Middle Bajocian 

A·mmonites from the 

Cook Inlet Region 

Alaska 

By Rf\LPH W. IMLAY 

JUR.ASSIC AMMONITES FROM SOUTHERN ALASKA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B 

Desc"ription and illustrations of cephalopods of 

Middle Jurassic (middle Bajocian) age 

LIBRAR~ 

BUR!AU OF UfNEI 

'-IBRARV 

SPOkANl. NASH. 

Jl.I\J 3 1971 ...... . '4'f 0 ··±irtF ~ 

•.• f l S f R E T U R N 

ID liBRAIY 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

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

Washington, D.C. 20402 - Price 

'l 
CONTENTS 

Abstract __________________________________________ _ 

Introduction ________________ · ______________________ _ 

Biologic analysis ______________ - ________ -- ___ -- _____ _ 

Stratigraphic summary _____________________________ _ 

Tuxedni Group along northwest side of Cook Inlet __ 

Red Glacier Formation _____________________ _ 

Gaikema Sandstone ________________________ _ 

Fitz Creek Siltstone _____ -- _____ ---_- _______ -

Cynthia Falls Sandstone ____________________ _ 

Tuxedni Formation in the Talkeetna Mountains ___ _ 

Ages of the faunas _________ -------------------------

Ages of the Tuxedni Group northwest of Cook Inlet_ 

Red Glacier Formation _____________________ _ 

Gaikema Sandstone ______ - _________________ -

Fitz Creek Siltstone ________________________ _ 

Cynthia Falls Sandstone ________ - _____ -_-_-_-

Ages of the Tuxedni Formation in the Talkeetna 

Mountains-----------------------------------

Page 

B1 

1 

2 

6 

6 

6 

8 

8 

9 

9 

10 

10 

10 

12 

12 

14 

14 

Comparisons with other faunas _____ - __ - ___ -_--------- Alaskan Peninsula _____________________________ _ 

Queen Charlotte Islands, British Columbia _____ -- __ 

Central British Columbia ____________________ -- __ 

Western Interior of Canada _____________________ _ 

Western Interior of the United States _________ -- _-

East-central Oregon ___________ - __ - ___ -----------

Northern California __________________ -_-_-_----- Southern Caluornia ____________________________ _ 

Southern MexicO------------------------------- South America ________________________________ _ 

Indonesia and Australia _______ ------------------ Europe _______________________________________ _ 

Geographic distribution ______ - ____ -------------------

Summary of results _______________ ------ _-----------

Systematic descriptions ___________________ -----------

Literature cited ___________________ ------------------

Index---------------------------------------------

ILLUSTRATIONS 

PLATE 1. Macrophylloceras and Holcophylloceras. 

2. Sonninia and Phylloceras. 

3. Sonninia. 

4. Witchellia?, Sonninia?, and Lissoceras. 

5. Witchellia? and Bradfordia?. 

6. Sonninia, Pelekodites?, and Witchellia. 

7. Witchellia. 

8. Bradjordia and Oppelia. 

9, 10. Labyrinthoceras. 

11. Emileia. 

12. Chondroceras. 

13. Normannites. 

14. Normannites (Itinsaites) and Otoites?. 

15-19. Stephanoceras. 

2Q-22. Stemmatoceras. 

23. Lissoceras, Strigoceras, and Teloceras. 

24. Teloceras and Zemistephanus. 

[Plates 1-29 follow Index] 

25. Otoites and Zemistephanus. 

26, 27. Zemistephanus. 

28. Zemistephamts, Leptosphinctes, and Arkelloceras?. 

29. Parabigotites. 

FIGURES 1-4. Index maps showing occurrences of middle Bajocian fossils. 

1. In the Talkeetna Mountains ___________________________________________________ ---_-_-_-------

2. In the Tuxedni Bay area--------------------------------------------------------------------- 3. North of Chinitna Bay __ -----------------------------------------·--------------------------- 4. On the Iniskin Peninsula---------------------------------------------------------------------

5. Correlation of spme Middle and Upper Jurassic formations and faunas in the Cook Inlet region ___ ------_-

m 

Page 

B18 

18 

19 

19 

19 

19 

19 

20 

20 

20 

20 

21 

21 

21 

27 

31 

55 

59 

Page 

B2 

3 

4 

5 

7 
TABLES 

TABLE 1. Ammonite genera and subgenera in beds of middle Bajocian age in the Cook Inlet region showing biologic relationships and relatiye numbers available for study______________________________________________ B2 

2. Thickness of the lower four formations of the Tuxedni Group along the northwest side of Cook Inlet________ 6 

3. Early Bajocian ammonites in the lower part of the Red Glacier Formation along the northwest side of Cook 

Inlet----------------------------------------------------------------------------------------- 6 

4-7. Middle Bajocian ammonites. 

4. In the Red Glacier Formation along the northwest side of Cook Inlet______________________________ 11 

5. In the Gaikema Sandstone along the northwest side of Cook Inlet_________________________________ 12 

6. In the Fitz Creek Siltstone along the northwest side of Cook Inlet_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 

7. In the Cynthia Falls Sandstone along the northwest side of Cook Inlet __________ ·- ______________ .___ 14 

Stratigraphic distribution of middle Bajo'Cian ammonite species within the formations of the Tuxedni Group along the northwest side of Cook Inlet___________________________________________________________ 15 

Stratigraphic distribution of certain Bajocian ammonite genera and subgenera within the Tuxedni Group 

8. 

9. 

along the northwest side of Cook Inlet___________________________________________________________ 16 

European ranges of certain Bajocian ammonites present in the Tuxedni Group in the Cook Inlet region____ 17 

Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region_____________ 22 

Geographic distribution of middle Bajocian ammonites in the Talkeetna Mountains______________________ 27 

Geographic distribution of middle Bajocian ammonites along the northwest side of Cook Inlet_ _ _ _ _ _ _ _ _ _ _ _ 28 

10. 

11. 

12. 

13. 

IV 
JURASSIC AMMONITES FROM SOUTHERN ALASKA 

MIDDLE BAJOCIAN AMMONITES FROM THE COOK INLET REGION, ALASKA 

By RALPH w. IMLAY 

ABSTRACT 

Jurassic ammonites of middle Bajocian age occur in the 

Tuxedni Group along the northwest side of Cook Inlet and in 

the Tuxedni Formation in the eastern part of the Talkeetna 

Mountains, Alaska. Numericaliy the dominant families are 

the Otoitidae and Stephanoceratidae. The familes Phylloceratidae, Sonninidae, Oppelidae, and Perisphinctidae together 

compose only about one-third of the total specimens. 

The Tuxedni Group has not furnished any ammonite genera 

that characterize the European zone of Sonninia sowerbyi at 

the base of the middle Bajocian. It has, however, furnished 

ammonites that characterize the next higher zones of Otoites 

sauzei and Stephanoceras humphriesianum. 

The Otoites sauzei zone northwest of Cook Inlet is represented 

by an association of the genera Sonninia, S. (Papilliceras), 

Witchellia, Bradfordia, Otoites, Emileia, Stephanoceras, S. 

(Skirroceras), Stemmatoceras, and Parabigotites. These ammonites occur throughout most of the Red Glacier Formation 

and some occur in the overlying Gaikema Sandstone of the 

Tuxedni Group. The presence of N ormannites in the upper 

third of the Red Glacier Formation suggests that this part 

correlates with only the upper part of the Otoites sauzei zone. 

T~e Otoites sauzei zone is also well represented throughout 

most of the Tuxedni Formation in the Talkeetna Mountains 

by the same association of ammonite genera and by many of 

the species that occur in the Red Glacier Formation northwest 

of Cook Inlet. With these in the Talkeetna Mountains occurs 

the ammonite Labyrinthoceras, which is typical of the Otoites 

sa~tzei zone in Europe. 

The Stephanoceras humphriesianum zone in the Cook Inlet 

region is represented by an association of the genera N ormannites, 

Ch(mdroceras, Teloceras, Stephanoceras, Stemmatoceras, and 

Zemistephamts. These range through most of the Fitz Creek 

Siltstone and the lower fourth of the overlying Cynthia Falls 

Sandstone. In addition Chondroceras, a genus not known above 

the middle Bajo~ian, ranges through the lower two-thirds of 

the Cynthia Falls Sandstone. The presence of a few specimens 

of Sonninia in the lower three-fourths of the Fitz Creek Siltstone 

suggests that this part of the member is not younger than the 

lower part of the 8tephanoceras humphriesianum zone. 

The middle Bajocian ammonites in the Tuxedni Group have 

closer affinities generically and specifically with those of the 

same age in other parts of the Pacific coast from Alaska. to 

California than \\•ith middle Bajocian ammonites in the western 

interior of Canada and of the United States. The Alaska ammonites also show affinities on a generic level with ammonites 

that are commoil in beds of middle Bajocian age in other continents except for the presence in Alaska of the genera Zemistephanus and Parabigotites and the absence to· date of certain 

other genera, such as Dorsetensia. 

New species described herein include Holcophylloceras costisparsum Imlay, Sonninia tuxedniensis Imlay, Witchellia adnata 

Imlay, W.? aquilonia Imlay, Oppelia stantoni Imlay, Bradfordia 

costidensa Imlay, B.? caribouensis Imlay, Otoites? filicostatus 

Imlay, Emileia constricta Imlay, Labyrinthoceras glabrum Imlay, 

Normannites kialagvikensis Imlay, N. variabilis Imlay, Stephenoceras obesum Imlay, S. nelchinanum Imlay, S. (Skirroceras) 

juhlei Imlay, S. (Skirroceras) kirschneri Imlay, Stemmatoceras 

ursinum Imlay, and Leptosphinctes evolutus Imlay. 

INTRODUCTION 

The ammonites described herein have been studied 

partly as an aid to field geologists in dating the beds 

of middle Bajocian age in the Cook Inlet region, Alaska, 

partly to determine the sequence of faunas in the Middle Jurassic beds, partly as biological documentation 

of the genera and species present, and partly to establish biologic and stratigraphic standards of reference. 

As a consequence, fragmentary or distorted ammonites 

from other areas may now be colnpared readily with 

well-preserved ammonites and age determinations can 

be made with greater confidence. Such can be very 

important in areas of poor exposures, of partly metamorphosed rocks, or of complicated structures, such as 

exist at many places in the Pacific coast States. 

The fossils from the middle Bajocian rocks of the 

Cook Inlet region, Alaska, were collected by A. A. 

Baker in 1921; Andrew Brown in 1904; R. L. Detterman 

in 1957 and 1958; L. F. Fay in 1954; C. N. Fenner in 

1919; Arthur Grantz in 1950-1952, 1955, 1957; J. K. 

Hartsock in 1949-1951; R. D. Hoare in 1952; R. W. 

Imlay in 1948 and 1952; Herbert Insley in 1920; 

Werner Juhle in 1952; L. B. Kellum in 1944; C. E. 

Kirschner in 1946; Adolph Knopf in 1906; G. C. Martin 

in 1904 and 1913; J. B. Mertie in 1913; D. J. Miller 

in 1948 and 1949; F. H. Moffit in 1920 and 1921; 

E. R. Orwig in 1957; R. M. Overbeck in 1913; T. W. 

Stanton in 1904; and Helmuth Wedow, Jr. in 1944. 

Bl 
B2 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

Most of these geologists have furnished stratigraphic 

and geographic information concerning some of the 

fossils. Thanks are due particularly, however, to 

Arthur Grantz and R. L. Detterman for preparing 

locality maps (figs. 1-4) and descriptions based on the . 

most recent topographic surveys and for furnishing 

and then checking all . the stratigraphic information 

presented herein. 

BIOLOGIC ANALYSIS 

The Alaskan Jurassic ammonites of middle Bajocian 

age described herein number about 7 40 specimens. 

Their distribution by families, subfamilies, genera, and 

subgenera is shown in table 1. . The table shows that 

the Otoitidae and the Stephanoceratidae are the dominant families, composing nearly two-thirds of the specimens. The families Phylloceratidae, Sonniniidae, 

Oppeliidae, and Perisphinctidae are much less common 

and together compose about one-third of the specimens. 

The Lytoceratidae, Strigoceratidae, and Haploceratidae 

are of minor importance. 

TABLE 1.-Ammonite genera and subgenera in beds of middle 

Bajocian age in the Cook Inlet region, Alaska, showing biologic 

relationships and relative numbers available for study 

Family Subfamily 

Phylloceratidae_______ Phylloceratinae ______ _ 

Calliphylloceratinae __ _ Lyto?e~~tidae_ ------- Lytoceratinae ________ _ 

Sonnmudae __ -------- ------------------------

Strigoceratidae _______ ------------------------ Haploceratidae __________ --------------------- Oppeliidae_ ---------- Oppeliinae ___________ _ 

Otoitidae_____________ Otoitinae ___ ----------

Sphaeroceratinae _____ _ 

Stephanoceratidae ___________________________ _ 

Perisphinctidae_______ Leptosphinctinae ____ _ 

Genus or subgenus Number of 

specimens 

Phylloceras ___________ _ Macrophylloceras __ ___ _ Holcophylloceras ______ _ 

~g!o;t~i::============= Sonninia? _ ------------ Sonninia (Papilli- ceras). 

Witchellia __ _ ---------- Witchellia? __ ---------- Strigoceras _____ _______ _ 

Lissoceras ___ ---------- Oppelia ___ ---------- __ Bradfordia ____________ _ 

Bradfordia? ------------ Otoites _ -------------~­ Otoites? _ -------------- Emileia ___ ------------ Emileia? ___ ----------- Labyrinthoceras _______ _ Chondroceras __ ------ __ Normannites ___ ------- Stephanoceras _ -------- Stephanoceras (Skirro- ceras). Stemmatoceras ________ _ 

Stemmatoceras? ------- Teloceras _____________ _ 

Zemiitephanus __ ------ Zemistephanus? _____ ~ _ Parasbigotites ____ -- ___ _ Leptosphinctes ________ _ 

1 

24 

33 

10 

20 

12 

12 

10 

13 

2 

9 

11 

36 

4 

4 

2 

12 

2 

13 

120 

105 

13 

50 

12 

2 

30 

105 

2 

69 

2 

r1_4~8-3~0~'------------------------~1_4,8_oo_o_' ______________ ~--------~1_4~7-3,o_,_-____________________ ~~-1_4,7°00' 

0 5 10 MILES 

62°15' + + + 62° 15' 

62°00' + + 62°00' 

61 045' -I- 61 045' 

~~------------------~------~~------------------~------~------~------------------~ 

148°30' 148°00' 147°30' 147°0~ 

FIGURE 1.-lndex map showing occurrences of middle Bajocian fossils in the Talkeetna Mountains, Alaska. (Numbers on maps refer to those given in tables 11 and 12.) 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B3 

152°50' 45' 40' 152°35' 

152°50 45' 40' 152°35' 

FIGURE 2.-Indcx map showing occurrences of middle Bajocian fossils in the Tuxedni Bay area, Alaska. (Numbers on maps refer to those given in tables 11 and 13.) 

The genus Zemistephanus is assigned herein to the 

Stephanoceratidae rather than to the Otoitidae (Arkell 

and others, 1957, p. L289) because it greatly resembles 

Telocm·as in shape, coiling, ribbing, in the presence of a 

simple aperture, and in having a broad deep first lateral 

saddle that is much larger than the second lateral 

saddle. It differs from Teloceras mainly by bearing 

tubercles nearer the umbilicus and by its adult body 

whorl becoming· serpenticone as a result of umbilical 

enlargement and whorl contraction. It differs from 

Pseudotoites by having a much wider first lateral saddle, 

a simple instead of a collared aperture, a more coronate 

form, more prominent umbilical tubercles, and stronger 

ribbing on its inner whorls. 

The ammonite NoTmannites presents a special problem taxonomically. It is used in a broad sense by 

Arkell and others (1957, p. L289) to include species 

showing considerable diversity in form, ribbing, and 

tuberculation. It is used in a narrow sense by Westermann (1954, p. 124-332; 1956b, p. 250, 251; 1958, p. 

451) as one of five genera under the subfamily Normannitinae. He further divides his restricted Normannites 

into four subgenera and divides another of the five 

genera, Masckeites, into two subgenera. Evidently 

the genus Normannites as defined by Arkell includes. all 

the ammonites that Westermann places . under the 

N ormannitinae. 

Arkell assumed ·apparently that the differences in 

form and sculpture of the ammonites in question merely 

reflect a highly variable rapidly developing population, 

such as has been demonstrated for the Triassic genus 

Tropites (Silberling, 1959, p. 42-44), the Jurassic genus 

Ermoceras (Arkell, 1952a, p. 272-277), the Cretaceous 

genera Neogastroplites (Reeside and Cobban, 1960, 

p. 51-54), and Barroisiceras (Basse, 1947, p. 97-178). 

In contrast, Westermann assumed that the differences 

are of considerable taxonomic significance and that the 

ammonites in question can be readily divided into 

distinct genera and subgenera. Both assumptions have 

precedents. Many paleontologists, including Arkell, 

who have studied a highly variable but closely related 

short-lived group of ammonites have decided that for 
B4 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

6o·oo' 

59 ° 55' 

Horn Mt 

X 

153°05' 

+ 

.. 

dil'q~~~ ... ... ......... . ........................ . 

......... :.:·::::::::::::::~:{}::;:::)~}(~{??::.:}(ff{~~f:::::::::.::::::::::: o.._ ____ .....L.._ ____ ---1..2 ____ _....13L_ ___ ____j 

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::-:::.:.:.:........... . ...... ·········· ..... . 

153"05' 153°00' 152°55' 

FIGURE 3.-Index map showing occurrences of middle Bajocian fossils north of Chinitna Bay, Alaska. (Numbers on maps refer to those given in tables 11 and 13.) 

practical purposes of systematic description such a 

group should be divided into genera, or at least subgenera (Spath, 1928, p. 166; Arkell, 1952a, p. 272, 273). 

Others have decided that such distinctions serve no 

practical systematic purpose (Reeside and Cobban, 

1960, p. 52) that cannot be handled adequately under 

descriptions of species, subspecies, and varieties. 

The family position of Normannites, or of the Nor-
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B5 

mannitinae of Westermann, is likewise in dispute. 

According to Arkell (1952b, p. 76; 1954, p. 568) 

Normannites appears to be closely related to Otoites and 

should be assigned, therefore, to the Otoitidae. According to Westermann (1954, p. 247; 1956b, p. 249; 1958, 

p. 451), however, some species of Normannites and 

ltinsaites of his N ormannitinae greatly resemble Stephanoceras and Stemmatoceras of the Stephanoceratidae 

and are difficult to distinguish from them except by the 

presence of lateral lappets and a slightly less intricate 

suture line. As lateral lappets occur on Polyplectites, 

153°25' 20' 

59°50' 

45' 

153°25' 20' 

15' 

Shark Tooth 

X 

+ 

15' 

which both Arkell and Westermann assign to the 

Stephanoceratidae, as well as on Otoites of the Otoitidae, 

their presence on Normannites does not determine its 

family relationship. 

Certain ammonites from beds of late Bajocian age in 

Alaska may have a bearing on the taxonomic position 

of Normannites. These ammonites were described by 

Imlay (1961, p. 471, 472) under the generic name 

Dettermanites and were assigned to the Stephanoceratidae on the basis of ribbing and sutural pattern. They 

show many resemblances to several genera including 

10' 153°00' 

59 ° 50' 

45' 

+ 

10' 05' 153°00' 

FIGURE 4.-Index map showing occurrences of middle Bajocian fossils on the Iniskin Peninsula, Alaska. (Numbers on maps refer to those given in tables 11 and 13.) 
B6 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

Stephanoceras, Polyplectites, and Normannites. They 

differ from typical species of Normannites by having 

more secondary ribs that are much weaker relative to 

the primary ribs and by the first lateral lobe being 

shorter relative to the ventral lobe. They greatly 

resemble, however, other species that Westermann (1954, 

p. 246-290, pls. 22-27) includes in Itinsaites McLearn 

and that Arkell and others (1957, p. L289) include in 

Normannites, differing from those species mainly by 

attaining a somewhat larger size. Evidently they are 

closely related if not congeneric with 1\ ormannites and 

should be placed in the same family. 

In summation, Normannites as defined by Arkell and 

others (1957, p. L289) shows considerable diversity of 

form and sculpture. This diversity has been used by 

Westermann as justification for raising Normannites to 

subfamily rank and for dividing it into many genera 

and subgenera. Taxonomically Normannites appears 

to be related both to the Otoitidae and to the Stephanoceratidae and might with equal logic be placed in 

either family. 

STRATIGRAPHIC SUMMARY 

TUXEDNI GROUP ALONG NORTHWEST SIDE 

OF COOK INLET 

Many of the ammonites of middle Bajocian age 

described herein were obtained from the lower four 

formations of the Tuxedni Group exposed along the 

northwest side of Cook Inlet between Tuxedni Bay and 

the Iniskin Peninsula. These formations, arranged 

from youngest to oldest, and their thicknesses are 

shown in table 2. This table, based on data supplied 

by R. L. Detterman between 1958 and 1961, not only 

shows the variations in thicknesses of the formations 

but in conjunction with tables 3-7 is useful in determining the relative stratigraphic positions of the fossil 

collections and the ranges of the species described 

herein (table 8). Table 2 does not include the two 

highest formations ofthe Tuxedni Group which contain 

faunas of late Bajocian (Imlay, 1962b), of probable 

Bathonian (Imlay, 1962a) and of early Callovian ages 

(Imlay, 1962a, p. C2-C3, table 2). 

TABLE 2.-Thickness, in feet of, the lower four formations of the 

Tuxedni Group along the northwest side of Cook Inlet, Alaska 

Tuxedni Lake 

Bay- Ricker- Chinitna Upper Fitz 

Formation Bear son-Red Bay area Creek area Creek Glacier area area 

Cynthia Falls Sandstone _____ 765 660 645 600 

Fitz Creek Siltstone _________ 640 825 1, 280 1.090 

Gaikema Sandstone __________ 600 880 850 500 

Red Glacier Formation ______ 1, 980 4, 540 1, 530+ In- Subsurface, 

complete 8, 000-8, 200 owing to outcrop, faulting. 300+. 

RED GLACIER FORMATION 

The Red Glacier Formation near Tuxedni Bay is 

nearly 2,000 feet thick and consists of alternate units of 

massive to thin-bedded gray, greenish-gray, or grayishgreen sandy siltstone and silty sandstone. Thin beds 

of pebble conglomerate occur locally. Most units 

contain fossiliferous concretions of limestone or of 

calcareous sandstone. The upper 790 feet is well exposed along the south shore of Tuxedni Bay west of 

Fossil Point. The remainder of the formation is 

mostly covered along the shore but is poorly exposed 

along H ungryman Creek and Difficult Creek from half 

a mile to several miles fromTuxedni Bay. The highest 

unit as exposed along the shore consists of sandy siltstone that is in fault contact with the upper part of the 

Fitz Creek Siltstone. The lowest unit of the Red 

Glacier Formation, as exposed near Difficult Creek and 

Hungryman Creek, consists mostly of light brown 

arkosic sandstone about 300 feet thick that rests on lava 

beds at the top of the Talkeetna Formation. 

The upper 500 feet of the formation exposed along the 

south shore of Tuxedni Bay has furnished many 

ammonites (table 4) of middle Bajocian age including in 

particular Sonnim·a, Pa.pilliceras, Strigoceras, Lissoceras, 

Otoites, Emileia, Normannites, Stephanoceras, Skirroceras, and Stemmatoceras. Farther west along the shore 

some beds from 700 to 730 feet below the top of the 

formation have furnished the ammonite Parabigotites 

crass/costatus Imlay in association with Sonninia and 

Stephanocera8. The middle part has not furnished any 

fossils, probably owing mainly to poor exposure and 

difficult access. The lower part has furnished ammonites of early Bajocian age, including Tmetoceras and 

Erycites (table 3, fig. 5) and, also, ammonites of middle 

Bajocian age including Stephanoceras and Emileia. 

The middle Bajocian ammonites were obtained from 

TABLE 3.-Early Bajocian ammonites from the lower part of the 

Red Glacier Formation along the northwest side of Cook Inlet, 

Alaska 

Position in Position in feet 

Mesozoic locality Fossils feet below above base of 

top of forma- formation 

tion 

21244, Iniskin Bay Assoc. 1 Erycites sp. 5,495-5,515 About 2,200-2,300 

at a depth of 6,339-6,359 ft. on the Iniskin Peninsula. 

24335, 4.2 miles N. 5° W. of TmetocerM regleyi 3,400-3,600 900-1,100 

Blue Lake, Red Glacier Dumortier. 

Area, north of Chinitna 

Bay. 

21233, 2.26 miles N. 77° W. Tmetoceras sp. About 1,500 380-480 

of Fossil Point on Tux- Erycites? sp. 

edni Bay. 

21234, float from same place Tmetoceras sp. About 1,500 380-480 

as 21233. Erycites sp. Pseudolioceras? 

sp. 

22718,3.4 miles N. 85° W. of 

Fossil Point on Tuxedni Erycites? sp. About 1,800 150-200 

Bay. 
European 

Standard zones Characteristic fossils in the Suggested guide Northwest side of Alaska Peninsula at in northwest Europe Alaskan Peninsula and Cook fossils in southern 

stages (Arkell, 1956; Callomon, 1955} Inlet regions, Alaska Alaska Cook Inlet, Alaska Wide Bay, Alaska 

Quenstedtoceras Lamberti 

Peltoceras athleta 

.;; 

~ Erymnoceras coronatum ::s 

~ Callovian 00 .. Pseudocadoceras tl Pseudocadoceras Q) .. Q, grewingki Chinitna Shelikof 

Kosmoceras jason I--.-- Q, ~ Formation Formation .:::> -~ 0 

~ 

.. ., ::::; 

Q) 0 "" "" ~ Sigaloceras calloviense ·~ :§ 0 )Paracadoceras and ...:l i~ Gowericeras ? ? ~~---- Xe'Mcephalites 

Macrocep_halites macrocephalus ~ X enocephalites and vicarius "0 tl Kheraiceras ~::·~ 

<1$.:.! 

., .., Bowser Clydoniceras discus "" "" A rctocephalites :~ -~ A rctocephalites Formation 

(Cra'Mcephalites) ~ ~ (Cranocephalites) ..c d 

pomeckji ..c .. pompeckji Oppelia aspidoides 8&; ? ' ? "----? 

Bathonian Tulites subcontractus 

Gracilisphinctes progracilis 

Zigzagiceras zigzag 

Q, 

::s 

Parkinsonia parkinsoni e 

C!l' 

·~ .. ·a Q) "0 Q, Ill Q, Garantiana garantiana Q) 

a$ :::> >< .. 

~ 

::s ? ~ ~Wist? creek 

Leptosphinctes, Sphaeroceras, Megasphaeroceras Q) Stre'Mceras subfurcatum Siltstone 

:a 

"0 Megasphaeroceras, and Liroxyites rotundum ~t:~ ~ Teloceras, Zemistephanus, Stephanoceras humphriesianum Normannites, and Chondroceras Teloceras itinsae Fitz Creek 

Siltstone 

~ Otoites, Emileia, Sonninia,. Skirrocerasjdrschnert r\ Gaikema J 

Bajocian "0 Otoites sauzei Witchellia, Parabigotites, Parabigotites Sandstone I-...__._?-'---...__ "0 

~ Skirroceras and Br;ro_fordia crassicostatus 

Sonninia, Witchellia, Oppelia, 

Sonninia sowerbyi Docidoceras. Strigoceras, and 

Pseudolioceras ? ? Red Glacier Kialagvik 

Tmetoceras regleyi, Formation Formation 

Ludwigia murchisoni Pseudolioceras whiteavesi, and 

Erycites howelli Tmetoceras regleyi .. •Q) 

~ Tmetoceras scissum 0 

...:l ? ? ? ? 

Leioceras opalinum 

----- -

FIGURE 5.-Correlation of some Middle and Upper Jurassic formations and faunas in the Cook Inlet region, Alaska. 

East-central Oregon 

? 

Lonesome Formation 

of Lupher, 1941 ? 

Trowbridge Formation 

of Lupher, 1941 ? 

~ ~~ 

~~ ~~ /' ___L E . 0 

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Formation 

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Hinchman Sandstone 

and 

Bicknell Sandstone 

~// ~ identifiod/ 

~au~lly 

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(Age uncertain} 

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B8 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

2 to 4 miles south of the early Bajocian ammonites and 

farther below the top of the formation. This situation, 

according to R. L. Detterman (written communication 

of ,luly 17, 1962), is a result of rapid southward thickening of the Red Glacier Formation by the addition of 

beds at its top. 

The Red Glacier Formation in the Hickerson LakeRed Glacier area appears to be about 4,500 feet thick, 

but according toR. L. Detterman (written communication, 1960) it is cut by a thrust_ fault of unknown 

displacement about 1,200 feet above its base. The 

upper 2,930 feet '\s similar lithologically to the formation 

as exposed near Tuxedni Bay. Below this occurs about 

a thousand feet of soft black silty shale and siltstone. 

Below follows 200 feet of arkosic sandstone, 200 feet of 

shale and some sandstone, and then 200 feet of arkosic 

sandstone that rests on the Talkeetna Formation. The 

exposures are rather poor, are difficult of access, and 

have furnished few fossils. About 300 feet below the 

top was obtained Parabigotites crassicostatus Imlay, 

Witchellia? sp., ·and Sonninia sp. juv. (Mesozoic loc. 

22529) of middle Bajocian age. About 1,300-1,400 

feet below the top was obtained Parabigotites sp. undet. 

(Mesozoic loc. 22695). From 900 to 1,100 feet above 

the base was obtained Tmetoceras sp. of early Bajocian 

age. 

The Red Glacier Formation exposed along the south 

shore of Chinitna Bay is only about 1,530 feet thick but 

its lower part is cut by a thrust fault having several 

thousand feet of displacement. Its upper 600 feet 

consists of olive to brown massive siltstone. Below 

follow units of gray to brown thin-bedded to massive 

sandstone alternating with units of gray sandy siltstone. 

The sequence is fairly fossiliferous and in its upper 1,200 

feet has furnished ammonites belonging to the genera 

Sonninia, Witchellia, Emileia, Normannites, Stemmatoceras, and Parabigotites (table 4). Most of the 

species are identical with those that occur in the upper 

730 feet of the Red Glacier Formation along the south 

shore of Tuxedni Bay. 

Only the upper 300 feet of the Red Glacier Formation 

is exposed in the upper part of Fitz Creek near Tonnie 

Creek, but deep drilling has revealed that the formation 

in the subsurface is about 8,000 feet thick. The early 

Bajoci~n ammonite Erycite$ associated with the pelecypod Inoceramus cf !.lucifer Eichwald was obtained from 

a core of the Iniskin Bay Association No. 1 well at the 

depths of 6,339-6,359 feet, which is from 2,200 to 2,300 

feet above the base of the Red Glacier Formation. 

In addition to ·ammonites, the Red Glacier Formation 

has. furnished some belemnites and many pelecypods. 

The pelecypod genera include Inoceramus, Pleuromya, 

Pinna, Astarte, 'Trigonia, Comptonectes, Meleagrinella, 

Isocyrina?, Goniomya, Pholadomya, Protocardia, Parallelodon, . Isognomon, and Thracia. Inoceramus lucifer 

Eichwald and Pleuromya dalli (White) are fairly common species. 

GAIKEMA SANDSTONE 

The Gaikema Sandstone of the Tuxedni Group near 

Tuxedni Bay, as mapped by R. L. Detterman, is about 

600 feet thick and consists mostly of massive to mediumbedded coarse- to fine-grained gray to greenish-gray 

sandstone that locally forms cliffs. Some beds are 

pebbly in its lower half and some beds are fossiliferous. 

It is absent on the south shore of Tuxedni Bay owing to 

faulting but is fairly well exposed away from the shore 

between Bear Creek and Hungryrnan Creek. At one 

place (Mesozoic loc. 22723) the lower 150 feet of the 

formation has furnished ·the ammonites Sonninia 

(Papilliceras), Emileia, and Lissoceras (table 5). 

The Gaikema Sandstone near Lake Hickerson consists 

of units of medium- to thin-bedded fine- to mediumgrained brown to gray sandstone and massive gray 

siltstone about 880 feet thick. It contains some fossiliferous layers that have furni~hed such pelecypods as 

Meleagrinella, Trigonia, Plagiostoma, Inoceramus, and 

Isognomon. 

The Gaikema Sandstone on the south shore of 

Chinitna Bay is well exposed, about 850 feet thick, and 

consists mostly of medium- to thin bedded mediumgrained gray to greenish-gray sandstone but contains 

interbeds of siltstone and of conglomerate. It has 

furnished a few ammonites (table 5) belonging to 

Witchellia?, Bradjordia?, Stephanoceras, and Macrophylloceros. Pelecypods are much more common than 

ammonites and belong mostly to the genera Inoceramus, 

Meleagrinella, Trigonia, and Pleuromya. All the specimens of Inoceramus that can be specifically identified 

belong to I. lucifer Eichwald. 

The Gaikema Sandstone exposed on Fitz Creek is 

about 500 feet thick, is similar lithologically to the same 

formation on the south shore of Chinitna Bay, and 

likewise contains the same pelecypod faunule. The 

only ammonites found include Bradjordia? carib01.tensis 

Imlay, n. sp. and Lytoceras. 

FITZ CREEK SILTSTONE 

The Fitz Creek Siltstone of the Tuxedni Group near 

Tuxedni Bay, as mapped by R. L. Detterman, is about 

640 feet thick. The upper 150 feet, well exposed on 

Fossil Point, consists mostly of dark-gray massive 

siltstone that is interbedded with some thin beds of 

gray sandstone and sandy limestone and with minor 

amounts of grit and conglomerate. The remainder of 

the formation is absent on Fossil Point owing to faulting. 

It is exposed, however, at the head of Bear Creek and 

along the divide between Bear Creek and H ungryman 

Creek where it consists mostly of brownish-gray 

massive siltstone that contains some sandy beds. The 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B9 

upper 150 feet has furnished many ammonites (tables 

6, 8) including in particular Sonninia, Lissoceras, 

Oppelia, Chor"droceras, Normannites, Stephanoceras, 

Stemmatoceras, Teloceras, and Zemistephanus. The 

lower part of the formation has furnished few ammonites and these include Sonninio, Oppelia, and Stephunoceras (Mesozoic locs. 22706, 22721, and 22722). 

The Fitz Creek Siltstone in the Lake Hickerson-Red 

:Glacier area is about 825 feet thick, consists of gray 

massive siltstone that weathers brown and contains a 

few interbeds of arkosic sandstone and so'me small 

sandy limestone concretions. The ammonite Normannites variab1lis Imlay, n. sp., has been obtained from 

about the middle of the formation. 

The Fitz Creek Siltstone near the south shore of 

Chinitna Bay and along Gaikema Creek is about 

1,280 feet· thick and consists of gray to gray-green 

sandy siltstone interbedded with gray silty sandstone. 

One conglomeratic sandstone unit occurs near the 

middle. A fairly· large molluscan fauna, dominated by 

·ammonites, has been obtained from all parts of the 

formation except the lower 200 feet. These include the 

same genera and species of ammonites as occur in the 

Fitz Creek Siltstone near Tuxedni Bay but most of the 

species in common between the two areas have been 

found relatively much lower in the formation near 

Chinitna Bay than near Tuxedni Bay. 

The Fitz Creek Siltstone in the upper part of Fitz 

Creek is only partly exposed, is about 1,090 feet thick, 

and consists dominantly of gray sandy siltstone. · It 

contains the same molluscan assemblage as characterizes the formation elsewhere, but, as near Chinitna 

Bay, the comn1on species of ammonites occur relatively 

lower within the formation than near Tuxedni Bay. 

In general the Fitz Creek Siltstone may be recognized 

by its stratigraphic position between two more resistant 

sandstone formations. It may also be distinguished 

rather easily from the underlying formations by the 

presence of the ammonites Teloceras, Normannites, 

Zemistephanus, and Chondroceras and by an abundance 

of the pelecypod Inoceramus ambiguus Eichwald, which 

species contrasts markedly with /. lucifer Eichwald 1n 

the underlying formations. 

CYNTHIA FALLS SANDSTONE 

The Cynthia Falls Sandstone of the Tuxedni Group 

gradually decreases in thickness southwestward from 

about 765 feet near Tuxedni Bay to 600 feet on the 

Iniskin Peninsula. Near Tuxedni Bay the lower 115 

feet of the forp1ation is well exposed on Fossil 

Point and the remainder of the formation is under the 

waters of Tuxeqni Channel. The part exposed on 

Fossil Point consists mostly of gray to greenish-gray 

medium- to thick-bedded sandstone but includes a little 

gra)7 siltstone. This part is easily accessible and has 

yielded most of the fossils that have been found in the 

Cynthia Falls Sandstone (table 7). These include 

many of the same species of the ammonites Chondroceras, N ormannites, · and Zemistephanus as occur 

in the underlying Fitz Creek Siltstone but in addition 

include Chondroceras allani (McLearn) and Lissoceras 

bakeri Imlay. On Bear Creek the exposures are rather 

poor and have not furnished many fossils. Chondroceras dejonti (McLearn), however, has been found about 

500 feet above the base of the formation (Mesozoic loc. 

22707). 

The Cynthia Falls Sandstone near Lake Hickerson 

and Red Glacier consists mostly of olive-gray to dark 

green medium- to thick-bedded sandstone and graywacke. Some pebbles occur in its lower part. The 

upper part has furnished a few belemnites and pelecypods. 

The Cynthia Falls Sandstone on the south side of 

Chinitna Bay contain~ much coarse-grained material 

and has not furnished any fossils. The upper 200 feet 

consist of coarse conglomerate, the lower 220 feet of 

massive sandstone containing conglomerate interbeds, 

and the middle part of sandy siltstone and sandstone. 

The Cynthia Falls Sandstone in the upper part of 

Fitz Creek consists mostly of massive gray-green 

sandstone. The ammonite Chondroceras dejonti (MeLearn) was obtained from the lower 150 feet of the 

formation (Mesozoic loc. 21771) and fragments suggestive of Chondrocer-as (Mesozoic loc. 20004) were 

obtained about 400 feet above the base of the formation. 

Between Tuxedni Bay and the upper part of Fitz 

Creek, the massive sandstone or conglomerate forming 

the upper part of the Cynthia Falls Sandstone is overlain abruptly but apparently conformably by massive 

dark gray siltstone, sandy silt'lotone, and claystone. 

The lower. contact of the Cynthia Falls with the 

underlying Fitz Creek Siltstone is also f~irly abrupt in 

most sections. 

TUXEDNI FORMATION IN . THE TALKEETNA 

MOUNTAINS 

The Tuxedni Formation in the N elchina area of the 

Talkeetna Mountains is rather variable in thickness 

and in lithologic character (written communication 

from Arthur Grantz, Sept. 1, 1961). Its thickness 

ranges from 0 to at least 1,200 feet but locally may be 

greater. At most places the lower 700-1,200 feet of 

the formation consists of greenish-gray predominantly 

fine- to medium-grained sandstone. The upper part of 

the formation ranges in thickness from 0 to 500 feet 

and consists of greenish to olive-gray thin- to n1edium-

. bedded siltstone interbedded with sandstone and locally 

with soft shale. The relative amount of silty material 

varie.3 from place to place: In some places the en tire 
BlO JURASSIC AMMONITES FROM SOUTHERN ALASKA 

formation is mostly sandstone. In other places the formation contains much siltstone throughout. The 

formation as a whole is characterized by the presence 

of sandy limestone concretions that weather reddishgray, and locally it contains pebbly beds and shelly or 

coquinoid beds. · 

The Tuxedni Formation, as mapped by Arthur 

Grantz, rests unconformably on the Talkeetna Formation of Early Jurassic age and is overlain unconfonnably 

either by the Chinitna Fonnation of Callovian age, or 

by slightly older beds containing the ammonite 

Arctocephalites ( Cranocepha lites) . 

The lower sandstone part of the Tuxedni Formation 

in the Talkeetna Mountains has furnished a few mollusks. Inoceramus lucifer Eichwald occurs throughout. 

Erycites howelli (White) (Mesozoic loc. 24235) and 

Pleydellia? cf. P. digna (Buckman) (Mesozoic loc. 

24149) were obtained from float which probably originated within about a hundred feet of the base, considering that they were found at places where only the 

basal part of the Tuxedni Formation is exposed. An 

immature ammonite probably representing Emileia or 

Docidoceras (Mesozoic loc. 25946) was obtained about 

200-300 feet above the base. Witchellia sp. and 

Sonninia? n. sp. undet. were found (Mesozoic loc. 

26723) in the upper half of the sandstone (table 12). 

The upper silty part of the Tuxedni Formation has 

furnished ·many pelecypods and cephalopods but also 

some gastropods, brachiopods, and one crinoid. The 

exact stratigraphic position of most of the fossil collections within the silty part has not been determined. 

These include Mesozoic localities 8584, 8585, 24120, 

24215, 24220, 25345, 25346, 25942 and probably 3696, 

3697 and 8567. One specimen of Stephanoceras (Skirroceras) (Mesozoic loc. 24134), however, was found at 

the very base of the silty part of the formation, and one 

large collection of mollusks (Mesozoic loc. 24113) was 

obtained from 50 to 250 feet above the base of the silty 

part. (See list in table 12.) Most of these collections 

contain some ammonites identical with species in the 

upper part of the Red Glacier Formation on the northwest side of Cook Inlet. One collection (Mesozoic loc. 

8584), however, from the upper silty part of the Tuxedni 

Formation contains Inoceramus ambiguus Eichwald, 

which occurs in the Cook Inlet area above the Red 

Glacier Formation. Also, another collection (Mesozoic 

loc. 24821) contains ammonites, including Megasphaeroceras, that in the Cook Inlet area occur in beds directly 

overlying the Cynthia Falls Sandstone. 

In the N elchina area of the Talkeetna Mountains, 

erosion of the upper silty beds before deposition of the 

Cranocephalites-bearing beds, or of the Chinitna Formation, is apparently responsible for the variable thickness 

of the Tuxedni Formation and for the absence at most 

places of any beds younger than the Red Glacier Formation of the Cook Inlet area (written communication 

from Arthur Grantz, Sept. 1, 1961). 

The above remarks concerning thicknesses, lithologic 

features, and uncomformable relations may not apply 

in the Boulder Creek area of the Talkeetna Mountains 

which has not been studied in recent years. In that 

area one collection (Mesozoic loc. 8567) contains species 

of Normannites and Chondroceras identical with species 

in the Fitz Creek Siltstone, and another collection 

(Mesozoic loc. 8572) contains ammonites identical with 

species in beds directly overlying the Cynthia. Falls 

Sandstone northwest of Cook Inlet. 

AGES OF THE FAUNAS 

AGES OF THE TUXEDNI GROUP NORTHWEST 

OF COOK INLET 

RED GLACIER FORMATION 

The Red Glacier Formation has yielded ammonites 

of early Bajocian age from its lower part (table 3) and 

of early middle Bajocian age from its lower, middle, 

and upper parts (tables 4, 8, 9). 

The early Bajocian ammonites from the Red Glacier 

Formation (table 3) are poorly preserved, but the 

presence of the genera Tmetoceras and Erycites clearly 

date the beds (Arkell, 1956, p. 34; Arkell and others, 

1957, p. L267). Associated with the ammonites are 

such pelecypods as Inoceramus cf. I. lucifer Eichwald, 

Meleagrinella, Oxytoma, and Pleuromya. Both on the 

Iniskin Peninsula and in the Lake Hickerson-Red 

Glacier area the Red Glacier Formation includes considerable thicknesses of strata below the occurrences of 

early Bajocian ammonites and conceivably such strata 

could be older than Bajocian. 

The early middle Bajocian ammonites from the Red 

Glacier Formation (table 4) have been found mainly in 

its upper part. This includes the upper 200 feet of the 

formation on the south shore of Chinitna Bay, the upper 

1,400 fee-t in the Lake Hickerson-Red Glacier area, and 

the. upper 730-800 feet on the south shore of Tuxedni 

Bay. In addition, some ammonites of the same age 

have been found in the lower part of the formation near 

Tuxedni Bay. These include Emileia cf. E. constricta 

Imlay, n. sp. (Mesozoic loc. 24334), found 1,700-1,800 

feet below the top of the formation and Stephanoceras 

(Skirroceras) juhlei Imlay, n. sp. (Mesozoic loc. 24333). 

found 1,800-1,900 feet below the top of the formation. 

