Nonmarine Mollusks 

From Barstow Formation 

of Southern /California 

II 

By DWIGHT W. TAYLOR 

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 254-C 

Descriptions and illustrations of new and 

already-described mollusks oj1 late Miocene 

age, and a discussion of their environment 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1954 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

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

Washington 25, D. C. -Price 30 cents (paper cover) 
CONTENTS 

Abstract __________________________________________ _ 

Introduction~--------------------------------------

Previouswork _____________________________________ _ 

Fauna ____________________________________________ _ 

Faunal analysis ________________________________ ~ ___ _ 

Paleoecology ______________________________________ _ 

Page 

67 

67 

67 

67 

67 

69 

Age and correlation ________________________________ _ 

Distributional relations of the Barstow fauna __________ _ Localities _________________________________________ _ 

Systematic descriptions _____________________________ _ 

Literature cited ____________________________________ _ 

Index ____________________________________________ _ 

ILLUSTRATIONS 

Page 

70 

71 

72 

72 

77 

79 

PLATE 20. Nonmarine mollusks from the Barstow formation ______________________________________________ Following index 

Ill 

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY 

NONMARINE MOLLUSKS FROM THE UPPER MIOCENE BARSTOW FORMATION, CALIFORNIA 

By DWIGHT w. TAYLOR 

ABSTRACT 

A molluscan fauna of eleven species is described from the continental upper Miocene Barstow formation near Barstow, in 

southern California. lt is associated with the type fauna of 

vertebrate paleontologists' Barstovian Age, and is the first nonmarine mollusk fauna of Tertiary age reported from the southern 

Great Basin. Four species are described as new: Lymnaea mohaveana, Menetus? micromphalus, Craterarion pachyostracon (new 

genus and species) and Helminthoglypta alfi. 

The fauna is most closely related to the one now living in the 

same region and is not known to occur in other areas. Other 

late Tertiary nonmarine molluscan faunas show geographic localization also. Correlation over the western United States by 

me::ms of these faunas is impossible at the present time, but 

practicable within areas of localization. 

INTRODUCTION 

This report describes a small late Miocene nonmarine 

molluscan fauna from the Barstow formation of Southern California, and presents certain conclusions concerning it and other molluscan faunas of western North 

America. 

Several late Miocene molluscan assemblages are 

known, although not well, from western North America. 

The Barstow fauna is the first Tertiary nonmarine fauna 

from the southern Great Basin. The large number of 

associated vertebrates provide an accurate age determination for the mollusks. 

The author is grateful to the following persons for 

advice and aid in the study and in the preparation of 

the report: Mr. R. M. Alf, Webb School, Claremont, 

Calif.; Dr. S. S. Berry, Redlands, Calif.; Dr. J. W. 

Durham, University of California; Mr. S. C. Gifford, 

Redlands, Calif.; Dr. W. 0. Gregg, Los Angeles, Calif.; 

Dr. D. F. Hewett, U. S. Geological Survey and California Institute of Technology; Dr. A. M. Keen, Stanford University; Dr. Thane McCulloh, California Institute of Tecb.rw>logy; Mr. M. C. McKenna, University of California; Dr. D. E. Savage, University of 

California; the late Dr. Chester Stock, California 

Institute of Technology; and Dr. A. 0. Woodford, 

Pomona College. 

The following abbreviations are used to indicate 

collections: B, S. Stillman Berry; G, W. 0. Gregg; P, 

Pomona College; S, Stanford University Paleonto-

. logical Type Collection; T, D. W. Taylor; UC, University of California Museum of Paleontology Invertebrate Type Collection; USNM, United States National 

~fuseum. 

PREVIOUS WORK 

Mollusks were first collected fron1 the Barstow formation by parties from the University of California in 

1911. From this material Hannibal (1912, p. 157) 

described Planorbis mojavensis; additional species were 

listed by Merriam (1919, p. 450). Other collections 

made by subsequent University of California parties 

are detailed in the systematic part of this report. 

1fore recent collecting, principally by R. M. Alf and 

parties from the Webb School, and by the writer, has 

yielded additional localities and SiJecies of mollusks. 

FAUNA 

The known molluscan fauna of the upper lvfiocene 

Barstow formation consists of the following species. 

Asterisks indicate terrestrial forms; others are freshwater. 

Gonidea n. sp.? 

Lymnaea mohaveana Taylor, n. sp. 

L. megasoma Say 

Helisoma? sp. 

Planorbula mojavensis (Hannibal) 

Menetus? rnicromphalus Taylor, n. sp. 

