiatus, Tetragraptus 

quadrimucronatus, Diplograptus 

(Orthograptus) . ..

Orthograptus 12,

cornutus, Orthograptus .... . . .... 

inequispinosus, Glossograptus ....... 

Orthograptus ... . ... .... ... 

quadrimucronatus, Orthograptus 

spinigerus, Orthograptus. ... . . ..... ..

R

Page

.. . 14

. 5, 8, 14 

. 14

.. . 14; pi. 1 

.. . 15

5, 14 

.... . 15 

14 

. 6, 14; pi. 1 

15 

3

17

... 12,17 

.. 17; pi. 2 

20, 24, 25, 27

30 

28

15

30 

14 

. .. 5, 8, 9, 

13, 14, 15, 16 

.... .. 9 

14 

27 

... 12, 26, 28

12, 27; pi. 3 

12

..... 8

26

.. .. 27

... 27

. ... 26

19, 24, 26, 27 

.. 12, 26

26 

27 

. ... .. 27 

. ...... 12, 26

27

29

. .... . 29, 30

. .... 32

... .. . 10

.. . ... 12

28

30

20

... . 30, 31, 32

. ... ...... 13, 31

.......... . 13, 31

	Page 

robustus, Orthoretiohtes hami 28

S

scalans, Chmacograptus 13

scharenbergi, Climacograptus 21

Pseudoclimacograptus 12, 26, 2H

scharenbergi . 12,27

scharenbergi, Pseudoclimacograptus 12, 27

sedgwickii, Graptohthus (Pnonotus) 3U

Monograptus . 13, 29, 30

serratus, Glyptograptus serratus . 25

serratus, Glyptograptus 25

sextans exilis, Dicellograptus 10

sinuatus, Glyptograptus sinuatus 25

sinuatus, Glyptograptus 25

socialis, Orthograptus amplexicaulis 1'2 

spinigerus, Orthograptus quadrimucronatus 27

spiralis, Monograptus 13, 29, 31

Summit Creek . 5

supernus, Climacograptus 23

symmetricus, Cyrtograptus . 31, 32

Systematic descriptions . 13

tau, Maeandrograptus 

tentaculatus, Paraglossograptus 

tenuicornis, Orthograptus calcaratus 

teretiusculus, Diplograptus 

(Glyptograptus)

Glyptograptus .

euglyphus, Glyptograptus 

Tetragraptus

amii

bigsbyi

pseudobigsbyi .

quadribrachiatus .. 

Trail Creek Formation 

tricornis, Cryptograptus

Diplograpsus

tridentatus, Climacograptus bicornis 

tubuliferus, Climacograptus ...

20,

typus, Phyllograptus 

uncinatus, Climacograptus 

urceolus, Monograptus

V, W

validus, Leptograptus validus .

validus, Leptograptus 

victoriae, Isograptus .

Tsograptus victoriae . .. .

lunatus, Isograptus

maximodivergens, Isograptus

victoriae, Isograptus .. ....

vulgatus, Orthograptus calcaratus 

wilsoni, Climacograptus 

Wood River ....

9, 16

13,21,24

25

24

10, 21, 24, 28 

24

5, 14

6, S, 9

14

. 14; pi. 1 

8 

5

. 10, 12, 21 

21

10, 12, 22

12, 17, 18,19,

23, 26, 27, 28

15

12,24 

29

.. 17 

.. 17

15

16

8

9

... 16 

25

16, 19, 21, 22, 25, 28 

. ... 3

PLATES 1-7

Contact photographs of the plates in this report are available, at cost, from U.S. Geological 

Survey Library, Federal Center, Denver, Colorado 80225
PLATE 1

FIGURE 1. Loganograptus logani pertenuis Ruedemann (p. 13) USNM 189095, x 5.1,

collection 62ICn 511. 

2,3. Phyllograptus anna prolatus n. subsp. (p. 14)

2. USNM 189143, x 5.0, holotype, collection 62ICn 511.

3. USNM 189144, x 5.1, collection 62ICn 511. 

4. Phyllograptus ilicifolius major Ruedemann (p. 14)

USNM 189145, x 2.5, collection 62ICn 511. 

5,8. Didymograptus protobifidus Elles (p. 15)

5. USNM 189147, x 4,9, collection 62ICn 511. 

8. USNM 189148, x 5.0, collection 62ICn 511.

6. Isograptus sp. (p. 16)

USNM 219001, x 5.1, collection 62ICn 521.

7. Tetragraptus pseudobigsbyi Skevington (p. 14)

USNM 189134, x 5.1, collection 62ICn 511. 

9. Didymograptus cf. D. gemminus (Hisinger) (p. 15)

USNM 189146, x 2.8, collection 62ICn 511.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 1

8 9 

LOGANOGRAPTUS, PHYLLOGRAPTUS, DIDYMOGRAPTUS, ISOGRAPTUS, AND TETRAGRAPTUS
PLATE 2

FIGURE 1. Leptograptus demissus n.sp. (p. 16)

USNM 189085, x 4.7, holotype, collection 69ICt 59.