These collections are of age significance because 

Stephanoceras and Em1'leia in Europe (table 10) are not 

known below the middle part of the European zone of 

Sonninia sowerbyi (Arkell, 1952b, p. 74--76) and the 

serpenticone subgenus Skirroceras is not known below 

the zone of Otoites sauzei. The presence of such genera 

low in the Red Glacier Formation near Tuxedni Bay 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION Bll 

TABLE 4.-Middle Bajocian ammonites in the Red Glacier Formation along the northwest side of Cook Inlet, Alaska 

[Fossils at locs. 3004, 3007, 3010, 20017, 21263 and 21268 were obtained as· float] 

Position In feet below top of Red Glacier formation USGS Mesozoic fossil localities 

Fossils 

Tuxednl Bay area Lake Hickerson Chlnltna Bay, Tuxednl Bay area Lake Hick· Chlnitna Bay, area south shore erson area south shore 

Macrophylloceras sp. undet. A ______ _ 

Holcophylloceras costisparsum Imlay, 

215 21265 

n. SP-------------------------- 170 ------------------------ 21267 

·sp. juv_______________________ 45Q-700? ------------ ------------ 3007, 3010 Lytoceras cf. L. eudisianum d'Orbigny. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 30Q-850 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 19958, 19966 

Sonninia tuxedniensis Imlay, n. sp___ · 10Q-230 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 21266, 21268 

cf. S. tuxedniensis Imlay, n. sp__ 500 ------------ ------------ 3009 

(Papilliceras) cf. S. (P.) arenata 

(Quenstedt) _ --------------- 48Q-515 ------------ 630 21262, 21263 ---------- ? n. sp. undet _________________ -------------- ------------ 1200 -------------------- ---------- ? sp. juv_____________________ 17Q-700? ------------ ------------ 3008-3010,21267 

19964 

21293 

Witchellia adnata Imlay, n. sp_ _ _ ___ 700? ------------ 725-800 3010 ---------- 19956 

sp ______ ----- _ _ _ _ _ ___ _ _ _ __ ___ _ _ _ __ ___ _ _ _ __ _ _ __ _ _ ___ __ _ _ 35Q-360 _________ -------- ___ _ _ _ _ _ _ _ _ _ _ 21296 

? SP- ------------------------ 25Q-700? 300 25Q-360 3004, 3010 22529 19957, 21296 Strigoceras sp_ _ __ ___ __ _ ____ __ ___ _ _ 10Q-230? _ _ _ ____ _ _ __ _ _ ____ _ _ ____ _ 21268 

Lissoceras cf. L. semicostulatum 

Buckman __ -------------------- SP---------------------------

Otoites cf. 0. contractus (Sowerby) __ _ . ? filicostatus Imlay, n. sp ______ _ Emileia constricta Imlay, n. sp _____ _ 

cf. E. constricta Imlay, n. SP----

Chondroceras cf. C. defonti (McLearn)_ 

Normannites kialagvikensis Imlay, n. 

100-230? 

48Q-515? 

500 

700? 

48Q-500, 515? 

170Q-1800 

48Q-515? 

45 

35Q-1200 

80Q-900? 

21268 

21263 

3009 

3010 

3009, 21262, 21263, 

21268 

24334 

21263 

19951 

19959, 21293 

20017 

SP----------------------------- 50Q-515, 700? ------------ ------------ 3010, 21261 

cf. N. kialagvikensis Imlay, n. sp_ -------------- ------------ 35Q-360 -------------------- ---------- 21296 

cf. N. (ltinsaites) crickmayi (McLearn) ________________ _ 95 ------------ ------------ 21269 

Stephanoceras cf. S. nodosum (Quenstedt)-------------------------- 95 ------------ ------------ 21269 

(Skirroceras) kirschneri Imlay, n. sp _____________________ _ 5Q-2&0 80Q-900? 3013, 21264, 21267, ---------- 21268 

20017 

(S.) juhlei Imlay, n. sp_________ 180Q-1900 ------------ ------------ 24333 

19966 

21296 

19966, 21~95 

SP--------------------------- 700? ------------ 850 3010 ---------- Stemmatoceras n. sp. undet_________ 480-515? ------------ 35Q-360 21263 ---------- sp_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 32Q-850 _________________ -- ___ -- _- __ --

cf. S. triptolemus (Morris and 

Lycett)____________________ 50Q-515 ------------------------ 21261 

Parabigotites crassicostatus Imlay____ 70Q-730? 300 850 3010 22529 19966 

21296 

21766 

sp ___ - -------- __ --- ___ --- __ _ _ _ _ _ __ _ _ __ _ _ _ _ _ 1300-1400 35Q-360 _ _ _____ _ _ _ _ _ _ _ _ __ _ _ _ 22695 

?sP------------------------- 700? ------------ 10Q-150 3010 ----------

shows that most of the formation at that place is of 

middle Bajocian age not older than the European zone 

of Oto1'tes sauzei. 

The ammonites from the upper part of the Red 

Glacier Formation that are most significant in determining its age include the following: 

Stephanoceras (Skirroceras) kirschneri Imlay, n. sp. 

Stemmatoceras n. sp. undet. 

Normannites, kialagvikensis Imlay, n. sp. 

Otoites? filicostatus Imlay, n. sp. 

cf. 0. contrachts (Sowerby) 

Emileia constricta Imlay, n. sp. 

Sonninia htxedniensis Imlay, n. sp. 

(Papilliceras) cf. S. arenata (Quenstedt) 

Witchellia adnata Imlay, n. sp. 

Lissoceras cf. L. semicost~dahtm Buckman 

Parabigotites crassicostat~ts Imlay 

Of these, Sonninia tuxedniensis Imlay, n. sp., and 

Lissoceras cf. L. semicostulatum have been found only 

in the upper 230 feet of the Red Glacier Formation on 

the south shore of Tuxedni Bay. Parabigotites crassicostatus Imlay has found from 730 to 800 feet below the 

top of the Formation at Tuxedni Bay (Martin, 1926, 

p. 143, unit 37 of section), 300 feet below the top of the 

formation near Red Glacier, and 850 feet below the 

top on the south shore of Chinitna Bay. Fragn1ents 

of Parabigotites have also been found near Red Glacier 

from 1,300 to 1,400 feet below the top of the fonnation 

and on the south shore of Chinitna Bay about 350 feet 

below the top of the formation. These figures suggest 

that Parabigotites does not range to the top of the 

formation. 

In addition to the ammonites listed, Normannites 

cf. N. crick'mayi (McLearn) was obtained in place 95 

feet below the top of the formation on Tuxedni Bay 

(Mesozoic loc. 21269). Strigoceras (Mesozoic loc. 
B12 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

21268) and Ohondroceras (Mesozoic locs. 21263, 20017) 

were obtained as float only and, therefore, may have 

been derived from the Fitz Creek Siltstone. Sonninia? 

n. sp. undet. was obtained 1,200 feet below the top 

of the Red Glacier Formation associated with Emileia. 

The ammonite fauna from the upper part of the Red 

Glacier Formation is correlated with part of the European zone of Otoites sauzei because of the association 

of certain genera and subgenera. Papilliceras, Otoites, 

and Emileia are not known above the Otoites sauzei 

zone; Normannites and Chondroceras are not known below the upper part of that zone; Skirroceras and Stemmatoceras are not known below that zone, and Otoites 

reached its climax in that zone, although present in the 

upper part of the older Sonnin·ia sowerbyi zone (table 

10). The presence of Normannites from 95 to about 700 

feet below the top of the Red Glacier Formation at 

Tuxedni Bay indicates that the upper part of the formation correlates with only the upper part of the Otoites 

sauzei zone. 

In summation, the Red Glacier Formation in its 

lower part contains ammonites of early Bajocian age, 

and in its lower, middle, and upper parts contains ammonites of middle Bajocian age correlating with the 

European zone of Otoites sauzei. The highest part 

probably correlates with the upper part of that zone. 

Near Tuxedni Bay soine ammonites belonging to that 

zone were obtained within a few hundred feet of the 

base of the formation. 

Interestingly, no ammonites indicative of the European zone of Sonninia sowerbyi have yet been found 

in the Red Glacier Formation, although that zone is 

well represented in the Kialagvik Formation on the 

Alaskan Peninsula by such ammonites as Docidoceras, 

Pseudotoites?, and Witchellia associated with strongly 

spinose Sonninia. These occur directly above beds containing .Tmetoceras, Erycites, and Pseudoliceras (Imlay, 

1952, p. 978). 

GAIKEMA SANDSTONE 

The presence of Sonninia (Papilliceras) and Emileia 

in the lower fourth of the Gaikema Sandstone (tables 

5, 9) of the Tuxedni Group in the Tuxedni Bay area 

shows that that part of the formation is not younger than 

the zone of Otoites sauzei. On the Iniskin Peninsula 

the formation has furnished the ammonites Bradjordia?, 

Witchellia?, and Stephanoceras which suggest a middle 

Bajocian age. However, one of the species, Bradjordia? 

caribouensis Imlay, n. sp., occurs elsewhere in the 

Talkeetna Mountains (Mesozoic loc. 3696) with 

Witchellia and Skirroceras, which in association (table 

10) indicate a correlation with the Otoites sauzei zone 

FITZ CREEK SILTSTONE 

The Fitz Creek Siltstone has furnished a fairly large 

ammonite fauna (tables 6, 9) of middle Bajocian age as 

TABLE 5.-Middle Bajocian ammonites in the Gaikema Sandstone 

along the northwest side of Cook Inlet, Alaska 

Position in feet above USGS Mesozoic fossil 

base of Gaikema localities 

Fossils 

Sandstone 

Tuxedni 

Bay area Chinitna Tuxedni 

Bay and Bay area FitzCreek 

Chinitna 

Bay and 

Fitz Creek 

MacrophyllocferasLsp. undd~~· B---- ------------ A

30

t

0

b-4a0se

0 ------------ ~~~~·~ Lytoceras c . . eu zswnum ------------ ------------ d' Orbigny ____ ----------------- Sonninia (Papilliceras) cf. S. 

(P.) arenata (Quenstedt) ______ Lower 150 ------------ 22723 

Witchellia? SP-------------------- ------------ 180-650 ------------ 19961,26600 Lissoceras sp _____________________ Lower 150 ------------ 22723 

Bradfordia? caribouensis Imlay, 

n. SP--------------------------- ------------ 50-100 ------------ 26601 Emileia constricta Imlay, n. sp___ Lower 150 ------------ 22723 Stephanoceras sp _________________ ------------ 120 ------------ 19989 

shown by the association of such genera and subgenera 

as Sonninia, Strigoceras, Lissoceras, Oppelia, Chondroceras, N ormannites, Stephanoceras, Skirroceras, Stemmatoceras, and Teloceras. Considering the reported ranges 

of these ammonites in Europe (table 10), the formation 

should be equivalent to the European zone of Stephanoceras humphriesianum. This is shown particularly by 

the presence of Teloceras, which is not known below 

that zone, 1n association with Chondroceras, Skirroceras, and Stemmatoceras, which are not known above 

that zone. It is also indicated by an abundance of 

Normannites which attained its greatest development 

in that zone. 

This age determination for the Fitz Creek Siltstone 

is in line with the fossil evidence obtained from the 

underlying members. Certain qualifications, however, 

need to be made. First, Telocera.s has not been found 

in the basal 200 feet of the formation on the Iniskin 

Peninsula or in the basal two-thirds of the formation 

near Tuxedni Bay. Hence, the basal part of the for 

mation could be as old as the zone of Otoites sauzei. 

Second, Sonnim·a in Europe has been recorded rarely 

above the zone of Otoites sauzei (Gillet, 1937, p. 11 

Dorn, 1935, p. 48, 120; Oechsle, 1958, p. 75, 124), 

and therefore its presence in the Fitz Creek Siltstone 

may conflict with the age evidence furnished by the 

other an1monite genera. 

Actually Sonm'nia has been found at only three 

places in the Fitz Creek Si).tstone, is represented by 

only four specimens, and one of the records may not 

be valid. One occurrence of Sonninia from near the 

top of the siltstone on the south shore of Tuxedn1 

Bay at Mesozoic locality 3000 is questioned because 

the genus has not been found there during recent 

collecting and the single specimen of Sonnim'a from 

Mesozoic locality 3000 has a different matrix than the 

associated fossils. A second occurrence of Sonninia 

consists of one small fragment, comparable to the small 

septate whorls of S. tuxedm'ensis Imlay, n. sp., found 

near the base of the formation M~sozoic loc. 22706) 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B13 

TABLE 6.-Middle Bajocian ammonites in the Fitz Creek Siltstone along the northwest side of Cook Inlet, Alaska 

[Fossils at locs. 2999, 2002o-20022, 20756, 21272 and 21274 were obtained as float] 

Position in feet below top of Fitz Creek Siltstone USGS Mesozoic fossil localities 

Tuxedni 

Bay area Lake 

Hickerson area 

Chinitna Bay, 

south shore 

Fitz Creek, upper part 

Lake Chinitna Bay, 

Tuxedni Bay area Hickerson south shore 

.Macrophylloceras sp. undet. 

A •••••• --•••••••••• --·----- sp. undot. B •.•••.••••••• Holcophylloceras costisparsum 

ImluyJ.n. SP--------------- cf. H. coatis par sum Im- 150 ---------------- ------------------ ----------------

10515 

2999 

2999,3000 

area 

22533 

sp~alJv~:-5~: ::::::::::::: :::::::::::: :::::::::::::::: --------Near -top- ___________ -~~~- :::::::::::::=:::::::: :::::::::::: --------------i9932-

sonninta tuxedniensis Imlay, 

2999,3000 

22706 ------------

n. c1.s.-itixednien8iiii:iiiay:· 150 ---------------- ------------------ ----------------

n. SP------------------- Near top ---------------- 18G-230 ---------------- Strigoceras cf. S. languidum 

26596 

Buckman ••••••••• --------- • ----------•. -------- ___________ --------- __ ___ 640-690 _ ------- ________ ------ ------------ ------------- ______ _ 

Lissoceras sp................. 10G-150 ---------------- ------------------ ---------------- 2999,3000,21271 

Oppelia stantoni Imlay, n. sp. 150-490 ---------------- ------------------ ---------------- 3000,22721 

Learn) . 35-150 ---------------- 490-690 10245,10516,21270, ------------ --------------------- 21271,21275,21276 

20022 Chondroceras defonti (Me- { 2997,2999,3000, 

cf. C. defonti (McLearn). 25 ---------------- ------------------ 690-800 2996 ------------ -------------------- allani (McLcarn) ________ ------------ ---------------- 12G-320 5G-790 ---------------------- ------------ 19981,19984,20025 

cf. C. allani (McLearn).. 35 ---------------- ------------------ 54G-690 21276 ------------ -------------------- sp. ---------------------- ------------ ---------------- Near top-1, 080 Near top-790 ---------------------- ------------ 19974,26599,22533, 

Normannites SP--------------

(Itinsaites) crickmayi (M cLearn) •• _. _ ••••••• 

cf. (I.) crickmayi (Mc100 ---------------- ------------------

75-150 80G-930 

26594 

Near top-800 2998.21274 ------------ --------------------

{ 

2997,2999,3000, 

69G-840 21270,21271,21275, ------------ 19977,19978 

27056 

(l~~~f:Jai"<i'-""ic:LearnY:~: -----75:iso· :::::::::::::::: Near t~o:t8~8 ------------69o- ------------2997~2999- :::::::::::: 19974,21302,26599 

26599 

cf. (I.) itinsae (McLcarn). 100 ---------------- ------------------ ---------------- 21271 

(I.) variabilis Imluy, n. 

Fitz Creek, upper part 

26597 

19997' 20002 

27105 

21769,26597 

19940, 21767' 22441 20000, 21768, 21317 

20002, 21306, 27105 

19081, 19933,21303, 

21306, 22440, 22441, 

22534,27108,27109 

21767,22552 

19997,21305 

19997 

sp ••• __ • _ ••••••••••••••••••• __ • _ _ _ _ Near middle _______ •• _ -·- _____ _ 5G-790 ---------------------- 22528 -------------------- 11023,11024,11027-29, 19940, 19941,20002, 

cf. (1.) variabllis Imlay, 

n. sp ••••••• ------------ --------.--- ----·----------- ----------------·- 300-790 ---------------------- ------------ -------------------- Stephanoceras sp............. 34G-390 ·---·--··-···-·- 38o-480 94G-990 22722 ------------ 21292 (Skirroceras) kirschneri 

Imlay, n. sp........... 75-150? ---·---·-------- ? sp ••••••••••••• · •••••••.. ------·----- ·------·-··----- 98G-1,080 ---------------- 2999,21274,20756 ------------ 160 ---------------- ---------------------- ------------

26599 

19981 

21303,21316,21768, 

22440 

20000, 21306, 22439 

27111 

Stemmatoceras cf. S. palliseri • (l\1cLcarn) __ ••••• __ ••• __ •• 150 _____ -----•• __ ••. _ --------- _______ •• ___ -------•. __ 21270 