*Vallonia sp. cf. V. cyclophorella Sterki 

*Craterarion pachyostracon Taylor, n. gen. and sp. 

* Pristilorna chersinellurn (Dall) 

*Hawaiia.rninuscula (Binnery) 

*Helminthoglypta alfi Taylor, n. sp. 

FAUNAL ANALYSIS 

1. Gonidea, n. sp.? The genus is found only in the 

Pacific Coast drainage of North America, from Southern 

California north to British Columbia and east to Idaho 

(Gregg, 1947, p. 18). The one living species occurs in 

"rapid streams and rivers with considerable current, 

* * * sloughs, sluggish creeks, and slow-moving rivers," 

seldom in lakes (Hannibal, 1912, p. 128). 

Other described fossil species of Gonidea are as follows: 

a. G. coalingensis Arnold (1909, p. 92, pl. 30, fig. 11; 

including G. c. var. cooperi Arnold, 1909, p. 93, and 

Margaritana subangulata Cooper, 1894, p. 166, pl. 14, 

figs. 1-4 (not Anodonta angulata var. subangulata 

Hemphill [a recent Gonidea], 1891, p. 325, pl. 10, figs . 

1-2)) described from the Tulare formation (Pliocene 

and Pleistocene) in Kings Coun~y, California. Hannibal (1912, p. 127) also listed this species from the 

"Pliocene * * * Santa Clara, and Cache Lake beds, 

67 
68 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

California." These beds are now known as the Santa 

Clara formation (Pliocene and Pleistocene) and the 

Cache formation (Pleistocene). 

b. G. hemphilli Hannibal (1912, p. 128, pl. 7, fig. 19), 

described from "Miocene: Contra Costa Lake beds, 

California. Water-tunnel, head of Telegraph Canon; 

Berkeley Hills, California." This locality is in what 

is now considered the type Orinda formation (lower 

Pliocene in chronology of vertebrate paleontologists; 

upper 1\fiocene of marine sequence). 

c. G. sp., listed by Woodring, Stewart, and Richards 

(1940, p. 40, 92) from the San Joaquin forn1ation 

(Pliocene) in Kings County, California. 

2. Lymnaea mohaveana Taylor, n. sp. The nearest 

apparent relative of this species, L. palustris (Muller), 

is circumboreal. The common western American form 

of the latter, L. p. nutalliana Lea, is found from Southern California and ~izona (at high altitudes) northward. 

Found plentifully in bodies of water of greater or less size, on 

(loating sticks and submerged vegetation, on stones and on the 

muddy bottom. Inhabits both clear and stagnant water, but 

prefers a habitat in which the water is not in motion. (Baker, 

1911, p. 311). 

3. Lymnaea megasoma Say. Found living from 

northern New England and the Great Lakes area 

northward to Hudson Bay (Baker, 1911, p. 188). 

At Tomahawk Lake, Wisconsin, megasoma lives in swampy 

portions of sheltered bays where the water is quiet. The bottom 

of such a habitat is boggy and the water is so shallow that 

frequently little boggy islands are formed, and on these megasoma 

may be found, one or two specimens on each island * * * It 

would seem that the characteristic habitat of megasoma is a 

swamp or marshy pond or bay (Baker, 1911, p. 190). 

Other fossil occur:r:ences are in the lower Pleistocene 

Sand Draw fauna of Brown County, Nebraska, and in 

the lower Pliocene Laverne formation, Beaver County, 

Oklahoma. The present relatively restricted range 

may indicate a change in ecologic tolerance since its 

former wide distribution, so that this species cannot be 

used for fine habitat differentiation in the Barstow 

fauna. 

4. Helisoma? sp. The genus is widely distributed in 

North and Central America, in quiet or slow moving 

water. 

5. Planorbula mojavensis (Hannibal). The genus is 

found living from Louisiana and Georgia north into 

Canada (Baker, 1945, p. 176). One form," Planorbula 

armigera is largely a species of swales or of small and 

stagnant bodies of water" (Baker, 1928, p. 358). Other 

fossil species are known in the middle Pleistocene of the 

High Plains (Leonard, 1950, p. 17-18) and in the 

Oligocene of Washington. 

6. Menetus? micromphalus Taylor, n. sp. The subgenus lvfenetus s. s., to which this species may belong, 

is found living along the Pacific Coast from British 

Columbia to Southern California (at high altitudes). 

lvfenetus usually inhabits quiet or slow-moving shallow 

waters with abundant vegetation. Fossil species are 

known from the Tulare formation (Pliocene and Pleistocene) of the Kettleman Hills, California (Pilsbry, 1934, 

p. 568), and from Pliocene deposits in Malheur County, 

Oregon (Henderson and Rodeck, 1934, p. 268). 