2. Dicellograptus cf. D. elegans elegans (Carruthers)

(P. 19) 

USNM 189097, x 5.1, collection 69ICt 79.

3. Leptograptus n.sp.? (p. 17)

USNM 189086, x 4.9, collection 69ICt 71.

4. Pleurograptus linearis linearis (Carruthers)(p. 17) 

USNM 189087, x 1.0, collection 69ICt 59.

5. Dicellograptus divaricatus bicurvatus Ruedemann

(p. 19) 

USNM 189096, x 4.8, collection 69ICt 92.

6. Dicranograptus contortus Ruedemann (p. 17)

USNM 189088a (left), USNM 189088b (right), x 4.6, 

collection 69ICt 88.

7. Dicranograptus cf. D. kirki Ruedemann (p. 18) 

USNM 189089, x 4.8, collection 69ICt 86.

8. Dicellograptus cf. D. elegans rigens Elles and Wood

(p. 20) 

USNM 189098, x 4.5, collection 69ICt 74.

9. Isograptus aff. /. victoriae Harris (p. 15)

USNM 189111, x 5.1, collection 62ICn 511. 

10,11. Dicranograptus nicholsoni nicholsoni Hopkinson 

(p. 18)

10. USNM 189091, x 1.3, collection 69ICt 88.

11. USNM 189090, x 4.7, collection 69ICt 91. 

12. Corynoides calicularis Nicholson (p. 16) 

USNM 189084, x 5.0, collection 69ICt 88.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 2

9 10 11 12 

LEPTOGRAPTUS, DICELLOGRAPTUS, PLEUROGRAPTUS, DICRANOGRAPTUS, ISOGRAPTUS, AND CORYNOIDES
PLATE 3

FIGURE 1. Dicellograptus cf. D. angulatus Elles and Wood (p. 19)

USNM 189105, x 4.8, collection 69ICt 63. 

2,3. Dicellograptus n.sp.(?) (p. 20).

2. USNM 189104, x 5, collection 69ICt 77.

3. USNM 189103, x 4.7, collection 69ICt 77.

4. Glossograptus hincksii hincksii (Hopkinson) (p. 21) 

USNM 189107, x 4.6, collection 69ICt 91.

5. Cryptograptus tricornis Carruthers (p. 21) 

USNM 189108, x 4.8, collection 69ICt 91.

6. Pseudoclimacograptus scharenbergi scharenbergi 

(Lapworth) (p. 27) USNM 189132, x 4.9, collection 

691 Ct 91.

7. Diplograptus sp. (p. 22)

USNM 189109, x 5.1, collection 691 Ct 86. 

8,12,13,17. Dicellograptus alector Carter (p. 18).

8. USNM 189093b, x 5.1, collection 69ICt 73.

12. USNM 189094, x 4.8, collection 69ICt 61.

13. USNM 189092, x 4.8, collection 69ICt 73. 

17. USNM 189093a, x 5.1, collection 69ICt 73. 

9. Neurograptus margaritatus (Lapworth) (p. 28)

USNM 189133, x 4.6, collection 69ICt 84. 

10. Petalograptus minor Elles (p. 27)

USNM 189131, x 5.2, collection 69ICt 31.

11,14,15,16. Dicellograptus cf. D. ornatus minor Toghill (p. 20) 

11. USNM 189101, x 5.2, collection 69ICt 44.

14. USNM 189100, x 4.2, collection 69ICt 55.

15. USNM 189102, x 5.1, collection 69ICt 59.

16. USNM 189099, x 4.7, collection 69ICt 55.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 3

DICELLOGRAPTUS, GLOSSOGRAPTUS, CRYPTOGRAPTUS, PSEUDOCLIMACOGRAPTUSt DIPLOGRAPTUS,

NEUROGRAPTUS, AND PETALOGRAPTUS
PLATE 4

FIGURE 1,2. C/tmacogra/>£us?uncma£usKeble and Harris (p. 24)

1. USNM 189117, x 4.7 (tectonically stretched 

lengthwise), collection 69ICt 41.

2. USNM 189116, x 4.7, collection 69ICt 59.

3. Orthograptus pageanus pageanus Elles and Wood 

(p. 26) USNM 189127, x 5.0, collection 69ICt 86.

4. Orthograptus quadrimucronatus inequispinosus 

(Ruedemann)(p. 27) USNM 189130, x 4.9, collection 

69ICt 78.

5. Orthograptus cf. O. quadrimucronatus quadrimucronatus (J. Hall) (p. 26) USNM 189128, x 4.7, 

collection 69ICt 55.