21281,22705 

10245 

2998,2999,3000, 

21270, 2127 5 

26953 

~~~~l~t~7~-I-~!~~:-~~-s~: ::: Upp~~~~g :::::::::::::::: --------------i6o- :::::::::::::::: 19981 

Teloceras ftinsae (McLearn).. 75-150 ---------------- 92G-1,080 44G-840 19973, 19975, 27110 21304,21305,27107, 

27109 

afY. T. itinsae (McLcurn). Upper 150 26598 

Zemistephanus richardsoni 

(Whitcaves). -------------- 10G-150 Near top-1, 080 

cf. Z. richardsoni (Whit640-680 

64o-840 2998,2999,3000, 

10245, 10515, 10520, 

21270, 21271, 21274 

19978,20020,21772, 

22533, 26599 

19997,21304,21305, 

26598, 27108 

ouvcs).---------------- ------------ -------·-------- Near top 800 ••••• -----------. •• carlottensis (Whiteuves).. 75-100 ---------------- ------------------ ---------------- ----- 2998~ 2999,3000, --------- 20021,21302 21767 

21275 

? SP---------------------- ------------ ·--------------- Near top-840 ---------------- ---------------------- ------------ 19974,26595 

about 2~ miles from Tuxedni Bay. A third occurrence 

consists of two septate specimens, similar to S. tuxedniensis Imlay, n. sp., found in the upper fifth of the 

formation, above occurrences of Teloceras, on the south 

shore of Chinitna Bay (Mesozoic loc. 26596). This last 

occurrence may correspond to one of the scarce occurrences of the genus in the lower part of the European 

zone of Stephanoceras humphn~es1'anum. 

The known stratigraphic distribution of the ammonite species within the Fitz Creek Siltstone is shown 

in table 8. It app~ars from that table that the species 

of Chondrocm·as, N01·mannites, Teloceras, and Zemistephanus, which numerically compose the bulk of the 

fauna occur near the top of the formation at Tuxedni 

Bay and near th~ middle of the formation on the 

Iniskin Peninsula.. This relationship may be real, 

or it may reflect the accessibility of good exposures. 

Thus at Tuxedni Bay the upper 150 feet of the 

formation is well exposed along the shore, whereas 

the remainder of the formation is relatively poorly 

exposed and at a considerable distancP from the shore. 

As a consequence many collections have been made 

from the upper 150 feet and only two collections from 

the lower three-fourths of the formation. Clearly the 

stratigraphic distribution of species within the entire 

Fitz Creek Siltstone near Tuxedni Bay is not known. 

One species, Normannites variabilis Imlay, n. sp., 

from the Fitz Creek Siltstone, may be of stratigraphic 

importance because it has not been found in the many 

collections from the upper part of the formation on 

Tuxedni Bay, and it has not been found with the other 

species of Normannites. Also, on Fitz Creek it occurs 
B14 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

in greatest abundance near the middle of the formation, 

whereas the other species of Normannites have been 

found there in greatest a_bundance below the middle of 

the formation. Its most common associates are 

Chondroceras allani (McLearn) and 0. cf. C. allani 

(McLearn), which species likewise have not been 

found with the other species of 1Vor'f!iannites and occur 

most commonly higher in the formation. However, 

these stratigraphic ranges may be more apparent than 

real and need checking by additional collecting. 

Another species that may be of stratigraphic significance is Zemistephanus carlottensis (White aves) which 

has been found in Alaska only on the south shore of 

Tuxedni Bay in the upper 150 feet of the Fitz Creek 

Siltstone and in the basal 115 feet of the overlying 

Cynthia Falls Sandstone. 

In summation, ammonite evidence indicates correlation of the upper three-fourths of the Fitz Creek 

Siltstone with the European zone of Stephanoceras 

hu.mphriesianum. This correlation is also favored by 

the stratigraphic position of the Fitz Creek Siltstone 

above the Red Glacier Formation whose upper part 

may reasonably be correlated with the upper part of 

the Otoites sauzei zone. The lower one-fourth of the 

Fitz Creek Siltstone has furnished few ammonites and 

could be as old as the Otoites sauzei zone. 

CYNTHIA FALLS SANDSTONE 

The Cynthia Falls Sandstone has furnished a few 

ammonites of which most are from 'the lower 115 feet 

of the formation on the south shore of Tuxedni Bay 

(table 7). The genera and most of the species are 

TABLE 7.-Middle Bajocian ammonites in the Cynthia Falls 

Sandstone along the northwest side of Cook Inlet, Alaska 

Fossils 

Lissoceras bakeri Imlay-----

sp_-------------------- Chondroceras defonti 

(McLearn) __ ------------

allani (McLearn) ______ 

cf. c. oblatum (Whiteaves) __ ------------- sp--------------------- Normannites sp_ ----------- (Itinsaites) crickmayi 

(McLearn) _ --------- cf. N. (I.) crickmayi 

(McLearn)_ --------- Stephanoceras SP-----------

sp_-- ------------------ Zemistephanus carlottensis 

(Whiteaves) __ -----------

Position in feet above 

base of Cynthia Falls 

Sandstone 

Tuxedni 

Bay area 

60-115 

60-115 

1-500 

60-115 

47-115 

60-115 

Near base 

1-115 

60-115 

47-50 

60-80 

60-115 

Fitz 

Creek, 

upper 

part 

------------

------------

Lower 150 

------------

------------

------------

------------

------------

--------·---

------------

------------

........................... 

USGS Mesozoic fossil 

localities 

Fitz 

Tuxedni Bay area Creek, 

upper 

part 

10512 

10512 

2994, 10514, 10515, 21771 10519, 22707 

10511 

2993, 2995, 10511 

10512 

10523 

10513, 10519 

10512 

2995 

21280 

10513 

identical with those in the underlying Fitz Creek 

Siltstone and presumably are of nearly the same age. 

The presence of Chondroceras about 500 feet above the 

base of the formation on Bear Creek, about 2~ miles 

from Tuxedni Bay, shows that at least two-thirds of 

the formation at that place is not younger than middle 

Bajocian. Similarly on the Iniskin Peninsula the lower 

two-thirds of the formation has furnished Chondroceras 

or fragments suggestive of that genus. Correlation 

of the Cynthia Falls Sandstone with some part of the 

European zone of Steph.anoceras h1J:mphriesianum is 

indicated by its stratigraphic position above beds 

containing Teloceras, which is characteristic of that 

zone, and by the presence of Chondroceras, which is 

not known above that zone. 

AGES OF THE TUXEDNI FORMATION IN THE 

TALKEETNA MOUNTAINS 

The Tuxedni Formation in the N elchina area of the 

Talkeetna Mountains contains ammonites (table 12) 

of early, middle, and late Bajocian age. The early 

Bajocian age is based on the presence of Erycites 

howelli (White) (Mesozoic loc. 24235) from probably 

the lower 100 feet of the formation. This age assignment is supported by an ammonite resembling Pleydellia digna Buckman (1904, fig. 129 on p. cxLu) from 

the same stratigraphic position at a nearby locality 

(Mesozoic loc. 24149). The species Erycites howelli 

(White) has been found elsewhere in Alaska in the 

lower part of the Red Glacier Formation northwest of 

Cook Inlet and in _tp.e lower part of the Kialagvik 

Formation on the Alaskan Peninsula associated with 

the ammonite Tmetoceras. The lower 200-300 feet of 

the Tuxedni Formation in the Talkeetna Mountains 

has furnished one small ammonite that resembles the 

inner whorls of Emileia or Docidoceras (Mesozoic loc. · 

25946) and is suggestive of a middle rather than an 

early Bajocian age. The upper half of the sandstone 

that forms the lower 700-1,200 feet of the Tuxedni 

Formation has furnished ammonites of definite middle 

Bajocian age, including Witchellia (Mesozoic loc. 25945) 

and Sonninia? n. sp. undet. (Mesozoic loc. 26723). 

The last mentioned species has been· found elsewhere on 

the Iniskin Peninsula associated with Emileia (Mesozoic 

loc. 21293) 1,200 feet below the top of the Red Glacier 

Formation. 

Most of the fossil collections from the upper silty 

part of the Tuxedni Formation in the N elchina area 

of the Talkeetna Mountains contain the same ammonite 

genera and subgenera (see table 12) and some of the 

same ammonite species as occur in the upper part of 

the Red Glacier Formation (table 4) ana in the Gaikema 

Sandstone (table 5) along the northwest side of Cook 

Inlet. The presence of such ammonites permits a 

correlation with the European zone of Otoites sauzei 

as discussed above. The evidence is even stronger, 

however, for the silty part of the Tuxedni Formation 
MIDDLE BAJOCIAN ·AMMONITES FROM COOK INLET REGION 

TABL•; B.-Stratigraphic distribution of middle Bajocim;4\mmonite species within the formations of the Tuxedni Group along the 

northwest side of Cook Inlet, Alaska 

Fitz Creek area South side Chinitna Bay 

and Gaikema Creek 

Lake Hickerson and 

Red Glacier area Tuxedni Bay area 

Mu.c·,·ophulloce'l'ns n. sp. undet. A _____ _ cf. n. sp. undet. A _____________ _ - - sp.undet. B _________________ _ 

- - - Holco'11h1Jlloce·ra.s custispn'I'S11:111. Imlay, n. 

SP------------------------- - cf. H. cust:i.~pn:rswm Imlay, n. sp ____ _ sp. juv ____________________ _ - Lytoce·ras cf. L. e·udisiwnwm d'Orbigny __ - Sunni·n:ia. tuxedniensis Imlay, n. sp ___ _ - cf. S. tuxecln·ienwis Imlay, n. sp _____ _ - ( Pn1Jillice·rns) cf. S. ( P.) (t'l'enntn (Quenstedt)- _______________ _ 

? n. sp. undet_ _______________ _ -- '! sp. juv ___________________ _ - - W'itchc/.l·in iulnata. Imlay, n. sp ______ _ 

SP------------------------ ?sp ______________________ _ -

-- - - Stri{loceras cf. S. lwng·u:idu:m Buckman __ sp. juv ____________________ _ 

t·,:s.~o<:lJ'I'fl .. ~ lwke·n: Imlay __________ _ - - c f. t. se·m:1:cost:u.lu.tu:m Buckman ____ _ - SP------------------------ -- -- Omwl·,:u. .~ta:nton·1: Imlay, n. sp _______ _ - BrndfrFrrl-i:n? ca:l"ibouen.~is Imlay, n. sp __ _ 

Ot.oite.~ cf. 0. cuntn1.cl:u .. ~ (Sowerby) ___ _ 

? fU·icostatu.~ Imlay, n. sp ________ _ 

E''lll:ilm:a const:l"ictn Imlay, n. sp _____ _ 

cf. E. const·rictn Imlay, n. sp ______ _ -~ 

B15 

Clwnd:ruce·ru.s 

cf. C. rlefont:1: 

defont:i 

( McLearn) 

(McLearn) 

________ 

____ _ 

_ -~ -~ 

r1.lla:11:1: (McLearn) _____________ _ - cf. C. u.lla:m: (McLearn) _________ _ 

cf. C. oblatum (Whiteaves) ______ ~ 

SP------------------------ - No,·mu:nn·ites kinlag·m:kens·is Imlay, n. sp_ 

cf. N. kietl(tgvikensis Imlay, n. sp ___ _ 

SP------------------------ - (It:l:nsa:l:tes) c·n:ck'III.II.1J'I: (McLearn) ___ _ 

cf. (I.) C'l"ick'lll.n1Ji (McLearn) _____ _ (/.) ·U:1:n.~ae (McLearn) __________ _ 

cf. (/.) ·U:1:nsne (McLearn) ________ _ 

(I.) 'l;a:n:nbil·i.~ Imlay, n. sp _______ _ 

cf. (!.) vnr·in/n:L?:s Imlay,n.sp _____ _ - Stephu:noce·ru .. ~ cf. S. nodowu:m (Quenstedt 

SP------------------------

(Sk·ir,·oce·,·a.,q) k-l>rschne·n: Imlay, n. sp_ 

(S.) juhlei Imlay,n.sp _________ _ 

Ste·m:/1/.o.t.ocwras n. sp. undet ________ _ 

SP------------------------ cf. S. pnllise·n: (McLearn) _______ _ 

11rwinu:m Imlay, n. sp ___________ _ 

cf. S. t.d71tolew.us (Mor-ris and Lycett 

sp. juv ___________________ _ ?sp ______________________ _ 

Telocerns 'U.1:-n.me (McLearn) _______ _ 

aff. T. ·it·1:nsae (McLearn) ________ _ 

Ze'lll:i.~t.eplw:nus richnrdson1: (Whiteaves 

cf. Z. , .. ,:rhnrclso'll:i (Whiteaves) ____ _ - cu rlotlen.~·,:s (Whiteaves) ________ _ - ?sp ______________________ _ 

- Pu l'tl/l'i{lot?:tes r:rns,q·,:costatus Imlay __ _ 

SP----------------------- ?sp ______________________ _ 

-

-

·-

-

-

-

-

-

-

-~ 

-I-

-

-

-~ 

-

.-

--
B16 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE 9.-Stratigraphic distribution of certain Bajocian ammonite genera and subgenera within the Tuxedni Group along the northwest side of Cook Inlet, Alaska 

Genera 

and 

subgenera 

Spiroceras? __________ ..: _ 

Pseudolioceras _ _________ -r--

Tmetoceras _____________ ~ 

Erycites _ __ .:. __________ -~ 

Sonninia _ ____________ _ 

Papilliceras _ __________ _ 

Witchellia _ _________ ~ __ _ 

Strigoceras _____________ _ 

Lissoceras ____________ _ 

Oppelia (Oppelia) _______ _ 

0. (Lyroxyites) _________ _ 

Bradfordia _ ___________ _ 

Otoites ______________ _ 

Emileia ____________ _ · __ 

Normannites _ __________ _ 

Chondroceras _ _________ _ 

Sphaeroceras __________ _ 

Megasphaeroceras _ ______ _ 

Stephanoceras _ _________ _ 

Skirroceras ___________ _ 

Stemmatoceras _________ _ 

Telocerns _____________ _ 

Zemistephanus _________ _ 

Pn.rabigotites _ _____ .:.. ____ _ 

Leptosphinctes _________ _ 

Red Glacier 

Formation 

-

Gaikema 

Sandstone 

Tuxedni Group 

Fitz Creek 

Siltstone 

Cynthia Falls 

Sandstone 

-~ 

- -

Tilted Hills 

Siltstone 

Bowser 

Formation 

J, 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B17 

TABLE 10.-European ranges of certain Bajocian ammonites present. in the Tuxedni Group in the Cook Inlet region, A'laska 

Toarcian Bajocian Bathonian !." 

~ ~ 

j -~ 

"' ~ ~ .s j .,., ~ -~ l.l 

~ !- ~ 

"' ~ -1::! ~ !-

Genera "' c 8 ~ ~ 

~ "' ~ ·~ !- ~ ~ <.) 

·~ ~ ~ "' "' !- !- ;::! or ;::! $ "' ~ .I ·~ . .,. ;::! .;:, ~ ..:..: ~ ~ <.) ~ ;::! ;::., <.) 

s g "' "' -1::! ...0 -1::! ~ !- N 

"' ~ -~ subgenera l.l ~ ·~ -~ <.) !- ...0 !- ~ -~ c 

~ $ ~ !- ~ . .,. "' ;::! ~ ~ N ~ 

~ ~ ~ 

"' !- ~ <.) ;::! ;:! ~ ~ "' ~ <.) 

~ "' ...0 -~ "' ~ c N !- "' ~ ·~ "' ·~ <.) -~ ~ "' !- ~ ~ ~ ~ "' c "' "' ;::! <.) 

~ § 8 !- -1::! ...0 "' !- ~ !- ~ "' ~ ·~ ~ ~ c ~ ~ ;::! ~ ~ <.) Q) !- ~ "' . .,. "' § ~ . .,. "' ·~ "' ~ -~ ~ <.) Q) !- ~ ~ 

-~ ·~ "' <.) 

·~ ~ "' 8 c <.) Q) !- ~ ~ ~ g> .a> ~ c <.) Q) 

~ ! ~ -1::! ~ ..:..: ~ Q) 

~ .s <.) ~ '_§ ~ ~ !- N <.) 

<.) ~ ~ ~ 

~ ~ ;::., ·~ ~ ;::! ~ 

~ ~ !-

~ ~ 

~ ~ ~ 

~ ~ ~ ~ 0 U) \.!) ~ c3 0 C,.) 

Spiroceras _ __________ _ 

Pt~eudolioceras _________ _ 

Tmetocents ____ - ____ - __ 

Erycites ___________ ~ __ 

Sonninia _ ___________ _ 

Pa.pill1:ceras _ _________ _ 

Witchellia. _ ________ - __ -

Stn:gocera.s _ __________ _ 

Lissoce1·as _ __________ _ 

Oppelia. (Oppelia) ____ - __ 

Brn.dfordia ___________ _ 

Otoites ______________ _ 

E-m.ile?:a ___________ - - -

Norma.nnites __________ _ 

Ln.bryinthoceras ________ _ 

Chondrocern.s _ _________ _ -~ 

Spha.erocern.s _ _________ _ 

Stephanocern.s _________ _ 

Skirrocern.s ___________ _ 

Stemmatoceras ________ _ 

Teloceras ___ - - - _ - - - - - -

Leptosphinctes _________ _ 
B18 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

in the Talkeetna Mountains because of the presence 

of Labyrinthoceras at two localities. 

Locally the Tuxedni Formation in the N elchina area 

of the Talkeetna Mountains has yielded fossils that 

are of slightly younger age. One collection (Mesozoic 

loc. 24821) contains ammonites of late Bajocian age 

(Imlay, 1962, p. A-6). Another collection (Mesozoic 

loc. 8584) contains Inoceramus ambiguus Eichwald, 

which in the Cook Inlet area is not known below the 

Fitz Creek Siltstone. With these exceptions the 

Tuxedni Formation in the N elchina area correlates 

very well on the basis of ammonites with the Red 

Glacier Formation and the overlying Gaikema Sandstone northwest of Cook Inlet. This correlation is 

also confirmed by the presence of Inoceramus lucifer 

Eichwald at many localities throughout most of the 

Tuxedni Formation in the Talkeetna Mountains. This 

species elsewhere in southern Alaska ranges throughout 

the Kialagvik Formation on the Alaska Peninsula and 

throughout the Red Glacier Formation and the Gaikema 

Sandstone northwest of Cook Inlet. Its oldest occurrence in these areas, as well . as in northern Alaska 

(Imlay, 1955, p. 86), is with Tmetoceras or Eryc~tes of 

early Bajocian age. The presence of this species in 

the basal beds of the Tuxedni Formation in the Talkeetna Mountains is good evidence, therefore, that· the 

basal beds are not older than Bajocian. 

The Tuxedni Formation in the Boulder Cre.ek area 

of the Talkeetna Mountains has yielded only two fossil 

collections. One (Mesozoic loc. 8572) contains an ammonite of late Bajocian age (Imlay, 1962b, p. 6). The 

other (Mesozoic loc. 8567) contains Normannites variabilis 

Imlay, n. sp. and Chondroceras aliani (McLearn), which 

species in the Cook Inlet area occur together' in the 

middle and upper parts of the Fitz Creek Siltstone. 

With these in the Boulder Creek area occurs the ammonite Leptosphinctes, which in Europe is characteristic 

of the late Bajocian. It is not known, however, 

whether the fossils from Mesozoic locality 8567 were 

collected from a few feet of beds or from a much greater 

thickness. Even if they were collected from a single 

bed, a correlation with the European zone of Stephanoceras humphriesianum is favored by the presence of 

Chondroceras and Normannites. In addition, the presence of Inoceramus ambiguus Eichwald shows that tha 

beds containing the fossils are younger than the Gaikema 

Sandstone on Cook Inlet, which sandstone is correlated 

with the upper part of the Otoites sauzei zone. 

COMPARISONS WITH OTHER FAUNAS 

ALASKAN PENINSULA 

At Wide Bay the upper 200-400 feet of the IGalagvik 

Formation contains many of the same ammonites that 

occur in the upper part of the Red Glacier Formation 

southwest of Cook Inlet and in the upper silty part of 

the Tuxedni Formation in the Talkeetna Mountains. 

These ammonites may be listed as follows: 

Phylloceras cf. P. kunthi Neumayr (Mesozoic loc. 19838) 

Macrophylloceras n. sp. undet. (Mesozoic loc. 19795) 

cf. M. undulatum Imlay, n. sp. (Mesozoic locs. 19823, 21255) 

Holcophylloceras costisparsum Imlay, n. sp. (Mesozoic locs. 12402, 

19877) 

Lytoceras sp. (Mesozoic loc. 21255) 

Sonninia tuxedniensis Imlay, n. sp. (Mesozoic loc. 10809) 

(Papilliceras) cf. S. (P.) arenata {Quenstedt) (Mesozoic locs. 

19840, 19852) 

Witchellia? aguilonia Imlay, n .. sp. (Mesozoic locs. 12402, 19742, 

19773, 19858, 19876, 19877, 19923, 21258) 

cf. W? aguilonia Imlay, n. sp. (Mesozoic locs. 19822, 19823, 

19825) 

sp. (Mesozoic loc. 21255) 

Bradfordia costidensa Imlay, n. sp. (Mesozoic locs. 19786, 19823, 

19838, 19798, 19850, 19742, 19884, 21257) 

cf. B. costidensa Imlay, n. sp. (Mesozoic locs. 19852, 19853, 

21256) 

sp. (Mesozoic loc. 21255) 

Otoites sp. (Mesozoic loc. 21257) 

Normannites kialagvikensis Imlay, n. sp. (Mesozoic loc. 19773) 

Stephanoceras sp. (Mesozoic locs. 19786, 21257) 

Stemmatoceras sp. (Mesozoic,, locs. 19823, 19836) 

Arkelloceras? sp. juv. (Mesozoic loc. 21255) (pl. 28, figs. 7-9) 

Parabigotites crassicostatus Imlay (Mesozoic locs. 11349, 11352, 

12402, 12404, 19773, 19796, 19800, 19811, 19824, 19926, 21258) 

. cf. P. crassicostatus Imlay (Mesozoic locs. 19823, 21256) 

The faunule listed above is correlated with the 

European zone of Otoites sauzei because of the association of such genera as Bradfordia, Otoites, Stemmatoceras, Normannites, Sonninia, and Witchellia 

(table 10). Of these, Sonninia and Witchellia are 

uncommon above the Otoites sauzei zone, Bradjordia 

and Otoites are unknown above that zone, Stemmatoceras and Normannites are unknown below that zone, 

and Otoites is characteristic of that zone although it 

occurs also in the upper part of the underlying zone of 

Sonninia sowerbyi. 

Below this faunule on the southeast shore of Wide 

Bay another ammonite faunule of middle Bajocian 

age has been obtained from 225 to 500 feet below the 

top of the Kialagvik Formation. This older faunule 

is characterized by the genera Sonni.nia, Witchellia, 

Docidoceras, Pseudotoites?, and Strigoceras. Of these, 

only Sonninia has been recorded from beds older than 

the European zone of Sonninia sowerbyi (Arkell and 

others, 1957, p. L267); Docidoceras is characteristic of 

that zone. Pseudotoites has been recorded previously 

only from Australia (Arkell, 1954, p. 556, 572-577) 

and Argentina (Arkell, 1954, p. 592). In Australia it 

is associated with ammonites indic·ating a correlation 

with the zone of Sonninia sowerbyi. In Argentina 

the exact stratigraphic position of Pseudotoites has not 

been described, but it occurs in a sequence of beds 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B19 

containing ammonite genera that apparently represent 

both the Sonninia sowerbyi and Otoites sauzei zones. 

QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA 

On Maude Island the lower beds of the Y akoun 

Formation contain ammonites identical specifically with 

those in the Fitz Creek Siltstone and in the Gaikema 

Sandstone northwest of Cook Inlet. On the southeast shore of Maude Island ha.ve been found species 

of Stephanoceras and Chondroceras (McLearn, 1929, 

p. 13-18; 1932, p. 54, 55) that Arkell (1956, p. 542) 

correlated with the European zone of Stephanoceras 

humphriesianum, presumably because of the presence 

of Chondroceras. On the northwest shore of Maude 

Island have been found species of Zemistephanus, 

Normannites, and Teloceras (McLearn, 1929, p. 18-27; 

1932a, p. 51-52) that Arkell (1954, p. 587, 588; 1956, 

p. 542) correlated tentatively with the European zone 

of Otoites sauzei. This last correlation was based 

apparently on the absence of Chondroceras; on the 

fact that Teloceras was obtained as float and, therefore, 

is of little age value; on an identification of Ammonites 

carlottensis Whiteaves (1876, p. 38, pl. 6) with Pseudotoites instead of Zemistephanus (Arkell, 1954, p. 594); 

and on the presumption that Zemistephanus was 

obtained from older beds than the float specimen of 

Teloceras (Arkell, 1954, p. 596). However, the various 

species of Chondroceras, N ormannites, and Teloceras 

that were obtained from these localities on Maude 

Island occur together in the Fitz Creek Siltstone in 

in Alaska and belong to a single faunule. The evidence, 'as presented herein, is decidedly in favor of 

correlating this faunule with only the zone of Stephanoceras humphriesianum. 

CENTRAL BRITISH COLUMBIA 

The presence of rocks of middle Bajocian age in 

central British Columbia is proved by occurrences of 

Stephanoceras, Sonninia; and Witchellia (McLearn, 

1926; 1927, p. 65; Frebold, 1957a, p. 16 and fig. 4). 

The last two genera provide a broad correlation with 

the European zones of Sonninia sowerbyi and Otoites 

sauzei, but Arkell (1956, p. 542) favored a correlation 

with only the zone of Sonninia sowerbyi. The few 

species that have been described are not identical with 

any known from the Tuxedni Group in Alaska. 

WESTERN INTERIOR OF CANADA 

The middle part of the Fernie Group at rnany places 

in western Alberta and southeastern British Columbia 

has furnished middle Bajocian ammonites including 

the genera Teloceras, Stemmatoceras, Stephanoceras, 

Zemistephanus, J\Tormannites, and Chondroceras -(MeLearn, 1927, p. 72; 1928, p. 21, 22; 1~32b; Warren, 

1947; Frebold, 1957a, p. 12-18, 47-53). These genera 

are the same as occur in the lower beds of the Yakoun 

Formation on the Queen Charlotte Islands and in the 

Fitz Creek Siltstone of the Cook Inlet region, Alaska, 

but the species appear to be different except for Chondroceras. allani (McLearn), which is recorded herein 

from Alaska. On the basis of these ammonites the 

middle part of the Fernie Group has been correlated by 

Arkell (1956, p. 542) and Frebold (1957a, p. 13) with 

the European zone of Stephanoceras humphriesianum 

and Otoites sauzei. The evidence for correlation with 

the first named zone is particularly strong as shown 

by the association of Teloceras, Normannites, ~nd 

Chondroceras and the absence of Sonninia and 

Witchellia, provided that these genera have the same 

stratigraphic ranges as in northwest Europe (table 10). 

Below the beds characterized by Teloceras at one 

locality have been found coarsely ribbed specimens of 

Sonninia that are indicative of early middle Bajocian 

age (Frebold, 1957a, p. 13, 48, 49) by comparison with 

the European faunal succession. Its presence below 

the Teloceras-bearing beds corresponds with the stratigraphic positions of the two genera in Europe. 

WESTERN INTERIOR OF THE UNITED STATES 

Some ammonites of middle Bajocian age have been 

found in the northern part of the western interior region 

(Imlay, 1948, p. 13, 14, 19; 1952, p. 967, 968). They 

have been obtained from the middle part of the Gypsum 

Spring Formation in northwestern Wyoming (Imlay, 

1956, p. 583), from the middle part of the Piper Formation in southern Montana (Imlay, 1956, p. 577), from 

the lower part of the Sawtooth Formation in western 

Montana (Imlay, 1948, p. 19) and from Members B 

and C of the Twin Creek Limestone in southeastern 

Idaho and westernmost Wyoming (Imlay, 1950, p. 39). 

The genera present include at least Stemmatocei'as, 

Zem1"stephanus, Stephanoceras, Chondroceras, and Normannites. Most of the specimens are crushed and 

poorly preserved, but as far as their preservation pPrmits 

comparisons they resemble the species of those genera 

from the middle part of the Fernie Group in western 

Alberta. 

EAST-CENTRAL OREGON 

In east-central Oregon, an1monites of middle Bajocian 

age have been found in the Weberg, Warn1 Springs, and 

Snowshoe Formations of Lupher (1941, p. 227, 248-252, 

259, 260). The evidence furnished by the an1monites 

has been discussed by Lupher (1941, p. 253-255, 261-:-

263) and Arkell (1954, p. 589, 590; 1956, p. 555). In 

recent years the writer has restudied the ammonites 

collected by Lupher as well as many ammonites collected by himself and by other geologists and can 

confirm that Luphers age determinations are mainly 

correct. 
B20 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

The basal beds of the Weberg Formation contain a 

constricted species of Tmetoceras that furnishes a correlation with ~he European zone of Tmetoceras scissum. 

The overlying beds have furnished Tmetoceras, 

Praestrig1'tes ~nd Docidoceras. These furnish a correlation with both the upper part of the lower BaJocian 

and with the\ basal part of the middle Bajocian considering that :~n Europe Tmetoceras ranges to the top 

of the Grapho'ceras concavum zone (Arkell, 1956, p. 34); 

Praestrigites ranges through the zones of Graphoceras 

concavum and Sonninia sowerbyi (Arkell, and others 

1957, p. L271), and Docidoceras is characteristic of the 

lower part of :;the zone of Sonninia sowerbyi and is not 

known from older beds. 

The highest part of the Weberg Formation has furnished many ~pecimens of Euhoploceras and W1~tchellia 

and some sp~cimens of Docidoceras and Praestrigites. 

These genera ;in association are excellent evidence for 

a correlation 'f!th the zone of Sonnin~a sowerbyi because 

in Europe Witchellia is unknown below that zone, 

Praestrig~tes i~ unknown above it, and Euhoploceras 

and Docidoceras are typical of its lower part. 

The Warm:, Springs For~ation overlies the Weberg 

Formation transitionally and apparently is only slightly 

younger. Tlte presence of such ammonites as Witchellia, Sonninia (Papilliceras), Euhoploceras, and Stemmatoceras? shows that it is of middle Bajocian age. 

The Snowshoe Formation in its iowPr 50 feet contains 

ammonites of late Toarcian age including such genera 

as Haugia, Grammoceros, Catulloceras? and Harpoceras. 

Directly above, throughout a stratigraphic thickness of 

about 150 feet, occurs Tmetoceras cf. T. scissum (Benecke) of Parly Bajocian age. Still higher in the lower 

and middle parts of the formation occur the ammonites 

Witchellia, Sonninia, S. (PapilUceras), and Stephanoceras (Skirroceras), which suggest correlations with both 

the zones of Sonninia sowerbyi and Otoites sauzei. At 

a few places in the Snowshoe Formation have been 

found an association of the ammonites Normannites, 

Chondroceras, Teloceras, and Stephanoceras. These appear to be identical specifically with ammonites in the 

Fitz Creek Siltstone in Alaska and are correlated 

similarly with the European zone of Stephanoceras 

humphriesianum. 

NORTHERN CALIFORNIA 

From the 1-Iormon Sandstone in the Taylorsville 

area, California, have been obtained a few ammonites 

of middle Ba]ocian age (Crickmay, 1933, p: 898, 899, 

909-913, pl. 27, figs. 6-11, pis. 28-31, pl. 32, fig. 1) 

including speties of Sonninia, S. (Pap·dliceras), Normannites, and Chondroceras. These were referred by 

Crickmay to the early Middle Jurassic (1933, p. 899) 

and by Arkell (1954, p. 590; 1956, p. 555) with qualifications to the European zones of Sonninia sowerbyi 

and Otoites sauzei. In addition from the upper part of 

the formation Crickmay (1933, p. 898) obtained a small 

ammonite that he identified with Teloceras but did not 

describe. If this identification is correct the upper 

part of the Morman Sandstone may correspond with 

the zone of Stephanoceras humphriesianum. The published evidence for correlation of the Mormon Sandstone with this zone, or with the zone of Sonninid 

sowerbyi is not decisive, but a correlation of part of the 

formation with the Otoites sauzei zone is confirmed by 

the association at one place of the genera Normannties, 

Chondroceras, and Sonninia (Papilliceras). As noted 

by Lupher (1941, p. 262) some of the species of Papilliceras described by Crickmay from the Mormon Sandstone appear to be identica,J with species in the Snowshoe 

Formation of eastern Oregon. 

SOUTHERN CALIFORNIA 

A few fossils of middle Bajocian age have been obtained from a limestone lens in the Bedford Canyon 

Formation in the Santa Ana Mountains southeast of 

Corona, Calif. The exact locality is near the head of 

McBride Canyon in the NE. cor. sec. 31, T. 4 S., R. 6 

W., Corona South quadrangle, Orange County. The 

fossils include the ammonites Dorsetensia sp. and T(lloceras? sp. JUV. and the pelecypods Posidonia ornati 

Quenstedt and Inoceramus cf. I. hamadae Hayami. 

SOUTHERN MEXICO 

Most of the ammonites from southern Mexico that 

Burckhardt (1927, p. 19-28, 92-94; 1930, p. 25, 26) considered to be of middle Bajocian age areeonsidered by 

Arkel~ (1954, p. 590; 1956, p. 564, 565) to be of Bathonian age, or perhaps in part of late Bajocian age. 

He assigned Stephanoceras undulatum Burckhardt 

(1927, pl. 12, figs. 1-4), however, to Normannites which 

genus is typical of the upper part of middle Bajocian 

(table 10) although ranging into the lower part of the 

upper Bajocian. Except .for this species of Normannites, which bears a little resemblance to N. crickmayi 

(McLearn), the Middle Jurassic ammonites from 

Mexico that Burckhardt described are unlike the middle 

Bajocian ammonites from Alaska and, judging from the 

preliminary studies of Erben (1956, p. 28, 29), are 

mostly of late Bajocian age. 

SOUTH AMERICA 

The presence of middle Bajocian ammonites in 

Argentina, Chile, Peru, and Bolivia has been discussed 

recently by Arkell (1954, p. 590-593; 1956, p .. 585). 

Evidence for the European zone of Stephanoceras 

humphriesianum is meager and is based mainly on one 

specimen of Stephanoceras (Steinmann, 1881, p. 268, 

pl. 12, figs. 7, 7a). In contrast, evidence for the zones 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B21 

Otoites sauzei and Sonninia sowerbyi is excellent. In 

the lower part of the Middle Jurassic sequence occur 

the genera Eudmeto~eras, Bradfordia, and Fontannesia 

that Arkell (1954, p. 591) considered to represent the 

zone of Sonninta sowerbyi. In the overlying limestone 

occur the genera Sonninia, S. (Papilliceras), Witchellia, 

Shirbu·irnia, Otoites, Chondroceras, Emileia, Fontannesia, Eudmetor.eras, Bradfor-dia, and Pseudotoites that 

Arkell considered to represent both the S. sowerbyi 

and the Otoites sauzei zones. Of the genera listed, 

however, only Chondroceras is not known from beds 

older than the Otoites sauzei zone. 

INDONESIA AND AUSTRALIA 

Beds of Middle Bajocian age have been identified 

in eastern Indonesia, in New Guinea, and in western 

Australia. The zone of Stephanoceras humphriesianum 

is represented in eastern Indonesia by Teloceras and 

Chondroceras (Arkell, 1954, p. 583, 584; 1956, p. 440), 

in New Guinea by Stephanoceras, Chondroceras, and 

Normannites (Arkell, 1954, p. 583; 1956, p. 448), and 

is possibly represented in western Australia by specimens of Stemmatoceras (Arkell, 1954, p. 581-583). 

The zone of Otoites sauzei has not been identified 

anywhere in Indonesia or Australasia. The zone of 

Sonninia sowerb.yi has been identified in western 

Australia (Arkell, 1954) by an association of the 

ammonites Sonninia, Witchellia, Fontannesia, Otoites, 

and Pseudotoites. An occurrence of the same zone in 

eastern Indonesia is indicated by the presence of 

Pseudotoites (Kruizinga, 1926, pl. 6, figs. 1, 2; pl. 12, 

fig. 3) according to Arkell (1954, p. 576, 584; 1956, 

p. 440). None of the described ammonites are closely 

similar specifically to the n1iddle Bajocian ammonites 

of the Cook Inlet region, Alaska, although the species 

of Teloceras and Stephanoceras are compared by Arkell 

(1954, p. 583) with species from western Canada. 

EUROPE 

Many ammonite genera that in Europe are common 

in or characterize beds of middle Bajocian age are 

likewise common, in the Co~k Inlet region, Alaska, in 

the Tuxedni Group. In general, as· discussed under 

the heading "Ages of the faunas," the association of 

ammonite genera and the stratigraphic succession of 

those genera are nearly the same in Alaska as in Europe. 

A possible exception is the genus Sonninia which at 

the top of its range in Alaska occurs with Teloceras, 

Chondroceras, and Normannites, an association typical 

of the zone of Stephanoceras humphriesianum in Europe. 

Even in Europe, however, Sonninia has been reported 

from the lower part of that zone (Dorn, 1935, p. 120; 

Gillet, 1937, p. 11). Another possible· exception is 

713-993 0 - 64 - 2 

Leptosphinctes which at one locality in A1aska (Mesozoic 

loc. 8367) is associated with ammonites such as 

Normannites, Zemistephanus, and Chondroceras; which 

indicate a rr1iddle rather than a late Bajocian age. 

One difference between the middle Bajocian ammonite assemblages of Europe and Alaska is the presence 

in Alaska of the genera Zemistephanus and Parabigotites, 

which are as yet unknown in Europe. Similarly 

some genera found in Europe and Asia in beds of 

middle Bajocian age have not been found in Alaska. 

Their absence from Alaska may be due to collection 

failure and hence only apparent, or their absence may 

actually reflect provincial differences. This last possibility is suggested by the fact that not a single specimen of Dorsetensia has yet been found in Alaska, 

although the genus ranges through most of the middle 

Bajocian in Eurasia and Africa and is particularly 

common in the zone of Stephanoceras humphriesianum 

(Ar~ell, 1954, p. 559; 1952a, p. 295;·1956, p. 122-124, 

264, 268, 278, 300, 325, 342, 413, 487). 

Similarly on the specific level the middle Bajocian 

ammonites from the Cook Inlet region, Alaska, show 

many resemblances to those in beds of middle Bajocian 

age in Europe, as mentioned under the specific descriptions. For example, in the Fitz Creek Siltstone the 

species of Teloceras, Stemmatoceras, Normannites, and 

Chondroceras are similar to species in the European 

zone of Stephanoceras humphriesianum. The species 

of Strigoceras and Sonninia, however, resemble species 

in the Otoites sauzei zone. In the Red Glacier Form~­

tion most of the ·species resemble European species 

from the Otoites sauzei zone or the Sonninia sowerbyi 

zone. However, Stephanoceras cf. S. nodosum (Quenstedt) and S. (Skirroceras) kirschneri Imlay, n. sp. 

from near the top of the formation resemble species 

from the lower part of the Stephanoceras humphriesianum zone of Europe. These species of Stephanoceras 

are not good evidence for correlation with that zone 

because the Gaikema Sandstone, overlying the Red 

Glacier Formation contains the genera Emileia and 

Bradfordia which in Europe are not known above the 

Otoites sauzei zone. 

Overall the 1niddle Bajocian am1nonites from the 

Cook Inlet region, Alaska, show many rese1nblances, 

both generically and spe~ifically, to the middle Bajocian 

am1nonites of Europe. There are differences, however, 

that suggest some provincial develop1nents. 

GEOGRAPHIC DISTRIBUTION 

Detailed descriptions of the individual fossil localities 

are given in table 11. The occurrence of the fossils by 

area and locality are indicated in table.s 12 and 13. 

The positions of the areas are shown in figures 1-4. 
B22 

Locality 

No. on figs. 1-4 

1 

2 

3 

4 

5 

5 

6 

7 

8 

8 

9 

10 

10 

10 

11 

11 

12 

13 

14 

14 

14 

14 

15 

15 

16 

17 

17 

17 

18 

18 

18 

JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE H.-Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region, Alaska 

Geological 

Survey 

Mesozoic 

localities 

27577 

24113 

25945 

26723 

25345 

25346 

24176 

25946 

24215 

25942 

24134 

8585 

24120 

24220 

3696 

3697 

8567 

3010 

3009 

21261 

21262 

21263 

3007 

3008 

3004 

21264 

21265 

21266 

3013 

21267 

21268 

Collector's field Nos. 

52AGz85 __________ _ 

55AGz245a ___ ""' ____ _ 

57 AGz43N ________ _ 

54AFy28 __________ _ 

54AFy29 __________ _ 

52AHr51 __________ _ 

55AGz309 _________ _ 

52AGz182 _________ _ 

55AGz163 _________ _ 

52AGz275 _________ _ 

13AM36 ___________ _ 

52AGz198 _________ _ 

52AGz215 _________ _ 

6AK88A __________ _ 

6AK88B __________ _ 

13AM16 ____ -------

917j ______________ _ 

917i ______________ _ 

48AI56 ____________ _ 

48AI57 ____________ _ 

48AI58 ____________ _ 

917g ______________ _ 

917h ______________ _ 

917d ______________ _ 

48AI59 ____________ _ 

48AI60 ____________ _ 

48AI61 ____________ _ 

917n ______________ _ 

48AI62 ____________ _ 

48AI63 ____________ _ 

Collector, year of collection, description of locality, and stratigraphic assignment 

Western Gulf Oil Co., 1959. Talkeetna Mountains (A-1) quad., near Crooked Creek 

south of Nelchina, lat 62°02'00" N ., long 147° 18'00" W., Tuxedni Formation, 

lower part. 

Arthur Grantz, Richard Hoare, and R. W. Imlay, 1952. Talkeetna Mountains (A-1) 

quad. From a landslide scar 1.63 miles north of the mouth of Albert Creek. Tuxedni Formation, 5Q-250 ft above base. 

Arthur Grantz, 1955. Talkeetna Mountains (A-1) quad., lat 62°02'28" N., long 

147°22' 59" W., Tuxedni Formation, upper half of lower sandstone. 

Arthur. Grantz, 1957. Talkeetna Mountains (A-1) quad., lat 62°02'00" N., long 

147°25'15" W., Tuxedni Formation, upper half of lower sandstone. 

L. F. Fay, 1954. Talkeetna Mountains (A-2) quad., lat 62°00'46" N., long 147°34'-

02%" W., Tuxedni Formation, upper siltstone. 

L. F. Fay, 1954. Talkeetna Mountains (A-2) quad., lat 62°00'41" N., long 147°34'-

16%" W., Tuxedni Formation, upper siltstone. 

Richard Hoare, 1952. Anchorage (D-2) quad., Pass Creek, 0.35 mile above its mouth. 

Basal sandstone of the Tuxedni Formation, 10Q-200 ft above base. 

Arthur Grantz, 1955. Anchorage (D-2) quad., lat 61° 57' 47" N., long 147°24'21" W., 

Tuxedni Formation, 20Q-300 ft above base. 

Richard Hoare and Arthur Grantz, 1952. Anchorage (D-2) quad., Alfred Creek, 0.8 

mile east of Papoose Creek. Tuxedni Formation, upper siltstone. 

Arthur Grantz, 1955. Anchorage (D-2) quad., lat 61°57'09" N., long 147°27'56" W., 

Tuxedni Formation, upper siltstone. 

Arthur Grantz1 Richard Hoare, and R. W. Imlay, 1952. Anchorage (D-2) quad., 2.63 

miles N. 52}2 miles E. of mouth of Sheep Creek. Tuxedni Formation, base of upper 

siltstone. 

G. C. Martin, 1913. Talkeetna Mountains. North bank of Caribou Creek 0.75 mile 

below Billy Creek. Tuxedni Formation, upper siltstone. 

Arthur Grantz, Richard Hoare, and R. W. Imlay, 1952. Anchorage (D-2) quad., 

Caribou Creek 0.62 mile east of Billy Creek. Tuxedni Formation, upper siltstone. 

Arthur Grantz, Richard Hoare, and R. W. Imlay, 1952. Anchorage (D-2) quad., 

north side of Caribou Creek 0. 73 mile east of Billy Creek. Tuxedni Formation, upper 

siltstone. 

Adolph Knopf, 1906. Talkeetna Mountains. Tributary of Caribou Creek from the 

west, 0.25 mile above Billy Creek at altitude of 4,050 ft. Tuxedni Formation, 

probably upper siltstone. 

Adolph Knopf, 1906. Talkeetna Mountains. Boulder in stream bed at same location as Mesozoic loc. 3696. 

G. C. Martin, R. M. Overbeck, and J. B. Mertie, Jr., 1913. Talkeetna Mountains. 

About 3.2 miles up second creek entering Boulder Creek from the north above the 

Canyon. This creek is north of extreme west end of Anthracite Ridge. Tuxedni 

Formation. 

T. W. Stanton, 1904. Tuxedni Bay area, 1.4 miles west of Fossil Point. Red Glacier 

Formation. Float about 700ft below top. 

T. W. Stanton, 1904. Tuxedni Bay area, 1.24 miles west of Fossil Point. Red Glacier 

Formation, about 500ft below top. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 1.26 miles N. 87° W. of Fossil 

Point. Red Glacier Formation. From silty sandstone 500-515 ft below top of 

formation in unit 34 of section measured by Stanton and Martin. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 1.25 miles N. 88° W. of Fossil 

Point. Red Glacier Formation. Massive gray siltstone 480-500 ft below top of 

formation in unit 33 of section measured by Stanton and Martin. 

R. W. Imlay and D. J. Miller, 1948. Same geographical location as 21261. Red 

Glacier Formation. Float from 480 to 515ft below top of formation. 

T. W. Stanton, 1904. Tuxedni Bay area, 1.2 miles west of Fossil Point. Red Glacier 

Formation. Float about 450ft below top of formation. 

T. W. Stanton, 1904. Tuxedni Bay area, 1.22 miles west of Fossil Point. Red Glacier 

Formation, about 475ft below top. 

T. W. Stanton, 1904. Tuxedni Bay area, 0.96 mile west of Fossil Point. Red Glacier 

Formation. Float on beach 250-300 ft below top of formation. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, ::3,650 ft S. 80° W. of Fossil 

Point. Red Glacier Formation. Massive gray siltstone 250 ft below top of formation and from bas8 of unit 23 of section by Stanton and Martin. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 3,500 ft S. 86° W. of Fossil 

Point. Red Glacier Formation, 215ft below top in massive gray siltstone. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 3,250 ft S. 85° W. of Fossil 

Point. Red Glacier Formation, 200ft below top in massive gray siltstone. 

T. W. Stanton, 1904. Tuxedni Bay area, 1.0 mile west of Fossil Point. Red Glacier 

Formation, upper 50 ft. 

R. W. Imlay and D. J. Miller, 1948. , Tuxedni Bay area, 3,075 ft S. 84° W. of Fossil 

Point. Red Glacier Formation, 170 ft below top in massive gray siltstone. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 3,250-3,500 ft S., 85°-86° W. 

of Fossil Point. Red Glacier Formation. Float from 100 to 230 ft below top of 

formation. 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B23 

TAB I.E H.-Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region Alaska-Continued 

Locality Geological No. on Survey figs. 1-4 Mesozoic 

localities 

18 21269 

19 24333 

20 24334 

21 22723 

22 2999 

22 3000 

22 10245 

22 10520 

22 20756 

22 21270 

22 26953 

23 2997 

23 2998 

23 10515 

23 10516 

23 21271 

23 21274 

23 21275 

24 2996 

24 21276 

25 22721 

26 22722 

27 21281 

27 22705 

28 22706 

28 22707 

29 2995 

29 10513 

29 10514 

29 10519 

29 10523 

30 2993 

30 10511 

Collector's field Nos. 

48AI63 _____________ 

52AJuN5 ___________ 

52AJu-F15 _________ 

51AHalL _____ ----- _ 

916e _______________ 

916f _______________ 

B __________________ 

20-AM-10 __________ 

46AKr33 ___________ 

48AI65 _____________ 

-------------------- 916c _______________ 

916d _______________ 

20AM-4 ____________ 

20-AI-5 ____________ 

48AI66 _____________ 

48AI73 _____________ 

48AI74 _____________ 

916b _______________ 

48AI75 _____________ 

51AHa9 ____________ 

51AHa1Q ___________ 

48AI8Q _____________ 

51AGz136 __________ 

51AGz137 ----------

51AGz138 __ --------

916a _______________ 

2Q-AI-2 ____________ 

2Q-AI3 _____________ 

2Q-AM-7, 8, 9 ______ 

20AM-3 ____________ 

914 ________________ 

2Q-AI-1 ____________ 

Collector, year of collection, description or locality, and stratigraphic assignment 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 2,800 ft S. 86° W. of Fossil 

Point. Red Glacier Formation, about 95 ft below top in massive gray siltstone. 

Werner Juhle, 1952. Tuxedni Bay area, on ridge top between Difficult Creek and 

Hungryman Creek 4.8 miles S. 79° W. of Fossil Point. Red Glacier Formation, 

1,800-1,900 ft below top. 

Werner Juhle, 1952. Tuxedni Bay area, on a ridge south of the headwaters of Hungry- man Creek, 5.5 miles S. 78° W. of the mouth of Hungryman Creek. Red Glacier 

Formation, 1, 700-1,800 ft below top. 

J. K. Hartsock, 1951. Tuxedni Bay area. Near Bear Creek about 3 miles S. 62° W. 

of mouth of Bear Creek. Gaikema Sandstone. From gray sandy shale in lower 150ft. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area, 2,500 ft 

west of Fossil Point. Fitz Creek Siltstone. Float from 100 to 150 ft below top. 

T. W. Stanton, 1904. Tuxedni Bay area, 3,000 ft west of Fossil Point. Fitz Creek 

Siltstone 150 ft below top. 

C. N. Fenner, 1919. Tuxedni Bay area, south shore west of Fossil Point. Fitz Creek 

Siltstone. 

F. H. Moffit, 1920. Tuxedni Bay area, 3,000 ft west of Fossil Point. Fitz Creek 

Siltstone, 150 ft below top. 

C. E. Kirschner, 1946. Tuxedni Bay area, south shore west of Fossil Point. Float 

from both Fitz Creek Siltstone and Cynthia Falls Sandstone. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 0.52 mile N. 87° W. of Fossil 

Point. Fitz Creek Siltstone. From silty sandstone 150 ft below top. Same as unit 19 of section by Stanton and Martin. 

E. R. Orwig, 1957. Tuxedni Bay area, west of Fossil Point. Fitz Creek Siltstone. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area, 1,500 ft 

west of Fossil Point. Fitz Creek Siltstone, sandy limestone 7 5 ft below top. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area, 2,000 ft 

west of Fossil Point. Fitz Creek Siltstone, siltstone and sandstone 100 ft below top. 

F. H. Moffit, 1920. Tuxedni Bay area, 0.32 mile west of Fossil Point. Fitz Creek 

Siltstone, 100 ft belpw top. ' 

Herbert Insley, 1920. Tuxedni Bay area, 0.28 mile west of Fossil Point. Fitz Creek 

Siltstone, 7 5 ft below ·top. · R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 0.40 mile N. 87° W. of Fossil 

Point. Fitz Creek Siltstone, from silty sandstone, 100 ft below top. Same as unit 

14 of section by Stanton and Martin. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 0.40 mile N. 87° W. of Fossil 

Point. Fitz Creek Siltstone, from silty sandstone, 100 ft below top. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 0.3 mile N. 87° W. of Fossil 

Point. Fitz Creek Siltstone, from silty sandstone, 75 ft below top. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area, about 

1,300 ft west of Fossil Point. Fitz Creek Siltstone, 25 ft below top. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 0.25 mile N. 87° W. of Fossil 

Point, Fitz Creek Siltstone, from silty sandstone, 25-60 ft below top. Same as unit 

8 of section by Stanton and Martin. · J. K. Hartsock, 1951. Tuxedni Bay area. On tributary of Bear Creek, 3.56 miles S. 

38° W. of mouth of Bear Creek. Fitz Creek Siltstone, 150ft above base. 

J. K. Hartsock, 1951. Tuxedni Bay area. Near Bear Creek, 3.75 miles S. 38° W. of 

mouth of Bear Creek. Fitz Creek Siltstone, 25Q-300 ft above base. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area. Same outcrop as loc. 22705. 

Fitz Creek Siltstone. 

Arthur Grantz, 1951. Tuxedni Bay area, on Bear Creek 2.36 miles from Tuxedni 

Channel. Fitz Creek Siltstone, 50Q-600 ft above base. 

Arthur Grantz, 1951. Tuxedni Bay area, 0.12 mile above mouth of tributary entering 

Bear Creek from southeast 2.53 miles from Tuxedni Channel. Fitz Creek Siltstone. 

Sandy siltstone 600-650 ft above base. · Arthur Grantz, 1951. Tuxedni Bay area, 600 ft above mouth of a tributary entering 

Bear Creek from southeast 2.53 miles from Tuxedni Channel. Cynthia Falls Sandstone, 40Q-500 ft above base. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area. At 

Fossil Point between Mesozoic locs. 2993 and 2994. Cynthia Falls Sandstone, about 

4 7 ft above base. 

Herbert Insley, 1920. Tuxedni Bay area, just west of extreme end of Fossil Point, 

Cynthia Falls Sandstone. From same unit as Mesozoic loc. 2993. 

F. H. Moffit and Herbert Insley, 1920. Tuxedni Bay area at same place as Mesozoic 

loc. 10523 but about 20 ft lower stratigraphically. 

F. H. Moffit, 1920. Tuxedni Bay area, \Vest of Fossil Point. Cynthia Falls Sandstone, 

from basal 39 ft. 

F. H. Moffit, 1920. Tuxedni Bay area, 200 ft west of the point on Fossil Point. 

Cynthia Falls Sandstone near base. 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area at Fossil 

Point. Cynthia Falls Sandstone from 55 ft of shaly sandstone whose base is about 

50 ft above base of formation. 

Herbert Insley, 1920. Tuxedni Bay area, just southeast of end of Fossil Point, Cynthia 

Falls Sandstone. 
B24 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE H.-Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region, Alaska-Continued 

Locality 

No. on figs. 1-4 

30 

30 

31 

32 

33 

34 

35 

36 

36 

37 

37 

38 

38 

38 

39 

40 

40 

41 

42 

43 

43 

44 

45 

Geological 

Survey 

Mesozoic 

localities 

Collector's field Nos. 

10512 2Q-AM-L _________ _ 

21280 48AI 79 ___________ _ 

2994 915 _______________ _ 

22695 51AGz-97 ----------

22529 50AGz 82 _________ _ 

22528 50AGz 83 ___ -------

21766 49AGz-2 __________ _ 

21295 48AI-6 ____________ _ 

21296 48AI-7 ____________ _ 

19956. F-24 ______________ _ 

21293 48AMr-143 ________ _ 

19957 F-25 ______________ _ 

19958 F-26 ______________ _ 

19959 F-27 _______________ _ 

19964 F-32 _______________ _ 

19966 F-34 _______________ _ 

20017 F-84 _______________ _ 

19951 F-20 _____________ _ 

27115 58ADt 44 _________ _ 

10980 F-3 ______________ _ 

19961 F-29 _____________ _ 

26600 57ADt 11_ _________ . 

26601 57ADt 6 __________ _ 

Collector, year of collection, description of locality, and stratigraphic assignment 

F. H. Moffit, 1920. Tuxedni Bay area. South side of Fossil Point. Cynthia Falls 

Sandstone. From same unit as Mesozoic loc. 2993. 

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay area, 900ft south of Fossil Point. 

Cynthia Falls Sandstone. Sandstone and siltstone in lower 20 ft of unit 1 of section 

measured by Martin (1926, p. 142.) 

T. W. Stanton, G. C. Martin, and Andrew Brown, 1904. Tuxedni Bay area, about 

half a mile south of Mesozoic loc. 2993 and probably at about same stratigraphic 

position. 

Arthur Grantz, 1951. Lake Hickerson area, 2.5 miles N. 30° W. of Lake Hickerson 

and approximately 1.3 miles S. 80° W. of the junction of Squirrel Creek and the ice 

margin of Red Glacier. Red Glacier Formation, about 1,30Q-1,400 ft below top in 

brownish-gray siltstone. 

Arthur Grantz, 1950. Lake Hickerson area, 5.3 miles S. 55° E. of peak of Mount 

Iliamna, Red Glacier Formation, about 300 ft below top. 

Arthur Grantz, 1950. Lake Hickerson area, 6.0 miles S. 55° E. of peak of Mount 

Iliamna. Fitz Creek Siltstone near middle. 

D. J. Miller, 1949. Iniskin Peninsuia. South shore of Chinitna Bay in gully 1.66 

miles N. 53 ° W. of Fitz Creek. Red Glacier Formation, 100-150 ft below top. 

In massive green siltstone. 

R. W. Imlay, 1948. Iniskin Peninsula. South shore of Chinitna Bay in gulch 1.62 

miles N. 55 ° W. of dock at mouth of Fitz Creek. Red Glacier Formation, 320-330 

ft stratigraphically below top in gray siltstone. .. R. W. Imlay, 1948. Iniskin Peninsula. South shore of Chinitna Bay in gulch 1.62 

miles N. 54 ° W. of dock at mouth of Fitz Creek. Red Glacier Formation, 350-360 

ft stratigraphically below its top in gray siltstone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Cliffs on south 

shore of Chinitna Bay 1.15 miles N. 44° W. of mouth of Fitz Creek. Red Glacier 

Formation, 725-800 ft below top. 

D. J. Miller, 1948. Iniskin Peninsula. Gulch draining into Chinitna Bay from south, 

1.20 miles N. 42° W. of dock at mouth of Fitz Creek. Red Glacier Formation, 

about 1,200 ft below top. From concretions in siltstone about 100 ft below a sandstone unit. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. South shore of 

Chinitna Bay, about 360 ft up the second left tributary gully of small stream that 

flows almost on axis of the Gaikema Creek anticline (Kirschner and Minard, 1948)6 about 1000 ft above mouth of stream at Chinitna Bay and aboq,t 1.02 miles N. 48 

W. of the mouth of Fitz Creek. Red Glacier Formation from 250-300 ft below top 

in shaly sandstone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. South shore of 

Chinitna Bay about 100ft up the same tributary gully as Mesozoic loc'. 19957 and 1.0 

mile N. 50° W. of mouth of Fitz Creek. Red Glacier Formation from 300-350 ft 

below top in shaly sandstone containing concretions 6 in. in diameter. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula, 3ft below Mesozoic 

loc. 19958. Red Glacier Formation. Consolidated sandstone. ~ 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsuia. South shore of 

Chinitna Bay in small gully 2,600 ft west of mouth of Gaikema Creek and 0.90 mile 

N. 39° W. of mouth of Fitz Creek. Red Glacier Formation, 630ft below top. Thin 

bedded brown to gray shaly sandstone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsu,la. North side of 

Gaikema Creek about 400 ft upstream from mouth of South For];{; of Gaikema Creek or 1.0 mile N. 80° W. of the mouth of Fitz Creek. Red Glacier Formation, 850 ft . below top. Shaly sandstone interbedded with sandy shale. 

L. B. Kellum and Helmuth Wedow, Jr., 1944. Iniskin Peninsula. Float from streambed about 100ft upstream from confluence of Gaikema Creek an<;l the South Fork of 

Gaikema Creek and 1.0 mile N. 80° W. from mouth of Fitz C.reek. Red Glacier 

Formation. Float obtained about 800-900 ft below top. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Gaikema Creek 

about 1,200 ft upstream and 1.18 miles N. 82° W. of mouth of Fitz Greek. Red Glacier 

Formation, about 45 ft below top. Silty limestone with partings pf sandy shale. 

R. L. Detterman, 1958. Iniskin Peninsula. South shore of Chinitna Bay, 2.36 miles 

N. 74° W. of mouth of Fitz Creek. Gaikema Sandstone. Float obtained from 300 

to 400 ft above base of member. Olive-gray to dark-yellow sand~tone and siltstone. 

F. H. Moffit, 1921. Iniskin Peninsula. South shore of Chinitna· Bay, 0.78 mile N. 

33 ° W. of mouth of Fitz Creek. Gaikema Sandstone at base. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula .. Sea cliffs on south 

shore of Cbinitna Bay, 1,600 ft west of the mouth of Gaikema ,Creek and 0.7 mile 

N. 35° W. of the mouth of Fitz Creek. Gaikema Sandstone, .180 ft above base. 

Fine-grained evenly bedded sandstone just below a coarse congldmerate. 

R. L. Detterman, 1957. Iniskin Peninsula. On Gaikema Creek 1.1 miles N. 80° W. 

of mouth of Fitz Creek. Gaikema Sandstone 600-650 ft above base. Green sandstone and conglomerate. . R. L. Detterman, 1957. Iniskin Peninsula. Roadcut along Fitz C.r,eek, 3,000 ft S. 70° 

W. of mouth of Cliff Creek. Gaikema Sandstone, 50-100ft above base. Soft chocolate brown coquinoid sandstone. 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B25 

TABI .. E H.-Localities at which fossils of middle Bajocian age have been collected in the Co9k Inlet region, Alaska-Continued 

Locallty Geological 

No. on Survey 

figs. 1-4 Mesozoic 

localltles 

46 19989 

47 19984 

48 19981 

48 20025 

49 26599 

49 27110 

50 20020 

50 20021 

51 19975 

51 19977 

51 21305 

52 19973 

52 19974 

53 19978 

53 20022 

54 19933 

54 21772 

54 22533 

54 22552 

55 21302 

56 21292 

Collector's field Nos. 

F-56 _______________ 

F-51--------------

F-47 ______________ 

44AWWF-49_ ------

57ADt 12 __________ 

58ADt.12 ___ -------

F-87 _______________ 

F-88 _______________ 

F-42 _______________ 

F-44 _______________ 

48AI 28 ____________ 

F-40 _______________ 

F-41 _______________ 

f-45 _______________ 

F-89 _______________ 

44A WW 2a _________ 

49AGz1 ____________ 

49AHa3 ________ · ____ 

29AHaL ___________ 

48AHa9 ____________ 

48AHa8 ____________ 

Collector, year of collection, description of locality, and stratigraphic assignment' 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Southwef:!t side of 

Tonnie Creek about 700ft upstream from the trail crossing at the mouth of the canyon 

and 1.47 miles S. 60° E. from Tonnie Peak. Gaikema Sandstone, 120ft above base. 

Firmly consolidated sandstone 25 ft below a 2Y2-ft thick boulder conglomerate bed. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. North side of 

Gaikema Creek about 200ft downstream from the falls and 2.1 miles N. 85° W. of 

the mouth of Fitz Creek. Fitz Creek Siltstone, 120 ft below top. Greenish-gray 

sandy shale and numerous small concretions. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Small gully on south side of Gaikema Creek about 800 ft upstream from the crest of lower falls and 

1.85 miles N. 84° W. of the mouth of Fitz Creek. About 125ft above stream level. 

Fitz Creek Siltstone, 160ft below top. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. In Gaikema Creek 

about 400 ft downstream from twin falls, which are about 2~ miles upstream from 

the mouth of Gaikema Creek on the south shore of Chinitna Bay and 2.02 miles N. 

85 ° W. of the mouth of Fitz Creek. Fitz Creek Siltstone 320 ft below top. Gray 

sandy shale containing a few thin layers of soft greenish gray medium-grained sandstone and some lenticular calcareous sandstone concretions. 

R. L. Detterman, 1957. Iniskin Peninsula. On Gaikema Creek, 1.72 miles N. 81° W. of 

mouth of Fitz Creek. Fitz Creek Siltstone, 200-300 ft above base. Sandstone and 

conglomerate interbedded in siltstone. 

R. L. Detterman 1958. Iniskin Peninsula. Gaikema Creek 1.72 miles N. 81° W. of 

mouth of Fitz Creek. Same as Mesozoic loc. 26599. Fitz Creek Siltstone, 200-300 ft 

above base. Sandstone and siltstone containing conglomerate interbeds. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Float from streambed of Gaikema Creek about 3,300 ft upstream from the mouth of South Fork and 1.61 

miles N. 82~0 W. of the mouth of Fitz Creek. Fitz Creek Siltstone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Float on northeast 

side of Gaikema Creek about 3,300 ft upstream from the mouth of South Fork and 1.6 

miles N. 82° W. of the mouth of Fitz Creek. Fitz Creek Siltstone. 

Helmuth Wedow, Jr., 1944. Iniskin Peninsula. North side of Gaikema Creek about 

3,200 ft upstream from the mouth of South Fork and 1.60 miles N. 82° W. from the 

mouth of Fitz Creek at stream level. Fitz Creek Siltstone, 360ft above base. Sandy 

shale containing wood fragments. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. North side of 

Gaikema Creek about 3,400 ft upstream from the mouth of South Fork and 1.60 miles 

N. 82° W. of the mouth of Fitz Creek. Fitz Creek Siltstone, 480 ft above base sandstone. · R. W. Imlay, 1948. Iniskin Peninsula. Gaikema Creek, 1.63 miles N. 81° W. of mouth 

of Fitz Creek. Fitz Creek Siltstone, 250-300 ft above base. 

Helmuth Wedow, 1944. Iniskin Peninsula. North side of Gaikema Creek about 2,800 

ft upstream from the mouth of South Fork and 1.54 miles N. 81° W. of mouth of Fitz 

Creek at an altitude of 180 ft above stream level. Fitz Creek Siltstone, 320 ft above 

base. Sandy shale, light gray to rusty yellow and limestone stringers. 

Helmuth Wedow, 1944. Iniskin Peni:p.sula. North side of Gaikema Creek about 3,000 

ft upstream from the mouth of South Fork, 1.58 miles N. 81~0 W. of the mouth of Fitz 

Creek and about 100ft above the streambed. Fitz Creek Siltstone, 440ft above base. 

Shaly sandstone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. South side of 

Gaikema Creek about 3,300 ft upstream from the mouth of South Fork and 1.68 miles 

N. 83° W. from the mouth of Fitz Creek. Fitz Creek Siltstone, 410ft above base. 

Gray to grayish green shaly sandstone interbedded with sandy shale, which weathers 

rusty yellow brown. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. Float on southwest 

side of Gaikema Creek in small gully about 50ft upstream from USGS Mesozoic loc. 

19978 and about 1.7 miles N. 83° W. of the mouth of Fitz Creek. Probably from Fitz 

Creek Siltstone. 

Helmuth Wedow, 1944. Iniskin Peninsula. South shore of Chinitna Bay, about 0.9 

mile N. 66° E. of the mouth of Fitz Creek. Fitz Creek Siltstone just below top and 

above loc. 19932. 

D. J. Miller, 1949. Iniskin Peninsula. South shore of Chinitna Bay. Float in gully 

0.9 mile northeast of Fitz Creek. Fitz Creek Siltstone near top. 

J. K. Hartsock, 1949. Iniskin Peninsula. South shore of Chinitna Bay, 0.92 mile N. 

67° E. of mouth of Fitz Creek. Fitz Creek Siltstone near top. 

J. K. Hartsock, 1949. Iniskin Peninsula. South shore of Chinitna Bay near axis of 

Fitz Creek anticline (Kirschner and Minard, 1948) 1.00 mile N ., 68° E. of mouth of 

Fitz Creek. Fitz Creek Siltstone near top. · J. K. Hartsock, 1948. Iniskin Peninsula. South shore of Chinitna Bay, 1.2 miles N. 

72° E. of mouth of Fitz Creek on bluffs above beach. Fitz Creek Siltstone, near top. 

R. W. Imlay, D. J. Miller, and J. K. Hartsock, 1948. lniskin Peninsula. South shore 

of Chinitna Bay, 1.4 miles N. 74° E. of mouth of Fitz Creek, Fitz Creek Siltstone. 

Gray siltstone. 
B26 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE H.-Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region, Alaska-Continued 

Locality Geological 

No. on Survey figs. 1-4 . Mesozoic 

localities 

56 26596 

57 26594 

57 26595 

58 19932 

59 10981 

59 11023 

59 11024 

59 11027 

59 11028 

59 11029 

59 19940 

59 21317 

59 22441-

60 19941 

61 27107 

62 21316 

62 22440 

63 22439 

64 20000 

65 19997 

65 26597 

66 21769 

67 27105 

67 20002 

68 21306 

69 27111 

70 22534 

71 21768 

72 21304 

72 21767 

Collector's field Nos. 

57 ADt-10 __________ 

57 ADt-8 ___ ----.,-- __ 

57 ADt-9 ___________ 

44WW 2 ___________ 

F-4----------------

ABF-3Q ____________ ABF-3L ___________ ABF-34 ____________ 

ABF-35 ___ -- ____ - __ ABF-36 ____________ 

44AW g ____________ 

48AI 34 ____________ 

50AHa41 ___________ 

44AWW 10 _________ 

58ADt 6-----------

48AI 33 ____________ 

50 AHa 42 _________ 

50AHa 40 __________ 

F-67 _______________ 

44AWWF64 ________ 

57ADt-2 ----------

49~r 39 ____________ 

58ADt-7 ___________ 

44AW\VF 69 _______ 

48A~r 144 _________ 

58AH w 44 __________ 

50AHa 60_- ________ 

49AMr 38----------

48A~r 147 _________ 

49A~r 37----------

Collector, year of collection, description of locality, and stratigraphic assignment 

R. L. Detterman, 1957. lniskin Peninsula. South shore of Chinitna Bay at axis of 

Fitz Creek anticline, 1.3 miles N. 73° E. of mouth of Fitz Creek. Fitz Creek Siltstone, 1,05Q-1,100 ft above base. 

R. L. Detterman, 1957. lniskin Peninsula. South shore of Chinitna Bay near mouth 

of Park Creek, 2.12 miles N. 65° E. of mouth of Fitz Creek along road. Fitz Creek 

Siltstone, upper 150 ft. Green sandstone lenses and concretions in siltstone. 

R. L. Detterman, 1957. lniskin Peninsula. South shore of Chinitna Bay, 1.8 miles 

N. 71° E. of mouth of Fitz Creek. Fitz Creek Siltstone, near top. Bluish-gray 

siltstone containing sandstone interbeds and calcareous concretions. 

Helmuth Wedow, 1944. Iniskin Peninsula. South shore of Chinitna Bay, about 1.2 

miles N. 69° E. of the mouth of Fitz Creek,. Fitz Creek Siltstone, just below the top. 

F. H. ~offit, 1921. Iniskin Peninsula. East side Fitz Creek, 2.24 miles N. 82° E. of 

Tonnie Peak. Fitz Creek Siltstone, 30Q-400 ft above base. Concretions in siltstone. 

A. A. Baker, 1921. lniskin Peninsula. Same as loc. 10981. 

A. A. Baker, 1921. Iniskin Peninsula. Same as loc. 10981. 

A. A. Baker, 1921. Iniskin Peninsula. Same as loc. 10981. 

A. A. Baker, 1921. Iniskin Peninsula. Same as loc. 10981. 

A. A. Baker, 1921. Iniskin Peninsula. Same as loc. 10981. 

Helmuth Wedow, 1944. lniskin Peninsula. Right side of Fitz Creek about 900 ft 

downstream from the mouth of Forky Creek and 2.16 miles N. 86° E. of Tonnie 

Peak. Fitz Creek Siltstone, 300-400 ft above base. 

R. W. Imlay, 1948. Iniskin Peninsula. East side of Fitz Creek 2.12 miles N. 86° E. 

of Tonnie Peak. Fitz Creek Siltstone, 30Q-400 ft above base. Same location as loc. 

10981. 

J. F. Hartsock, 1950. Iniskin Peninsula. East bank of Fitz Creek 0.75 mile, S. 37° 

W. from Cliff Creek. Fitz Creek Siltstone, 30Q-400 ft above base. 

Helmuth Wedow, 1944. lniskin Peninsula. About 1,300 ft above mouth of a northwest flowing tributary of Fitz Creek and 2.4 miles N. 79° E. from Tonnie Peak. Fitz 

Creek Siltstone, near middle. 

R. L. Detterman, 1958. Iniskin Peninsula on Forky Creek 1.4 miles N. 82° E. of 

Tonnie Peak. Fitz Creek Siltsotne, 650 ft above base. Gray silty shale and siltstone in faulted sequence. 

R. W. Imlay, 1948. Iniskin Peninsula. East side of Fitz Creek, 2.02 miles N. 86° E. 

of Tonnie Peak. Fitz Creek Siltstone, 300-400 ft above base. 

J. K. Hartsock, 1950. Iniskin Peninsula. East bank of Fitz Creek at mouth of Forky 

Creek. Fitz Creek Siltstone, 300-400 ft above base. 

J. K. Hartsock, 1950. Iniskin Peninsula. East bank of Fitz Creek 1.3 miles S. 40° W. 

of mouth of Cliff Creek. Fitz Creek Siltstone, 300-400 ft above base. 

L. B. Kellum, 1944. Southwest Alaska, Cook Inlet, Iniskin Peninusla. Northeast 

side of Tonnie Creek about 200ft downstream from a rapids, and 1.23 miles S. 54° E. 

of Tonnie Peak. Fitz Creek Siltstone, 300 ft below top. Gray . shale containing numerous small light gray sandy concretions. 

L. B. Kellum, 1944. Iniskin Peninsula. Southwest side of Tonnie Creek 1.30 miles 

S. 54° E. of Tonnie Peak. Fitz Creek Siltstone, 400 ft above base. Greenish-gray 

and reddish-brown shale containing thin layers of shaly sandstone. 

R. L. Detterman, 1957. Iniskin Peninsula. On Tonnie Creek 1.3 miles S. 55° E. of 

Tonnie Peak. Fitz Creek Siltstone, 400-450 ft above base. Greenish-gray nodular 

weathering siltstone containing interbeds of sandstone. 

D. J. ~iller, 1949. Iniskin Peninsula. On northeast bank of Fitz Creek 0.2 mile 

below Iniskin Bay Assoc. 1, 1.86 miles S. 62° E. of Tonnie Peak. Fitz Creek Siltstone, 

about 600 ft above base. 

R. L. Detterman, 1958. lniskin Peninsula. Base of Havenstrite Ridge, 0.1 mile S. 

30° E. of Iniskin Bay Assoc. 1. Fitz Creek Siltstone, 400-450 ft above base. Silty 

shale contains small amount of limestone. 

Helmuth Wedow, Jr., and L. B. Kellum, 1944. Iniskin Peninsula. East side of Fitz 

Creek at mouth of small tributary about 400 ft southeast of the abandoned oil well, 

Iniskin Bay Assoc. 1. 1.88 miles S. 54° E. from Tonnie Peak. Fitz Creek Siltstone, 

650ft below top. Gray sandy shale containing thin beds of sandstone. 

D. J. ~iller, 1948. Iniskin Peninsula. Stream entering Fitz Creek from southeast near Iniskin Bay Assoc. 1, 2.00 miles S. 53° E. of Tonnie Peak. Fitz Creek Siltstone, 

450-500 ft sbove base. 

R. L .. Detterman and D. W. Hinckley, 1958. Iniskin Peninsula. On Twist Creek 0.9 

miles N. 72° W. of Iniskin Bay Assoc. 1. Fitz Creek Siltstone, 100-150 ft above 

base. Gray siltstone and sandstone. 

J. K. Hartsock, 1950. Iniskin Peninsula. 1.2 miles S. 45° W. of Iniskin Bay Assoc. 1 near head of Fitz Creek. Fitz Creek Siltstone 98Q-1,000 ft above base. 

D. J. ~iller, 1949. Iniskin Peninsula 2.35 miles south of Tonnie Peak. Fitz Creek 

Siltstone 50-150 ft below top. 

D. J. Miller, 1948. Iniskin Peninsula. Fitz Creek, near head, 2.45 miles S. 9° E. of 

Tonnie Peak. Fitz Creek Siltstone, about 800 ft below the base of the Cynthia Falls 

Sandstone. 

D. J. ~il\er, 1949. Iniskin Peninsula. Near axis of anticline on north bank of Fitz 

Creek 2.36 miles S. 10° E. of Tonnie Peak, Fitz Creek Siltstone, about 800 ft below 

top. 

1 

.. 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B27 

TABLE H.-Localities at which fossils of middle Bajocian age have been collected in the Cook Inlet region, Alaska-Continued 

Locality Ocologlcal 

No. on Survey Collector's field Nos. Collector, year of collection, description of.- locality, and stratigraphic assignment figs. 1-4 Mesozoic 

localities 

72 26598 57ADt 15---------- R. L. Detterman, 1957. lniskin Peninsula. Upper part of Fitz Creek, 1.72 miles S. 

42° W. of lniskin Bay Assoc. 1. Fitz Creek Siltstone, 400-450 ft above base. Dark 

gray silty shale and limestone concretions. 

R. L. Detterman, 1958. Iniskin Peninsula. On Fitz Creek near axis of anticline 1.72 

miles S. 42° W. of Iniskin Bay Assoc. 1. Fitz Creek Siltstone, 400-450 ft above 

base. Silty shale containing calcareous concretions. 

72 27108 58ADt 8 ___ -- ------

72 27109 

73 21303 

58ADt 9 ___ --------

48AMr 146 _________ 

R. L. Detterman, 1958. Middle Jurassic. On Fitz Creek on west limb of anticline, 

1.93 miles S. 47° W. of lniskin Bay Assoc. 1 and 2.38 miles S. 20° E. of Tonnie Peak. 

Fitz Creek Siltstone, about 600ft below top. Silty shale containing limy concretions. 

D. J. Miller, 1948. Iniskin Peninsula. Near head of Fitz Creek, 2.45 miles S. 11° E. 

of Tonnie Peak. Fitz Creek Siltstone, 500-550 ft above base. 

74 21771 48AMr 42 __________ R. W. Imlay and D. J. Miller, 1948. Iniskin Peninsula. Right side of Fitz Creek, 

2,000 ft S. 41° W. of mouth of Cliff Creek and 2.26 miles N. 78° E. of Tonnie Peak. 

Cynthia Falls Sandstone, lower 150 ft. 

TABLE !~.-Geographic rlistri1mtinn of mi'idle Bajoc1:an amn:onites 

in the Talkeetna Mountains, Ala.~ka 

[Nos. 1-!2 refer to numbers In fig. 1. Higher numbers are Gcol. Survey Mesozoio 

loc. numbers.] 

Nelchina area 

1 2 3 4 5 6 7 8 9 10 11 12 

-----------1-----------------

Phylloceras cf. P. kunthi Neumayr •.• __ X _______________________________ _ Macrophylloceras sp. undet. A ________ X ________________________ X X----

sp. undet. B--------------------- ________________________ x __ __ __ X 

1-Iolcophylloceras costfsparsum Imlay, n. SP------------------------------ __ X __ ---- ______________________ ---· sp. juv •. ------------------------ -- -- __ -- ----X-- X __________ X-- X Lytoceras cf. L.eudisianumd'Orbigny. __ X ______________________ x _______ _ sp -· --------------------------- __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ X 

Sonninia cf. S. projectifer (Buckman). __ X _______________________________ _ cf. S. nodata Buckman ___________________________________ X ______ ----

cr. S. patella Waagcn ____________ -- X __ -------- __________ X __ -- __ ---- sp. juv ________________________________________________________ X----

? n. sp. undct __________________________ X ________________________ ----

(Papilliceras) of. S. espinazitensis Tornquist _______________________ X ____________________________ ----

Witchellia cf. W. adnata Imlay, n. sp .. __ X ____________ X _________________ _ 

cf. W. laeviuscula (J. do C. Sowcrby) ____________________________ -- ________________ X ______ ----

SP------------------------------- -- -- X -- -- -- -- -- -- -- -- -- -- __ X -- ---- ?aquilonia Inlay, n. sp ____________ X __ ---- ______________________ ---- ? atf. W.? aqnilonia Imlay, n. sp ____ X ____________________________ ----

? SP----------------------------- -- -- -- -- -- -- -- ----X------ X-------- Lissoceras? SP------------------------ __ X __ -- -- -- -- ______________ -- -- ---- Bradfordia costidensa Imlay, n. sp. _____ X ____ X ______ X _________________ _ 'l caribouensis Imlay, n. sp ___________________________________ X _____ _ Otoites cf. 0. 1Jauper Westermann ______ X _______________________________ _ 

Emileia? SP-------------------------- __ X __________ X ___________________ _ Labyrinthoceras glabrnm Imlay, n. sp _________________ X X _______________ _ Chondroceras allani (McLearn) ______________________________________ X 

cf. C. marshalli (McLearn) ______________________________________ X 

Normannites (Itinsaites?) variabilis 

In1lay, n. SP----------------------- __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ X 

Ste1Jhanocera8 obes1~m Imlay, 11. sp. ____ X __ -- ___________________________ _ (Skirroceras) }1thlei Imlay, 11. sp ____ X ____________________ X _________ _ (S.) nelchinanmn Imlay, 11. sp _____ X __ -- -- ____________ X X __ -- -- ----

(S.) cf. S. nelchinanum Imlay, 

Ste7~~~i~~~~~~¥~~~1i~~-:_:_:_~=:::::::::: :: ~ :: :: :: ~ :: :: :: :: ~ :: ~ ~ ~ ~ :::: Par:~;(iotiie8-cra88iC:'O;iai1~;i-,niaY'.--~~: x x :: ::1:: :: :: :: :: :: :: :: :: :: :: :: -~- Leptosphtnctes evolutus Imlay, n. sp __ --. ________________________ -~ __ __ X 

SUMMARY OF RESULTS 

1. The Alaskan ammonites of middle Bajocian age 

described herein include 23 genera and subgenera and 

49 species. Of these, 18 species are described as new, 9 

species are identified or compared with previously 

described ammonites from Canada, 2 species are identified with previously desGribed species from Alaska, 14 

are compared with species from other con tin en ts, and 6 

are probably new species but are too poorly preserved 

to merit description. Numerically the dominant families are the Otoitidae and the Stephanoceratidae. The 

dominant genera in decreasing abundance include 

Chondroceras, Normannites, Zemistephanus, Parabigotites, Stephanoceras, Bradjordia, and Sonninia. Zemistephanus is assigned to the Stephanoceratidae rather 

than to the Otoitidae because of its great resemblance 

to Teloceras. 

2. The middle Bajocian ammonites in the Tuxedni 

Group of the Cook Inlet region consists of two faunules. 

The lower faunule northwest of Cook Inlet extends 

through most of the Red Glacier Formation into the 

Gaikema Sandstone. In the Talkeetna Mountains it 

has been found throughout most of the Tuxedni 

Formation. It is characterized by the genera Sonninia, 

S. (Papilliceras), Witchellia, Bradjordia, Otoites, Emileia, Stephanoceras, S. (Skirroceras), Stemmatoceras, and 

Parabigotites which in association furnish a correlation 

with the European zone of Otoites sauzei. The presence 

of a few specimens of Normannites in the upper third of 

the Red Glacier Formation suggests that that part 

correlates with the upper part of the Otoites sauzei zone. 

3. The upper faunule of middle Bajocian age northwest of Cook Inlet extends through most of the Fitz 

Creek Siltstone into the overlying Cynthia Falls 

Sandstone. In the Talkeetna Mountains it has been 

sparsely found in the upper part of the Tuxedni Formation. It is characterized by the genera Normannites, 

Chondroceras, Teloceras, Stephanoceras, Stemmatoceras, 

and Zemistephanus. Of these the first three in association are good evidence for a corr.elation with the 

European zone of Stephanoceras humphriesianum. 

The presence, however, of a few specimens of Sonninia 
B28 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE 13.-Geographic distribution of middle Bajocian ammonites along the northwest side of Cook Inlet, Alaska 

[Nos. 13-74 refer to numbers on figs. 2-4. Higher numbers are Geol. Survey Mesozoic loc. numbers] 

Tuxedni Bay area 

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 

- ----------------1-------1------·---------·-· 

-----------------··----------1------------------- -~--:---:---:--;---;·- --.-...... -;--;--;--;--!--.-- ------

Macrophyllocera., sp. undet. A---------------------------------------- ________________ -- ______ -- ______________ •• __ -- ____ X __ ......•• __ -- .. ____ .. --

cf. M. sp. undet. A------------------------------------------- .• -- -- ...... ____ .. X .. -- .... -- .... -- .. -- .. -- .... -- -- -- ...• -- -- -- .... -- -- •. __ -- -- sp. undet. B.·-------------------------------------------------- •... __ .. ________ .• -- ______ .. __ .. __ X ______ •• __ -- ________ •••••••••• -- •••••••••• 

Hol~~~~~l~g;[i~~~~!~~~~~~.I~l:~~-~~-~~======================== == == == == == == == == == == == == : == == == == == : : == == == : == == == == == == == == == == == == == == == == 

Lvt:fe~~~~t~ ·r,~-iuiiisianum·ci··oi-iiig.D:V==~~======================== : == == == == : == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == Sonninia tuxedniensis Imlay, n. SP-------------------------------- .............. ______ X ____ X .• __ .•.• X X ____ •••••. ____ ••.••••• __ •. __ .• ______ •••• 

~J:,~~;m;:~~i{~ti~"~~r·a~ti;~a-<<iU.eiisie<itL================ == : == x x == == == == == == == == == == == == x == == == == == == == == == == == == == == == == == == == == : == ? n. sp. undet .... --------------------------------------------- -- .. -- __ .•.. ____ .• __ -- .. ____ .. ____________________ .... ____ ...... __ .......•.....• ? sp. juv ...................................................... X X-- •• -- •• X ••.•.• -- .• X •• ------ .•.• ---- •.•••• -- ••••..••.• ---- ..•. ---- __ •• -- •• Witchellia adnata Imlay, n. sp ....... ------------------------------ X •• -- __________ •••••• ______________________ X __ •••••• __ •• __ •••• __ •••••••••••••• 

SP------------------------------------------------------------ -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ? sp -------------······--·······----------------------------- X------ .•.• X X-------- __ ---------- .• ---- •• -- •. -- •..•••.• ---------------- •• ---- .Pelekodites? SP-------------------------------------------------- .... -- ........ ____ .. ________ .... __ .. ____ .... ____ .. __ .. ____ .............. ____ ... . Strigoceras cf. S. Tanguidt£m Buckman ..... ________________________ -- •.•. ______ .... __ ...• __ .... c. ________ •••• __ •••••••• ____ •••••• __ •• __ •••• __ ••.• __ 

sp. juv. ------------------------------------------------------ -- .• -- __ -- __________ .. ____ X ______________ •• __ •••••••••• ____ •• __ •• __ •••••• __ •••• Lissoceras bake.ri Imlay .. ----------------------------------------- .. -- -- ________ •....•.• __ .• ____________________ .. __ .. ____ .. __ ...... __ .......•.• __ cf. L. semico.,tulatum Buckman .••.•••••..........••.•.....•.... __ .. ____________ .... ____ X .• ____________ ••••.. __ •...•..... __ .• ____ .. ____ •• __ .• 

sp ......... L ..•... ----------------------------------------·-- -- -- -- -- X -- •.•• -- -- -- .. -- -- •• -- -- X X X -- •• -- -- -- -- -- -- -- X -- -- -- -- -- -- -- -- -- -- Oppelia .,tantoni Imlay, n. SP------------------------------------- -- __ .. ____ .. ________ .. __ .... __ .... ____ X •••• ____ •••• ________________ X ____ •• __ •• Brad.fordia? caribouensis Imlay, n. !:p .............. ---------------- ________ ...... ______ .. ______________________ .. ______ .. __ .. __ .....••...••••..•• __ Otoites cf. 0. contractus (Sowerby) ________________________________ -- X-- •• X ••••.••• __ .•.•••.• ________ •• ______________ •• ______________ .••••• __ •. -- ? filicostatus Imlay, n. sp ...................................... X •••• ________________________ .• ________________ •• __ •••• __ •••••• __ •••••• __ •••••• 

Emileia constrict.a Imlay, n. SP------------------------------------ .. X -- X X ____ .••• __ •• ____ X __ .••• X ________________________ -- ____ •••.•• __ .. -- .• cf. E. constricta Imlay, n. SP---------------------------------- .. __ .. ______________ .. ______ .. -- X ______ •• __ .• __ •••••.•• ____ •• __ •••••••• ____ •••• Chondrocera.~ de[onti (McLearn) ___________________________________ .•.. -- .... __ .. __ ...... ______ ...• ____ X X X __ X X X ____ X X X •• X •• X ••.• ____ •• X 

cf. C. defonti (McLearn) .. ----------------------------------- .. __ -- ____ .. ________ -- ____________ .. ______ .. ________________ .. __ X __ -- •• ____ •• __ 

allani (McLParnL.------------------------------------------- -- -- -- -- -- -- -- .. -- -- -- -- .... -- -- -- -- -- -- -- -- -- -- -- -- .. -- -- -- -- -- -- -- -- -- -- -- -- -- cf. C. allani (McLearn) _______________________________________ .......... __ .... ____ ...... ______ .. ______ .... __ ...... __ .. __ .... __ .. X .. ________ .. 

cf. C. oblatum (Whiteaves) ...... ------------------------------ .............. __ .......... __ ............ ______ .... ____ .. __ .................... .. 

SP-----------------------------------------------------------~ -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

Nor~~~i~i~t't:g{,ff%~~1:~~~~al.' ~-~:=========================== : == : == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == SP------------------------------------------------------------ -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- X -- -- -- X -- -- -- -- -- -- -- -- -- (Itinsaites) crickmayi (McLearn) ______________________________ ...... __ .. ____ .... __ ............ __ .. X X .. __ X X .. X .. ____ X .. X .. __ .... __ .... .. 

cf. (y}fdnC:d;~MgL~f:~t~~~~~==·:=============================== :: == == == == == :: :: == == == == == == == == == == X == :: == == :: :: X == == == == :: == :: == == == == == == == (/.) itinsae (McLearn) _____________________________________ ...... ______________ .. ______ .. ________________________ .... X .. ____ ............ .. 

(I.?) variabilis Imlay, n. sp ...... ------------------------------- ........ __ .. ____ .. ____ .. ____ .. -- ____ .. __ .. ________________ .............. __ .... .. cf. (1. ?) variabilis Imlay, n. sp .. _______________________________ ...... ________________________ .. ________ .. ______ .. ________ .. __ .. ____ .... ______ .. Stephanoceras cf. S. nodosum (Quenstedt) _________________________ ...... __ ...... ______ .... ____ X ______ .... ______ ...... ______ ........ __ .. __ ...... __ 

SP------------------------------------------------------------ X __ ...................... __ .... __ .. __ ............ __ .... __ .... ____ .... X ____ .. .. (Skirroceras) kir.~chneri Imlay, n. sp ___________________________ ............ ____ X ____ X X X .. ______ X .. ____ X __ .. __ .. ____ .. X .. __ ...... __ .... __ 

(S.) juhlei Imlay, n. sp. -------------------------------------- .. ____ .... __ .. __ .. ____ .. __ .... X ________ .. ______ .. ________ .... ____ .. __ ...... __ .. Stemmatocera.~ n. sp. undet _____________________________________ :_ ...... __ X .... ______ .... ____ X ______ ...... ________________ .... __ .. __ .... __ .... .. 

SP------------------------------------------------------------ -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- cf. S. palliseri (McLearn) _____________________________________ ...... __ .... ____ .. __ .. ______ -~ ________ ~- ______ X __________ ...... ____________ .. .. 

ursinum Imlay, n. SP----------------------------------------"- ........ ____________ .... __ .. ____ .. ____ ...... ____ .. ____ .. ____ ............ X X .. .. cf. S. triptoTemus (Morris and Lycett) ......... ~------~------- .... X ...... ____ .. __ .... ______ .. ____ .. __ .. ~- ____ .. ________ .......... ______ .... __ sp. juv. _________________________________________ _. ______ _. __ ~-~ ........................ __ ........ __ .. __ X ...... __ .. ____ .... __ ........ __ ...... .. 

? sp .. ---------------------------------------·----~--~---~----- ........ X .. __ .... __ .... ____ .... ____ .. __ · __ -~ ____ .. ________ .... ____ ............ .. Teloceras itinsae (McLearn). ..... "-------------'-~---------------- .. __ .. __ .... ____ .. ____ .. ____ .... ____ X X .. __ :. X ____ X ____ .... X ____ ........ __ .. 

zem~~e~~~~~s~fck~Ji.;~~r(~I1it'e-a'ves)~==:::::::'::::::::::::::::: :: :: :: :: :: :: == :: :: :: :: :: :: :: :: :: :: ~= x x x x x x : == x x :: x x :: :: :: == :: :: :: :: :: ~~-r~it~~~~rt~~:t~~~~~~~~~s::~==::::::::::::::::::::::::::::: :: :: :: == :: == := == == :: :: :: :: :: :: :: :: :: x x :: :: :: :: :: :: x :: :: :: :: x :: :: :: :: :: :: :: :: ? sp. --------------------------------------------------------- -------------------------------------------------------------------------------- Parabigotites crassicostatus Imlay--~------------------------------- X __ .................. ____ .......... _._ ............ -- .... -- -- -- -- -- -- -- -- .. -- -- --

SP-----------------------------·------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- .. -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ? sp. --------------------------------------------------------- X .... __________________ .. __ .. ________ .. ________ ........ __ .... ______ .. __ .... __ .. 

~1 I 
·~,. 

MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION 

TABLE 13.-Geographic distribution of middle Bajocian ammonites along the northwest side of Cook Inlet, Alaska-Continued 

[No~. 13-74 refer to numbers on figs. 2-4. Higher numbers are Geol. Survey Mesozoic Joe. numbers] 

Tuxedni Bay area- Continued 

29 30 

Lake 

Hickerson area 

31 32 33 34 35 36 37 

Iniskin Peninsula 

38 39 40 41 42 43 44 45 46 47 48 49 50 51 

B29 

52 

1-----1--------------------------------------

-----·--------------J--,--,-,--,·-------------..,..,-- --------------------------- Macrophylloceras sp. undet. A----------------------- ______________________________________________ -- ______ -- -- -- ____ -- -- -- ____ -- -- ____ -- -- -- -- -- cr. M. sp. undct. A----------------------------- __________ .. __ .. ________________________________ .. ____ .... ____ .... __ .. ____ -- ______ -- __ -- ___ _ sp. undct. B •• ---------------------------------- ______________________________________________ -- ________ -- X ____ .. ---- .. __ -- ____ ...... ---- .. -- 1-IolcophiJlloceras costisparsu.m Imlay, n. sp ________________________________________________________ -- ______ -- -- ______ -- -- -- -- __ -- -- __ -- -- -- -- -- --

cr. 11. costisparsum lmloy, n. sp _________________ -- -- -- -- -- -- -- -- -- -- ---- ---- ---- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ·- -- -- ·- -- -- -- ·- -- -- -- -- -- --

~~~~:~:~1 ~{xfd~:h~:~i¥~~~~:~~~:f.~=============== == == == == == == == == == == ==== ==== ==== == == == == == == ~ == == ~ == == ~ == == == == == == == == == == == == == == == == == 

~~~~;~~i~~~~:~!~j~~~!~~~~?~~~~~~~~~~~~~~t!:::: == == == == == == == == == == ==== ==== ==== ~~ == == == ~ == == == ~ == == == == == == == == == == == == == == == == == == == == == wit~h~Yi;!ua~niiia-iilliii;.~-n~sP'~==::::::::::::::::::: :: :: :: :: :: :: :: :: :: :: :::: :::: ===: :: :: :: x :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: BP---------------------------------------------- .. ______________ -- __ ---- ____ ---- __ .. X ________ -- ____ .. -- -· __ -- __ -- -- -- -- -- -- -- -- -- -- -- -- -- --

~g~£~~~~~c~l" ~~;~~=i~ij~~=~~~~~~~=-~::::::::::::: :: :: :: :: :: :: :: :: :: :: =::: =~= :::: :: :: ~ :: :: ~ :: :: :: :: :: :: :: :: ~ ~ :: :: :: :: :: :: :: :: :: :: :: :: :: :: Liss~~e~~svbiik·e~i"imJ[)y::::::::::::::::::::::::::::: :: :: :: :: :: :: :: x :: :: :::: :::: ==== :: :: :: == :: == :: :: == == == :: == == :: :: == == == :: :: :: :: :: :: :: :: :: :: :: 

cf. L. semicostulatum Buckman.---------------- -- -- ____ -- ____ -- -- -- ---- ---- ---- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- .. -- -- -- -- -- -- -- -- -- -- -- -- -· 

~!!~iii~~~l~)_;_:_;_!!lliiil! !! l! ~ :: :; ~; !l ; ;: ~ :::: :::: !!!l !! !! ~: ~; ! !! l! ! :: !l ~; 1 !! !! l! !l ~ ~: !! !! l! !! !l !! ;; i! l! ll !! !! 

~tg; ~~~!l~~E~t¥ei>~is:):_~==================== ~ == == == == ~ ~ == == == ==== ==== ==== == == == == == == == == == == == == == == == == == == ~ ~ ~ == == == == == == == == == 

Nor~~w.ifts:~l~!ii;~~~ii~f~I~i_;~~~~============= (Vtin'SaiiisYcriciimaiiffM:C:i:earii):::::::::::::::: :: == == x :: == == x == 

~ :: 

== :: == :: ~ :: :: == == :::: ==== :::: ==== :::: ==== :: == :: == :: ~ :: == :: == :: == :: == :: 

:: :: :: 

== == :: == :: == :: :: :: == == == :: == :: == == == :: == :: == :: == :: ~ :: == :: == :: == :: == == x == x :: == :: ~ cr. (1.) crickmavi (McLearn) •. ------------------ -- ______ -- ____ X -- -- ---- ---- ---- __ -- -- -- -- ____ -- -- -- -- -- -- -- -- -- -- -- -- -- •• X -- .• -- -- -- -- -- X 

(1.) itinsae (McLcarn) __________________________ -- -- ____ -- __ -- __ -- -- ---- ---- ---- -- -- -- -- -- -- -- -- -- -- .. -- -- -- -- -- -- .. -- -- -- X----------------

s...¥&~1~~~tj~~~lf~~~~~~~;;~=~~~==~=~= ~: :~ ~~ ~= :: ~: ~~ ~~ ~: =~ ::~: ::~: :~: =~ ~: :~ ~~ ~= ~~ ~~ =~ :: ~~ ~= :: ~= :: =~ ~~ ~: ~~ ~~ =~ =~ ~~ :: =~ =~ ~= :: ~~ ~~ =~ SP---------------------------------------------- X ______ -- ______ X __ ---- ---- ---- ____ -- -- -- ____ -- -- X .. ---- .. -- .•.• X---------- .• ------------

StJ~~iZ~~!i~~~~t~~t~:~J~~~~?=~=~~·=~I;::::::::::::: == == :: :: :: :: == :: :: == ==== :::: :::: :: == == == == == == == == == ~ == == == == == == :: == == == ~ == == :: == :: == :: == SP---------------------------------------------- -- ______ -- ______ -- .. ---- --·· ---- -· X -- -- -- .. __ -- -- X __ .. · .. -- .... -- -- -· -- -- -- -- -- -- -- -- -- -- -- cf. S. palliseri (McLcorn) _______________________ -- -- -- -- -- -- -- ... : -- ---- ---- ---- -- -- -- -- -- -- -~ -- -- ~- -~ -- -- -- -- -- -- -· -- -- -- -- -- -- -- -- -- -- -- --

~{.s~~t:~iit~~~~r~t(iforris"anclLycctt)-~=:::::::: :: :: :: :: :: :: :: :: :: :: :::: :::: :::: :: :: :: :: :: :: == :: ~= -:: ::: ::· :: :: :: :: :: :: :: :: == :: :: :: :: :: :: :: :: :: sp juv·----------------------------------------- .. ____________________________________________ -- ~- .. __ .. :. -- __ .. -- __ .. X __ ------------------

? SP---······--·---·--------------------~------- -- -·- -·- -- -- -- -- -- -~ -- ---- ---- ---· ·- -- -- -- -- .: :_ -- -- -~ -- -- ·-- -- -- -- -- -· -- -- ·- -- -- -- -- -- -- ·- -- -- Teloceras itinsae (McLcorn) _________________________ -- ____ .. -- ______ -- -- ---- ____ ---- ____ .. -- -- ____ .. _._ .. __ -- -- .... -- -- -- -- -- -- -- X -- -- X -- X X --

Zemiref·~~K~7J;~rr~\t~~~~t~1£~~~~~~~~~============ :: :: :: :: :: :: :: :: :: :: ==== :::: :::: :: :: :: :: :: :: :: :: ;: :: :: :: :: :: :: ~~ :: :: :: :: :: ~ ~~ ~ ~ :: :: ~ :: :: 

carlottcnsis (Whitcovcs) _________________________ -- X •. -- -- -· -- .. -- -- ---- ---- ---- -- -- -- -- -- -- -- -- -- -- -- -- -· -- -- -- -- -- -- -- -- -- -- -- -- ·- ·- -- -- --

Pardb~Cotites-crcissicostatu8"illiiay:::::::::::::::::::: :: :: :: :: :: :: :: :: :: :: :::: ·x· ==~= :: :: :: :: :: :: :: :: :: x :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: == :: :: :: ~ ~~[):::::::::::::::::::::::::::::::::::::::::::: :: :: :: :: :: :: :: ~~ :: :: -~- :::: :::: x :: ~ :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :: :~ :: :: :: 
L .. 

B30 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

TABLE 13.-Geographic distribution of middle Bajocian ammonites along the northwest side of Cook Inlet, Alaska-Continued 

[Nos. 13-74 refer to numbers on figs. 2-4 Higher numbers are Geol. Survey Mesozoic lor:. numbers] 

Iniskin Peninsula-Continued 

53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 

--------------------1----------------------

----------------------1-~ ------- ~-- -----------------------1---:---:--:---:--1-

Macrophylloceras sp. undet. A •. -------------------------- _____________________________________________________________________________________ _ 

:~ffll~~~1~JJ.W~u;m, .. )l!li!!~!j~ !I~; I! X::!! !i !! X!!~! X ;I !j ~~ !~!~!I~!:~!!;; j~ !! i! !; ;! X X;!;~ X !iII!! i! jl j~ ii !i :! li !I 

~:;~~~~~ij:~:~~~~~~~~:~~~~~~-:~~~~=mj~=jj~=jm == ~~ jj j~ jj :j jj jj ~ =~ j~ j~ =j =j j~ =~ :j ~j j~ jj j= j~ ~j =~ jj jj ~j jj jj jj ~ =j j= ~~ jj =~ jj =j jj == jj jj =~ Lisroceras bakeri Imlay __ -------------------------------- _____________________________________________________________________________ _ cf. L. semicostulatum Buckman_______________________ __ __ __ __ __ _ _____ -- -- __ -- _______________________________________________________ _ 

~~~::i.:b~~~Z1:"ii~;i¥i~t:~;;~::::~~:~:::~:~~~:::~~: :~ :: :: ~: ~~ :: :: :: :: ~: ~~ ~: :: :: ~: :: ~~ ~~ ~: :: :: ~~ ~~ ~~ :~ ~~ ~~ ~~ :: :: ~: =~ ~: ~: :: ~~ ~~ :: :~ ~: :: :~ ~~ ? jilicnsf.ntns Imlay, n. SP------------------------------ ____ -- -- __ -- -- -- __ -- __ -- -- -- -- -- -- -- ____ -- -- -- -- __ -- -- -- -- ______ -- -- -- -- -- -- ________ -- Emileia constricl.n Imlay, n. SP---------------------------- __________ -- -- -- ____________ -- -- __________ -- -- _______________________________________ _ 

aoi?;,~;~~f&~~;~r=~~:==:::~==~~~::~:~:~::: cf. C. allani (McLearn) ___________________________________ :: ~ --~ ~= -- ~: __ --=~ :: 

-- --

=~ :: 

__ ~: -- ~= ____ ~~ :: -- :: -- :: -- --

~~ ~= __________ :: ~ ~ ~ :: 

-- --

~= :: 

-- :~ ______ ~: ~ :: -- ~ ____ ~ ~~ X X X ~= :: :~ ___________________ :: ~ ~= ~ :: ~~ :: :: ~ _ cf. C. oblatum (Whiteaves) ________________________________ -- ____ -- -- -- ________ -- -- -- -- ________ -- -- -- _______________________________________ _ 

SP---------------------------------------------------- ----X-- X---------- X-- X-------------- X------ X------------ __ X-- X-------- X X X--

Nor~tN:i~fai'r:~~7ff~~~~;1~~~~Ai:.' ~P-~~=================== == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == SP---------------------------------------------------- __ -- -- -- -- X------ __ ---------------- ____ ------ ____ ------ ________ ---- __ -- __ X-- _______ _ (Itinsaites) crickmnvi (McLearn) __________________________ -- ____ -- -- -- ________ -- -- -- -- __ -- ____ -- -- -- ____ -- ______________ -- _________________ _ cf. (J.) crickmayi (McLearn) ________________________________ -- ----X---- ______ -- -- -- -- -- -- ____ -- -- -- ____ -- __ -- __________ -- __ -- _____________ _ (J.) itinsae (McLearn) ______________________________________ -- -- -- -- -- -- ______ -- -- -- -- __ -- ____ -- -- -- ____ -- __ X _____________________________ _ cf. (J.) itins"e (McLearn) ___________________________________ -- -- -- -- -- ______ -- -- -- -- -- __ -- ____ -- -- -- ____________________ -- __ -- _____________ _ 

(J.?) variabilis Imln.y, n. SP---------------------------- ____ -- -- -- -- -- -- -- ____ -- -- X X X X X X __ -- X-- X X __ -- ________ X -- -- __ X __________ X--

cf. (J.?) variabilis Imlay, n. SP------------------------- ______ -- -- __ -- -- -- ______ -- -- -- -- __ -- ____ -- -- ______ X X __________ X ____ -- _____________ _ Stephanoceras cf. S. nodosum (Quenstedt) _______________________ -- -- -- -- -- -- ______ -- -- -- -- __ -- ____ -- -- -- ______ -- ________________ -- _____________ _ 

SP---------------------------------------------------- ______ -- -- -- -- X-- __ ------------ __ -- __ -- -- -- -- ______ -- ____________ X __ -- _____________ _ 

~~3ift~~r;r~in~~;~~~e;~~~ _a_~~~-·-~~=================== == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == Stemmatoceras n. sp. undeL.----------------------------- ______ -- -- -- -- -- -- ____ -- -- -- -- -- __ -- ____ -- -- -- ______ -- -- ______________ -- ____ -- __ -- __ --

sp_. -------------------------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- cf. S. palliseri (McLearn) ___________________________________ -- -- -- -- -- -- -- __ -- -- -- -- -- -- -- ____ -- -- -- -- __ -- -- -- -- ____________ -- __ -- -- __ -- -- --

~£BW'.~-:1P~~~~?lsn(~rrisand-Lycett)-~=============== == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == == sp. juv ----------------------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ? SP-------------------------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Teloceras itinsae (McLcarn) _____________________________________ -- ____ -- -- -- ____ -- -- -- -- -- -- -- ____ -- -- -- X-- __ -- ________________ -- __ -- -- -- X----

Ze;;~~£,;~~~~8~fch!:Js~~~T#iiitca~es)·::================= x == == x x == == == == == == == == == == == == == == == == == == == == == == x == == == == == == == == x == ~ x == == == cf. Z. richardsoni (Whiteaves)------------------------- -- -- -- -- ____ X------ __ ---------------- -- -- -- -- -- -- -- -- -- ____ -- __ -- -- -- -- -- X----.!----

carlottensis (Whiteaves)------------------------------- -- __ -- -- ____ -- -- -- -- ____ -- -- -- -- -- -- __ -- -- -- -- -- -- -- -- -- __________ -- -- -- -- -- -- -- -- -- -- ? sp ------------------------------------------------ -- -- -- -- -- __ -- -- -- -- X---------------------------------------------------------------- Parabigotites crassicostatus Imlay __________________________ -- -- __ -- ____ -- -- -- -- ________ -- -- -- -- __ -- -- -- -- -- -- -- -- -- __________ -- -- -- -- -- -- -- -- -- --

SP---------------------------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ?sp. -------------------------------------------------- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

in the lower three-fourths of the Fitz Creek Siltstone 

suggests by comparison with the European sequence, 

that that part of the member is not younger than the 

lower part of Stephanoceras humphriesianum zone. 

The upper third of the Cynthia Falls Sandstone has 

not furnished any ammonites and hence cannot be 

dated definitely as middle Bajocian. 

4. Ammonites indicative of the European zone of 

Sonninia sowerbyi have not yet been found in the Red 

Glacier Formation northwest of Cook Inlet. This 

failure on the Iniskin Peninsula is related in part to 

thrust faulting. On the peninsula between Chinitna 

Bay and Tuxedni Bay, failure to find such ammonites 

may be related to poor exposures that are difficult to 

reach. Ammonites of early Bajocian age, however 

including Tmetoceras and Erycites, have been found a 

five places in the lower part of the Red Glacier Formation (table 3). Consequently the absence of any 

ammonites representing the Sonnin~a sowerbyi zone 

may have stratigraphic significance rather than reflecting inadequate collecting. 

5. Similarly in the Talkeetna ~fountains no ammonites definitely belonping to the Sonninia sowerbyi zone 

have yet been found in the Tu.xedni Formation. One 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B31 

small ammonite resembling the inner whorls of Emileia 

or Docidoceras could represent that zone, or could 

represent the Otoites sauzei zone. The discovery of 

Eryc~tes howelli (White) at one place in float probably 

-fron1 near the base of the Tuxedni Formation is evidence 

that the basal beds are of early Bajocian age equivalent 

to the lower part of the Red Glacier Formation northwest of Cook Inlet. 

6. The affinities of the middle Bajocian ammonites 

in the Tuxedni Group in Alaska are closest with those in 

other parts of the Pacific coast from Alaska to Cali-

·rornia. Thus the common ammonites in the Red 

Glacier Formation are identical specifically with ammonites in the upper part of the Kialagvik Formation 

on the Alaskan Peninsula. The common ammonites 

in the Fitz Creek Siltstone are identical specifically 

with ammonites in the lower beds of the Y akoun 

Formation in the Queen Charlotte Islands and in the 

upper part of the Snowshoe Formation in east-central 

Oregon. In contrast the affinities with middle Bajocian 

ammonites in the western interior of Canada and of the 

United States are mostly on the generic level. 

7. The ammonites of middle Bajocian age in the 

Tuxedni Group show affinities on the generic level with 

ammonites of the same age in South America, Australia, 

Indonesia, and Europe except for the presence in 

Alaska of the genera Zemistephanus and Parabigotites 

and the absence in Alaska of some genera that occur in 

beds of middle Bajocian age outside of North America. 

SYSTEMATIC DESCRIPTIONS 

Family PHYLLOCERATIDAE Zittel, 1884 

Genus PHYLLOCERAS Suess, 1865 

Phylloceras cf. P. kunthi N eumayr 

Plate 2, figures 3, 4 

The genus is represented by one septate specimen 

that has a compressed shell and bears very fine nearly 

radial lirae. Compared with the Toarcian species P. 

hete7'0phyllum (J. Sowerby) (1820, pl. 226; Zittel, 1869, 

pl. 1, fig. 11; d'Orbigny, 1844, pl. 109), it has a thinner 

whorl section, less flexuous lirae, and lacks any trace 

of radial folds. In these respects it shows more resemblance toP. kunthi Neumayr (1871, p. 312, pl. 12, fig. 6: 

pl. 13, fig. 1) from the Callovian of Europe. 

Figured specimen: USNM 131326. 

Occ1trrence: Tuxedni Formation in Talkeetna Mountains· 

at USGS Mesozoic loc. 24113. 

Genus MACROPHYLLOCERAS Spath, 1927 

Macrophylloceras sp. undet. A 

Plate 1, figures 1-7 

The species is represented by 18 septate specimens. 

The shell is moderately compressed, occluded. The 

whorls are higher than wide and become more compressed during growth. The flanks are gently convex. 

The ventor is evenly arched. The body chamber is 

unknown. 

On the smallest specimens the surface bears faint 

. growth lines and vague flexuous undulations that are 

irregular in strength and spacing. Weak lirae appear 

at diameters of 35-40 mm and weak ribs occur on the 

ventral region at diameters greater than 50-60 mm. 

The sutures have slender di phyllic saddles and high 

ventral lobe. 

The dimensions in millimeters are as follows: 

Specimen Diameter Whorl Whorl 

height thickness 

USNM 131321------------------ 70 45 30 

USNM 131328 ____________ ------ 58 35 26 USNM 13133L _________________ 43 27 18 

USNM 131332 ____________ - _____ 29 18 13. 5 

This species is characterized by the presence of 

flexuous undulations on its smaller septate whorls 

and by the weakness of the ribbing on its larger septate 

whorls. 

Figured specimens: USNM 131327-131332. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic loc. 

10515; Tuxedni Formation in Talkeetna Mountains at Mesozoic locs. 3696, 3697, 24113. 

Macrophylloceras sp. undet. B 

Plate 1, figures 8, 9, 13 

The species is represented by four septate specimens. 

The shell is compressed, occluded. The whorls 

are much higher than wide, the flanks are flattened, 

and the venter is highly arched. 

The smaller septate whorls bear fine dense raised 

lines, or lirae, that incline forward on the flanks but 

cross the venter transversely. In addition, broad 

faint regular widely spaced ribs appear on the venter 

and on the upper two-thirds of the flanks at a diameter 

of about 25 mm and gradually become stronger adorally. 

As these ribs become stronger the lirae become weaker. 

Constrictions are not present. 

The suture cannot be traced accurately. 

The figured specimen at a diameter of about 55 mm 

has a whorl height of 33 mm and a whorl thickness of 

17 mm. 

This species is distinguished from Macrophylloceras sp. undet. A by a much n1ore con1pressed whorl 

section, flatter flanks, and the earlier development 

of lirae and ribs. 

'Figured specimens: USNM 131333, 131334. 

Occurrences: Upper part of the Fitz Creek Siltstone at USGS 

Mesozoic locs. 2999, 22533, 26597; Tuxedni Formation in 

Talkeetna Mountains at Mesozoic loc. 8567; Gaikema Sandstone 

at Mesozoic loc. 10980. 
B32 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

Genus HOLCOPHYLLOCERAS Spath, 1927 

Holcophylloceras costisparsum Imlay, n. sp. 

Plate 1, figures 10-12, 14-17 

The genus is represented in the middle Bajocian beds 

of the Cook Inlet region by 25 specimens of which 10 

are less than an inch in diameter. The larger specimens 

all appear to belong to a single species that is characterized by a moderately compressed shell, a small number 

of constrictions per whorl, and very weak riblets on the 

venter and on the upper parts of the flanks. These 

riblets are not visible at diameters less than 50 mm and 

are weak at greater diameters even where the shell is 

preserved. The number of constrictions ranges from 

five on a specime:q 45 mm in diameter to six on the 

holotype at a diameter of about 90 mm. One large 

specimen that probably belongs to this species has 

seven constrictions at a diameter of 160 mm. 

The suture line has diphyllic saddles. 

The holotype has been crushed laterally, but at a 

diameter of about 90 mm has a whorl height of 52 mm 

and a whorl thickness of 31 mm. On the smaller specimens that are not crushed the whorl thickness ranges 

from 65 to 70 percent of the whorl height. 

The Alaskan species is distinguished from H. mediterraneum (N eumayr) (1871, p. 340, pl. 17 ,. figs. 2-5) 

from the Bathonian of Europe by having much weaker 

ribbing. H. ultramontanum (Zittel) (1869, p. 66, pl. 1, 

figs. 4-6; Roman, l938, pl. 2, figs. 14, 14a) from the 

lower Bajocian ha.s · fewer constrictions per whorl, 

develops stronger ribbing on its large outer whorls, and 

has a more compressed shell. 

Types: Holotype USNM 131335; paratypes USNM 131336-

131339. 

Occurrences: Red Glacier Formation at USGS Mesozoic loc. 

21267 · Fitz Creek Siltstone at Mesozoic locs. 2999, 3000, 20002, 

21270; probably repr~sented in the Fitz Creek Siltstone .at 

Mesozoic loc. 19997; Tuxedni Formation in Talkeetna Moun tams 

at Mesozoic loc. 24113. 

Family LYT:OCERATIDAE Neumayr, 1875 

Genus LYTOCERAS Suess, 1865 

Lytoceras cf. L. eudisianum d'Orbigny 

The genus is represented by 10 septate fragments 

from 5 localities. The whorls are ovate in section, 

higher than wide. The surface bears crinkled growth 

lines and riblets that incline slightly forward on the 

flanks. The interQal mold bears weak constrictions. 

The largest fragment (USGS Mesozoic loc. 24113) has 

a whorl height of 106 mm and a whorl thickness of 82 

mm. The ornamentation is similar to that on Lytoceras 

jimbriatum (J. Sowerby) in Buckman (1919, pl. 130a-c) 

but the whorls are stouter and the constrictions are less 

pronounced. L. e1Ulesianum (d'Orbigny) (1846, pl. 

128) differs from the Alaskan specimens mainly by 

having stouter whorls. 

Occurrences: Gaikema Sandstone at USGS Mesozoic loc. 

27115· Red -Glacier Formation at Mesozoic locs. 19958, 19966; 

Tuxedni Formation in Talkeetna Mountains at Mesozoic locs. 

2411~ 2422Q / / 

I Family SONNINllDAE Buckm,n, 1892 

Genus SONNINIA Bayle, 1879 

Sonninia tuxedniensis Imlay, n. sp. 

Pia te 2, figures 5-10 

The species is based on 11 specimens. The shell is a 

moderately compressed planulate. The whorls are 

higher than wide, thickest at about a third of the height 

of the flank, and bear a single hollow keel. T.he largest 

whorl embraces about two-fifths of the preceding whorl. 

The inner whorls are more evolute .. The umbilicus is 

moderately wide; the umbilical wall is steeply inclined 

but rounds eve~y into the flanks. The length .of the 

body chamber js unknown but is at least half a w~orl. 

The innermdst whorls bear backwardly or radmlly 

inclined irregularly strong ribs, some of which bear 

prominent lateral nodes. Adorally the nodes beco~e 

less prominent and are absent at diameters greater than 

30 mm. As the nodes disappear the ribs become more 

uniform in strength and spacing. The larger septate 

whorls bear strong ribs that begin on the upper part of 

the umbilical wall, are nearly radial on the flanks, and 

that fade out at about three-fifths of the height of the 

flanks. On the body chamber the ribs gradually 

become weaker adorally. Growth striae are gently 

flexuous on the flanks and curve forward strongly on 

the venter. 

The suture line has a short ventral lobe and a stout 

first lateral lobe. 

The holotype at a diameter of 111 mm (not counting 

the keel) has a whorl height of 42 mm, a whorl thickness 

of 30 mm, and an umbilical width of 42 mm. On the 

largest paratype at an estimated diameter of 120 mm, 

the same dimensions are 45, 33, and 44 mm respectively. 

On a smaller para type the same dimensions are 79, 

30, 20, and 29 mm respectively. 

This species resembles Sonninia nodatipinquis 

(Buckman) (1923, pl. 398) in evolution and rib pattern, 

but its ribs are stronger on the larger outer whorl and 

its whorls are stouter. S. cf. S. nodatipinquis Buckman 

in Gillet (1937, p. 43, pl. 4, fig. 6) has closer spaced 

ribs that are inclined slightly backward on the flanks. 

S. pseudocostata Maubeuge (1951, p. 18, pl. 9, fig. 1) 

has somewhat stronger ribs that persist higher on the 

flanks. Guhsania bella McLearn (1926, p. 98, pl. 25) is 

very similar in lateral view and in suture line but has 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B33 

a much narrower venter and an angular umbilical 

margin. 

Types: Holotype USNM 131340; paratypes USNM 131341-

131343. 

, Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

2999 (float) and 3000; Red Glacier Formation at Mesozoic 

locs. 21266, 21268 (float), and probably 3009. The species has 

been found in the upper 500 ft of the Red Glacier Formation 

and questionably in the upper 150ft of the Fitz Creek Siltstone. 

The species has not been collected in place in the Fitz Creek 

Siltstone during recent years. One specimen from Mesozoic 

loc. 3000 is not labeled as float, but it appears to be worn. 

Fragments of Sonninia similar to S. tuxedniensis have been 

found in place in the upper part of the Fitz Creek Siltstone at 

Mesozoic locs. 22706 and 26596. 

Sonninia cf. S. projectifer (Buckman) 

Plate 3, figures 1, 5 

Three septate fragments from the Talkeetna 

Mountains resemble Sonninia projectijer (Buckman) 

(1923, pl. 411) in size, coiling, eoarseness of ribbing, 

and in the prominence of their lateral tubercles. They 

differ mainly by having a higher whorl section. The 

fragments do not show the characteristics of the 

innermost whorls. 

Figured specimen: USNM 131344. 

Occurrence: Tuxedni Formation in Talkeetna Mountains a 

USGS Mesozoic loc. 24113. 

Sonninia. cf. S. nodata Buckman 

Plate 2, figures 1, 2 

One small compressed evolute keeled ammonite 

bears tuberculate ribs of irregular strength and spacing. 

The inner whorls are ovate in section. The outer 

whorl is su bquadrate, has flattened flanks, and a tubulate venter. On the innermost whorls every second 

to fourth rib is tuberculate. On the outermost whorl 

every fourth to fifth rib is tuberculate. The tubercles 

become weaker adorally. The ribs are flexuous, 

incline backward on the flanks, and curve forward 

on the ventral margins. 