6. Orthoretiolites hami robustus Skevington (p. 28) 

USNM 189129, x 4.5, collection 69ICt 72.

7. Climacograptus hastatus T. S. Hall (p. 22) USNM 

189118, x 4.7, collection 69ICt 42, immature specimen. 

8,9. Climacograptus pacificus Ruedemann (p. 23).

8. USNM 189115, x 4.7, collection 69ICt 33.

9. USNM 189113, x 4.7, collection 69ICt 33.

10. Orthoraptus aff. O. calcaratus calcaratus (Lapworth) (p. 25) USNM 189123, x 4.6, collection 

69ICt 86.

11. Orthograptus cf. O. calcaratus tenuicornis Elles 

and Wood (p. 25) USNM 189122, x 4.8, collection 

69ICt 59.

12,13. Climacograptus longispinus hualross Ross and 

Berry (p. 22)

12. USNM 164466, x 4.0, also figured by Riva 

(1974c, text-fig. 7e), collection 69ICt 55.

13. USNM 189112, x 5.1, showing reduction of

basal spines, collection 69ICt 42. 

14. Climacograptus bicornis tridentatus Lapworth

(p. 22). USNM 189110, x 2.2, collection 69ICt 88. 

15-17. Orthograptus calcaratus cf. subsp. acutus Elles and 

Wood (p. 26).

15. USNM 189124, x 2.7, collection 69ICt 88.

16. USNM 189126, x 2.1, collection 69ICt 92.

17. USNM 189125, x 5.1, collection 69ICt 88.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 4

CLIMACOGRAPTUS, ORTHOGRAPTUS, AND ORTHORETIOLITES
PLATE 5

FIGURE 1. Glyptograptus cf. G. euglyphus (Lapworth) (p. 24)

USNM 189119, x 5.2, collection 69ICt 79. 

2,3. Glyptograptus(?) sp. (p. 25).

2. USNM 189121, x 4.9, collection 69ICt 86.

3. USNM 189120, x 5.1, collection 69ICt 86.

4. Monograptus sedgwickii (Portlock) (p. 30) 

USNM 189139, x 2.7, collection 69lCt 32.

5. Cyrtograptus rigidus rigidus Tullberg (p. 31)

USNM 189142, x 4.8, collection 69ICt 21. 

6-8. Monograptus cf. M. flemingii flemingii (Salter)(p. 29)

6. USNM 189138, x 2.8, collection 69lCt 21.

7. USNM 189136, x 4.2, collection 69ICt 21.

8. USNM 189137, x 2.7, collection 69ICt 21. 

9,10. Monograptus cf. M. decipiens decipiens Tbrnquist 

(P- 29).

9. USNM 189141, x 4.8, collection, 69lCt 31.

10. USNM 189140, x 4.8, collection 69lCt 31. 

11. Monograptus convolutus (Hisinger) (p. 28) 

USNM 189135, x 5.0, collection 69ICt 31.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 5

8 11 

GLYPTOGRAPTUS, MONOGRAPTUS, AND CYRTOGRAPTUS
PLATE 6

FIGURE 1. Cyrtograptus kirki Ruedemann (p. 30).

USNM 219002, x 2, collection 69ICt 21; from U.S. 

Geological Survey loc. 1371.

2. Dicellograptus n.sp.? (p. 20)

USNM 189106, x 5, collection 69ICt 76.

3. Cyrtograptus laqueus Jackson and Etherington 

(p. 31) USNM 219003, x 2, collection 69ICt 21; also 

figured by Ruedemann (1947, pi. 89, fig. 11), from 

U.S. Geological Survey loc. 1371.

4. Cyrtograptus rigidus rigidus Tullberg (p. 31) 

USNM 219004, x 5, collection 69ICt 21.

5. Goniograptus geotnetricus Ruedemann (p. 13) 

USNM 189114, x 5, collection 621 Cn 511.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 6

CYRTOGRAPTUS, DICELLOGRAPTUS, AND GONIOGRAPTUS
PLATE 7

FIGURE 1. Maeandrograptus tau Harris (p. 16)

USNM 164425, x 5, collection 62ICn491. 

2,3. Leptograptus demissus, n.sp. (p. 16)

2. USNM 164427, x 5, collection 69ICt 59.

3. USNM 189085, holotype, x 5, collection 69ICt 

59.

4. Dicranograptus contortus Ruedemann (p. 17) 

USNM 219006, x 5, collection 69ICt 91.

5. Climacograptus tubuliferus Lapworth (p. 23) 

USNM 164424, x 3, collection 69ICt 61.

6. Cyrtograptus rigidus rigidus Tullberg (p. 31) 

USNM 219005, x 4, collection 69ICt 21.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1020 PLATE 7

SKETCH OF MAEANDROGRAPTUS, LEPTOGRAPTUS, DICRANOGRAPTUS, CLIMACOGRAPTUS,

AND CYRTOGRAPTUS