The ornamentatipn resembles that on the small 

specimens of Sonninia nodata Buckman (1893, pl. 89, 

figs. 1, 4) from England, but it also greatly resembles 

that on the inner whorls of other spinose species of 

Sonninia (see Buckman, 1892, pl. 65, figs. 1, 3; pl. 73, 

fig. 1; pl. 74, fig. 4; 1893, pl. 89, fig. 6). 

Figured specimen: USNM 131345. 

Occurrence: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic loc. 24120. 

Sonninia cf. S. patella. Wa.a.gen 

Plate 3, figures 2-4 · 

This species is represented by one large crushed 

internal mold that retains about half of a whorl of the 

adult body chamber. The whorls embrace each other 

by about half. The smallest inner whorl that is preserved (pl. 3, fig. 2) bears strong widely spaced tubercles 

low on the flanks from which pass pairs of moderately 

strong ribs that curve forward on the upper parts of 

the flanks. Between the paired ribs are two or three 

ribs of equal strength that arise near the middle of the 

flanks. 

On the next larger whorl (pl. 3, fig. 3) the tubercles 

have been replaced by radially elongate swellings 

and the ribs are weaker. On the next whorl both 

swellings and ribs gradually become weaker adorally. 

At a diameter greater than about 175 rom the internal 

mold is nearly· smooth. 

In size and smoothness the whorl of the Alaskan 

specimen compares with that of Sonninia undijer 

(Buckman) (1923, pl. 427), but the strong ribbing and 

tubercles of its inner whorl contrast markedly. S. 

trigonalis (Buckman) (1910, p. 92, pl. 10, figs. 2, 3) 

has similar pronounced umbilical tubercles on its inner 

whorls but is much more involute. S. patella Waagen 

(Dorn, 1935, pl. 14, figs. 1, 6) appears to have weaker 

denser ribbing on its inner whorls and is more involute. 

Figured specimen: USNM 131346. 

Occurrences: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic loc .. 24120. A fragment that appears to be 

an inner whorl of this species occurs at Mesozoic loc. 24113. 

Sonninia.? n. sp. undet. 

Plate 4, figures 5, 6, 1Q-12 

This. species is represented by two septate internal. 

molds. The shell is compressed and evolute. The 

whorls are subquadrate in section, nearly as wide as 

high, and embrace each other about one-fourth. The 

flanks are gently convex. The venter is fairly broad 

and bisulcate. The keel is low. The umbilicus is 

wide. The umbilical wall is low, steeply inclined, and 

rourids evenly into the flanks. The body chamber is 

unknown. 

The ribbing on the smallest whorls that are preserved, 

at diameters of 24-4 7 · rom, consist of very strong 

fairly regular widely spaced flexuous ribs that become 

swollen near the middle of the flanks and curve forward 

considerably on the ventral margins. Between these 

ribs are intercalated much weaker ribs that begin on 

the middle third of the flanks and cmve forward on the 

ventral margins. Some of the weaker ribs are connected with the strong ribs. 

During growth the ribs remain strong but become 

. broader and many of the strong ribs bifurcate at or 

below the middle of the flanks. On the largest whorl 

all secondary and intercalated ribs are swollen where 

they curve forward along the ventral margins and then 

fade out rather abruptly. 
B34 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

The suture line is not preserved. 

The largest specimen at a diameter of 86 mm has 

a whorl height of 26 mm, a whorl thickness of 24 mm 

(between ribs), and an umbilical width of about 42 mm. 

The assignment of this species to Sonninia is questioned because of the regularity of its ribbing, the 

tendency of many ribs to bifurcate near the middle of 

the flanks, and because most species of Sonninia with 

comparable strong ribbing bear pronounced tubercles. 

The ribbing shows a little resemblance to that on some 

specimens of Sonninia figured by Quenstedt (1887, pl. 

63, figs. 2, 4). 

Figured specimens: USNM 131347, 131348. 

Occurrences: Red Glacier Formation at Mesozoic loc. 21293. 

Tuxedni Formation in Talkeetna Mountains at Mesozoic 

loc. 26723. 

Subgenus PAPILLICERAS Buckman, 1920 

Sonninia (Papilliceras) cf. S. arenata (Quenstedt) 

Plate 6, figures 1-3 

Eight fragments of body chamber and several associated septate fragments belong to a large evolute nearly 

smooth species comparable with S. (Papilliceras) arenata 

(Quenstedt) (1887, pl. 60, fig. 10; Buckman, 1927, pl. 

709; Dorn, 1935, pl. 7, figs. 1, 2). On the Alaskan 

specimens the whorl section is quadrate and is somewhat 

higher than wide. The inner whorls embrace each 

other about half and the outer whorls about a third. · 

The flanks are flattened and subparallel. The venter 

is flattened and moderate in width. The keel is fairly 

low. The umbilicus is moderately wide. The umbilical 

wall is steeply inclined and rounds abruptly into the 

flanks. The body chamber is incomplete but occupies 

at least half a whorl. 

The ribbing on the innermost whorls is not known, 

but the immature specimen shown on plate 6, figures 

2, 3 has low broad ribs of irregular strength that are 

nearly radial on the flanks and curve forward strongly 

on the margins of the venter. Adorally the ribbing 

gradually becomes fainter and at a diameter of 80 mm 

is barely visible on the internal mold. The penultimate 

and body whorls are nearly smooth except for a row of 

small round nodes a little above the middle of the 

flanks. In addition some specimens show flexuous 

growth lines and some have faint broad ribs on the 

lower part of the flanks. The strength of the nodes 

varies considerably from one specimen to another. 

The sutvre line cannot be traced accurately but 

appears to be very similar to that of Sonninia tuxedniensis Imlay, n. sp. illustrated herein. 

Most of the specimens are so crushed or fragmentary 

that measurements are useless. An immature specimen 

shown on plate 6, figures 2, 3 at a diameter of 82 mm 

has a whorl height of 35 mm, a whorl thickness of 24 mm, 

and an umbilical width of 23.5 mm. On a larger 

septate specimen from Mesozoic locality 19964 the 

same dimensions are 195, 75, 48, and 65 mm respectively. This specimen includes part of a large body 

chamber that has a whorl height of 104 mm and a 

whorl thickness of about 66 mm between the tubercles. 

The body whorl must have had a diameter of 300 mm. 

Judging from these dimensions the species is 

considerably stouter than Sonm'nia (Papilliceras) blackwelderi Crickmay (1933, p. 911, pl. 30) from the Mormon 

Sandstone in California. 

Figured specimens: USNM 131349, 131350. 

Occurrences: Red Glacier Formation at USGS Mesozoic loc. 

19964, 21262, 21263; Gaikema Sandstone at Mesozoic loc. 22723. 

Sonninia (Papilliceras) cf. S. espinazitensis Tornquist 

Four fragments of which one is part of a body chamber resemble S. (Papilliceras) papillatum (Buckman) 

(1920, pl. 150A, B) from Europe in strength and density 

of ribbing. They differ by their ribs being more uniform in strength and by not bearing tubercles on the 

small septate fragments .. In these respects they resemble Sonninia espinazitensis Tornquist (1898, p. 20, 

21, pl. 3, figs. 2, 3; pl. 4, fig. 1) but they differ by having 

stouter whorls and by their venter becoming evenly 

rounded on the adult body chamber. 

Occurrence: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic loc. 24113. 

Genus WITCHELLIA Buckman, 1889 

Witchellia adnata Imlay, n. sp. 

Plate 6, figures 6-10 

This species is represented by three internal molds 

of which the smallest retains some shelly material. 

The shell is compressed and moderately evolute. The 

whorls are subquadrate, higher than wide and embrace 

each other nearly half. The lower parts of the flanks 

are flattened and parallel, but the upper parts converge 

gently toward a narrow flattened venter. The keel is 

fairly high. The umbilicus is moderate in width. The 

wall is vertical, fairly low, and rounds abruptly into the 

flanks. The body chamber on the holotype occupies a 

complete whorl and is probably nearly complete. 

The ribs are flexuous and variably strong on the 

flanks, incline forward on the venter, and fade out 

before reaching the keel. Many ribs arise in pairs on 

the umbilical margin or low on the flanks. Adorally 

the ribs gradually become broader, stronger, and more 

widely spaced. 

The ventral lobe is not exposed. The first latPral 

lobe is well developed and is much longer than the 

second lateral lobe. 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B35 

The holotype has been crushed somewhat laterally, 

but at a diameter of 105 mm has a whorl height of 45 

mm, a whorl thickness of 29 mm, and an umbilical 

width of 30 mm. 

This species differs from most species of Witchellia 

by being more evolute, by the tendency for its ribs to 

be variable in strength, and by the persistence of its 

ribs on specimens of large size. W. zugophorus (Buckman) (1922, pl. 341) is similarly evolute but has much 

stronger and n1ore uniform ribbing. W. jalcata (Buckman) (1926, pl. 688) appears to be more involute and 

has much stronger ribbing. W. connata (Buckman) 

(1927, pl. 750) appears to have stronger and more 

flexuous ribbing, but its resemblance to the small 

pa1~atype of W. adnata Imlay, n. sp. is striking. W. 

p1·opinquans Bayle (Dorn, 1935, p. 110, pl. 3, figs. 34; 

pl. 4, fig. 3; pl. 7, fig. 3) has stronger more uniform ribbing. A specimen assigned by Dorn (1935, pl. 9, fig. 2) 

to vV'itchellia CO'rrugata Sowerby is similar to the immature specimens of W. adnata Imlay, n. sp. but 

appears to have finer denser ribbing. 

Types: Holotype USNM 131351; paratypes USNM 131352, 

131353. 

Occurrences: Red Glacier Formation at USGS Mesozoic locs. 

3010 and 19956. Float on surface of Fitz Creek Siltstone and 

Cynthia Falls Sandstone at Mesozoic loc. 20756 (possibly derived 

from the Red Glacier Formation by ice movements). 

Witchellia cf. W. laeviuscula (J. de C. Sowerby) 

Plate 7, figures 1-5-

On one large completely septate ammonite from 

Alaska the small inner whorls (pl. 7, figs. 1, 3) are ovate 

in section, slightly higher than wide, and embrace each 

other about half. The umbilical wall is steeply inclined 

and rounds evenly into the flanks. The venter is 

evenly rounded, bisulcate, and the keel is low. 

During growth the whorls become compressed, much 

higher than wide, and embrace each other nearly 

three-fourths. The un1bilical wall remains steeply 

inclined but rounds abruptly into the flanks. The 

venter becomes narrow, tabulate, and bears a moderate 

keel. 

The ornamentation of the innermost whorls consists 

of strong irregular ribs of which some bear prominent 

nodes just below the line of involution. During growth, 

however, the ribs become weaker, more uniform in 

size, and the nodes disappear. At a diameter greater 

than 18 mm the ornamentation consists entirely of 

rather weak slightly irregular unevenly spaced ribs. 

These arise on the umbilical margin, are flexuous on 

the flanks, and incline strongly forward on the ventral 

margins. They are thin on the lower two-thirds of the 

flanks and become fairly broad on the ventral margins. 

A few ribs arise in pairs or are closely associated with 

other ribs near the umbilical margin. On the largest 

septate whorl the ribbing weakens considerably adorally 

suggesting that the body chamber was smooth or nearly 

smooth. 

The ventral lobe is shorter than either the first 

lateral lobe or second lateral lobes. The first lateral 

lobe is characterized by a long slanting accessory lobe 

on its inner side. The second lateral lobe is shorter 

than the first lateral lobe but is longer comparatively 

than on the other species of Witchellia described herein. 

The first and second lateral saddles are fairly broad. 

At a diameter of 165 mm the whorl height is 75 mm, 

the whorl thickness 40 mm, and the umbilical width 

35 mm. 

The Alaskan specimen resembles 8. zitteli Gottsche 

(1878, p. 10, pl. 1, figs. 4, 5; Tornquist, 1898, p. 17, 

pl. 2, figs. 1, 3; Jaworski, 1926, pl. 3, figs. 7a-c) from 

Argentina in whorl shape and degree of involution, 

but its small septate whorls appear to have sharper ribbing. Its large septate whorl resembles Witchellia 

laeviuscula (J. de 0. Sowerby) (1824, pl. 451, fig. 1; 

Buckman, 1927, pl. 745; Gillet, 1937, pl. 1, fig. 8; 

pl. 2, fig. 6; pl. 3, fig. 1; pl. 5, fig. 1) in shape, coiling, 

and ribbing but attains a much larger size. Other 

similar appearing ammonites, once referred to W. 

laeviuscula (J. de 0. Sower by), have been illustrated 

by Buckman (1923, pl. 410; 1926, pls. 642, 659, 687). 

Figured specimen: USNM 131354. 

Occurrence: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic loc. 24120. 

Witchellia 1 aguilonia Imlay, n. sp. 

Plate 4, figure 9; plate 5, figures 4, 7-9 

The species is represented by 16 internal molds of 

which some show parts of the body chamber. The 

shell is compressed and involute. The whorls are 

much higher than wide, become relatively higher during 

growth, and are thickest at about two-fifths of the 

height of the flanks. The inner septate whorls embrace 

each other four-fifths, or more, but the outermost 

septate whorl becomes gradually less involute, and the 

adult body whorl embraces only about half of the 

preceding whorl. The flanks are flattened below, are 

swollen just below the middle of the flanks, and converge above the middle to a narrow venter. The 

umbilicus is fairly narrow on the septate whorls but 

begins to widen near the adoral end of the largest 

septate whorl and widens markedly on the body whorl. 

The umbilical wall is nearly vertical, fairly low, and 

rounds fairly abruptly into the flanks. The adult 

body chamber occupies about three-fourths of a whorl. 

The aperture is projected on the venter and is sinuous 

on the flanks. The keel is fairly low, hollow, and floored. 
B36 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

The ribs on the small septate whorls are low, broad, 

flexuous, and fasciculate. Most of them arise in 

bundles on the lower fourth of the flanks. During 

growth the ribs become weaker on the lower part of 

th~ flanks and less flexuous but remain strong on the 

upper part of the flanks. Near the adapical end of the 

larger septate whorl the ribs are weak, closely and uniformly spaced, gently flexuous, and inclined forward. 

They are variably weak on the lower part of the flanks 

but become fairly broad and a little stronger ventrally. 

Some ribs begin at the umbilicus, others near the middle 

of the flanks, and still others begin higher. Toward 

the adoral end of the largest septate whorl the ribs on 

the upper part of the flanks become broader and lower 

but remain uniform in spacing, forwardly inclined, and 

persist to the end. In contrast the ribs on the lower 

part of the flanks become much weaker and more widely 

spaced adorally and finally disappear near the adoral 

end. The adult body chamber, at least on the internal 

mold, shows no trace of ribbing. 

The suture line is similar to that of Sonninia patella 

Waagen (Dorn, 1935, text-figure table 5, fig. 2). The 

first lateral lobe is broad, deep, and trifid and twice as 

long as the second lateral lobe. The suspensive lobe 

is slightly retracted. The holotype at a diameter of 

145 mm has a whorl height of 73 mm, a whorl thickness 

of 33 mm, and an umbilical width of 22 mm. On the 

largest paratype at a diameter of 132 mm the same 

dimensions are 66, 33, and 20 mm, respectively. 

A few of the internal molds of Witchellia? aguilonia 

Imlay, n. sp. bear faint spiral markings similar to that 

noted by Dorn (1935, p. 56-58) on several species of 

Sonninia. Similar markings occur on the genus 

Strigoceras, which differs from the Alaska species by 

having a much smaller urn bilicus and a different 

suspensive lobe. 

This Alaskan species is distinguished from any described species of Witchellia by the persistence of ribbing 

on the upper part of the flanks after the ribbing has disappeared from the middle and lower parts. It is 

comparable in involution and coiling with W. celans 

(Buckman) (1924, pl. 461) but has less projected ribbing 

on its ventral Inargins. Its general appearance is 

similar to that of Eudmetoceras amplectens Buckman 

(1920, pl. 180 a, b; Maubeuge, 1951, p. 34, pl. 6, figs. 

45) from the lower part of the European zone of Sonninia. sowerbyi, but it appears to have more flexuous 

less regular ribbing that tends to be more fasciculate. 

It is much more involute than most species of Eudmetoceras (Buckman, 1920, pls. 179a, b; 1922, pl. 299; 1923, 

pis. 396, 397; Jaworski, 1926, pl. 2, figs. 5 a, b, 6 a, b; 

pl. 4, figs. 12, 29). It also greatly resembles Fissilobiceras Buckman (1920, pl. 181 a, b; Dorn, 1935, p. 

56-60; Maubeuge, 1951, p. 51, pl. 3, fig. 1) in shape and 

coiling but is distinguished by the persistence of ribbing 

on the upper parts of the flanks and by less complicated 

suture line. Some species of Dorsetensia (Buckman, 

1892, pls. 55, 56; Dorn, 1935, pl. 24, figs. 1, 5; pl. 26, 

figs. 1, 4) resemble the Alaskan species in size, shaper, 

and coiling but become fairly smooth at a much smaller 

size. The genus Strigoceras has a much smaller umbilicus and a different suture line. 

Types: Holotype USNM 131355; paratype Calif. Univ. at Los 

Angeles paleont. cat. 34975; paratype USNM 131356. 

Occurrences: Tuxedni Formation in the Talkeetna Mountains 

at USGS Mesozoic locs. 24113; Kialagvik Formation at Mesozoic 

locs. 12402, 19742, 19773, 19876, 19877, 19923, and 21258. 

Witchellia 1 aff'. W1 aguilonia Imlay, n. sp. 

Pia te 4, figures 1-4 

One specimen from the Talkeetna Mountains and six 

specimens from the Alaskan Peninsula are possibly a 

coarsely ribbed variant of W? aguilonia Imlay, n. sp. 

They differ by having a relatively wider umbilicus and 

stronger more widely spaced primary and secondary ribs 

that persist to a later growth stage. The primary ribs 

arise on the umbilical margin, are widely spaced, are 

variable in strength and spacing, and pass into pairs 

of somewhat weaker ribs at or below the middle of the 

flanks. Between these primary ribs on the lower part 

of the flanks arise from one to three weaker ribs that 

become stronger ventrally and do not branch. The 

secondary ribs on the upper parts of the flanks are low, 

broad, uniform in strength and spacing, are broader 

than the interspaces, and incline forward on the margins 

of the venter. During growth the primary ribs become 

weaker and more widely spaced apd the secondary ribs 

become broader and lower. 

The suture line has a well-developed first lateral lobe 

that is larger than the ventral lobe. The second lateral 

lobe is small and very narrow. The first lateral saddle 

is very broad. 

Figured specimen: USNM 131357. 

Occurrences: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic loc. 24113. Kialagvik Formation at Mesozoic 

locs. 12402, 18822, 19823, and 19825. 

Pelekodites1 sp. 

Plate 6, figures 4, 5, 11 

One ammonite from the Coo~ Inlet region appears 

to represent the genus Pelekodites as defined by.Arkell 

(1954, p. 563; Arkell and others, 1957, p. L270). It 

is small, evolute, and bears lateral lappets. The venter 

is narrow and bears a low blurtt keel that near the 

aperture is bordered by weak furrows. The whorl 

section is ovate and higher than wide. The umbilical 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B37 

slope is vertical on the inner whorls, steeply inclined 

on the outermost whorl, and rounds evenly into the 

flanks. The body chamber occupies slightly more than 

half a whorl. The innermost whorls bear prominent 

tubercles on the flanks, but during growth the tubercles 

are replaced by blunt swellings. The outer two whorls 

are marked only by weak widely spaced ribs that 

incline backward slightly on the flanks and then curve 

forward considerably near the venter. The ribbing 

becon1es weaker adorally and near the aperture is barely 

visible. 

The suture has a broad bifid first lateral saddle, a 

shallow trifid first lateral lobe, and three small auxilliary 

lobes. 

Within the genus Pelekodites, Arkell (1954, p. 563) 

included Nannoceras nannomorphum Buckman (1923, 

pl. 445), Macerites aurijer Buckman (1928, pl. 766), 

Spatulites spatians Buckman (1928, pl. 765), and 

Pelekodites pelekus Buckman (1923, pl. 399) from the 

Sonninia sowerbyi zone in England. He indicated 

that the genus also included similar small lappeted 

ammonites from the lower part of the Stephanoceras 

humph..riesian11m zone in southern Germany (Dorn, 

1935, p. 113, pl. 3, figs. 2a, b; Hiltermann, 1939, p. 170-

176, pl. 12, fig. 7). These had been described as 

immature specimens of Witchellia or of Sonninia 

deltajalcata (Quenstedt), differing from typical specimens of that species by being smaller and by bearing 

lateral lappets. Arkell (1954, p. 563; Arkell and others, 

1957, p. L90) contended, however, that specimens 

with lateral lappets are adults and hence cannot be 

placed within such genera as Witchellia or Sonninia 

that do not have lateral lappets. Interestingly Hiltermann's (1939, p. 171, 177) inclusion of Pelekodites 

pelekus Buckman in the synonymy of his Sonninia. 

deltajalcata (Quenstedt) strengthened Arkell's opinion 

that all the lappeted species mentioned above are 

closely related. 

The lapp_eted arrunonite from Alaska is herein 

referred questionably to Pelekodites because it has 

appreciably weaker ribbing than the· similar European 

species of Pelekodite's and because its innermost 

whorls bear few lateral tubercles that are not apparent 

in the illustrations of .the .European species. 

The Alaskan ammonite in question should be o£ about 

the same age as the l~ppeted specimens from Germany 

considering that it is associated with Sonninia similar 

to S. tuxedniensis Irplay, n. sp. and that it occurs 

in a sequence contain.ing Teloceras, Chondroceros, and 

Normanm'tes. 

Figured specimen: USNM 131358. 

Occurrence: Fitz Creek SiltstOne at USGS Mesozoic loc. 26596 

Family STRIGOCERATIDAE Buckman, 1924 

Genus STRIGOCERAS Quenstedt, 1886 

Strigoceras cf. S. languidum (Buckman) 

Plate 23, figures 2-4, 8 

One septate specimen from Alaska is a representative of the genus Strigoceras. The shell is discoidal. 

The whorls are more than twice as high as wide. The 

keel is tall, holl~w, and floored. The umbilical wall 

is low, vertical, and rounds evenly into the flanks. 

The body chamber is not preserved. 

The shell is ornamented with spiral grooves, strigations, and falcoid ribbing. One groove lies just below 

the middle of the flanks and another lies just above 

the umbilical margin. The strigations are faint and 

are visible only at one place where some of the shell is 

preserved. The falcoid ribs are broad and strong 

on the upper part of the flanks. They appear to 

arise in pairs near the middle of the flanks from faint 

broad ribs on the lower part of the flanks. 

The suture line is too poorly preserved to be traced 

accurately, but it includes a long umbilical lobe consisting of four or five au~iliaries that descend evenly 

toward the umbilicus. 

The specimen at a diameter of about 61 mm has a 

whorl height of 35 mm, a whorl thickness of 15.5 mm, 

and an umbilical width of 6 mm. 

The Alaskan specimen is closely similar to Strigoceras 

languidum (Buckman) (1924, pl. 477 a, b) from the 

European zone of Otoites sauzei. Its umbilicus is a 

little wider and its ribs are a little broader, higher, and 

more sigmoid. S. protrusus (Buckman) (1922, pl. 

317) from the European zone of Sonninia sowerby1' has 

a much smaller umbilicus and apparently weaker 

narrower ribbing. 

Figured specimen: USNM 131359. 

Occurrence: Fitz Creek Siltstone at USGS Mesozoic loc. 27105. 

Strigoceras sp. juv. 

Plate 23, figures 5-7 

One small discoidal shell consists of nearly half a 

whorl of a body chamber and several septate inner 

whorls that are exposed mostly in cross section. 

The outer whorl is nearly twice as high as wide. The 

inner whorls are relatively stouter. The venter on 

the body chamber bears a high narrow hollow keel that 

is not floored. The venter on the septate whorls bears 

a low keel that appears to be hollow and floored. 

The umbilicus is very narrow. The umbilical wall is 

low and rounds evenly in to the flanks. 

The inner septate whorls bear traces of broad faint 

flexuous ribs and striae but are only partly exposed. 

The outer whorl bears a broad spiral groove just 

below the middle of the flanks and broad falcoid ribs 
B38 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

that are weak on the lower part of the flanks but 

become strong on the upper part. In addition the 

shell bears fine striae of growth that on the ventral 

margins incline forward much more strongly than do 

the falcoid ribs. There is no trace of strigation. 

The suture line is not preserved. 

The outer whorl at a whorl height of 16 mm has a 

whorl thickness of 8 mm. 

This specimen is possibly an immature representative 

of the species herein described as Strigoceras cf. S. 

languidum (Buckman), but it appears to have somewhat stronger ribbing. 

Figured specimen: USNM 131360. 

Occurrence: Red Glacier Formation at USGS Mesozoic loc. 

21268. 

Family HAPLOCERA TIDAE Zittel, 1884 

Genus LISSOCERAS Bayle, 1879 

Lissoceras bakeri Imlay 

Plate 23, figure 1 

Lissoceras bakeri Imlay, n. sp., 1962, U.S. Geol. Survey Prof. 

Paper 418-A, p. 6, pl. 1, figs. 1-6, 9-12. 

One large specimen of this species agrees very well 

with the type specimens from the Twist Creek Siltstone, 

although found some hundreds of feet lower. It 

includes about haLf a whorl of the body chamber, of 

which part is dislocated. The specimen is characterized by its vertical umbilical wall, compressed whorl 

section, narrowed venter, and fine flexuous striae. 

Type: Plesiotype USNM 131361. 

Occurrence: Cynthia Falls Sandstone at USGS Mesozoic 

loc. 10512. 

Lissoceras cf. L. semicostulatum Buckman 

Plate 4, figures 7, 8 

Two laterally crushed internal molds, consisting 

mostly of body chamber, bear sigmoidal growth striae 

on the lower and n1iddle parts of the flanks and broad 

low rursiradiate ribs on the upper part of the flanks. 

The venter is nearly smooth, but· in places is marked 

by faint continuations of the ribs. The umbilical wall 

is low, vertical at its base, and rounds evenly into the 

flanks. 

The fairly strong ribbing on these Alaskan specimens 

resembles that on Lissoceras semicostulatum Buckman 

(1923, pl. 400) from the Sonninia sowerbyi zone of 

England. 

Figured specimen: USNM 131362. 

Occurrence: Red Glacier Formation at USGS Mesozoic loc. 

21268. 

Family OPPELIIDAE Bonarelli, 1894 

Genus OPPELIA Waagen, 1869 

Oppelia ( Oppelia) stan toni Imlay, n. sp. 

Plate 8, figures 11-18 

This species is represented by 11 small to mediumsized specimens and one large septate specimen. 

Small specimens below 8 mm in diameter are compressed, have a sharpened venter, and their whorls 

overlap each other about half. During growth the 

venter becomes somewhat sharper, and the whorls 

become more compressed and more involute. At 

diameters greater than 25 mm the outer whorl embraces 

the preceding whorl almost completely. The flanks 

are flattened below and converge above to the venter. 

On the innermost whorls the umbilical wall is low, 

steep, and rounds evenly into the flanks. During 

growth it becomes vertical and rounds rather abruptly 

into the flanks. The body chamber is unknown. 

The innermost whorls are entirely smooth. At a 

diameter of about 8 mm, faint falcoid riblets appear on 

the upper parts of the flanks, but the lower parts of 

the flanks remain smooth to a diameter of about 20 

mm. At greater diameters the lower parts of the 

flanks bear faint forwardly inclined striae that bend 

backward abruptly at the middle of the flanks and 

then pass into much stronger falcoid riblets on the 

upper parts of the flanks. These riblets curve backward, then strongly forward,. and on internal molds 

nearly disappear along the midline of the venter. In 

addition at a diameter of about 38 mm, widely spaced 

falcoid swellings appear on the upper part of the flanks. 

These at first are separated by two or three weak 

falcoid riblets, but during growth the riblets disappear 

and the swellings become stronger. During this stage 

of development, the ventrolateral margin is marked 

by many very fine forwardly inclined riblets of which 

some arise from the swellings. and some arise between 

the swelling. There are from six to eight such riblets 

for each swelling on the flanks but the exact number 

cannot be determined. On some specimens these fine 

riblets are finer and denser than on other specimens. 

One large septate specimen (pl. 8, fig. 18) on the 

adapical part of its outer whorl shows the same kind of 

ornamentation as on the specimens just described and, 

therefore, is considered to be the same species. Its 

appearance suggests that the adult body whorl was 

nearly smooth. 

The suture line is poorly preservPd and does not 

show the ventral lobe. The second lateral saddle is 

higher than the first lateral saddle. There are four 

auxiliary lobes in addition to the second lateral lobe. 

The specimens are too imperfect for measurements. 

This species differs from Oppelia subradiata (J. de C. 

~-
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B39 

Sowerby) (1823, v. 5, p. 23, pl. 421, fig. 2; Arkell, 1951, 

p. 50, text fig. 11) and from the species described by 

Buckman (1924, pls. 478, 480, 481; 1925, pls. 524, 

525 a, b) by having much finer denser ribbing on its 

ventrolatera] margins. The large septate specimen 

shows considerable resemblance, however, to the large 

septate specimen of Oppelia lectotypa Buckman (1924, 

pl. 124) which Arkell (1951, p. 50) suggested is probably 

the adult of 0. subradiata. 

The species is named forT. W. Stanton who collected 

the type specimens. 

Types: Holotype USNM 131363; paratypes USNM 131364-

131368. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 3000 

and 22721. 

Genus BRADFORDIA Buckman, 1910 

Bradfordia costidensa Imlay, n. sp. 

Plate 8, figures 1-10 

The species is represented by 51 specimens of which 

most have been crushed laterally. The shell is compressed and moderately involute. The whorls are 

elliptical in section, much higher than wide, and are 

thickest at about a third of the height of the flanks. 

The flanl\s are gently convex, converging above to a 

narrowly rounded venter. The umbilicus is fairly 

narrow. The umbilical wall is vertical, develops a 

sharp umbilical edge at an early growth stage, and 

becomes raised on the adult body whorl. The body 

chamber occupies about half a whorl.. The aperture 

is not perfectly preserved on any specimen, but it 

terminates simply in a curve that is roughly parallel 

to the falcoid ribbing. 

The septate whorls bear closely spaced fine to 

moderately fine falcoid ribs that are very weak on the 

lower thirq of the flanks, become strongrr ventrally, 

and either fade out or become very weak on the venter. 

On the smaller whorls the ribs vary somewhat in 

sharpness and spacing but during growth become nearly 

uniform in strength on any one specimen. The strength 

of the ribbing varies, however, from one specimen to 

another. On most specimens the ribs are nearly radial 

on the upper part of the flanks, but on some specimens 

the ribs incline backwards. 

On the body whorl the ribbing becomes markedly 

weaker adorally and near the aperture is replaced 

by falcoid growth lines. Internal molds of the· body 

chamber are nearly smooth. 

The ventral lobe is too poorly preserved to trace 

accurately but is clearly much shorter than the first 

lateral lobe. The first lateral saddle is much lower than 

the second lateral saddle. There are three auxiliary 

lobes in addition to the second lateral lobe. 

The holotype appears to br slightly crushed. At 

a diameter of 73 mm its whorl height is 36 mm, its 

whorl thickness is 22 mm, and its umbilical width is 

13 mm. The paratype shown on plate 8, figure 6 

appears to be uncrushed. At a diameter of 63 mm, 

the same dimensions are 31, 19, and 12.5 mm, respectively. The largest specimen in the collection has a 

diameter of about 104 mm. 

The Alaskan species is assigned to the genus Bradjordia rather than Lissoceras because of the presence 

of a sharp raised umbilical edge, but it is much finer 

ribbed than the described species of Bradjordia (Buckman, 1910, p. 93-95, pls. 9, figs. 2, 3; pl. 10, figs. 4-6; 

pl. 11, fig. 1; 1922, pl. 303: Douville, 1884, p. 33, pl. 3, 

figs. 6, 7; Jaworski, 1926, p. 253, pl. 3, figs. 12a-d, 13). 

Except for its sharp umbilical edge it resembles Lissoceras sem.icostulatum Buckman (1923, pl. 400) in shape, 

· coiling, and ribbing. 

Type: Holotype USNM 131369; paratype USNM 131370-

131375. 

Occurrences: Tuxedni Formation in Talkeetna Mountains at 

Mesozoic locs. 24113, 24215, and 25345. 

Bradfordia1 caribouensis Imlay, n. sp. 

Plate 5, figures 1-3, 5, 6 

The species is represented by four specimens all of 

which have been crushed a little laterally. The shell 

is compressed and moderately involute. The whorls 

are subquadrate in ·section, much higher than wide, 

and are thickest slightly below the middle of the flanks. 

The flanks are slightly convex. The venter is narrow 

and somewhat flattened. The umbilicus is fairly 

narrow. The umbilical wall is low, vertical, and 

develops a raised fairly sharp umbilical edge at an early 

growth stage. The body chamber is incomplete but 

occupies at least two-fifths of a whorl. The aperture 

is unknown. 

The septate whorls bear closely spaced broad falcoid 

ribs on which are superimposed fine falcoid striae. 

The ribs are faint on the lower fourth of the flanks, 

become stronger ventrally, are strongest on the margin 

of the venter, and nearly disappear on the venter. 

They curve forward strongly on the lower third of the 

flanks, recurve backward near the middle, curve forward again strongly on the margins of the venter, 

and arch forward 'on the venter. The venter is nearly 

smooth, being marked only by faint continuations of 

·some of the ribs. 

Adorally on the body whorl the ribs become less 

projected forward on the margins of the venter and 

weaker along the midline of the venter. 

The holotype, which is slightly crushed, at a dian:eter 

of 29 mm, has a whorl height of 18 mm, a whorl thickness of 12.5 mm, and an umbilical width of 6.5 mm. 
B40 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

The ventral lobe is much shorter than the first lateral 

lobe. The first lateral saddle is lower than the second. 

There are three auxiliary lobes in addition to the second 

lateral lobe. 

This species is ·included in Bradjordia rather than 

Toxambly·ites because of its raised umbilical margin. 

Otherwise the projected ribbing on the upper parts of 

the flanks resembles that on Toxamblyites arcijer 

Buckman (1924, pl. 473). B. incluse Buckman (1910, 

p. 94, pl. 9, figs. 2, 3) from England is similar in shape 

and in general appearance, but its ribs are only slightly 

projected forward on the ventral margins. 

Types: Holotype, USNM 131376; paratypes USNM 131377-

131379. 

Occurrences: Gaikema Sandstone at USGS Mesozoic loc. 

26601; Tuxedni Formation in Talkeetna Mountains at Mesozoic 

loc. 3696. 

Family OTOITIDAE Mascke, 1907 

Genus OTOITES Mascke, 1907 

Otoites cf. 0. pauper Westermann 

Plate 25, figures 1-3 

Two specimens bear strong sparse ribbing similar to 

that on Otoites pauper Westermann (1954, p. 106-109, 

pl. 3, figs. 5a, b, 6; text figs. 10, 26) from Europe. The 

most complete specimen represents an adult body 

whorl that has been so crushed vertically that the 

umbilicus is nearly hidden. It does show the large 

lateral lappets, the small conical tubercles near the 

umbilicus, and the' long secondary ribs that are characteristic of the genus. The number of tubercles 

cannot be determitied exactly but appears to be 11 or 

12. The other specimen, also representing part of a 

body chamber, has been crushed somewhat laterally. 

It shows that the .umbilicus was ·moderate in width 

and that the tubercles are sparser· than on the body 

chamber of most d~scribed species of Otoites. On both 

specimens the secondary ribs arise in pairs and cross 

the venter transver~ely. Some pairs are separated by 

single ribs that aris~ freely on the flanks. 

Figured specimen: USNM 131380. 

Occurrence: Lower p1art of Tuxedni Formation in Talkeetna 

Mountains at USGS M'esozoic loc. 24113. 

Otoites ~f. 0. contractus (Sowerby) r 

Plate 25, figures 4, 5 

Two specimens ~rom Alaska resemble Otoites contractus (J. de C. Sower by) (1825, pl. 500, fig. 2; Buckman, 1920, pl. 15.8; Westermann, 1954, pl. 1, figs. 

4a-c, 5; pl. 2) in whorl shape, coiling, and ribbing and 

possibly belong to.: that species. The specimen illustrated has 17 coriiqal umbilical tubercles on its body 

whorl. These form the terminations of short rounded 

primary ribs. At the adapical end of the body whorl 

three secondary rib~ arise from each tubercle and a few 

single ribs arise freely. Toward the aperture the 

number of secondary ribs decreases to two for each 

tubercle. The adoral half of the body whorl contracts 

considerably from the rest of the shell and also decreases 

in width. 

Figured specimen: USNM 131381. 

Occurrences: Red Glacier Formation at USGS Mesozoic locs. 

3009 and 21263. 

Otoites 1 filicostatus Imlay, n. sp. 

Pia te 14, figures 9-11 

Two ammonite specimens are characterized by large 

lateral lappets, fairly tightly coiled inner whorls, a 

contracted body chamber, and fine high dense nontuberculate ribs. The primary ribs incline forward 

on the lower third of the flank where they pass into 

two or rarely three secondary ribs. The furcation 

points are swollen but not tuberculate. The secondary 

ribs curve backward on the upper part of the flanks 

and then cross the venter nearly transversely or with a 

slight backward arching. 

The suture line is not preserved. 

The holotype at a diameter of 18 mm has a whorl 

height of 7.5 mm, a whorl thickness of 9.5 mm, and an 

umbilical width of 4.5 mm. At a diameter of 20 mm 

the same dimensions are 8.3, 9.8, and 6.2 mm, respectively. 

This species is assigned tentatively to Otoites rather 

than to Normannites because of the tight coiling of its 

inner whorls and the strong contraction of its body 

chamber. It differs from typical species of Otoites in 

having longer and weaker primary ribs that do not. 

terminate in tubercles. Its general appearance, however, is similar to that of 0. delicatus Buckman (1919. 

pl. 141, figs. 1-3; Westermann, 1954, pl. 4, figs. 3a-c, 

4, 5) which likewise has swollen rather than tuberculatf\ 

furcation points. The backward curvature of the 

secondary ribs on the flanks is not a feature of either 

Otoites or Normannites. 

Types: Holotype USNM 131382; paratype USNM 131383. 

Occurrences: Red Glacier Formation at USGS Mesozoic locs. 

3010 and 19951. 

Genus EMILEIA Buckman, 1898 

Emileia. constricts. Imlay, n. sp. 

Plate 11, figures 1-8 

This species is represented by nine specimens of which 

five are adults. The shell is large and moderately stout. 

The innermost whorls are coronate and much wider 

than high but during growth they become subovate and 

only a little wider than high. Most of the septate 

whorls overlap each other about three-fourths, but the 

adoral third of the outermost septate whorl begins to 

contract from the inner whorls. This contraction 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B41 

continues on the body whorl which near the aperture 

overlaps only a third of the preceding whorl. The 

umbilicus on the inner whorls is small but open. It 

enlarges rapidly adorally on the outermost lYa whorls. 

The body chamber occupies from IX to 1~~ whorls. 

The aperture on the internal mold is marked by a pronounced forwardly inclined constriction that is followed 

by a collar. Both the constriction and collar are much 

stronger on the flanks than on the venter. 

The small inner whorls (pl. 11, figs. 4, 5, 7) bear 

moderately strong and numerous primary ribs that 

trend radially on the umbilical wall and terminate in 

radially elongate tubercles on the edge of the umbilicus. 

From the tubercles pass two or three weaker secondary 

ribs that cross the venter transversely. Other secondary 

ribs are intercalated along the zone of tuberculation 

resulting in at least four secondary ribs for each primary rib. All secondary ribs widen ventrally and on 

the venter are a little wider than the interspaces. 

During growth the primary ribs become stronger 

relative to the secondary ribs. The tubercles gradually disappear but the passage from the primary to 

the secondary ribs is marked by an abrupt weakening 

of the ribbing. The secondary ribs broaden ventrally 

but on the venter are narrower than the interspaces. 

The ratio of secondai:y to primary ribs increases to 

about fi~e to one on the outermost septate whorl. 

In addition the outermost septate whorl bears from 

three to five constrictions of which some are followed 

by swellings. Those constrictions are present on four 

such septate whorls and hence appear to be characteristic of the species. 

Adorally on the adult body whorl the primary ribs 

gradually become stronger and more widely spaced; 

whereas the secondary ribs become weaker and more 

widely spaced. Near the aperture the secondary ribs 

outnumber the primary ribs only about three to one. 

Most of the specimens have been crushed laterally. 

The holotype at a diameter of 84 mm, however, appears 

to be only slightly deformed. At this diameter its 

whorl height is 34 mm, its whorl thickness 47 mm, and 

its umbilical width 24 mm. On the smallest paratype 

the same dimensions are 28, 13.5, 23, and 7 mm. 

The suture line is very complicated and is not well 

enough preserved to trace. Its general plan as shown 

in a specimen from USGS Mesozoic locality 24334 is 

similar to that of E. brocchii (J. Sowerby) as illustrated 

by Buckman (1908, pl. 4, fig. 1c). Details of part of 

the suture can be observed in a specimen from USGS 

Mesozoic locality 22723. 

Emileia cpnstricta Imlay, n. sp. greatly resembles 

Emileia brocchii (Sowerby) (Buckman, 1908, pl. 4; 

1927, pl. 710a-d) in ribbing but has a much higher 

whorl section and its body whorl appears to be more 

contracted. Its immature whorls resemble the equally 

small E. subcadiconica Buckman (1927, pl. 711). E. 

vagabunda Buckman (1927, pl. 723a, b) i~ more compressed, 

n1uch larger, and probably has weak~r ribbing on the 

adult. E. multijida Buckman (1927, pl. 733) has much 

sharper ribbing and fewer secondary ribs. None ·of 

these species exhibit constrictions sudh as are ·present 

on the Alaskan species. 

Types: Holotype USNM 131384; paratypes USNM 131385-

131388. ' 

Occurrences: Red Glacier Formation at VSGS Mesozoic l<?cs. 

3009, 21262, 21263, 21268; Gaikema Sandstone at Mesozoic 

loc. 22723. Based on these occurrences . the species ranges 

through the upper 500 ft of the Red Gla:cier Formation and 

the lower 150 ft of the Gaikema Sands~one. Fragments of 

Emileia that may belong to E. constricta I~lay, n. sp., however, 

have been found in the Red Glacier For).nation at Mesozoic 

locs. 21293 and 24334, which are about 1,200 and 1,800 ft, 

respectively, below the top of the formation. 

Family SPHAEROCERATIDAE Buckman, 1920 

Genus LABYRINTHOCERAS Buc~man, 1919 

Labyrinthoceras glabrum Imlar, n. sp. 

Plate 9, figures 1-3 ;. plate 10, fi~ures 1-7 

This species is represented by 13 specimens that 

show the various growth stages and probably also by 5 

small specimens less than an inch in piameter. 

The shell is a large sphaerocone. The septate whorls 

are elliptical in section and wider than high. The 

umbilicus on the early whorls is n~row, but on the 

body whorl it widens rapidly. The outermost septate 

whorl embraces about two-thirds of the preceding 

whorl. Adorally the body chamber contracts from the 

inner whorls and near the aperture e~braces only about 

a third of the preceding whorl. the body chamber 

occupies nearly one complete whorl. This whorl 

adorally diminishes both in height and thickness for 

more than half of its length and th~n expands slightly 

near the aperture. The aperture is marked on the 

internal mold by a forwardly inplined constriction 

that is stronger on the flanks than qn the venter. 

On the septate whorls the ribb~ng is fine, closely 

spaced, and nearly radial. The primary ribs divide a 

little below the middle of the flanks into two or three 

secondary ribs that are nearly as strdng as the primaries. 

The furcation points are not swollen or tuberculate. 

At the beginning of the body whorl the ribbing becomes 

abruptly weaker and sparser. Adorally the flanks 

become nearly smooth, but the vent~r retains irregularly 

spaced and forwardly arched ribs that persist nearly to 

the aperture. , 

The holotype at the beginning o~ the body chamber 

has a diameter of 95 mm, a whorl height of 42 mm, a 

whorl thickness of 48 mm, and an umbilical width 
B42 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

of 24 mm. On the large paratype, shown on plate 10, 

figures 4, 5, at a diameter of 108 mm the other dimensions are 40, 49, and 39 mm, respectively. Near the 

aperture at a diameter of 140 mm the other dimensions 

are 48, 57, and 56 mm, respectively. 

The suture line is very complicated. The auxiliaries 

are well exposed at the beginning of the body chamber 

of one adult speciman. Another large specimen shows 

the plan of the ventral and first lateral lobes and the 

adjoining saddles. Judging from these examples, the 

suture line is similar to that of Emileia brocchii (J. 

Sowerby) as illustrated by Buckman (1927, pl. 710b). 

The first lateral lobe is stockier and less symmetrical 

and the first lateral saddle is broader. The suture 

lines of Labyrinthoceras illustrated by Buckman (1919, 

pl. 134, fig. 4; pl. 135, fig. 4) appear likewise to have 

narrower saddles than the Alaskan species of Labyrinthoceras. The comparison may not be valid, however, 

because the· specimens from which Buckman traced the 

sutures are small and apparently immature. 

The Alaskan species in lateral view greatly resembles 

Labryrinthoceras perexpansum Buckman (1921, pl. 

134a-d) from England but is much less inflated at all 

growth stages and appears to have weaker and sparser 

ribbing on its body chamber. 

Types: Holotype USNM 131389; paratypes USNM 131390-

131392. 

Occurrences: Tuxedni Formation in Talkeetna Mountains at 

USGS Mesozoic locs. 24215 and 25942. 

Genus CHONDROCERAS Mascke, 1907 

Chondroceras defontii (McLearn) 

Plate 12, figures 8, 11-14 

Defonticeras defontii Mcl. .. earn, 1927, Royal Soc. Canada Trans., 

3d ser., v. 21, sec. 4, p. 72, pl. 1, fig. 3. 

1929, Canada Natl. Mus. Bull. 54, p. 13, pl. 12, figs. 1-3. 

Defonticeras colnetti McLearn, 1929, Canada N atl. Mus. Bull. 54, 

p. 15, pl. 13, figs. 4, 5. 

Chondroceras (Defonticeras) defontii (McLearn), 1949, Canada 

Geol. Survey Bull. 12, p. 10, 16. 

Westermann, 1954, Geol. Jahrb Beihefte, no. 15, p. 100, pl. 

11, fig. 3, text figs. 57, 59, 60. 

. Ghondroceras dejontii (McLearn) is characterized by 

a fairly stout to nearly globose shell, an extremely 

small umbilicus, a scaphitoid body chamber, and in 

particular by the secondary ribs on the adult body whorl 

changing rather. abruptly from extremely fine and closely spaced on the adapical end to moderately coarse and 

widely spaoed on the adoral end. 

This species, as herein interpreted, is represented by 

42 specimens from the Cook Inlet region, · Alaska. 

Compared with the holotype, some are stouter, some 

are more compressed, and some have slightly coarser 

ribbing. There does not appear to be any correlation 

between the amount of stoutness and the strength of 

the ribbing. Judging from these specimens, "Dejonti..., 

ceras" colnetti McLearn (1929, p. 15, pl. 13, figs. 4, 5) is 

a variant of G. dejontii (McLearn) that differs by having 

slightly sharper and sparser ribb.ing and a less robust 

shell. "Dejonticeras" maudense McLearn (1929, ,p. 14,. 

pl. 14, figs. 2, 3) is possibly also a stout variant of 

Ghondroceras dejontii (McLearn) as suggested by 

Westermann (1954, p. 100), but it appears to have con.:: 

siderably coarser ribbing on the adapical end of the 

body whorl than any of the specimens of that species 

from Alaska. "Saxitoniceras" marshalli McLearn (1928, 

p. 22, pl. 8, figs. 3, 4; Frebold, 1957a, p. 54, pl. 25, figs. 

3a, b; pl. 26, figs. 2a, b) is similar to G. dejontii (McLearn) 

in stoutness of whorls but has somewhat coarser and 

sparser ribbing. 

Types: Holotype Canada Natl. Mus. 9009; plesiotypes USNM 

131393-131395. 

Occurrences: Cynthia Falls Sandstone at USGS Mesozoic locs. 2994, 

10514, 10515, 10519, 21771 and 22707. Fitz Creek Siltstone at 

Mesozoic locs. 2997, 2999, 3000, 10245, 10516, 20022, 20756, 

21270, 21271, 21275, 21276, 21769, and 26597. 

Ohondroceras dejontii (McLearn) near Tuxedni Bay 

ranges through the upper 150 ft of the Fitz Creek 

Siltstone and the basal 40 ft of the Cynthia Falls 

Sandstone. The species on the Iniskin Peninsula has 

been found at and just below the middle of the Fitz 

Creek Siltstone and in · the lower 400-500 ft of the 

Cynthia Falls Sandstone. 

Chondroceras a~ani (McLearn) 

Plate 12, figures 4-7, 9, 10 

Saxitoniceras allani McLearn, 1927, Royal Soc. Canada Trans.• 

3d ser., v. 21, sec. 4, p. 72, pl. 1, fig. 4. 

1928, Canada Geol. Survey Bull. 49, p. 21, pl. 8, figs. 1, 2. 

Chondroceras (Saxitoniceras) allani (McLearn). Westermann, 

1956a, Geol. Jahrb. Beihefte, no. 24, p. 107, pl. 12, fig. 3 

a-d. 

Chondroceras allani (McLearn). Frebold, 1957a, Canada Geol. 

Survey Mem. 287, p. 53, pl. 27, figs. 2a, b. 

The collections from the Cook Inlet region contain 

30 specimens of Ghondroceras that are closely similar 

to the type specimens of G. allani (McLearn). They 

are characterized by coarse rather short primary ribs 

that incline or curve forward strongly on the lower 

two-fifths of the flanks. From them arise somewhat 

weaker secondary ribs that recurve backward slightly 

near the middle of the flanks and then cross the venter 

transversely. At the adapical end of the adult body 

chamber there are three secondary ribs for each primary 

rib, but adorally secondary ribs become scarcer and 

near the aperture number two for each primary rib. 

The type specimens have 16-17 primary ribs on the 

adult body whorl. The specimens from Alaska have 

from 17 to 22 depending on the size of the adult body 

whorl. The specimens from Alaska agree with the 

f' 

t• 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B43 

type specimens in whorl shape and in the gradual 

umbilical enlargement of the adoral half. of the adult 

body whorl. Some of them are a little stouter or 

finer ribbed than the type specimens, but the species 

includes, similar variants judging by a collection (USGS 

· Mesozoic loc. 14630) from the mountains west of the 

TuFnler Valley oil field, Alberta. 

These specimens of Chondroceras allani (McLearn) 

from Alaska appear to differ from C. oblatum (Whiteaves) by having sparser coarser and more strongly 

inclined primary ribs and a more depressed whorl 

section. Comparisons are difficult, however, because 

the holotype of C. oblatum is poorly preserved. lf that 

species includes both C. marchandi (McLearn) (1929, 

p. 14, pl. 12, figs. 4, 5) and C. ellsi (McLearn) (1929, 

p. 16, pl. 13, figs. 2, 3; pl. 14, fig. 1), as considered 

probable by Westermann (1956a, p. 102, 103), it is 

very different than C. allani (McLearn). 

Types: Holotype Canada Natl. Mus. 9021; plesiotype Canada 

Geol. Survey 12893; plesiotypes, USNM 131396-131399. 

Occurrences: Cynthia Falls Sandstone at USGS Mesozoic loc. 

10511; Fitz Creek Siltstone at Mesozoic locs. 19981, 19984, 

20000, 20025, 21317, 21768. Specimens comparable with C. 

allani (McLearn) occur in the Fitz Creek Siltstone at Mesozoic 

locs. 20002, 21276, 21306, 27105; Tuxedni Formation in the 

Talkeetna Mountains, at Mesozoic loc. 8567~ 

Chondroceras allani (McLearn) near Tuxedni Bay occurs in. 

the upper 50 feet of the Fitz Creek Siltstone and in the lower 

40 feet of the Cynthia Falls Sandstone. The species on the 

Iniskin Peninsula ranges through the middle and upper parts 

of the Fitz Creek Siltstone. 

Chondroceras cf. C. marshalli (McLearn) 

Plate 12, figures 1-3 

Several specimens from the Talkeetna Mountains, 

Alaska, greatly resemble Chondroceras marshalli (MeLearn) 1928, p. 22, pl. 8, figs. 3, 4; Frebold, 1957a, 

pl. 25, figs. 3a, b; pl. 26, figs. 2a, b) from the Rock 

Creek Member of the Fernie Group in Alberta and 

eastern British Columbia. They differ from C. allani 

(McLearn) by having a much wider more depressed 

whorl section, somewhat weaker more closely spaced 

primary ribs, and more secondary ribs for each primary 

near the aperture. They differ from the holotype of 

C. oblatum (Whiteaves) (1876, p. 29, pl. 4, figs. 2, 2a: 

1884, p. 209) by having a much wider whorl section and 

more closely spaced primary and secondary ribs on 

the adoral half of the adult body whorl. 

Figured specimen: USNM 131400. 

Occurrence: Tuxedni Formation in the Talkeetna Mountains 

at USGS Mesozoic loc. 8567. 

Family STEPHANOCERATIDAE Neumayr, 1875 

Genus NORMANNITES Munier-Chalmas, 1892 

Normannites kialagvikensis Imlay, n. sp. 

Plate 13, figures 1-8, 10, 11, 17 

Dactylioceras sp. A, 1945, Kellum, Daviess, and Swinney, U.S. 

Geol. Survey Spec. Pub., figs. 5 C-E (not A, B). 

This species is represented by six specimens. The 

shell is smalL and. compressed. The inner whorls are 

depressed ovate, wider than high, and embrace about 

two-fifths of the preceding whorls. During growth 

they become more depressed and nearly quadrate. 

The umbilicus is fairly wide and shallow. The body 

chamber occupies about half a whorl. The aperture 

bears lateral lappets. 

The septate whorls bear high sharp primary ribs 

that curve gently forward and terminate in pointed 

tubercles near the middle of 'the flanks. From most 

tubercles pass pairs of slightly weaker secondary ribs 

that arch slightly forward on the venter. From a few 

tubercles pass only single secondary ribs. 

Adorally on the body chamber the ribs become higher 

and thicker, the primary ribs incline more strongly 

forward, tubercles disappear, and some of the secondary 

ribs are indistinctly connected with the primary ribs. 

The suture line is fairly simple. The ventral and 

first lateral lobes are nearly of the same length. 

The holotype at a diameter of 36 mm has a whorl 

height of 11 mm, a whorl thickness of 14.5 mm, and an 

umbilical width of 17 mm. On the paratype shown on 

plate 13, figures 1-3, the same dimensions are 26.5, 

8.5, 11.5, and 11.5 mm; respectively. 

This species bears a general resemblance to Normannites rugosus Westermann (1954, p. 231-235, pl. 19, 

figs. 4-6; pl. 20, figs. 1-3) from Germany but is much 

smaller, has more widely spaced primary ribs on its 

inner whorls, and loses its tubercles on its body chamber. 

Types: Holotype USNM 131401; pa~atypes USNM 131402-

131404. 

Occurrences: Red Glacier Formation at USGS Mesozoic locs. 

3010, 21261; probably present in the Red Glacier Formation 

at Mesozoic loc. 21296; Kialagvik Formation on Wide Bay, 

Alaskan .Peninsula, at Mesozoic loc. 19773. 

SubgenusiTINSAITES McLearn, 1927 

N ormannites (Itinsaites) crickmayi (McLearn) 

Plate 14, figures 3-8, 13 

Kanastephanus crickmayi McLearn, 1927, Royal Soc. Canada 

Trans., 3d ser., v. 21, sec. 4, p. 73, pl. 1, figs. 5, 6. 

1929, Canada Natl. Mus. Bull. no. 54, p. 22. pl. 16, figs. 7, 8. 

?Kanastephanus canadensis McLearn, 1929, Canada Natl. Mus. 

BulL no. 54, p. 25, pl. 15, figs. 4, 5. 

?Kanastephanus mackenzii McLearn, 1929, Canada Natl. Mus. 

Bull. no. 54, p. 23, pl. 16, figs. 1-3. 

'?Kanastephanus altu~J McLearn, 1929, Canada Natl. Mus. Bull. 

no. 54, p. 24, pl. 16, figs. 4-6. 
B44 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

Normannites (Kanastephanus) crickmayi (McLearn), 1949, 

Canada Geol. Survey Bull. 12, p. 16. 

Itinsaites crickmayi (McLearn), Westermann, 1954, Geol. Jahrb. 

Beihefte, no. 15, p. 290, pl. 27, fig. 3, text figs. 102, 123. 

The species is characterized by a stout to moderately 

stout shell, a depressed whorl section, and fairly wide 

umbilicus that enlarges on the adult body whorl owing 

to contraction of the body chamber. The ribbing 

is coarse and fairly widely spaced. On the inner 

whorls the secondary ribs outnumber the primary ribs 

about three to one. On the adult body chamber there 

are about two secondary ribs for each primary. The 

tubercles are acute and prominent. 

This species may include all four species of Kanastephanus describPd by McLearn (1929, p. 22-25) on the 

basis of four specimens from a single locality in the 

Queen Charlotte Islands. These four specimens were 

described as similar in general proportions and in 

ribbing but differentiated specifically by minor differences in size,. whorl shape, number of primary ribs, 

and sharpness of ribs. They can all be matched very 

well, however, by specimens from the Cook Inlet 

region, Alaska, that appear to belong to a single variable 

species. 

The 55 specimens from Alaska assigned to Normannites crickmayi (McLearn) vary mainly in the stoutness 

of their whorls. ·Some are more compressed than the 

holotype specimen described by McLearn and some are 

stouter, but most of the s~ecimens are intermediate 

in stoutness. 

Likewise the variation in the number of primary ribs, 

in the sharpness of the ribs, and in the size of the adult 

shell among the 55 Alaskan specimens does not afford 

means of separating them into species. The number of 

primary ribs ranges from 20 to 26 on the adult whorls 

but .is directly related to the size of the adult whorl. 

The larger adultsi-are nearly twice the size of the smaller 

adults, but size appears to have no relation to whorl 

shape or to ribbing. Sharpness of ribbing is related 

mainly to preservation of shell material. Where the 

shell is preservedithe ribs are high and rounded; but on 

the internal mold the ribs are lower, sharper, and more 

widely spaced. 

The European! species most similar to Normannites 

crickmayi (McLe.arn) have been fully discussed, illustrated, and compared by Westermann (1954, p. 247-292, 

pls. 22-27, table 5). 

Types: Holotype Canada Natl. Mus. 9016; plesiotypes USNM 

131405-131406, 131452. 

Occurrences: Fitz ·Creek Siltstone at USGS Mesozoic locs. 

2997,2999,3000,19977,19978,19997,20756,21270,21271,21275, 

21305; Cynthia Falls Sandstone at Mesozoic locs. 10513 and 

10519. The species is probably represented also in the Fitz 

Creek Siltstone at Mesozoic locs. 19974, 21302, and 26599 and 

in the Cynthia· Fails Sandstone at Mesozoic loc. 10512. One 

comparable specimen was found in the upper part of the Red 

Glacier Formation on Tuxedni Bay at Mesozoic loc. 21269. 

Normannites crickmayi (McLearn) near Tuxedni Bay ranges 

through the upper fourth of the Fitz Creek Siltstone and the 

lower sixth of the Cynthia Falls Sandstone. On the Iniskin 

Peninsula it ranges from 200 to 480 feet above the base of the 

Fitz Creek Siltstone which varies from 1,100 to 1,300 feet in 

thickness. 

Normannites (Itinsaites) itinsae (McLearn) 

Plate 14, figures 1, 2 

Itinsaites itinsae McLearn, 1927, Royal Soc. Canada Trans., 3d. 

ser., v. 21, sec. 4, p. 73, pl. 1, fig. 7. 

1929, Canada Natl. Mus. Bull. no. 54, p. 26, pl. 15, figs. 2, 3. 

(McLearn). Westermann, 1954, Geol. Jahrb. Beihefte, 

no. 15, p. 251-254, pl. 26, fig. 5; pl. 27, fig. 1, text figs. 

101-107. 

Normannites (Itinsaites) itinsae (McLearn), 1949, Canada Geol. 

Survey Bull. 12, p. 16. 

This species is represented by 11 specimens from the 

Cook Inlet region. It resembles Normannites crickmayi 

(McLearn), with which it is associated, in general 

proportions but on the adult body whorl has much 

finer closer spaced_ secondary ribs that outnumber the 

primary ribs about three to one instead of two to one. 

'Types: Holotype Canada Natl. Mus. 9020; plesiotype USNM 

131407. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

2997, 2999, 19997, 26599 and probably 21271; Red Glacier 

Formation at Mesozoic loc. 21268 (float). 

Normannites (ltinsaites1) variabilis Imlay, n. sp. 

Plate 13, figures 9, 12-16; plate 14, figures 12, 14 

This species is represented by 20 specimens of which 

all are somewhat crushed laterally. The shell is 

planulate, moderately stout, moderately evolute. The 

whorls are rounded, wider than high on inner whorls, 

becoming as high as wide on the adult whorl. The 

inner whorls overlap one another about half. The 

outer adult body whorl contracts gradually from the 

inner whorls and overlaps the penultimate whorl only 

about%-%. The umbilicus is moderate to fairly wide. 

The umbiUcal wall is steep and rounds evenly into the 

flanks. The body chamber occupies about threefourths of a whorl. The aperture is marked by elongate 

lateral lappets. On the internal mold it is marked by 

a constriction, followed by a collar, and then by lappets. 

The ribbing on the inner whorls consists of sharp 

fairly closely spaced primary ribs that are nearly 

radial on the umbilical wall and then curved forward 

slightly to the middle of the flanks where they terminate 

in tiny acute tubercles. From these pass bundles of 

two or three much weaker secondary ribs that incline 

forward slightly on the flanks but cross the venter 

transversely. Between successive bundles may occur 

one or rarely two ribs that begin along the zone of 

furcation. 

t 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B45 

On the body chamber all ribs become markedly 

coarser and more widely spaced adorally. The secondary ribs in particular become coarser and sparser 

relative to the primary ribs and near the aperture ar·e 

nearly as strong as the prin1ary ribs. The shell at the 

apertural constriction and on the lappets bears only 

growth striae. 

The suture line, partly exposed on the holotype, has 

a long symmetrical first lateral lobe and a much shorter 

second lateral lobe. The character of the ventral lobe 

is not known. 

The adult body whorl bears from 33 to 39 primary 

ribs and from about 95 to 110 secondary ribs. There 

does not appear to be any relation between the number 

of primary and of secondary ribs; however, the specimens having fewest ribs have the coarsest ribs. 

The ho]otype at a diameter of 103 rom has a whorl 

height of 37 rom and an umbilical width of 42 rom. 

The paratype shown on plate 13, figures 12-14, at a 

diameter of 84 rom has a whorl height of 30 rom, a whorl 

thickness of 32 rnm, and an umbilical width of 33 rom. 

Both specimens have been compressed a little laterally. 

This species shows considerable variation in the 

coarseness of its ribbing. The holotype has the coarsest 

and sparsest ribbing. The specimen shown on plate 

14, figure 14, has the finest and densest ribbing. The 

specimen shown on plate 13, figures 12-14, has ribbing 

of intermediate ·coarseness, but it is associated (Mesozoic loc. 8567) with a specimen as coarsely ribbed as 

the holotype. Seven specimens exhibiting ribbing of 

fine to intermediate coarseness were obtained at one 

spot on the Iniskin Peninsula (Mesozoic loc. 11023, 

11024, 11027-11029, 19940). About 50-100 feet higher 

was obtained the coarsely ribbed holotype (Mesozoic 

loc. 20002) and i'about a hundred feet still higher was 

obtained a large··finely ribbed specimen (Mesozoic loc. 

19941). One specimen obtained near the top of the 

formation (Mesozoic loc. 21768) has ribbing of intermediate coarseness. These associations and occurrences 

indicate that the differences in coarseness. of ribbing 

have no stratigraphic or taxonomic significance. 

The fine ribbing on the inner whorls of this species 

is similar to that of species of Cadomites and Polyplectites (Arkell, 19,52b, p. 79, 80; Westermann, 1954, p. 

335-348, pl. 32, figs. 3-6). The presence of lateral 

lappets and coatse ribbing on the body chamber, however, rules out an assignment to Cadomites. Polyplectites is much smaller and does not develop as coarse 

ribbing on its body chamber. 

The coarsely ribbed specimen of N. variabilis Imlay, 

n. sp., such as .the holotype, shows some resen1blance 

to N. (1.) joTmosus (Buck1nan) (1920, pl. 151; Westermann, 1954, pl. 23, figs. la-c) but have somewhat 

weaker tubercles and secondary ribs. Most of the 

'713-903 0 - 64 - 3 

specimens of N. variabilis have. weaker and denser 

ribbing than the holotype and are comparable with 

N. (Itinsaites) gracilis Westermann (1954, pl. 26, figs. 

3a, b, 4). They appear, however, to have stronger 

tubercles and to develop sparser ribbing near the aperture. The most finely ribbed specimen of N. variabilis 

has ribbing as dense as that on N. (1.) densus (Buckman) 

(1920, pl. 152). 

N. variabilis Imlay, n. sp. is characterized by its 

rounded whorl section, by having fine dense ribbing 

on its septate whorls, and by its ribbing becoming 

coarse and sparse on the adult body chamber. 

Types: Holotype USNM 131408; paratypes USNM 131409-

131412. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

11023, 11024, 11027-11029, 19940, 19941, 20002, 21303, 21316, 

21768, 22440, 22528 and probably at 20000, 21306, 22439. 

Tuxedni Formation in the Talkeetna Mountains at Mesozoic 

loc. 8567. 

Most of the specimens of this species from the northwest side 

of Cook Inlet were obtained at or just below the middle of the 

Fitz Creek Siltstone and from 300 to 550 ft above its base. The 

species, however, is represente<;l by one specimen obtained from 

50 to 150 ft below the top of the formation at Mesozoic loc. 

21768 and is probably .represented by two fragments obtained 

300 ft below the top at Mesozoic loc. 20000. 

Genus STEPHANOCERAS Waagen, 1869 

Stephanoceras obesum Imlay, n. sp. 

Plate 18, figures 5-11 .. 

Five specimens of this species are available. The 

shell is an evolute serpenticone. The whorls are 

depressed, much wider than high. The innermost 

whor-ls embrace each other about half. The outermost 

septate whorl embraces the preceding whorl about 

a third. The complete aperture is unknown, but one 

frag1nent shows that it was terminated by a collar. 

The primary ribs are sharp, prominent, fairly widely 

spaced, incline forward slightly on the flanks, and 

terminate at about two-fifths of the height of the 

flanks in acute tubercles. From each tubercle pass 

three weaker secondary r-ibs that cross the center 

transversely or with a slight backward arching. Other 

· ribs arise freely along the zone of furcation, resulting 

in about four secondary ribs for every primary rib. 

The suture line is poorly exposed and has not been 

traced. 

The holotype at an estimated diameter of 96 min has 

a whorl height of 29 mm, a whorl thickness of 39 m1n, 

and an un1bilical width of 46 nun. On the small 

paratype the same dimensions are 55, 22, 30, and 211nm, 

respectively. 

This species con1pared with Stephanoceras (Skirroceras) 

nelchinanum Imlay, n. sp. has a 1nuch stouter form, a 

1nore depressed whorl section, stronger, sparser primary 
B46 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

ribs, and is more involute. S. kreter (Buckman) (1927, 

pl. 755) is more evolute, has a higher whorl section, 

and much coarser secondary ribs. S. brodiaei (J. de C. 

Sowerby) (1823, p. 383, pl. 351; Buckman, 1908, pl. 5, 

fig. 1; pl. 7, fig. 3; Fallot and Blanchet, 1923, pl. 13, 

figs 2a-c) differs mainly by having a higher whorl 

section and somewhat stronger sparser secondary ribs. 

Types: Holotype USNM 131413; paratypes USNM 131414, 

131415. 

Occurrence: Lower part of the Tuxedni Formation in the 

Talkeetna Mountains at USGS Mesozoic loc. 24113. 

Stephanoceras cf. S. nodosum (Quenstedt) 

Plate 16, figures 7, 8 

This species is represented by one large specimen and 

by one fragment of a body whorl. The shell is compressed and evolute. The inner septate whorls embrace 

the preceding whorls about half. At diameters greater 

than 65 mm the umbilical seam rises higher on the 

flanks resulting in an overlap of about a third by the 

body whorl. The whorls are ovate in section, slightly 

wider than high. The flanks, venter, and umbilical 

wall round evenly into each other. The umbilicus is 

fairly wide and shallow, and the umbilical wall is 

steeply inclined. The body chamber is incomplete, 

is represented by about five-sixths of a whorl, and the 

imprint of the umbilical seam indicates that the body 

chamber occupied about 1~ whorls. 

The outermost septate whorl has 19 primary ribs. 

The succeeding body whorl has about 21 primary ribs. 

These are moderately strong, nearly radial, and terminate at about two-fifths of the height of the flanks 

in prominent round tubercles. From each tubercle 

on the penultimate whorl pass three weaker secondary 

ribs that incline forward on the flanks and then cross 

the venter transversely. Other ribs arise freely along 

the zone of tubercles resulting in about four secondary 

ribs for each primary. On the body chamber the 

secondary ribs become sparser adorally and on the part 

nearest the aperture number three for each primary rib. 

The suture line cannot be traced accurately. 

The illustrated specimen at the beginning of the body 

chamber has a diameter of 87 mm, a whorl height of 

29 mm, a whorl thickness of 35 mm, and an umbilical 

width of 54 mm. 

The Alaskan specimen is very similar· to S. nodosum 

(Quenstedt) (1858, pl. 54, fig. 4; 1887, p. 532, pl. 65, 

fig. 17; Weisert, 1932, p. 136-138, pl. 15, figs. 1, 2) in 

involution, whorl shape, and ornamentation. It may 

have sparser secondary ribbing, but the resemblances 

are striking. 

Figured specimen: USNM 131416. 

Occurrence: Red Glacier Formation at USGS Mesozoic loc. 

21269. 

Subgenus SKIRROCERAS Marcke, 1907 

Stephanoceras (Skirroceras) nelchinanum Imlay, n. sp. 

Plate 15, figures 1, 3, 4-6; plate 16, figure 2 

This species is represented by 13 specimens of which 

6 show the adult body whorl. The shell is an evolute 

serpenticone. The whorls are ovate depressed, wider 

than high. The inner whorls embrace each other 

nearly half but at diameters greater than 50 mm the 

whorls gradually uncoil, and the adult body whorl 

embraces only a fourth of the preceding whorl. The 

body chamber occupies about 1Ya whorls. The aperture on the internal mold is marked by a forwardly 

inclined constriction that is followed by a collar that 

is flared on the lower part of the flanks. 

The holotype at a diameter of 83 mm has 28 primary 

ribs and 95 secondary ribs. The large paratype at a 

diameter of about 170 mm has 43 primary ribs and 

133 secondary ribs. The primary ribs on the septate 

whorls are sharp, fairly prominent, incline slightly 

forward, and terminate at about two-fifths of the height 

of the flanks in small acute tubercles. From the 

tubercles pass two or three much weaker secondary 

ribs that incline forward on the flank and then cross 

the venter transversely or with a slight backward 

arching. Other ribs arise freely along the zone of 

furcation. On the septate whorls there are about 

3~ secondary ribs for each primary rib. On the adult 

whorl the ratio is about three to one. On the adult 

body whorl the ribs weaken somewhat toward the 

aperture and the tubercles on the internal mold become 

inconspicuous. 

The suture line is characterized by its first lateral 

lobe being slender, trifid, and appreciably longer than 

the ventral lobe. 

The holotype at a diameter of 83 mm has a whorl 

height of 26 mm, a whorl thickness of 33 mm, and an 

umbilical width of 38 mm. On the large paratype at 

a diameter of 170 mm the same dimensions are 38, 

43, and 104 mm, respectively. 

Compared with the European species of Stephanoceras 

(Skirroceras), such as S. macrum (Quenstedt) (1886, 

pl. 65, fig. 11; Buckman, 1921, pl. 248), this species 

is distinguished by having fewer whorls and weaker 

ornamentation on its adult body whorl. 

It differs from S. (Skirroceras) kirschneri Imlay, 

n. sp. by its depressed whorl section, slower rate of 

uncoiling, stronger ribbing on its inner whorls, weaker 

ribbing in its outer whorls, and by its tubercles being 

higher on the flanks. Its inner whorls have denser 

primary ribs than those of S. humphriesianum (J. de C. 

Sower by) (1825, pl. 500, fig. 1; Buckman, 1921, pl. 238; 

Weisert, 1932, pl. 17, fig. 5), and its outer body whorl 

has much weaker ribbing. 
.. 

MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B47 

Types: Holotype USNM 131417; paratypes USNM 131418, 

131419. 

Occurrences: Lower part of Tuxedni Formation in Talkeetna 

Mountains at USGS Mesozoic locs. 8585, 24113, and 24120. 

Stephanoceras (Skirroceras) cf. S. nelchinanum Imlay, n. sp. 

Plate 15, figure 2 

Ten specimens from USGS Mesozoic locality 24113 

and single specimens fron1 Mesozoic localities 24120 

and 24220 in the Talkeetna Mountains differ from the 

typical forn1s of S. nelchinanum Imlay, n. sp. by having 

s01newhat stronger more widely spaced primary ribs 

that ren1ain fairly strong on the adult body whorl. 

l\1ost of the specirnens are crushed or are poorly preserved. They n1ay represent a distinct species or may 

be a coarsely ribbed variant of S. nelchinanum. 

Figt,red specimens: USNM 131420. 

Stephanoceras (Skirroceras) kirschneri Imlay, n. sp. 

Plate 18, figures 1-4; plate 19 

This species is represented by 20 specimens of which 

n1ost have been crushed laterally. The shell is rnoderately compressed. The whorls are wider than high 

at diameters less than 45 nun but at larger diameters 

becorne somewhat higher than wide. The coiling is 

serpenticonic in the middle and adult growth stages. 

At diameters less than about 45 rom, the whorls embrace 

each other about two-thirds and the lateral tubercles 

are barely exposed below the umbilical seam. The 

coiling then becomes n1uch rnore evolute and after one 

volution, at a diameter of about 80 rom, the umbilical 

sean1 rises to about two-thirds of the height of the flanks. 

During further growth uncoiling continues but at a 

slower rate, and on the large adult whorl of the holotype 

the umbilical seam is about four-fifths of the height of 

the flanks. The body chamber on the holotype and on 

another equally large specimen occupies nearly 1~ 

whorls. The aperature bears a prominent collar. 

At a diameter of 79 mm the paratype shown on plate 

19, figures 3-5, has 27 prin1ary ribs and 112 secondary 

ribs. The primary ribs are fairly sharp, curve forward slightly, and pass into conical tubercles at about 

a third of the height of the flanks. From these tubercles pass three or rarely four weaker secondary ribs 

that incline forward slightly on the flanks but cross 

the venter transversely. Other secondary ribs arise 

freely on the flanks at or above the zone of tubercles. 

On the same paratype within one volution the number 

of secondary ribs diminishes to about three for each 

primary rib. Likewise on the much larger holotype the 

outer two whorls bear nearly three secondary ribs for 

each primary. Otherwise the changes during growth 

are very slight. The conical tubercles and secondary 

ribs gradually hecome stronger. The primary ribs 

gradually become lower and broader. Near the aperture 

the lower half of the flank becomes smooth, and the 

upper half bears several weak secondary ribs. 

The holotype is too crushed for accurate measurements. An equally large paratype (pl. 18, ·fig. 4) about 

half a whorl from the aperture has a diameter of 285 

mrn, a whorl height of 69 min, a whorl thickness of 

58 rom, and an umbilical width of 210 rom. On the 

smaller paratype at a diameter of about 45 n1m, the 

same dimensions are 16.5 m1n, 20.5 mm, and 16 rom, 

respectively. At a diameter of 79 n1n1 the same dimensions are 27, 28, and 33 mn1, respectively. At a 

diameter of 110 mm the san1e dimensions are 38, 36, 

and 70 rom, respectively. These measurements show 

that the umbilicus becomes wider and the whorl section 

higher during growth. 

The suture .line, partly exposed at the end of the last 

septate whorl of the largest paratype, shows broad 

deeply dissected saddles and a long narrow first lateral 

lobe. 

This species greatly resembles Stephanoceras (Skirroceras) macrum (Quenstedt) (1887, pl. 65, fig. 11; 

Bucklnan, 1921, pl. 248; Weisert, 1932, pl. 15, fig. 3) in 

ribbing and coiling but has a 1nuch higher whorl section 

in the adult growth stages. 

The species is named for C. E. Kirschner who made 

n1any excellent collections of fossils in the Cook Inlet 

region. 

Types: Holotype USNM 131421; paratype USNM 131422-

131424. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 2999, 

20756, 21274 and 26599; Red Glacier Formation at Mesozoic 

locs. 3013, 20017, 21264, 21267 and 21268. The specimens at 

Mesozoic locs. 2999, 20756 and 20017 are labeled float. The 

collections at Mesozoic locs. 21274 and 26599 contain single 

weathered specimens of Stephanoceras that may represent float. 

The only collections that were definitely obtained in place are 

from the upper 250 ft of the Red Glacier Formation. 

Stephanoceras (Skirroceras) juhlei Imlay, n. sp. 

Plate 16, figure 1, 3-6; plate 17 

The species is represented by three specimens of 

which the holotype has been crushed laterally. The 

shell is a highly evolute serpenticone. The whorls are 

ovate depressed and n1uch wider than high. The inner 

whorls embrace each other nearly a third but during 

growth gradually uncoil, and the ,adult body whorl 

embraces only about a si.xth of the preceding whorl. 

The body chamber occupies about 1% whorls. The 

aperture on the internal mold is 1narked by a shallow 

constriction that is followed by a low collar. 

One small septate speci1nen, shown on plate 16, 

figures 1, 6, at a dia1neter of 93 mrn, has 37 primary 

ribs and about 140 secondary ribs. The primary ribs 

are sharp, fairly low, incline forward on the flanks, and 

terminate in acute tubercles at about two-fifths of the 
B48 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

height of the flanks. From the tubercles pass two or 

three weaker secondary ribs that cross the venter 

transversely or in places arch forward. Other ribs 

arise freely along the zone of furcation resulting in four 

secondary ribs for each primary rib. 

On the holotype the inner whorls are not well preserved but they bear the sarne sharp dense ribbing as 

on the specimen just described. During growth the 

zone of tuberculation gradually becomes lower on the 

flanks and the secondary ribs become sparser. On the 

adult body whorl the ratio of secondary to primary 

ribs is about 2~-1. 

The suture line has ·a narrow first lateral lobe that is 

slightly longer than the ventral lobe. The saddles are 

broad. The second lateral lobe is much shorter than 

the first. The auxiliary lobes incline steeply to the 

umbilical seam . 

The paratype. at a diameter of 93 111m has a whorl 

height of 25 mm, a whorl thickness of 32 mm, and an 

umbilical width of 50 mm. 

This species differs from S. (Skirroceras) nelchinanum 

Imlay, n. sp. in its more evolute coiling, more depressed 

whorl section, and finer denser ribbing. It differs frOln 

S. (Skirroceras) kirschneri Imlay, n. sp. by having 

somewhat finer ribbing, smaller tubercles that are lower 

on the flanks, more slowly enlarging whorls, and a n1uch 

lower whorl section. The fineness of its ribbing compa.res with that of S. rhytus (Buckman) (1921, pl. 250 

a, b), but it has longer primary ribs on its septate 

whorls. The rather weak ribs and tubercles on its 

body chamber suggests comparisons with S. (Skirrocera.s) baylei (Oppel) (d'Orbigny, 1846, pl. 133; Fallot 

and Blanchet, 1923, pl. 5, figs. 1-3) rather than with 

S. (Skirroceras) macrum (Qlienstedt): · (1887, pl. 65, fig. 

11; Buckman, 1921, pl. 248). ·· .. · · 

The species is named in honor of.Werner Juhle, geologist of the U.S. Geological Survey,' who collected the 

holotype specimen. 

Types: Holotype USNM 131425; paratypes USNM 131426, 

131427. 

Occurrences: Tuxedni Formation in the Talkeetna Mountains 

at USGS Mesozoic locs. 24113 and 24120; Red Glacier Formation at Mesozoic loc. 24333. 

Genus STEMMATOCERAS Mascke, 1901 

Stemmatoceras n. sp. undet. 

Plate 20, figures 1-4 

The species is represented by two specimens. The 

shell is moderately stout, has evolute coiling and 

becomes more evolute during growth. The whorls are 

quadrate in section, thickest above the middle, n1uch 

wider than high but become less depressed adorally on 

the body chamber. The umbilicus is inoderately wide 

and rather shallow. T4e flanks diverge outward from 

the umbilical seam and round fairly abruptly into the 

broadly rounded venter. The body chamber is incomplete but is represented by at least half a whorl. The 

aperture is unknown. 

The primary ribs are strong, widely spaced, and 

nearly radial or inclined slightly forward. On the 

septate whorls they terminate near the n1iddle of the 

flanks in acute tubercles. On the body whorl they 

terminate at about two-fifths of the height of the flanks 

in prominent tubercles. FrOln the tubercles pass three 

or four rather weak secondary ribs that cross the venter 

transversely. Other ribs arise freely along the zone 

of tuberculation, resulting in nearly five secondary ribs 

for each primary rib. 

The suture line is not preserved. The largest specimen at an estin1ated diameter of 122 n1m has a whorl 

height of 24 mm, a whorl thickness of 40 Jnm not 

counting the tubercles, and an mnbilical width of 69 

mn1. 

The species is characterized by its strong widely 

spaced prin1ary ribs, its prominent ti~bercles high on 

the flanks, and its rather weak secondary ribs. The 

sparse coarse ribbing on its flanks is similar to that on 

some species of Teloceras, such as T. multinodum 

(Quenstedt) as figured by Weisert (1932, pl. 19, fig. 2), 

but its whorl section is narrower, and its umbilicus 

wider and shallower than in Teloceras. 

Figured specimens: USNM 131428; USNM 131429. 

Occurrences: Red Glacier Formation at Uf?GS Mesozoic locs. 

21263 and 21296. Small specimens possibly representing this 

species occur at Mesozoic locs. 19966 and 21295 in the Red 

Glacier Formation. 

Stemmatoceras cf. S. palliseri (M~Learn) 

Plate 20, figures 5, 6; plate 21, fig~res 2, 4 

This species is represented by one adult specimen. 

The shell is a very stoiit serpenticope. The whorls 

are ovate and depressed. The septate·_ whorls are more 

than twice as wide as high, but durin'g growth gradually become less wide. The adult bq:dy whorl is less 

than twice as wide as it is high and becomes progressively higher toward the aperture ·:owing to whorl 

contraction. The septate whorls em'Qrace the preceding whorls about half. The body' whorl becomes 

progressively more evolute and ne~r the aperture 

embraces the penultimate whorl abo1:rt a third. On 

the inner septate whorls the flanks ar~ strongly divergent to near the middle of the whorl anfl then round abruptly into a broad gently arched venter:, During growth 

both flanks and venter become evenlY, rounded. The 

umbilicus is moderately wide and wide4s during growth 

in proportion to the diameter. The:.· body chamber 

occupies a little more than one compl~te whorl. The 

aperture terminates simply. 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET . REGION B49 

The outermost septate whorl has 24 primary ribs 

and about 115 secondary ribs, or nearly 5 secondaries 

for each pri1nary. The next smaller septate whorl 

has 20 primary ribs and fron1 4 to 5 secondaries for 

each primary. The body whorl is incomplete but is 

estimated to have had 27 primaries. At the beginning 

of the body whorl there are four secondaries for each 

primary. Near the aperture there are only three 

secondaries for each primary. 

The primary ribs on the septate whorls are fairly 

prorninent, nearly radial, and terminate in prominent 

tubercles near the middle of the flanks. Front these 

pass three or four n1uch weaker secondary ribs that 

arch forward gently on the venter. The pri1nary 

ribs and tubercles on the body whorl remain strong for 

three-fourths of a whorl and then weaken considerably 

near the aperture. The secondary ribs on the body 

whorl become considerably stronger and n1ore widely 

spaced adorally and near the aperture are nearly as 

strong as the primary ribs. 

The suture line cannot be traced accurately. 

The dimensions in millimeters and ratios of the 

diameter (in parentheses) are as follows: 

Diameter Whorl height Whorl thickness Umbilical width 

- -

91 26(0. 28) 48(0. 52) 41(0. 45) 

130 ~3(0. 25) 55(0. 42) 67(0. 51) 

160 .5(0. 28) 58(0. 36) 87(0. 54) 

This species resembles Stemmatoceras albertense MeLearn (1928, p. 2,0, pis. 5-7; Warren, 1947, p. 67, pl. 5, 

fig. 1; Frebold, 1957a, p. 50, pl. 21, figs. 2a, b; pl. 23, 

figs. la-c) in whorl shape, coiling, and density of 

secondary ribs." It differs by having considerably 

fewer ribs at a coinparable diameter and much stronger 

tubercles. It differs fron1 S. palliseri (l\tfcLearn) 

(1932b, p. 114, Pt'. 2; pl. 5, fig. 1.; Warren, 1947, p. 68, 

pl. 3, fig. 1) by having a n1uch broader whorl section. 

Its inner whorls. at diameters less than 90 nun are 

similar to the 'inner whorls of Teloceras dowlingi 

McLearn (1932b,· p. 112, pl. 1; pl. 5, figs. 2, 3), but its 

larger whorls are n1uch less arched. S. coronatum 

(Quenstedt) 1887·; pl. 66, fig; 11; Weisert, 1932, p. 159, 

pl. 18, figs. 1, 4) a't a comparable size has a higher whorl 

section, fewer sqcondary ribs, and weaker tubercles. 

Figured sper.imen:' USNM 131430. . . 

Occ1trrence: Fitz Qreek Siltstone at USGS Mesozoic loc. 21270. 

Stemm'a.toceras ursinum Imlay, n. sp. 

Plate 22, figures 1-3 

T'he species is represented by four specimens of which 

all are crushed SQinewhat laterally. The sectional view 

illustrated was d;i'awn fr01n near the adoral end of the· 

largest septate whorl where the shell appears to be only 

slightly deformed. The shell 'is a moderately stout 

serpenticone .. The whorls are ovate depressed and 

become higher during growth. The septate whorls 

embrace each other nearly half. The body whorl gradually con tracts fr01n the remainder of the shell and near 

the aperture embraces only about a third of the penultin1ate 

whorl. As a consequence the umbilicus widens during 

growth. The flanks round evenly into the venter and 

into the umbilical wall. The body chamber occupies 

a little more than one complete whorl. The aperture 

on the internal mold is slightly flared on the upper part 

of the flanks and rather strongly flared on the lower 

third. 

On the septate whorls the primary ribs are only 

moderate in strength, are nearly radial or are curved 

slightly forward, and terminate slightly below the nliddle of the flanks in pronounced tubercles. From these 

pass three or four slightly weaker secondary ribs that 

arch forward on the venter. Other ribs arise by intercalation, along the zone of tuberculation. The penultimate whorl has 19 primary ribs and about 95 

secondary ribs. 

Adorally on the adult body whorl the primary ribs 

become broader, lower, and finally indistinct, the 

secondary ribs· become sparser and much stronger, 

and the tubercles remain strong to near the aperture 

where the last two weaken somewhat. This whorl 

has 23 primary ribs and about 90 secondary ribs. 

Accurate measurements cannot be made because 

the specimens are crushed. 

The suture line has broad deeply dissected saddles. 

The first lateral 'lobe is narrow, trifid and a little longer 

than the ventral"lobe. · ·The first auxiliary lobe is long 

and obliquely inclined. · 

This species shows considerable resemblance to S. 

cf. S. palliseri (McLearn), described herein, but has a 

higher whorl section, weaker and fewer primary ribs 

on its outer two whorls, and sparser secondary ribs 

that become much stronger adorally on the adult body 

whorl. It resembles S. palliseri McLearn (1932b, p. 

114, pl. 2; pl. 5, fig. 1; Warren, 1947, p. 68, pl. 3, ~g. 1) 

in whorl shape and coiling, but its body whorl has fewer 

primary ribs and much stronger tubercles. 

Type: Holotype USNM 131431. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

21281 and 22705. 

Stemmatoceras cf. S. triptolemus (Morris and Lycett) 

Plate 21, figures 1, 3 

The figured specimen is crushed laterally, but allowing 

for crushing its form n1ust have been very stout. An inner 

whorl at a diameter of about 40 mm has a whorl thickness of 21 nun and a whorl height of 11 111m. · The 
B50 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

outer whorls were probably nearly as broad. The 

whorl section on. the inner whorls is ovate depressed, 

but during growth both flanks and venter become less 

convex. The inner whorls embrace the preceding 

whorls about half·but during growth the coiling become 

more evolute and the outermost whorl embraces only 

a third of the preceding whorl. The umbilicus is 

moderately wide and becomes wider during growth. 

The body chamber is incompletely preserved but is 

represented by at least half a whorl. The aperture 

terminates simply. 

The primary ribs are prominent, moderately spaced, 

radial or inclined slightly backward, and terminate 

near the middle of the flanks in acute tubercles. From 

the tubercles on the penultimate whorl pass three or 

less commonly two weaker secondary ribs. In addition 

a few secondary ribs arise freely along the zone of 

tubercles resulting in nearly four secondary ribs for 

each primary. On the adult body whorl secondary 

ribs become less common but coarser relative to the 

primary ribs and number about three per primary. 

The secondary ribs cross the venter with a slight forward 

arching. Both ribs and tubercles persist to very near 

the aperture. 

The ventral lobe is not preserved. The saddles are 

fairly broad and descend regularly to the umbilical seam. 

The first auxiliary lobe is inclined obliquely. 

This species compared with S. albertense McLearn 

(1928, p. 20, pls. 7-8) is more evolute and has much 

stronger and ·sparser ribbing; compared with S. 

coronatum (Quenstedt, 1887, pl. 66, fig. 11; Weisert, 

1932, pl. 18, figs. 1, 4), it is more evolute and has 

sparser. secondary ribs. It shows even greater resemblance to S. triptolemus (Morris and Lycett) (1851, 

p. 111, pl. 14, fig. 1; Arkell, 1954, p. 582, 583) but has 

sparser primary ribs. The coarseness of its ribbing 

is similar to that on species of Teloceras, such as T. 

acuticostatum Weisert (1932, p. 180, pl. 19, fig. 3), 

but it appears to have a more shallow umbilicus than 

any species of Teloceras. 

Figured specimen: USNM 131432. 

Occurrence: Red Glacier Formation at USGS Mesozoic loc. 

21261. 

Genus TELOCERAS Mascke, 1907 

Teloceras itinsae McLearn 

Plate 23, figures 9, 10; plate 24, figures 1-5, 7 

Teloceras· itinsae McLearn, 1932a, Royal So(}. Canada Trans., 3d 

ser., v. 26, sec. 4, p. 51, pl. 10, figs. 1, 2. 

The holotype of Teloceras itinsae McLearn from the 

Queen Charlotte Islands is an immature specimen of a 

species that is represented by 28 specimens in the 

middle Bajocian beds of the Cook Inlet region. 

The septate whorls are much wider than high and 

embrace nearly· half of the preceding whorls. The 

adult body whorl gradually becomes higher adorally 

and near the aperture is nearly as high as wide. This 

change is accompanied by contraction of the body 

chamber. which near the aperture embraces the preceding whorl only about a third. The body chamber 

occupies slightly more than one complete whorl. The 

aperture terminates abruptly and simply. 

On the septate inner whorls the primary ribs are 

nearly radial, moderately stout, widely spaced, and 

terminate in pronounced conical tubercles. From these 

pass two or three somewhat weaker secondary ribs that 

arch gently forward on the venter. Between successive 

bundles of secondary ribs are intercalated one or rarely 

two ribs that arise above the zone of tuberculation. 

On the adult body whorl the primary ribs gradually 

become lower and broader; the secondary ribs gradually 

become stronger and more arched; and the tubercles 

become stronger, more widely spaced, and arise somewhat higher on the flanks. This condition persists to 

near the aperture where the last tubercle is slightly 

weaker than the preceding tubercles. The shell bordering the apertural margin is marked only by growth 

striae. 

The holotype at a diameter of about 71 mm has 19 

primary ribs and 63 secondary ribs. The plesiotype 

shown on plate 24, figures 1, 2, at a diameter of 123 mm 

has 15 primary ribs and 57 secondary ribs. The 

complete adult plesiotype shown on plate 2?, figure 9, 

at a diameter of 163 mm has 18 primary ribs and 66 

secondary ribs. The similar adult specimen shown on 

plate 23, figure 10, has 19 primary ribs and 65 secondary 

ribs. This indicates that there are 3.3-3.8 secondary 

ribs for each primary rib. 

The suture line is not well exposed on any of the 

specimens. 

The holotype at a diameter of 68 mm has a whorl 

height of 24 mm, a whorl thickness of 36 mm, and an 

umbilical width of 32 mm. On the plesiotype shown 

on plate 24, figures 5, 7, the same dimensions measured 

at the beginning of the body chamber are 106, 41, 60, 

and 41 mm, respectively. On the plesiotype shown on 

plate 23, figure 10, these dimensions measured near the 

adoral end of the body chamber are 163, 45, 51, and 

82 mm, respectively. 

Teloceras itinsae McLearn was compared by McLearn 

(1932a, p. 52) with T. multinodum (Quenstedt) (1887, 

p. 545, pl. 67, fig. 2; Weisert, 1932, p. 175, pl. i9, fig. 2), 

but it has fewer and much weaker primary ribs, and its 

adult body whorl becomes higher and more evolute. 

It shows more resemblance to T. sparsinodum (Quenstedt) as figured by Weisert (1932, p. 177, pl. 19, fig. 1) 

but differs by having weaker primary ribs, somewhat 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B51 

stronger secondary ribs, and a more evolute body 

charnber. 

Types: Holotype Canada Natl. Mus. 6481; plesiotypes USNM 

131433-131436 

Occurrences: Fitz Creek Siltstone at. USGS Mesozoic locs. 2998, 

2999, 3000, 19973, 19975, 21270, 21275, 21305, 27107, 27109, 

27110. 

Teloceras itinsae McLearn near Tuxedni Bay has been found· 

from 75 to 150 ft below the top of the Fitz Creek Siltstone 

which is about 650 ft thick. In the Iniskin Peninsula it has 

been found from 200 to 650 ft above the base of the Fitz Creek 

Siltstone which ranges in thickness from 1,100 to nearly 1,300 ft. 

Genus ZEMISTEPHANUS McLearn, 1927 

Zemistephanus richardsoni (Whiteaves) 

Plate 25, figures 6, 7; plate 26, figures 1-7 

Ammonites richardsoni Whiteaves, 1876. Canada Geol. Survey, 

Mesozoic Fossils, v. 1, pt. 1, p. 32, 33, pl. 5, figs. 1, 2. 

Zemistephanus richardsoni (Whiteaves). McLearn, 1929, Canada Natl. Mus. Bull., no. 54, p. 19, pl. 9, figs. 1, 2; pl. 10, 

fig. 2. 

Arkell, 1954, Royal Soc. London Philos. Trans., ser. B, 

Biol. Sci., no. 651, v. 237, p. 587, text fig. 10. 

This species is abundant in the Cook Inlet region, 

being represented in the Geological Survey collections 

by 95 specirnens. These show all stages of growth 

and amount of variation within the species. 

The .shell is an evolute cadicone. The whorls are 

coronate and much wider than they are high but vary 

appreciably in these dimensions. On the septate 

whorls the ratio of the height to the width of the whorl 

ranges frOin 35 to 45 percent. On the adult body 

whorl the ratio of height to width increases toward the 

aperture as a result of contraction of the body chamber, 

and at the aperture may be from 60 to 80 percent. 

The umbilicus is wide and craterlike and enlarges 

considerably on the adult body whorl. The body 

cham her occupies about lYs whorls. The aperture 

terminates simply. On the internal molds the aperture 

is preceded by a weak constriction but such is not 

apparent where the shell is preserved. 

The inner septate whorls bear narrow weak radial 

widely spaced primary ribs that terminate in conical 

tubercles at the edge of the umbilicus. From the 

tubercles pass three or four secondary ribs that arch 

forward gently on the venter. In addition one or two 

secondary ribs arise freely between the branched ribs 

above the zone of furcation. All secondary ribs are 

round, become broader ventrally, and on the venter are 

as broad as the in terspaces. They vary somewhat in 

coarseness and in spacing fron1 one specimen to another. 

During growth the primary ribs gradually become 

broader and less conspicuous; the tubercles gradually 

become stouter except for the last tubercles preceding 

the adult aperture; and the secondary ribs gradually 

become broader and more widely spaced except where 

they are replaced locally by small riblets and striations 

at diameters ranging frorn 50 to 100 mrn. Such 

riblets and striations in places are superimposerl on the 

much larger secondary ribs as well as the interspaces 

but in other places may replace the secondary ribs 

entirely. They may replace the secondary ribs for as 

little as a fourth of a whorl or as much as 1~ whorls 

and may dominate over the normal secondary ribs on 

part of the adult body whorl. 

The adoral .%-% of the adult body chamber is 

characterized by a rejuvenation of broad secondary 

ribs averaging about three per tubercle. These ribs 

where the shell is preserved are overlain by striae and 

riblets. 

The suture line is characterized by its first lateral 

saddle being broad and deep and much larger than the 

second lateral saddle. The first lateral lobe is irregularly trifid and as long as the ventral lobe. The 

second lateral lobe is short, wide, and trifid. The 

auxiliaries descend regularly to near the un1bilical 

seam. The suspensive lobe is highly retracted. 

The dimensions in millin1eters and ratios of the diameters (in parentheses) are as follows: 

Specimen Diameter Whorl Whorl Umbilical 

height thickness width 

Plesiotype (pl. 26, figs. 3, 5)_ 54 14 (0. 26) 36 (0. 66) 20.5 (0. 38) 

Do ________ ------------- 81 18.5 (0. 23) 53 (0. 65) 31 ~0. 38) Plesiotype (pl. 26, fig. 1) ___ 71 19 (0. 27) 42 (0. 59) 23 0. 32) 

Pleslotype (pl. 26, fig. 2) ____ 94 25 (0. 26) 58 (0. 61) 31.5 ~0. 33) 

Pleslotype (pl. 26, figs. 6, 7)_ 118 26 (0. 22) 72.5 (0. 61) 46 o. 39) 

Pleslotype (pl. 25, fig. 7) ___ 128 28 (0. 22) 65 (0. 51) 51 (0. 40) 

Plesiotype (pl. 25, fig. 6) ___ 148 42 (0. 28) 54 (0. 36) 73 (0. 49) 

This species shows considerable variation in width of 

whorls, in coarseness and density of ribbing, and in the 

first appearance and e~tent of the fine riblets that 

replace the regular secondary ribs. These features 

show no correlation with each other. The most 

finely ribbed variant of Z. richardsoni (Whiteaves) 

has six secondary ribs per tubercle which is fewer than 

is reported to occur on Z.junteri McLearn (1929, p. 20, 

pl. 10, fig. 1). 

Types: Holotype Canada Natl. Mus. 5013; plesiotype Canada 

Natl. Mus. 9006; plesiotypes USNM 131437-131443. 

Occv.rrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

2998, 2999, 3000, 10245, 10515, 10520, 19978, 19997, 20020, 

20756, 21270, 21271, 21274, 21304, 21305, 21772, 22533, 26598, 

26599, 27108. Specimens probably belonging to this species 

occur in the Fitz Creek Siltstone Mesozoic locs. 20021, 21302, 

21767. 

This species near Tuxedni Bay occurs in the upper fourth of 

the Fitz Creek Siltstone and ranges from 100 to 150 ft below its 

top. On the Iniskin Peninsula most of the occurrences of the 

species are well below the middle of the Fitz Creek Siltstone and 

range from 200 to 480 ft above its base. One occurrence 

(Mesozoic loc. 22533), however, is near the top of the siltstone 
B52 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

Zemistephanus carlottensis (Whiteaves) 

Plate 24, figure 6; plate 27, figures 1-3; plate 28, figures 1-3 

Ammonites carlottensis Whiteaves, 1876. Canada Geol. Survey, 

Mesozoic Fossils, v. 1, pt. 1, p. 38, pl. 6. 

Perisphinctes carlottensis (Whiteaves). Neumayr, 1885, K. 

Akad. Wiss., Math.-naturh. Cl. Denkschr., v. 50, p. 96. 

Stephanoceras? carlottense (Whiteaves). Martin, 1926, p. 142, 

149, 152. 

? Zemistephanus vancouveri McLearn. 1929, Canada N atl. Mus. 

Bull. 54, p. 20, 21, pl. 11, figs. 1, 2. 

Pseudotoites carlottense (Whiteaves). Arkell, 1954, p. 587, figs. 

11 and 12 on p. 588 and 589. 

Five specimens from the Tuxedni Group on the 

northwest side of Cook Inlet were labeled by T. W. 

Stanton as Perisphinctes cf. P. carlottensis (Whiteaves). 

These identifications were listed by Martin (1926, p. 

142, 149, 152) variously as Stephanoceras carlottensis 

(Whiteaves) and Perisphinctes cf. P. carlottensis (Whiteaves). 

The largest specimen is comparable in size with the 

holotype of A. carlottensis (Whiteaves), includes the 

complete adult body chamber and part of the penultimate septate whorl, and has been slightly compressed 

laterally. The other four specimens are much smaller, 

are crushed laterally, and are closely similar in coiling, 

tuberculation, and ribbing with the penultimate whorl 

of the largest specimen. 

In addition the sp~cies is represented in more recent 

collections by three well-preserved specimens, including 

one adult, from the Cook Inlet area. 

The shell during growth changes from stout to cadicone on the septate whorls and then to planulate 

ellipticone on the adult body chamber. The smaller 

septate whorls embrace each other about three-fifths 

and are probably nearly circular in section. During 

growth the coiling of the septate whorls become more 

involute and the whorls become much stouter. The 

adult body whorl is characterized by abrupt contraction 

and at the aperture embraces only about a fourth of 

the penultimate whorl. Accompanying this contraction the body whorl ·develops a lower rounder whorl 

section that is not much wider than it is high. The 

innermost whorls have a fairly wide umbilicus and the 

umbilical wall rounds evenly into the flanks. On the 

larger septate whorls' the umbilicus becomes relatively 

less wide, and the um-bilical wall becomes nearly vertical 

and rounds fairly abruptly into the flanks. On the 

adult body whorl the· umbilicus becomes very wide and 

the umbilical wall becomes low and gently inclined. 

The adult body chamber occupies a complete whorl. 

The aperture terminates simply. It is not constricted 

or collared. · 

The smaller septate whorls bear high widely spaced 

primary ribs that terminate in small acute tubercles at 

about two-fifths of the height of the flanks. From 

these tubercles pass pairs of weaker secondary ribs 

that incline forward slightly on the flanks. Between 

the rib pairs are one or two secondary ribs that arise 

freely along the zone of tuberculation. 

During growth the primary ribs on the septate whorls 

become stouter, the tubercles become much stronger 

and much lower on the flanks, and the secondary ribs 

become more numerous. On the penultimate whorl 

three secondary ribs arise from each tubercle. In 

addition one or two ribs arise freely on the flanks 

between successive rib bundles. All secondary ribs 

incline forward gently on the flanks but cross the 

venter nearly transversely. 

On the adult body chamber the ornamentation 

changes considerably adorally. The tubercles gradually become weaker, elongate radially, and nearly 

disappear. The secondary ribs become more prominent 

sparser, and more strongly inclined forward but weaken 

near the aperture. The number of secondary ribs 

decreases from four to five per tubercle to two per 

tubercle. 

The suture line is closely similar to that of Zemi.-

stephanus richardsoni (Whiteaves) as illustrated herein, 

differing mainly by its narrower second lateral lobe. 

The most conspicuous feature is the very broad and 

deep first lateral saddle. 

All the Alaskan specimens assigned to A. carlottensis 

Whiteaves have been crushed or distorted so much 

that measurements would have little value. Allowing 

for deformation, however, the two large adults probably 

had nearly the same relative dimensions as the holotype 

specimen (Arkell, 1954, p. 588, 589). 

The identification of certain Alaskan· specimens with 

Ammonites carlottensis (Whiteaves) from the Queen 

Charlotte Islands is based solely on comparisons of the 

adult body whorl, as the holotype specimen does not 

show the inner whorls and no other specimens of the 

species from the Queen Charlotte Islands have been 

described. The resemblances are so close, however, 

that the identification seems reasonable. 

The assignment of these specin1ens to the genus 

Zemistephanus is based on the rather marked uncoiling 

of the body chamber, the low position of the tubercles 

on the flanks of the body chamber, a tendency for the 

tubercles to weaken near the aperture of the large adult 

specin1ens, and a striking resemblance in the pattern 

of the suture line. The genus Teloceras has a coronate 

adult body chamber, its tubercles occur higher on the 

flanks and remain strong on the adult body chamber, 

and the adult body whorl contracts little or none at 

all from the preceding whorl, The genus Pseudotoites 

differs mainly by having a much narrower first lateral 

saddle (Arkell, 1954, pl. 34, figs. 3a, b, 5a, b; pl. 36, 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B53 

fig. 3c), but its inner whorls appear to have much weaker 

and denser primary ribs. 

"Ammonites" carlottensis Whiteaves was assigned by 

Arkell (1954, p. 587-589) to Pseudotoites rather than to 

Zemistephanus because its adult body whorl shows 

great resemblance to that of some Australian species 

such as P. robiginosus (Crick) (Arkell, 1954, p. 574, 

pl. 34, figs. 1-4; pl. 35). He did not know, however, 

the featw·es of the suture line of "A." carlottensis 

Whiteaves or of Z. richardsoni (Whiteaves), or that 

the adult body whorls of both species are similar in 

coiling and in the simple terminations of their apertures. 

Z. carlottensis (Whiteaves), as herein defined, differs 

from Z. 1-ichardsoni (vVbiteaves) by being much less 

coronate, by having stronger ribbing on its septate 

whorls, by not developing riblets or striae in place of 

ribs during its development, and perhaps by its narrower second lateral lobe. The septate specimens of 

Z. carlottensis (Whiteaves) appear to be identical specifically with the completely septate holotype of Z. 

vancouve1·i McLearn (1929, p. 20, pl. 11, figs. 1, 2). 

Most of the Alaskan specimens of Zemistephanus 

cm·lottensis (Whiteaves) are from the upper 150 feet of 

the Fitz Creek Siltstone and from the basal beds of the 

Cynthia Falls Sandstone on Tuxedni Bay. Theircommon associates are Teloceras itinsae McLearn,· 

Zemistephanus richardsoni (Whiteaves), Normannites 

c1-ickmayi (McLearn), N. itinsae (McLearn), and 

Ohondrocm·as dejontii (McLearn). 

The exact geographic and stratigraphic position of 

the holotype of Ammonites carlottensis Whiteaves is 

unknown although Arkell (1956, p. 542) stated that it 

is probably fron1 the lower part of the Yakoun Formation on the northwest shore of Mauqe Island. If so, 

its associates (McLearn, 1949, p. 13) would be the 

same as listed above fron1 the Fitz Creek Siltstone. On 

the basis of the u.mmonite succession in Alaska, these 

are considered to correspond with the European zone 

of Stephanoceras humpkriesianum. Their age is somewhat younger, therefore, than the Pseudotoites-bearing 

beds in Australia that Arlmll (1954, p. 559, 594) correlated with the European zone of Sonninia sowerbyi. 

Plesiotypes: USNM 131444-131447. 

Occurrences: Fitz Creek Siltstone at USGS Mesozoic locs. 

2998, 2999, 3000, 21275; Cynthia Falls Sandstone at Mesozoic 

loc. 10513. 

Arkelloceras1 sp. juv. 

Plate 28, figures 7-9 

One small septate ammonite frmn 'Vide Bay is worth 

recording because of its resemblance to Arkelloceras 

Frebold (1957b, p. 9-12, pJs. 9-13; 1960, p. 8-10, pl. 3, 

fig. 1: pl. 4: pl. 5, figs. a-c) from which it differs by the 

presence of distinct lateral tubercles. The inner 

whorls of A. mclearni Frebold (1957b, pl. 12, figs. 2d 

and 2g), however, show thickening of the ventral ends 

of the primary ribs which are sim~ar to tubercles. 

On the Alaskan specimen the outer whorl embraces 

about three-fifths of the preceding whorl. The whorl 

is subhexagonal in section and much wider than it is 

high. The primary ribs are strong, incline slightly 

forward, and terminate at about two-fifths of the 

height of the flanks in prominent acute tubercles. 

From the lateral tubercles pass pairs of fairly strong 

forwardly inclined secondary ribs that are weakest 

near the furcation points and terminate on the edge 

of a fairly broad venter in radially elongate tubercles. 

These tubercles alternate in position with tubercles on 

the opposite side of the venter and are connected 

with those tubercles in a zigzag rp.anner by ribs that 

weaken along the midventral line. The ventral 

tubercles are lower and much more elongate than the 

lateral tubercles. All tubercles become somewhat 

weaker during growth. The lateral tubercles are 

especially pro min en t in the two small inner whorls 

exposed in the umbilicus. Wherever the shell is preserved, its surface is marked by weak radial striae that 

occur on both ribs and interspaces. 

The suture line is not well preserved. The ventral 

lobe, however, ·is of about the sarrie length as the first 

lateral lobe. 

The specimen at a diameter of 15.5 mm has a whorl 

height of 4.2 mm, a whorl thickness of 9 mm, and· an 

umbilical width of 5.7 mm. 

'fhe shape and ornamentation of the Alaskan specimen 

is similar to that of immature specimens of Garantia, 

as figured by Robert Douville (1915, pl. 1, figs. 2, 

2a; pl. 2, figs. 3, 5, 5a), and it q.ould belong to that 

genus. However, it occurs in older beds than any 

known ·genus of the Parkinsoniidae, it does show 

resemblances to the immature wporls of Arkelloceras 

fron1 northern Canada, and the s~ture line suggests a 

relationship with Arkellocera.s rather than with Garantia. 

Like Arkelloceras it is associat¢d with Inoceramus 

lucifer Eichwald, which in Alaska has not been found 

above beds containing Otoites, Emileia, Parabigotites, 

and Sonninia (Papilliceras). 

Arkelloceras? sp. juv. was found with the ammonites 

Bradjordia and an immature .sonniniid, probably 

representing Witchellia, at a position about 400 feet 

below the top of the Kialagvik Formation. Eighty 

feet higher were found Parabigdtites and Bradjord1:a 

(Mesozoic loc. 21256). Directly above were found 

Otoites sp., Stephanoceras (Skirroeeras) sp., Bradjordia 

cost1:densa Imlay, n. sp., and lnol;eramus lucifer Eich-

. wald (Mesozoic loc. 21257). · 

On the basis of associated fossils the age of 

Arkelloceras? sp. juv. must correspond either to the 
B54 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

zone of Sonn1'nia sowerbyi or to the zone of Otoites 

sauzei. (See table 10.) Its stratigraphic position only 

a little below beds containing Otoites and Skirroceras 

suggests that it is probably not older than the zone of 

Otoites sauzei. This is supported by the presence of 

ammonites representing the zone of Sonninia sowerbyi 

at a lower position in the Kialagvik Formation. 

Figured specimen: USNM 132014. 

Occurrence: Kialagvik Formation, 400 ft below top, at USGS 

Mesozoic loc. 21255, on north side of Wide Bay, 4.7 miles N. 74° 

W. of west end of Hartman Island, Alaska Peninsula. 

Family PERISPHINCTIDAE Steinmann, 1890 

Genus PARABIGOTITES, Imlay, 1961 

The original description (Imlay, 1961, p. 472) 1s as 

follows: 

This genus is characterized by highly evolute coiling; by ovate 

depressed whorl sections; by high, sharp, forwardly inclined 

ribs that bifurcate above the middle of the flanks and are not 

interrupted on the venter; by the ribbing remaining strong on 

the body chamber; by the peristome terminating simply, and 

by the suspensive lobe being strongly retracted. 

It greatly resembles Bigotites Nicolesco (1918, p. 36) in shape, 

coiling, and ribbing. It differs by lacking a smooth band along 

the midventral line, by the secondary ribs merely arching forward gently on the venter instead of forming an obtuse angle, 

by its constrictions being less strongly developed, and by having 

a strongly retracted suspensive lobe. Furthermore its constrictions are not followed by segmental enlargements of the 

shell or by changes in the ribbing such as described by Nicolesco 

(1931, p. 9-12) for Bigotites. 

Parabigotites shows great resemblances, also, to Prorsisphinctes 

Buckman (1921, pl. 200; Siemeradzki, 1899, pl. 22, fig. 27) 

which Arkell (1957, L 314) consider to be a subgenus of Leptosphinctes. It differs by having sharper, higher ribbing that 

becomes stronger adorally on the adult whorls instead of weakening or fading. It appears also to be more evolute and to have 

a lower whorl section. 

The type species of Parabigotites is Parabigotites crassicostatus 

Imlay, n. sp. 

Parabigotites crassicostatus Imlay 

Plate 29, figures 1-16 

Dactylioceras sp. A. 1945, Kellum, Daviess, and Swinney, U.S. 

Geol. Survey, figs. 5A-B (not C-E). 

Parabigotites crassicostatus Imlay, 1961, Jour. Paleontology, v. 

35, no. 3, p. 472-473, pl. 64, figs. 4-10. 

The original description is as follows: 

This species is represented by about 65 specimens of various 

sizes of which most are crushed and fragmentary. The shell is 

discoidal and moderately compressed. The whorls are ovate in 

section, a little wider than high, and embrace about on~-fourth 

of the preceding whorls. The flanks and venter are evenly 

rounded. The umbilicus is wide and shallow. The umbilical 

wall is low, nearly vertical, and rounds evenly into the flanks. 

The incomplete body chamber on the holotype is represented by 

four-fifths of a whorl. The apertural margin is simple, is projected forward slightly on the venter, and is preceded by a nearly 

smooth area. 

The small and intermediate sized whorls bear prominent, 

widely spaced primary ribs that incline forward gently on the 

lower parts of the flanks and pass abruptly into weaker secondary 

ribs at about two-fifths of the height of the flanks. The ventral 

ends of the primary ribs are strongly swollen but are not distinctly tuberculate. The secondary ribs arise in pairs that 

incline forward on the flanks more strongly than the primary 

ribs. All secondary ribs arch forward gently on the venter 

which they cross without interruption. Two or three weak 

constrictions occur on each whorl. 

Adorally on the penultimate and body whorls the ribbing 

becomes increasingly coarser, the secondary ribs become nearly 

as strong as the primary ribs and the constrictions become more 

pronounced. Many of the secondary ribs are indistinctly connected with the primary ribs and some arise freely along the 

zone of furcation. All secondary ribs arch forward on the 

venter which they cross without weakening. 

The suture line, partly exposed on the holotype, is characterized by broad saddles, by the second lateral saddle being almost 

as wide and high as the first lateral saddle, and by the suspensive 

lobe being well retracted. 

The holotype has been crushed somewhat laterally, but at a 

diameter of 102 mm, has a whorl height of 28 mm, a whorl 

thickness of 32 mm, and an umbilical width of 54 mm. On 

paratype USNM 130910, the same dimensions are 83, 20, 23, 

and 46 mm respectively. 

The appearance of this species in lateral view is strikingly 

similar to that Bigotites · pulcher Nicolesco (1931, p. 21, pl. 2, 

fig. 1) from Europe, differing mainly in its somewhat higher, 

sharper, and more closely spaced ribs, and less pronounced 

constrictions. In ventral view it is readily differentiated however, by lacking a smooth midventral area and by the ribs 

arching evenly· across the venter instead of meeting at an angle 

along the midveiJ.tral line. It differs from most of the species 

of Leptosphinctes (Prorsisphinctes) (Buckman, 1921, pl. 200, 211, 

24 7; 1922, pl. 326; 1923, pl. 386, 446; 1925, pl. 544, 545) by 

having. much coarser ribbing that becomes stronger on the body 

chamber , instead of becoming weaker. However, its inner 

whorls are similar in appearance to the small specimen described 

as Phanerosphinctes phanerus Buckman (1921, pl. 211), which 

Arkell (1958, p. 168) assigqs questionably to Prorsisphinctes. 

/The ammonite· most commonly associated with Parabigotites 

is Stemmatoceras. In the Talkeetna Mountains (Mesozoic loc. 

24113) the 'associated ammonites include Otoites, Stemma toceras, 

Sonninia,, Witchellia and Lissoceras. This assemblage probably 

corresponds to the lower part of European Otoites sauzei zone. 

Types: Holotype USNM 130909; paratypes USNM 130910-

13091,6. 

Ocburrences: Kialagvik Formation at USGS Mesozoic locs. 

11349, 11352, 12402, 12404, 19773, 19796, 19800, 19811, 19824, 

19926, 21258 in the Alaska Peninsula; Fitz Creek Siltstone at 

Mesozoic locs. 3010, 19966, 22529, on the north side of Cook 

Inlet; Tuxedni Formation in the Talkeetna Mountains at 

Mesozoic locs. 24113, 27577. 

Genus LEPTOSPHINCTES Buckman, 1920 

Leptosphinctes evolutus Imlay, n. sp. 

Plate 28, figures 4-6 

The species is represented by two internal molds. 

The coiling is highly evolute. The whorls are ovate 

in section, nearly as wide as high, and embrace the 

preceding whorls about one-fifth. The flanks and 

t.: 
MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B55 

venter are evenly rounded. The umbilicus is very 

wide and shallow. The body chamber occupies about 

three-fourths of a whorl and is nearly complete. It 

is terminated by a broad forwardly inclined constriction that is followed by a broad collar. 

The ornan1entation of the septate inner whorls, 

as exposed in the un1bilicus, consists of deep, forwardly 

inclined constrictions and high, sharp, widely spaced 

pri1nary ribs that terminate in tubercles just below 

the umbilical seam. On the outermost septate whorl 

the primary ribs divide at about three-fifths of the 

height of the whorl into pairs of secondary ribs that 

arch forward strongly on the venter. The body 

chan1ber is marked by similar deep constrictions and by 

moderately strong pri1nary ribs that gradually weaken 

adorally and ventrally. The ribs incline forward 

gently on the lower three-fifths of the flanks and then 

curve forward strongly. Some pass into pairs of ribs 

high on the flanks and others remain single. All 

ribs arch forward strongly and become much weaker on 

the venter. 

The suture line cannot be traced accurately. The 

holotype, which is slightly distorted, at a dian1eter of 

91 mm has a whorl height of 25 nun, a whorl thickness 

of 24 nun and an un1bilical width of 51 mm. 

This species is differentiated by its coarse, widely 

spaced ribbing, its deep constrictions and its highly 

evolute coiling frOin any described European species of 

Leptosphinctes. 

Types: Holotype USNM 131448; paratype USNM 131449, 

131450. 

Occurrence: Tuxedni Formation in the Talkeetna Mountains 

at USGS Mesozoic loc. 8567. 

LITERATURE CITED 

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B56 JURASSIC AMMONITES FROM SOUTHERN ALASKA 

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MIDDLE BAJOCIAN AMMONITES FROM COOK INLET REGION B57 

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INDEX 

!Italic numbers indicate descriptions] 

A Page Page 

awticostatum, 1'eloceras •. __ __ ____ __ ___ _ _ _ ___ __ __ B50 colnetti, Defonticeras _____________________ -__ _ _ _ _ _ 1342 

aclnatu, Witchellia ________________ 11,15,27,28,94; pl. 6 Comparisions with other faunas________________ 18 

agnilonia, lVitchellia ______________ 18, 27, 95, 96; pis. 4, 5 con cavum, Graphoceras .. __ _ ___ __ _ _ __ _ __ __ _ _ _ _ _ _ _ 20 

Alaskan Peninsula. __ -------------------------- 18 connata, Witchellia_______________________________ 35 

albertense, Stemmatoceras ________________________ 49,50 constricta Emileia _________ 10,11,12,15,28,40,41; pl.ll 

allani, Chonclroceras_____________________________ 9, contractus, Otoites. _________________ 11, 15, 28, 40; pl. 25 

13, 14, 15, 18, 19, 27, 28, 4S, 43; pl. 12 coronatum, Stemmatoceras ____ ___________________ 49, 50 

Chondroceras (Saxitoniceras)_________________ 42 corrugata, Witchellia. _ __ __ _ __ __ _ __ __ __ __ _ _ ___ ___ 35 

Saxitonicerus ______ ______________ -------- ___ _ 42 costidensa, Bradfordia ________________ 18, 27, 89, 53; pl. 8 

alt-us, J(anastephanns___________________________ 43 costisparsum, Holcophylloceras ________________ .- 11, 

umbigmts, Inocera?mts ___________________________ 10, 18 13, 15, 18, 27, 28, SS; pl. 1 

Ammonites carlottensis.---------------------- 19, 52,53 Cranocephalites. __ ---------------- ___ __ _ _ _ __ __ __ 10 

richardsonL ________ __ ----- ____ _ _ __ ____ ____ _ 51 (Cranocephulites), Arctocephalites ____ ___________ . 10 

umplectens, E·udmetoceras_______________________ 36 crassicostatus, Parabigotites .• _ __ __ __ ___ __ __ _ __ ___ 6, 

urcijer, 1'oxamblyites. _______ ----- __ _ _ __ __ __ ____ _ 40 8, 11, 15, 18, 27, 28, 54; pi. 29 

Arctoce]Jhulites (Cranocephalites). _______ -------- 10 crickmayi Itinsaites. __ __ ______ _ __ _ _ __ __ ____ _ ____ 44 

arenutn, Sonninia (Papilliceras)_________________ 11, Kanastephanus ____________ ---------------- 43 

12, 15, 18, 28, 94; pl. 6 Normannites _____ ________________________ 11, 20,53 

Arkellocerus mclearnL__________________________ 53 (Itinsae) ___ __ __ __ ___ _ ___ __ ___ __ __ __ _ __ __ 28 

SP---------------------------------- 18, 59; pl. 28 (ltinsaites) _________________ 11, 13, 14,49; pl. 14 

Astarte. __ .--------------_______________________ 8 (Kanastephanus) ____________ ---------- 44 

cmrijer, 111ucerites. __ -------------- -~-- ____ ------ 37 Cynthia Falls Sandstone_______________________ 1, 

Australia •••• --------------- ______ -------------- S1 9, 10, 14, 23, 24, 30, 35, 38, 42, 43, 44, 53 

B D 

bnkeri, Lissoceras. _______________ 9, 14, 15, 28, 98; pl. 23 Dactylioceras sp. A------------------------------ 43,54 

Barroisiceras ..•.••••• ______ .••• ____ __ ___ __ _ __ _ __ 3 dalli, Pleuromya ________ -------------------- ___ - 8 

baylei, Stephanocerns (Skirroceras)_______________ 48 defonti, Chondroceras _________________ .9, 11, 13, 14, 15,28 

Bedford Ctmyon Formation____________________ 20 

bellu, Guhsania ••••• -------~-------------------- 32 Defod:~:~;~~s- ~~~~~~~:~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ :; 

Bigotites. ___ .••• _____________ •• --------- ___ _ _ ___ 54 maudense .. __ _ __ __ __ __ _____ _____ ___ _ _ __ __ __ _ 42 

pulcher __ •.••••• ------- _________ •• __ _ __ __ _ __ 54 (Defonticeras) defonti, Chondroceras______________ 42 

Biologic analysis ________________________ -------- s defonti, Chondroceras. ____________________ 4S, 53; pl. 12 

blackwelderi, Sonninin (Papilliceras)_____________ 34 Chondroceras (Defonticeras) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 42 

Brucljordia ••••••.••...• 2, 8, 12, 16, 17, 18, 21, 27, 39, 40, 53 Defonticeras_____ __ _ _ __ __ _ _ _ __ _ _ ____ _ __ _ _ _ _ __ 42 

caribouensis. ______________ 8, 12, 15, 27, 28, 99; pl. 5 delicatus, Otoites _______________________________ . 40 

costictensa ••.••••• _______________ 18, 27, 99, 53; pl. 8 deltafalcata, Sonninia. -- ____________________ --- 37 

incl·use •••• _______ •••••. ________ •• ___ ----- ___ 40 densus, Normannites (Itinsaites)----------------- 45 

sp ••••••••• ----••••••••.• ___ _ __ __ ___ _ __ __ __ _ 18 Dettermnnites. ___________________ -.-------------

British Columbia, ccntruJ..____________________ 19 diona, Pleydellia .. ------------------------------ 10,14 

brocchii, Emileia •• --------- _____ ------------- ___ 41, 42 Docidoceras _________________________ 10, 12, 14, 18, 20,31 

broctiaei, Ste1JIIllnoceras. ____ •• __ ••.••• ___ _____ __ _ 46 Dorsetsensia. _______ • ---------- _______ ------ ____ 21, 36 

sp __ ------ _____________ ----- __ __ __ __ ___ __ ___ 20 

c dowlingi, 1'eloceras______________________________ 49 

Cactomites •••••••• _______ __ •• ________________ .• __ 45 

California, northern •• ------- ____ •• ---------____ SO E 

southern ___________ •••••• ___________________ SO ellsi, Chondroceras. ________________________ ----- 43 

Cc17111Jlonectes •••••••••• ________ •• _____ -------- _ _ 8 Emileia ________ 2, 6,8, 10, 12, 14, 16, 17,21, 27,31,40,41,53 

Canndn, western interior_______________________ 19 brocchii. __________ ----- __________ ------ ___ -- 41, 42 

ccmcutensis, J(unustephumts______________________ 43 constricta ______________ 10, 11, 12, 15, 28, 40, 41; pl. 11 

caribouensis, Bracljorclia _______ 8, 12, 15, 27, 28, 99; pl. 5 multijida________ __ __ _ __ __ _ _ ____ __ __ __ __ __ __ _ 41 

carlottense, Pse·uclotoites ..••• _ •• ----- __ ___ ____ _ _ __ 52 subcadiconica_ _ _ _ _ ___ _ _ _ _ ____ _ _ __ __ __ __ _ _ _ __ 41 

Ste]Jhanoceras ••• __ _ _ __ _ _ _ ___ _ _ __ _ __ _ _ _ _ _ __ _ _ 52 vagabunda ____ . __________ ---- __ __ ___ ____ _ ___ 41 

carlottensis, Ammonites •• ____________________ 19, 52, 53 sp_ _ _ ____ __ ____ __ __ __ __ __ ____ _____ __ _ _______ 27 

Peris1JIIinctes ••• _ __ __ __ _ _ _ __ __ _ _ _ _ __ _ _ __ _ _ _ 52 Ermoceras .. ____________________________ ----- __ _ 3 

Zemistephmms ••.. 13, 14, 15, 28,5.e, 53; pis. 24, 27,28 Erycites. _____ ------------------ 6, 8, 10, 12, 16, 17, 18,30 

Cat·ullocerczs ••••• ________ .. ___ ___ ____ _ _ _ _ _ _ _ _ _ _ _ _ 20 howellL _________________________________ 10, 14,31 

celans, Witclzellia. __ __ __ ___ ___ _ __ __ _ _ _ __ __ _ _ __ __ 36 sp _________ -------- ___________________ ------ 6 

Chlnitn!\ :Formation ••••.. -------- __ ---------·__ 10 espinazitensis, Sonninia _________________________ 27,34 

Chonctroceras ___________________________________ 2, 9, 10, Sonninin (Papilliceras)_____________________ 94 

12, 13, 14, IG, 17, 18, 19, 20, 21, 27, 37, 42 eudisianum, Lytoceras _______________ 11, 12, 15, 27, 28, SS 

allcmi. _____ •.• 9, 13, 14, 15, 18, 19, 27, 28, 4S, 43: pl. 12 Eudmetoceras _______ __ ------ ________________ ---- .21, 36 

clefonti. •••..•.•..... 9, 11, 13, 14, 15, 28, 4S, 53; pl. 12 amplectens ______ _________________ ----------- 36 

ellsi. ••.• ____ •• _ •• ___________ .. ___ ___ __ _____ _ 43 Euhoploceras. __ -------------------------------- 20 

marshalli.. •••• ____ ---- _______________ 27, 49; pl. 12 evol·utus, Leptosphinctes __________________ 27,54; pl. 28 

oblatnm _______________________________ 14, 15, 28,43 

(Defonticeras) clefonti... _______________ ------ 42 F 

(Sa:l'itoniceras) allcmi..______________________ 42 falcata, Witchellia............................... 35 

SP------------------------------------ 13, 14, 15,28 Faunas, ages .• ____ •.••••••. __ ----------------· 10 

Page 

Fernie GrouP----------------------------------- B19 

filicostatus, Otoites. _____ ----------- 11, 15, 28, 40; pl. 14 

jimbriatum, Lytoceras. _. -------------- ___ ---· •• • 32 

Fissilobiceras .... -------.-----------------------. 36 

Fitz Creek Siltstone____________________________ 6, 

8, 9, 1S, 14, 18, 19, 20, 21, 23, 24, 25, 26, 

30, 31, 32, 33, 35, 37, 39, 42, 43, 44, 45, 47, 

49, 51, 53, 54. 

Fontannesia .••.•••• ------------------···· ____ •. 21 

formosus, Normannites (Itinsaites)............... 45 

funteri, Zemistephanus.......................... 51 

G 

Gaikema Sandstone. __ .------------------------- 6, 

8, 1.e, 18, 19, 21, 25, 27, 31, 32, 34, 40,41. 

Garantia ... _ ••. ___ • _ ••••••••• ___ •••• __ •.•••• --- _ 53 

Geographic distribution •• ----------··.......... S1 

glabrum, Labyrinthoceras .••.••.....•••• 27, 41; pis. 9,10 

Goniomya ...•. --------··· ----------------------- 8 

gracilis, Normannites (Itinsaites). _ --------······ 45 

Grammoceras. __ --------············------------ 20 Graphoceras concavum___________________________ 20 

Guhsania bella._------······--------------------. 32 

Gypsum Spring Formation...................... 19 

H 

hamadae, Inoceramus____________________________ 20 

Haploceratida.e. -------------------------------- 2, 38 

Harpoceras. _. ---------------------------------- 20 

Haugia. ____ •• _ •. --.. --.•.....••. --...•...• ---.. 20 

heterophyllum, Phylloceras . ••• ------------------ 31 

Holcophylloceras. _ --- --------------~---------··· 2 

costisparsum ___________ 11,13,15,18,27,28,SS; pl. I 

mediterraneum •. ------------------------.... 32 

ultramontanum. ---------------------------- 32 

SP------------------------------------ 11, 13, 27,28 

howelli, Erycites. ____ ------------------------ 10, 14, 31 

humphriesianum, Stephanoceras_________________ 12, 

13, 14, 18, 19, 20, 21, 27, 30, 37, 46,53 

incluse, Bradfordia ..... ----"·------------------- 40 

Indonesia _____ ----------------------···--------- St 

Inoceramus .••• --------------------------------- 8 

ambiguus. -------------------------------- 9, 10, 18 

hamadae. -------- ______ --------------------- 20 lucifer _______________________________ 8, 9, 10, 18,53 

Introduction .•••. ----- ___ ---------------------- 1 

Isocyrina. ___ .. --------.------------------------ 8 

Isognomon .. ------------------------------------ 8 

itinsae, Itinsaites. ___________ -------------------- 44 

Normannites _____ __________ ----------------- 53 

Normannites (Itinsae) .. --------------------- 28 

Normannites (Itinsaites) ______________ 13,44; pl. 14 

(Itinsae) crickmayi, Normannites________________ 28 

variabilis, Normannites______________________ 28 

1'eloceras ________________ 13, 15, 28, 50, 53; pls. 23,24 

Itinsaites ________ ------------······-------------. 5, 6 

crickmayi. ___________ ----------------------- 44 

itinsae. ------------------··· --------------.. 44 

crickmayi, Normannites ••••••• 11, 13, 14, 49; pl. 14 

densus, Normannites .. ---------------------- 45 

formosus, Normannites______________________ 45 

gracilis, Normannites .... -------------------- 45 

itinsae, Normannites.---------------- 13, 44; pl. 14 

variabiles, Normannites ••..•••• 13, 27, 44; pls. 13,14 

J 

juhlei, Stephanoceras (Skirroceras).------------·· 10, 

11, 27, 28, 47; pls. 16, 17 

B59 
B60 

K Page 

Kanastephanus. _____ --------------------------- B44 

altus ... ___________ -------------------------- 43 

canadensis. ______ ------- ___ ----------------- 43 

crickmayi_ __ -------------- _ ----------------- 43 

mackenziL. _______________ ----------------- 43 

(Kanastephanus) crickmayi, Normannites.------- 44 

kialagvikensis, Normannites ______ 11, 15, 18, 28, 1/J; pl. 13 

Kialagvik Formation _______________ 14, 18, 31, 36, 43,54 

kirschneri, Stephanoceras (Skirroceras)____________ 11, 

13, 21, 28, 46, 47, 48; pis. 18, 19 

kreter, Stephanoceras. --------------------------- 46 kunthi, Phylloceras ____________________ 18, 27, 81; pl. 2 

L 

Labyrinthoceras _________________ -------- 2, 17, 18, 41,42 

glabrum ___________________________ 27,41; pls. 9,10 

perexpansum. __ ---------------------------- 42 laeviuscula, Witchellia ____________________ 27, 85; pl. 7 

languidum, Strigoceras __________ 13, 15, 28, 87, 38; pl. 23 

lectotypa, Oppelia. _ ----------------------------- 39 

Leptosphinctes •. ------------------ 2, 16, 17, 18, 21, 54,55 

evolutus.----------------------------- 27, 54; pl. 28 

(Prorsisphinctes) ________ _ ------------------- 54 

Lissoceras ___________________ 2, 6, 8, 9, 12, 16, 17, 38, 39,54 

bakerL _____________________ 9, 14, 15, 28, 88; pl. 23 

semicostulatum ______________ 11, 15, 28, 88, 39; pl. 4 

SP--------------------------- 11, 12, 13, 14, 15, 27,28 

lucifer, Inoceramus ... -------------------- 8, 9, 10, 18,53 

(Lyroxyites), Oppelia.--------------------------- 16 

Lytoceras. __ ------------------------------------ 2, 8 

eudisianum .. ------------------- 11, 12, 15, 27, 28,82 

fimbriatum ______ _____ ----------------------- 32 

sp. __________ -------------------- ___________ 18, 27 

Lytoceratidae. _______ -------------------------. 2, 32 

M 

Macerites aurifer -------------------------------- 37 

mackenzii, Kanastephanus. ___ ------------------ 43 

Macrophylloceras _______________ __ -------------- 2, 8, 15 

undulatum _______ __ ------ ____ . -------------- 18 

sp. A--------------------- 11, 13, 15, 27, 28, 81; pl. 1 

sp. B.-------------------- 12, 13, 15, 27, 28,81; pl. 1 

macrum, Stephanoceras__________________________ 46 

Stephanoceras (Skirroceras).----------------- 47,48 

marshalli, Chondroceras __________________ 27,43; pl. 12 

Saxitoniceras. _ -------- __ ---------- ___ ------- 42 

Masckeites. ___ --------- ____ --------------------- 3 

maudense, De(onticeras__________________________ 42 

mclearni, Arkelloceras ____ ----------------------- 53 

mediterraneum, Holcophylloceras ___ ___ ---------- 32 

Megasphaeroceras ___________ ______________ ------ 10, 16 

Meleagrinella. ___ ------------ _ --------------- _ __ 8, 10 

Mexico, southern .•. ___ ------------------------_ 20 Mormon Sandstone_____________________________ 20 

multifida, Emileia_______________________________ 41 

multinodum, Teloceras __________________________ 48,50 

N 

Nannoceras nannomorphum_____________________ 37 

nannomorphum, Nannoceras____________________ 37 

nelchinanum, Stephanoceras____________________ 47 

Stephanoceras (Skirroceras)__________________ 27, 

45, 46, 47, 48; pis. 15, 16 

Neogastroplites ___ ______ ----- _ _ _ ___ __ _________ __ _ 3 

nodata, Sonninia __________________________ 27,83; pl. 2 

nodatipinquis, Sonninia. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 32 

nodosum, Stephanoceras _________ 11, 15, 21, 28, 46; pl. 16 

Normannites ________________________ 2, 3, 4, 5, 6, 8, 9, 10, 

12, 13, 14, 16, 17, 18, 19, 20, 21, 27, 37, 40,43 crickmayi_ _______________________________ 11, 20,53 

itinsae .. ___________________ ----------------- 53 

kialagvikensis ________________ 11, 15, 18, 28, 48; pl. 13 

rugosus .. ----- _______________________ ------- 43 

variabiliB---------------------------------- 9, 13,18 

(ltinsae) crickmayi__________________________ 28 

itinsae _____________________ -------- ____ _ 28 

variabilis __ _________________ .c __ --------- 28 

(Itinsaites) ____ ------------------------------ 43 

crickmayi_ ___ -------------- 11, 13, 14, 48; pl. 14 

densus __ ___________________ ------------- 45 

INDEX 

Page 

Normannites-Continued 

Itinsaites-Continuefl 

formosus ____ . _ -------------------------- B45 

gracilis. ______ -------------------------- 45 itinsae ___________________________ 13,44; pl. 14 

variabilis ___________________ 13, 27,44: pls. 13,14 

(Kanastephanus) crickmayi__________________ 44 

SP------------------------------------ 13, 14, 15,28 

Normahnitinae_________________________________ 3, 4 

0 

obesum, Stephanoceras.------------------- 27,45, pl. 18 

oblatum, Chondroceras _____________________ 14, 15, 28,43 

Oppelia _____ -------------------- ___ ------- __ 2, 9, 12,88 

lectotypa _________________ --------.---------- 39 

stantoni_ ______ ___ ---------- _ ---- ___ --------- 15 

subradiata. _ ----- _____ ---------------------- 38, 39 

(Lyroxyites) _________ ------------------------ 16 

( Oppelia) _____ _____ ---------- ______ ------ ___ 16, 17 

(Oppelia), Oppelia ______________________________ 16,17 

stantoni, Oppelia ___________________ 13, 28, 88, pl. 8 

Oppeliidae. __ ---------------------------------- 2, 38 

Oregon, east-centraL.-------------------------- 19 

ornati, Posidonia _________ ----------------------- 20 

Otoites .. ______ • _______ --- __ --.------------------ 2, 

5, 6,12, 16, 17, 18, 21, 27, 40, 53,54 

contractus .. -------------------- 11, 15, 28, 40; pl. 25 

delicatus. ____ ------------------------------- 40 filicostatus ______________________ 11, 15, 28, 40; pl. 14 

pauper .. ----------------------------- 27, 40; pl. 25 

sauzei. _______ 10, 11, 12, 14, 18, 19, 20, 21, 27, 31, 37,54 

s p ____________________ --- _. _. -- ______ ------. 18, 53 

Otoitidae •. -------------------------------- 2, 3, 5, 6, 40 

Oxytoma .. -------------------------------------- 10 

p 

palliseri, Stemmatoceras. __ ----- 13, 15, 48, 49; pls. 20,21 

papillatum, Sonninia (Papilliccras)______________ 34 

Papilliceras.------------------------- 6, 12, 16, 17, 20,34 

(Papilliceras), Sonninia _________ 2, 8, 1?, 15, 20, 21, 27,53 

arenata, Sonninia. _ ---------- 11, 12, 18, 28, 84; pl. 6 

blackwelderi, Sonninia_______________________ 34 

espinazitensis, Sonninia ... --------~--------- 84 

papillatum, Sonninia_______________________ 34 

Parabigotites-------------------- 2, 8, 11, 16, 21, 31, 53,54 

crassicostatus.-------- 6,8,11,15,18,27,28,54; pl. 29 

sp __ ------------------------------ __ 8, 11, 15,27, 28 

Parallelodon •. ---------------------------------- 8 

patella, Sonninia. ---------------------- 27, 83, 36; pl. 3 

pauper, Otoites.-------------------------- 27, 40; pl. 25 

Pelekodites .• ______________ ---------------------- 36,37 

pelekus ___ ---------------------------------- 37 

SP------------------------------------ 28, 36; pl. 6 

pelekus, Pelekodites. __ -------------------------- 37 

perexpansum, Labryrinthoceras------------------ 42 

Perisphinctes carlottensis. _ ---------------------- 52 

Perlsphinctidae ____ ---------------------------- 2, 54 

Phanerosphinctes phanerus---------------------- 54 

phanerus, Phanerosphinctes ..• ------------------ 54 

Pholadomya ____ -------------------------------- 8 

Phylloceras. __ ---------------------------------- 2 

heterophyllum ___ ---------------------------- 31 

kunthi. .... ------------------------ 18,27, 31; pl. 2 

Phylloceratidae ________ ------------------------- 2, 31 

Pinna •. ---------------------------------------- 8 

Plagiostoma _____ --------------------- _ ---------- 8 

Pleuromya ____________ -------------------------- 8, 10 dalli. ___________________________ -- ____ .- __ -- 8 

Pleydellia digna _________________________________ 10,14 

Polyplectites. _ --------------------------------- 5, 6, 45 

Posidonia ornati. ___ ---------------------------- 20 

Praestrigites. ____ ------------------------------- 20 projectifer, Sonninia _______________________ 27, 33; pl. 3 

propinquans, Witchellia.------------------------ 35 

Prorsisphinctes _____ ________________ -- _ --•• ----.. 54 

(Prorsisphinctes), Leptosphinctes. _ -------------- 54 

Protocardia. ___________ -------------------.----- 8 

protrusus, Strigoceras. ____ ---------------------- 37 

pseudocostata, Sonninia. __ --------------,------- 32 

Page 

Pseudolioceras ___ -------------------------- B12, 16,27 

sp _______ -- _____ --- _--- ____ •• -------- ___ ---- 6 

Pseudotoites .•• -------------------- 3, 12, 18, 19, 21, 52,53 

carlottense. ___ ------------------------------ 52 

robiginosus .... ------------------------------ 53 

pulcher, Bigotites .... ---------------------------- 54 

Q 

Queen Charlotte Islands, British Columbia_____ 19 

R 

Red Glacier Formation •• ----------------------- 6, 

8, 10, 14, 18, 21, 22, 23, 24, 27, 30, 32, 33,34, 

35, 38, 40, 41, 43, 44, 46, 47,48, 50. 

regleyi, Tmetocera8 .•.• -------------------------- 6 

rhytus, Stephanoceras. ____ ---------------------- 48 

richardsoni, Ammonites. __ ---------------------- 51 

Zemistephanus. ______ 13, 15, 28, 51, 52, 53; pis. 25,26 

robiginosus, Pseudotoites------------------------- 53 

rugosus, Normannites. -------------------------- 43 

s 

J!auzei, Otoites •••.. 10, 11, 12, 14, 18, 19, 20, 21, 27, 31, 37, li4 

Saxitoniceras allanL ..•••• -----------------· ---- 42 

marshalli. _. -------------------------------- (Saxitoniceras allani, Chondroceras---------------

Sawtooth Formation._~---------·--------------

scissum, Tmetoceras ... ___ ------------------·----

42 

42 

19 

20 

semicostulatum, Lissoceras ________ 11, 15, 28, 88,39; pl. 4 

Shirbuirnia. ____ -------------------------------- 21 

Skirroceras .•••. -----~---------------- 6, 10, 12, 16, 17,54 

Stephanoceras .•• ---------------- ____ 2, 10, 20, 27, 46 

(Skirroceras) baylei, Stephanoceras.-------------- 48 

juhlei, Stephanoceras .•.•• 10, 11, 27, 28, 47; pis. 16,17 

kirschneri, Stephanoceras •• ------------------ 11 

13, 21, 28, 46, 47, 48; pis. 18,19 

macrum, Stephanoceras ..•.•• ---------------- 47,48 

nelchinanum, Stephanoceras------------·---- 27, 

45, 46, 47, 48; pis. 15,16 

sp., Stephanoceras .. --------------------·---- 27,53 

Snowshoe Formation ..• -------------------·- 19,20,31 

Sonninia ____________________ -------------- 2, 6, 8, 9, 12, 

16, 17, 18, 19, 20, 21, 27, 33, 34, 36, 37,54 

deltafalcata ____ ------------------------------ 37 

nodata .... ----------------------------- 27, 88; pl2 

nodatipinquis. __ -------------·-------------- 32 

patella. __ -------------------------- 27, 88, 36; pl. 3 

projectifer.---------------------------- 27, 88; pl. 3 

pseudocostata. ___ --------------------------- 32 

sowerbyi. _____ 10, 12, 18, 19, 20, 21, ~0, 36,37, 38, 53,54 

trigonalis ___ • _ --••. ------------------------- 33 

tuxedniensis •..• __ 11, 12, 13, 15, 18, 28, 82, 34, 37; pl. 2 

. ~:t~~~~--~~~~:::~~:~~~:~:~:::::~~~~~~::::~~~~ :: (Papilliceras>----~---------- 2, 8, 12, 15, 20, 21, 27,53 

arenata ________________ 11, 13, 15, 18, 28, 84; pl. 6 

blackwelderL. -------------------------- 34 

espinazitensis. -------------------------- 27, 34 

~:=t~·f.~~~;~~~~~~~~~~~~~~~~~~~~~~~~~::~~~~' 12, 18, 19, 20, 21, 30, 36,37' 38, 53, ';:.~ 54 

sparsinodum, Teloceras.--------------- ---------- 50 

spatians, Spatulites __ ~ -------------------------- 37 

37 Spatulites spatians ..• ~ --------------------------

Sphaeroceras.--------~-- ------------------------ 16, 17 

Sphaeroceratlidae _______ -- ____ ------------------ 41 

Spiroceras. _ ------------------------------------ 16, 17 

stantoni, Oppelia •••. -~-------------------- ------ 15 Oppelia ( Oppelia) ___________ __ ---- 13, 28, 88; pl. 8 

Stemmatoceras. __ ----~--------------- -------- 2, 5, 6, 8, 

9, 11, 12, 15, 16, 17, 18, 19, 20, 21, 27, 48,54 

albertense. -------~-------------------- ------ 49, 50 

coronatum. _ -----~------------------------ -- 49, 50 palliserL •.•.•• __ 1 

__________ 13, 15, 48, 49; pis. 20,21 

triptolemus •... ---.----------- 11, 15, 28, 49, 50; pl. 21 

ursinum ..• -------"------------- 13, 15, 28, 49; pl. 22 
Page 

Stephanoceras •.•• ------------------------------- B2, 

5, 6, 8, 9, 10, 12, 16, 17, 19, 20, 21,27, 45,47 

brodiaei..-----------------------------------

carlottense. _____ -----------------------------

46 

52 

httmphriesianum. --------------------------- 12, 

13, 14, 18, 19, 20, 21, 27, 30, 37, 46,53 

kreter __ --••• -------------------------------- 46 

macntm. __ --------------------------------- 46 

nelchinanum ____ ------ __ -------------------- 47 

nodosum _________ _ •• -------- 11, 15, 21, 28, 46; pl.16 

obesum. ____ ---- _ -------------•• ------ 27, 46; pl.18 

rhytus __ ------------------------------------ undulatttm •• ____ -- ______ --------------------

48 

20 

(Skirroceras). _____________ ---------- 2, 10, 20,27, 46 

baylei. •• -------------------------------- 48 juhleL ________ ------ 10, 11, 27. 28, 47; pls.16, 17 

kirschnerL ---- 11, 13, 21, 28, 46, 47, 48; pls.18, 19 

macrum. ___ ---------------------------- 47, 48 nelchinanttm _____________ 27,45, 46, 47,48;pls.15 ,16 sp. __ • ________ • ____________________ --. __ 27, 53 

sp. -------------------------- 11, 12, 13, 14, 15, 18,28 

Stcphanoceratidae ___________________ ------ 2, 3, 5, 6, 43 

Stratigraphic summary_------------------------ 6 

Striooceras -------------- __ 2,6, 11, 12, 16,17, 18,21, 36,37 

lanouidum _________ __ ----- __ 13, 15, 28, 97, 38; pl. 23 

protrusus ••• __ • ----------------------------- 37 

sp ____ ----------------------------- 11, 28, 97; pl. 23 

Strigoccratldae. __ ------------------------------ 2, 37 

sttbcadiconica, Emileia. ___ ---------------------- 41 

subradiata, Oppelia ______ ------------------------ 38,39 

Summary of results ••••• ------------------------ f7 

T 

Talkeetna Formation___________________________ 8,10 

Teloceras •• -------. _ --------------------------- 2, 3, 9, 

12, 13, 14, 16, 17, 19, 20, 21, 27, 37, 48, 50,52 

INDEX 

Page 

Telocera&-Continued 

acuticostatum. ____ ---------------------- ____ B50 

dowlinoL ----------------.------------------ 49 itinsae. ___ ------- _______ 13, 15, 28, 50, 53; pls. 23,24 

multinodum _________________________________ 48,50 

sparsinodum. ------------------------------- 50 

Thracia ___ --------------------------- _ ---------- 8 

Tmetoceras. ____ ------------ 6, 10, 12, 14, 16, 17, 18, 20,30 

reoleyi.- ------------------------------------ 6 

scissum ___ ---------------------- _ ------- ____ 20 

SP------------------------------------------ 6, 8 

Toxamblyites ____ ------------ ____ ---------------- 40 

a rei fer ____ ---------------------------------- 40 

trioonalis, Sonninia _________ -------------------- 33 

Trioonia •• ______ -- ____________ -------------- __ -- 8 

triptolemus, Stemmatoceras ______ 11,15,28,49,50; pl. 21 

Tropites. _ ------------------------- _ ------------ 3 

Tuxedni Formation, in Talkeetna Mountains.__ 9, 

14, 18, 22, 30, 31, 32, 33, 34, 35, 36, 39, 40, 42, 43, 45, 

46,48,54. 

along northwest side of Cook Inlet__________ 6, 

8, 9, 10, 21, 27,31 

tuxedniensis, Sonninia. _______ ------------------ 11, 

12, 13, 15, 18, 28, 9B, 34, 37; pl. 2 

Twin Creek Limestone ••• ---------------------- 19 

u 

ultramontanum, Holcophylloceras________________ 32 

undifer, Sonninia •• _ ---------------------------- 33 

undulatum, Macrophylloceras •• ----------------- 18 

Stephanoceras ••. ---------------------------- 20 

United States, western interior.---------------- 19 

ursinum, Stemmatoceras ____________ 13, 15, 28, 49,· pl. 22 

0 

B61 

v Page 

vagabunda, Emileia _____ ------------------------ B41 

vancour,eri Zemistephanus.---------------------- 52 variabilis, Normannitea ________________________ 9, 13,18 

w 

Warm Springs Formation ______________________ 19,20 

Weberg Formation.---------------------------- 19,20 

Witchellia __________ ------ ____ ------------------ 2, 

8, 12, 14, 16, 17, 18, 19, 20, 21, 27, 34, 36, 37, 53,54 

adnata. ____ ------------------ 11, 15, 27, 28, 94; pl. 6 aouilonia _____________________ 18,27, 95, 96; pls. 4,5 

celans. _____ ---------------------------- ____ 36 

connata _____________ -------------------- ____ 35 

r.orruoata. ____ ------------------------------ 35 falcata_. _____ ••• _. ________ -----••••••• _ _ _ _ _ _ 35 

laeviuBcula ••• ___ ---------------------- 27, 95; pl. 7 

propinquans •• ------------------------------ 35 

zuoophorus. ____ -------------------------- __ 35 

sp. ------------------------ 8, 10, 11, 12, 15, 18, 27,28 

y 

Yakoun Formation ______________ . _______________ 19,31 

z 

Zemistephanus _______ 2,3, 9, 13, 16, 19, 21, 27, 31, 51, 52, 53 

carlottensis ________ 13,14,15,28,5B,53; pls. 24,27,28 

funteri.. _____ ----------------------.----- _ __ 51 

richardsoni. __ -------- 13, 15, 28, 51, 52, 53; pls. 25,26 

vancouveri. __ • ------------------------------ 52 sp _ ____ __ ____ ____ __ ____ __ __ _ ____ _ __ __ ___ _ 13, 15, 28 

zitteli, Sonninia ••• ------------------------------ 35 

zuoophoruB, Witchellia__________________________ 35 
PLATES l-29 
PLATE 1 

[All figures natural size) 

FIGURES 1-7. Macrophylloceras sp. undet.· A (p. B31). 

1. Specimen USNM 131332 from USGS Mesozoic loc. 3697. 

2. Specimen USNM 131331 from USGS Mesozoic loc. 3697. 

3. Specimen USNM 131329 from USGS Mesozoic loc. 24113. 

Note fine ribbing. 

4, 5. Specimen USNM 131328 from USGS Mesozoic loc. 24113. 

6. Specimen USNM 131327 from USGS Mesozoic loc. 24113. 

7. Specimen USNM 131330 from USGS Mesozoic loc. 3696. 

Illustrates sutures. 

8, 9, 13. Macrophylloceras sp. undet. B (p. B31). 

. 10-12, 14-17. 

.... -: :· 

8, 9. Figured specimen USNM 131333 from USGS Mesozoic loc. 

8567. 

13. Figured specimen USNM 131334 from USGS Mesozoic loc. 

2999. . 

Holcophylloceras costisparsum Imlay, n. sp. (p. B32). 

10. Paratype USNM 131337 from USGS Mesozoic loc. 24113. 

"11, 12. Paratype USNM 131336 from USGS Mesozoic loc. 24113 . 

.. 14, 15. Paratype USNM 131339 from USGS Mesozoic loc. 2999. 

:· 1·6,0 17. Holotype USNM 131335 from USGS Mesozoic loc. 24113 . 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 1 

14 15 16 17 

MACROPHYLLOCERAS AND HOLCOPHYLLOCFRAS 
PLATE 2 

[All figures natural size unless otherwise indicated] 

FIGURES 1, 2. Sonninia cf. S. nodata Buckman (p. B33). 

Figured specimen USNM 131345 from USGS Mesozoic loc. 24120. 

3, 4. Phylloceras cf. P. kunthi Neumayr (p. B31). 

Figured specimen USNM 131326 from USGS Mesozoic loc. 24113. 

5-10. Sonninia tuxedniensis Imlay, n. sp. (p. B32). 

5, 6. Cross section and suture line of paratype USNM 131342 from USGS 

Mesozoic loc. 2999. Suture line drawn at diameter of 60 mm and 

whorl height of 23 mm. 

7, 10. Suture line (X 2) and lateral view of holotype USNM 131340 from 

USGS Mesozoic loc. 21266. About one-third of largest whorl represents 

body chamber. 

8, 9. Paratype USNM 131341 from USGS Mesozoic loc. 2999. 

I' 

l 
, 

,,. 

GEOLOGICAL SURVEY 

5 

'I 

8 

\ 

\ 

I 

2 

~ell~~~~~ 

6 

3 

7 X2 

9 

SONNINJA AND PH YLLOCERAS 

PROFESSIONAL PAPER 418-B PLATE 2 

> 

,- ~· 

~J 

r-._ td. F ' . • ·.'~ I 

I ~ . 

I f 1 .~ ~ 

4 

10 
PLATE 3 

[All figures natural size unless otherwise indicated] 

FIGURES 1, 5. Sonninia cf. S. projectifer (Buckman) (p. B33). 

Lateral and ventral views of figured specimen, USNM 131344 from USGS 

Mesozoic loc. 24113. 

2-4. Sonninia cf. S. patella Waagen (p. B33). 

Lateral views of parts of two inner whorls and of part of large whorl 

(X %) of figured specimen, USNM 131346 from USGS Mesozoic loc. 

24120. The inner whorl shown in fig. 2 is illustrated also in fig. 4. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 3 

r" '" " ~ 'r-. .~ • ~ / 

..,., 

SONNINIA 

713-993 0 - 64 - 4 
PLATE 4 

[All figures natural size unless otherwise indicated] 

FIGURES 1-4. Witchellia? aff. W.? aguilonia Imlay, n. sp. (p. B36). 

Lateral and ventral views and suture line (X 2) of figured specimen 

USNM 131357 from USGS Mesozoic loc. 24113. Note faint 

spiral markings shown in fig. 1. 

5, 6, 10-12. Sonninia? n. sp. undet. (p. B33). 

5, 6, 12. Lateral and ventral views of specimen USNM 131348 

from USGS Mesozoic loc. 26723. 

10, 11. Ventral and lateral views of specimen USNM 131347 from 

USGS Mesozoic loc. 21293. In both views the adoral end is 

pointed downward. 

7, 8. Lissoceras cf. L. semicostulatum (Buckman (p. B38). 

Figured specimen USNM 131362 from USGS Mesozoic loc. 21268. 

9. Witchellia? aguilonia Imlay, n. sp. (p. B35). 

Ventral view of holotype USNM 131355 from USGS Mesozoic loc. 

24113. Note lateral view on pl. 5, fig. 9. 

··--
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 4 

'\ ,, 

'I 

'' \ I ' I i".J l'lj\J 

I ,, 

I X2 4 

9 10 12 

WITCHELLIA?, SONNINIA ?, AND LISSOCERAS 
PLATE 5 

[All figures natural size] 

FIGURES 1-3, 5, 6. Bradfordia? caribouensis Imlay, n. sp. (p. B39). 

1. Lateral view of paratype USNM 131378 from USGS Mesozoic loc. 26601. 

2, 3, 5. Holotype USNM 131376 from USGS Mesozoic loc. 3696. 

6. Paratype USNM 131379 from USGS Mesozoic loc. 26601. 

4, 7-9. Witchellia? aguilonia Imlay, n. sp. (p. B35). 

4. Suture line from paratype USNM 131356 from USGS Mesozoic loc. 21258, drawn at diameter of about 94 mm. 

7, 8. Paratype UCLA paleont. cat. 34975 from same place as USGS Mesozoic loc. 24113. 

9. Holotype USNM 131355 from USGS Mesozoic loc. 24113. Note ventral view on pl. 4, fig. 9. 

. ., 

p· ).> 
PLATE 6 

[All figures natural size unless otherwise indicated] 

FIGURE 1-3. Sonninia (Papilliceras) cf. S. arenata (Quenstedt) (p. B34). 

1. Lateral view of a part of body chamber, USNM 131349 from USGS 

Mesozoic loc. 22723. 

2, 3. Inner whorls of a larger immature specimen, USNM 131350 

from USGS Mesozoic loc. 21262. 

4, 5, 11. Pelekodites? sp. (p. B36). 

4. Lateral view of adult bearing a lateral lappet, USNM 131358 from 

USGS Mesozoic loc. 26596. 

5. Lateral view of rubber cast made from external mold of same 

specimen shown in fig. 4. 

11. Suture line near adoral end of outermost septate whorl of same 

specimen shown in figs. 4 and 5. 

6-10. Witchellia ad nata Imlay, n. sp. (p. B34). 

6. Paratype USNM 131353 from USGS Mesozoic loc. 3010. 

7, 8. Lateral view and suture line (X 2) of holotype USNM 131351 

from USGS Mesozoic loc. 19956. Suture line drawn at whorl 

height of 28 mm near adoral end of outermost septate whorl. 

9, 10. Paratype USNM 131352 from USGS Mesozoic loc. 20756. 
PLATE 6 

[All figures natural size unless otherwise indicated] 

FIGURE 1-3. Sonninia (Papilliceras) cf. S. arenata (Quenstedt) (p. B34). 

1. Lateral view of a part of body chamber, USNM 131349 from USGS 

Mesozoic loc. 22723. 

2, 3. Inner whorls of a larger immature specimen, USNM 131350 

from USGS Mesozoic lac. 21262. 

4, 5, 11. Pelekodites? sp. (p. B36) . 

4. Lateral view of adult bearing a lateral lappet, USNM 131358 from 

USGS Mesozoic lac. 26596. 

5. Lateral view of rubber cast made from external mold of same 

specimen shown in fig. 4. 

11. Suture line near adoral end of outermost septate whorl of same 

specimen shown in figs. 4 and 5. 

6-10. Witchellia adnata Imlay, n. sp. (p. B34). 

6. Paratype USNM 131353 from USGS Mesozoic lac. 3010. 

7, 8. Lateral view and suture line (X 2) of holotype USNM 131351 

from USGS Mesozoic lac. 19956. Suture line drawn at whorl 

height of 28 mm near adoral end of outermost septate whorl. 

9, 10. Paratype USNM 131352 from USGS Mesozoic lac. 20756. 

.6. 

~. 
GEOLOG ICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 6 

. -~ 

7 11 10 

SON NINJA, PELEKODITES?, AND WITCHELUA 
PLATE 7 

[Fig. 2 is X 2. Figs, 4 and 5 are slighty reduced] 

FIGURES 1-5. Witchellia cf. W. laeviuscula (J. de C. Sowerby) (p. B35). 

Specimen, USNM 131354 from USGS Mesozoic loc. 24120. Fig. 1 shows 

inner whorls. Suture line (X 2) drawn at whorl height of 43 mm. 

Cross section drawn at diameter of 165 mm near adoral end of largest 

preserved whorl. 

~I 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 7 

X2 

2 

; 

4 5 

WITCHELLIA 
PLATE 8 

[All figures natural size unless otherwise indicated] 

FIGURES 1-10. Bradfordia Costidensa Imlay, n. sp. (p. B39). 

1, 2. Paratype USNM 131372 from USGS Mesozoic loc. 24113. 

3-5. Holotype USNM 1 31369 from USGS Mesozoic loc. 24113. Shows 

nearly complete body chamber. 

6. Paratype USNM 131371 from USGS Mesozoic loc. 24113. 

7. Paratype USNM 131374 from USGS Mesozoic loc. 24113. 

8. Paratype USNM 131373 from USGS Mesozoic loc. 24113. 

9. Paratype USNM 131375 from USGS Mesozoic loc. 24113. 

10. Paratype USNM 131370 from USGS Mesozoic loc. 24113. Suture 

line (X 2) drawn at whorl height of 24.5 mm. 

11-18. Oppelia (Oppelia) stantoni Imlay, n. sp. (p. B38). 

11, 17. Suture line and lateral view of paratype USNM 131365 from 

USGS Mesozoic loc. 3000. Suture line drawn at whorl height of 28 mm. 

12. Lateral view of immature specimen, paratype USNM 131367 from 

USGS Mesozoic loc. 3000. 

13. Lateral view of immature specimen, paratype USNM 131366 from 

USGS Mesozoic loc. 3000. 

14, 15. Lateral and ventral views. Holotype USNM 13i363 from USGS 

Mesozoic loc. 3000. 

16. Paratype USNM 131364 from USGS Mesozoic loc. 3000. 

18. Paratype USNM 131368 from USGS Mesozoic loc. 22721. Note 

specimen is entirely septate. 
GEOLOGICAL SURVEY PROFESSWNAL PAPER 418- B PLATE 8 

9 

· 

/ 'jo / 

·i . 

r l < 

j " ' 

, ' 

16 18 

BRADFORDIA AND OPPELIA 
PLATE 9 

[All figures natural size] 

FIGURES 1-3. Labyrinthoceras glabrum Imlay, n. sp. (p. B41). 

Paratype USNM 131390 from USGS Mesozoic loc. 25942. Shows complete adult whorl. 

,, ... 
PROFESSIONAL PAPER 418 B PLATE 9 

GEOLOGICAL SURVEY 

2 3 

1 

LAHYRINTHOCERAS 
··•" 

PLATE 10 

[All figures natural size unless otherwise indicated] 

FIGURES 1-7. Labyrinthoceras glabrum Imlay, n. sp. (p. B41). 

1-3. Paratype USNM 131391 from USGS Mesozoic loc. 24215. Suture line drawn at whorl height of 38 mm and diameter of 84 mm. 

4, 5. Holotype USNM 131389 from USGS Mesozoic loc. 24215. Note trace of umbilical seam of contracting body chamber. 

6, 7. Last suture line and lateral view of paratype USNM 131392 from USGS Mesozoic loc. 24215. 
GEOLOGI CAL SURVEY 

5 

LAHYRINTHOCERAS 

PROFESSIONAL PAPER 418-1:! PLATE 10 

6 

, ( 

•' '' l 

: ~ '- ;- · 

" 

X2 

7 

\ 

\ 

.. 
[All figures natural size] 

FIGURES 1-8. Emileia constricta Imlay, n. sp. (p. B40). 

1, 6. Holotype USNM 131384 from USGS Mesozoic loc. 3009. 

2. Paratype USNM 131387 from USGS Mesozoic loc. 21268. 

3. Paratype USNM 131386 from USGS Mesozoic loc. 3009. 

4, 5, 7. Paratype USNM 131388 from USGS Mesozoic loc. 21262. 

8. Complete body chamber of paratype USNM 131385 from USGS 

Mesozoic loc. 3009. 

J 

J 

... Ji· 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 11 

,-

6 7 

EMILE! A 
PLATE 12 

[All figures natural size] 

FIGURES 1-3. Chondroceras cf. C. marshalli (McLearn) (p. B43). 

Figured specimen USNM 131400 from USGS Mesozoic loc. 8567. 

· 4-7, 9, 10. Chondroceras alla.ni (McLearn) (p. B42). 

4, 5. Plesiotype USNM 131399 from USGS Mesozoic loc. 21768. 

6. Plesiotype USNM 131397 from USGS Mesozoic loc. 21317. 

Suture line drawn at whorl height of 14 mm near adoral end of last 

septate whorl. 

7. Plesiotype USNM 131398 from USGS Mesozoic loc. 21768. 

9, 10. Plesiotype USNM 131396 from USGS Mesozoic loc. 19981. 

8, 11-14. Chondroceras defontii (McLearn) (p. B42). 

8. Adult showing complete body chamber, plesiotype USNM 131393 

from USGS Mesozoic loc. 10516. 

11. Plesiotype USNM 131394 from USGS Mesozoic loc. 22707. 

Part of body chamber removed to show fine ribbing on penultimate 

whorl. 

12-14. Plesiotype USNM 131395 from USGS Mesozoic loc. 21270. 

Lateral views show marked coarsening of ribbing at adapical end 

of body chamber. 

.J 

... 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 12 

6 

10 

11 12 13 14 

CHONDROCERAS 
f.· 

r: 

" 

PLATE 13 

[All figures natural size unless otherwise indicated] 

FIGURES 1-8, 10, 11, 17. Normannites kialagvikensis Imlay, n. sp. (p. B43). 

1-3. Paratype USNM 131403 from USGS Mesozoic loc. 3010. 

4, 5. Paratype USNM 131404 from USGS Mesozoic loc. 19773. 

6-8, 10. Holotype USNM 131401 from USGS Mesozoic loc. 

19773. Suture line drawn near adoral end of outermost 

septate whorl. 

11. Paratype USNM 131402 from USGS Mesozoic loc. 3010. 

17. Paratype USNM 131451 from USGS Mesozoic loc. 3010. 

9, 12-16. Normannites (Itinsaites?) variabilis Imlay, n. sp. (p. B44). 

9. Suture line (X 2) of paratype USNM 131409 from USGS 

Mesozoic loc. 19941. Suture line drawn at adoral end of 

outermost septate whorl. 

12-14. Paratype USNM 131411 from USGS Mesozoic loc. 8567. 

15. Holotype USNM 131408 from USGS Mesozoic loc. 20002. 

16. Paratype USNM 131412 from USGS Mesozoic loc. 19940. 

·" 

-. 

.-
GEOLOGICAL SURVEY _.._, 

1 2 3 

_J8f1 ~~r'l I 

wP\ I X 2 10 

15 

PROFESSIONAL PAPER 418-B PLATE 13 

4 5 

7 8 

17 

NORMANNITES 
PLATE 14 

[All figures natural size] 

FIGURES 1, 2. Normannites (Itinsaites) itinsae (McLearn) (p. B44). 

Plesiotype USNM 131407 from USGS Mesozoic loc. 26599. 

3-8, 13. Normannites (Itinsaites) crickmayi (McLearn) (p. B43). 

3, 4. Plesiotype USNM 131406 from USGS Mesozoic loc. 21270. 

5, 13. Plesiotype USNM 131452 from USGS Mesozoic loc. 21270. 

6-8. Plesiotype USNM 131405 from USGS Mesozoic loc. 21270. 

9-11. Otoites? filicostatus Imlay, n. sp. (p. B40). 

9, 10. Holotype USNM 131382 from USGS Mesozoic loc. 3010. 

11. Paratype USNM 131383 from USGS Mesozoic loc. 19951. 

12, 14. Normannites (Itinsaites?) variabilis Imlay, n. sp. (p. B44). 

12. Paratype USNM 131410 from USGS Mesozoic loc. 21303. 

14. Paratype USNM 131409 from USGS Mesozoic loc. 19941. Photograph made from rubber cast of external mold. Suture line of same 

specimen shown on pl. 13, fig. 9. 

( -~ 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418 - B PLATE 14 

13 

NORMANNITES (JTINSAITES) AND OTOITES? 
PLATE 15 

[All figures natural size) 

FIGURES 1, 3, 4-6. Stephanoceras (Skirroceras) nelchinanum Imlay, n. sp. (p. B46). 

1, 3. Inner septate whorls of holotype USNM 131417 from USGS 

Mesozoic loc. 24113. Outer whorl shown on pl. 16, fig. 2. 

4, 5. Adult body chamber of paratype, USNM 131419 from USGS Mesozoic loc. 8585. 

6. Suture line of paratype, USNM 131418 from USGS Mesozoic loc. 

24113. Suture line drawn at whorl height of 19 mm and diameter 

of 79 mm. 

2. Stephanoceras (Skirroceras) cf. S. nelchinanum Imlay, n. sp. (p. B47). 

Figured specimen USNM 131420 from USGS Mesozoic loc. 24113. 

-. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B P LATE 15 

STEPHANOCERAS 

71 3 - 993 0 - 64 - 5 
PLATE 16 

[All figures natural size] 

FIGURES 1, 3-6. Stephanoceras (Skirroceras) juhlei Imlay, n. sp. (p. B47). 

1, 5, 6. Paratype USN.M 131426 from USGS .Mesozoic loc. 24120. 

Suture line drawn at whorl height of 18 mm and diameter of 76 mm. 

3, 4. Lateral and ventral views of paratype USKM 131427 from USGS 

.Mesozoic loc. 24113. 

2. Stephanoceras (Skirroceras) nelchinanum Imlay, n. sp. (p. B46). 

Holotype USN.M 131417 from USGS Mesozoic loc. 24113. Inner 

septate whorls shown on pl. 15, figs. 1, 3. 

7, 8. Stephanoceras cf. S. nodosum (Quenstedt) (p. B46). 

Figured specimen USN.M 131416 from USGS .Mesozoic loc. 21269. 
GEOLOG ICAL SURVEY PROFESSIONAL PAPER 41 8-B PLATE 16 

STEL'HANOCEHAS 
PLATE 17 

[Figure three-fourths natural size] 

FIGURE 1. Stephanoceras (Skirroceras) juhlei Imlay, n. sp. (p. B4 7). 

Lateral view of holotype (X 3/4) showing 1% whorls of body chamber, 

USNM 131425 from USGS Mesozoic loc. 24333. 

I .-
GEOLOG ICAL SURVEY 

1 

STEPHANOCERAS 

PROFESSIONAL PAPER 418- B PLATE 17 
PLATE 18 

[All figures natural size) 

FIGURES 1-4. Stephanoceras (Sk?:rroceras) kirschneri Imlay, n. sp. (p. B47). 

1, 2. Small septate para type, USNM 131424 from USGS Mesozoic loc. 

2999. 

:3. Ventral view of inner whorls of paratype, USNM 131423 from USGS 

Mesozoic loc. 20756. Lateral view of same specimen shown on pl. 19, 

fig. 3. 

4. Cross section of two outer whorls at adapical and of adult body chamber 

of paratype, USNM 131422 from USGS Mesozoic loc. 3013. 

5-11. Stephanoceras obesmn Imlay, n. sp. (p. B45). 

5-7. Small septate paratype, USNM 131414 from USGS Mesozoic loc. 

24113. 

8, 9. Septate holotype, USNM 131413 from USGS Mesozoic loc. 24113. 

10, lL .. Cross section and lateral view of para type, USNM 131415 from 

·us·a.s···Mesozoic loc. 24113. 

·. _-;, 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 41 8- B PLATE 18 

--------------

4 

" " \\ 

II 

II 

6 " 1/ 

I 

10 

11 

STEPJ-JANOCERAS 
PLATE 19 

[All figures natural size unless otherwise indicated] 

FIGURES 1-6. Stephanoceras (Skirroceras) kirschneri Imlay, n. sp. (p. B47). 

1. Suture line drawn from adoral end of outermost septate whorl of paratype, USNM 131422 at USGS Mesozoic loc. 3013. Cross section of same 

specimen is shown on pl. 18, fig. 4. 

2, 3, 5, 6. Cross section, lateral and ventral views of inner whorls of paratype, USNM 131423 from USGS Mesozoic loc. 20756. 

4. Large adult reduced to three-fifths natural size showing adult body chamber and aperture. Holotype, USNM 131421 from USGS Mesozoic loc. 

21274. 

,, -- 1 - •I ., 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 19 

STEPHANOCERAS 
PLATE 20 

[All figures natural size) 

FIGURES 1-4. Stemmatoceras n. sp. undet. (p. B48). 

1-3. Ventral, cross sectional, and lateral views of specimen USNM 131428 

from USGS Mesozoic loc. 21263. 

4. Ventral view of specimen USNM 131429 from USGS Mesozoicloc. 21296 

5, 6. Ste1hmatoceras cf. S. palliseri (McLearn) (p. B48). 

Inner septate whorls and adapical end of adult body chamber of specimen 

USNM 131430 from USGS Mesozoic loc. 21270. Body whorl of same 

specimen is shown on pl. 21, fig. 4. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 20 

STEMMATOCERAS 
PLATE 21 

' ~- [All figures natural size] ~·t!\~·- ::.. ..... 

FIGUREs 1, 3. Stemmatoceras cf. S. triptolemus (Morris and Lycett) (p. B49). 

Lateral view and partial suture line of specimen USNM 131432 from USGS 

Mesozoic loc. 21261. Suture line drawn about 30 mm from adoral end 

of outermost septate whorl. 

2, 4. Stemmatoceras cf. S. palliseri (McLearn) (p. B48). 

Cross section and lateral view of specimen, USNM 131430 from USGS 

Mesozoic loc. 21270. Shows aperture and parts of adult body chamber. 

For other views of septate whorls see pl. 20, figs. 5 and 6. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 21 

3 4 

STEMMATOCERAS 
PLATE 22 

[All figures natural size) 

FIGURES 1-3. Stemmatoceras ursinum Imlay, n. sp. (p. B49). 

Holotype USNM 131431 from USGS Mesozoic loc. 22705. Cross section 

drawn near adoral end of outermost septate whorl. Suture line drawn 

at whorl height of 30 mm about 50 mm from adoral end of outermost 

septate whorl. 
GEOLOGICAL SURVEY 

/ 

I 

\ 

\ 

"" 

~ 

"-._/ 

PROFESSIONAL PAPER 418-B PLATE 22 

I 

I ~ 

3 

STEMMATOCERAS 
PLATE 23 

[All figures natural size] 

FIGURE 1. Lissoceras bakeri Imlay (p. B38). 

Plesiotype USNM 131361 from USGS Mesozoic loc. 10512. 

2-4, 8. Strigoceras cf. S. lanuuidmn (Buckman) (p. B37). 

Lateral, ventral, and cross sectional views of specimen USNM 131359 

from USGS Mesozoic loc. 27105. 

5-7. Strigoceras sp. juv. (p. B37). 

Figured specimen, USNM 131360 from USGS Mesozoic loc. 21268. 

9, 10. Teloceras itinsae McLearn (p. B50). 

9. Plesiotype USNM 131433 from USGS Mesozoic loc. 21270 showing 

complete adult body chamber. 

10. Plesiotype USNM 131434 from USGS Mesozoic loc. 21270 showing 

ventral view of adult body chamber. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 23 

/· 

, 

. 

/' 

r 

9 

LISSOCERAS, STRIGOCERAS, AND TELOCERAS 
PLATE 24 

[All figures natural sizcj 

Fw URES 1-5, 7. Teloceras itinsae Me Learn (p. B50). 

1, 2. Plesiotype USNM 131436 from USGS Mesozoic loc. 21270. 

3, 4. Holotype Canada Natl. Mus. 6481. Views from plaster cast of holotype. 

5, 7. Plesiotype USNM 131435 from USGS Mesozoic loc. 3000. Shows nearly half a whorl of adult body chamber. 

6. Zemistephanus carlottensis (Whiteaves) (p. B52). 

Crushed specimen showing strong primary ribbing in umbilicus. Plesiotype USNM 131447 from USGS Mesozoic loc. 10513. 
GEOLOGICAL SURVEY 

I_,..,-;;~ , ~· •• lo 

¥" 

TELOCERAS AND ZEMISTEPHANUS 

PROFESSIONAL PAPER 418-B PLATE 24 

,' ~ . 

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,..~~ ' 

7 
PLATE 25 

[All figures natural size) 

FIGURES 1-3. Otoites cf. 0. pauper Westermann (p. B40). 

1, 3. Lateral and ventral views of body chamber of specimen, USNM 131380a from USGS Mesozoic loc. 24113. 

2. Lateral view body chamber of specimen, USNM 131380b from USGS Mesozoic loc. 24113. 

4, 5. Otoites cf. 0. contractus (Sower by) (p. B40). 

Ventral and lateral views of body chamber of specimen, USNM 131381 from USGS Mesozoic loc. 3009. 

6, 7. Zemistephanus richardsoni (Whiteaves) (p. B51). 

6. Plesiotype USNM 131437 from USGS Mesozoic loc. 21270. Adult body chamber showing aperture and rejuvenation of coarse ribbing on 

adoral half of body chamber. 

7. PlE>..siotype USNM 131438 from USGS Mesozoic loc. 3000. Shows fine ribbing on penultimate whorl. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 25 

OTOITES AND ZEMISTEPHANUS 
PLATE 26 

[All figures natural size) 

FIGURES 1-7. Zemistephan1ls richardsoni (\Vhiteaves) (p. B51). 

1. Plesiotype USNM 131441 from USGS Mesozoic loc. 3000. 

2. Plesiotype USNM 131440 from USGS Mesozoic loc. 3000. 

3, 4. Small inner whorls of a larger specimen. Plesiotype USN.M 131442 

from USGS Mesozoic loc. 10520. 

5. Suture line drawn at whorl height of 31 mm and approximate diameter 

of 88 mm. Plesiotype USNM 131439 from USGS Mesozoic loc. 21274. 

6, 7. Penultimate whorl and part of body chamber showing rather abrupt 

change from coarse to fine ribbing. The adoral part of the body chamber, 

which has been removed, bears moderately strong ribbing on the venter. 

Plesiotype USNM 131443 from USGS Mesozoic loc. 2999. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418- B PLATE 26 

ZEMISTEPHANUS 
PLATE 27 

[All figures natural size unless otherwise indicated] 

FIGURES 1-3. Zemistephanus carlottensis (Whiteaves) (p. B52). 

1. Suture line (X 2) drawn at whorl height of 38 mm on plesiotype, USNM 

131445 from USGS Mesozoic loc. 2999. Same specimen is shown on pl. 

28, fig. 2. 

2, 3. Plesiotype USNM 131444 from USGS Mesozoic loc. 3000. Shows 

complete body chamber and aperture. Cross section drawn near adoral 

end of body chamber. 
GEOLOGICAL SURVEY 

713-993 0 - 64 - 6 

ZEMISTEPHANUS 

PROFESSIONAL PAPER 418- B PLATE 27 

( 

\ 
PLATE 28 

[All figures natural size unless otherwise indicated] 

FIGURES 1-3. Zemistephanus carlottensis (Whiteaves) (p. B52). 

1, 3. Lateral and a,pertural views of plesiotype, USNM 131446 from USGS 

Mesozoic loc. 21275. 

2. Plesiotype USNM 131445 from USGS Mesozoic loc. 2999. Suture line 

drawn near adoral end of same specimen is shown on pl. 27, fig. 1. 

4-6. Leptosphinctes evolutus Imlay, n. sp. (p. B54). 

4. Paratype USNM 131450 from USGS Mesozoic loc. 8567. 

5. Paratype USNM 131449 from USGS Mesozoic loc. 8567. 

6. Holotype USNM 131448 from USGS Mesozoic loc. 8567. 

7-9. Arkelloceras? sp. juv. (p. B53). 

Figured specimen USNM 132014 (X 2) from USGS Mesozoic loc. 21255. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 418-B PLATE 28 

ZEMISTEPHANUS, LEPTOSPHINCTES, AND ARKELLOCERAS? 
PLATE 29 

[All figures natural size unless otherwise indicated] 

FIGURES 1-16. Parabigotites crassicostatus Imlay (p. B54). 

1. Paratype USNM 130916 from USGS Mesozoic loc. 27577. 

2, 11. Paratypes USNM 130913 from USGS Mesozoic loc. 21258. 

3. Adult body chamber showing aperture. Paratype USNM 130911a 

from USGS Mesozoic loc. 19773. 

4, 5. Ventral and lateral views of paratype USNM 130912 from USGS 

Mesozoic loc. 19966. 

6, 7, 9. Ventral and lateral views and suture line (X 2) of paratype, 

USNM 130914 from USGS Mesozoic loc. 22529. Suture line drawn 

at whorl height of 7.5 mm. 

8, 14, 15. Holotype USNM 130909 from USGS Mesozoic loc. 11352. Suture line (X 2) drawn near adoral end of outer septate whorl. 

10. Paratype USNM 1309llb from USGS Mesozoic loc. 19773. 

12,13. Ventral and lateral views of paratype, USNM 130911c from USGS 

Mesozoic loc. 19773. 

16. Paratype USNM 130910 from USGS Mesozoic loc. 11352. 

t 1 
GEOLOGICAL SURVEY 

U.S. GOVERNMENT PRINTING OFFICE: I964 0- 713-993 

13 

PARABIGOTITES 

PROFESSIONAL PAPER 418- B PLATE 29 

15 16