7. 17 allonia sp. cf. V. cyclophorella Sterki. The living 

species is widely distributed in the western United 

States, west of the High Plains (Pilsbry, 1948, p. 1035-

1036). In Southern California it lives under stones, 

logs, etc. in damp leaf mold, usually at higher elevations. No previous records of fossil occurrence have 

been found. 

8. Craterarion pachyostracon Taylor, n. gen. and sp. 

The genus is not closely related to either of the two 

other genera of the subfamily, Binneya and Hemphillia, 

although it has characters of both. Binneya lives in 

in the semiarid areas of Santa Barbara Island, off 

Southern California, Baja California near San Quentin 

Bay, and Guadalupe Island, off Baja California (Pilsbry, 

1948, p. 733-737). Hemphillia is now found in the 

cool moist areas of Washington and Oregon to western 

1\[ontana (Pilsbry, 1948, p. 738). The number of 

Specimens of Craterarion found n1ay indicate a riparian 

habitat. 

9. Pristiloma chersinellum (Dall). This species is 

found living from Southern California (at high altitudes) north to southern Oregon; possibly also in Montana (Pilsbry, 1946, p. 413-415). In Southern California it lives under bark, logs, etc. on damp ground in 

the higher mountains. No previous record of its 

occurrence as fossil has been found. 

10. Hawaiia minuscula (Binney). This common and 

widely distributed species is found living from Alaska 

and l\tfaine south to Costa Rica (Pilsbry, 1946, p. 421). 

In Southern California it lives under stones, bark, etc. 

on damp ground, but may occur at lower elevations 

and under less moist conditions than Vallonia cyclophorella and Pristiloma chersinellum. Leonard and 

Franzen (1944, p. 29) reported it from the lower 

Pliocene Laverne formation of Oklahoma. 

11. Helminthoglypta alfi Taylor, n. sp. The nearest 

living relative is found around Victorville, California, 

about 35 miles from the Barstow Hills; all members 

of the sub-generic group (Pilsbry's "Mohave Desert 

Series") are found in the Mohave Desert region. · 

Helminthoglypta lives around Victorville on dry, rocky, 

mountain slopes, among boulders and in rock slides, or 

under rocks and leaves beneath cottonwood trees along 

the Mohave River. 
NONMARINE MOLLUSKS FROM BARSTOW FORMATION 69 

PALEOECOLOGY 

From the discussion of th~ habitats of the Barstow 

mollusks or their living relatives !t is seen that they 

may be classed in four groups, as follows: 

1. Aquatic species living in a pond or slow-moving 

stream with some aquatic vegetation. 

Gonidea n. sp.? 

Lymnaea mohaveana 

L. megasoma 

Helisoma? sp. 

Planorbula mojavensis 

Menetus? micromphalus (possibly) 

2. Land snails living under logs, bark, stones, etc., 

on moist leaf mould. In Southern California they now 

live only in the cooler, moister high altitude areas. 

Vallonia sp. cf. V. cyclophorella 

Pristiloma chersinellum 

Hawaiia minuscula 

3. Land snails living in a fairly dry habitat, under 

rocks among brush and leaves) perhaps beside a stream 

or pond. 

Helminthoglypta alfi 

Craterarion pachyostracon (possibly) 

4. Extinct species of uncertain significance. 

Menetus? micromphalus 

Craterarion pachyostracon (may possibly belong to group 3 

above) 

Ecologic interpretation of the individual species can 

be supplemented profitably by ·contrasting the fauna 

with the living Mohave Desert mollusks. Although 

the mollusks known from the Barstow fauna almost 

certainly represent but a fraction of the total molluscan 

fauna of that time, the comparison shows differences 

which appear significant. 

The Mohave Desert as here considered is bounded on 

the north by a line passing east from the Sierra Nevada 

through the southern ends of the Argus, Slate, Panamint 

and Black Mountains; on the east by the watershed of 

the .Colorado River; on tl·e south by the San Gabriel, 

San Bernardino, Little San Bernardino, and Pinto 

Mountains, and by an arbitrary line passing thence east 

to the Colorado watershed; and on the west by the 

Tehachapi Mountains and the southern Sierra Nevada. 

These limits thus exclude the north-south parallel ranges 

from Owens Valley to Death Valley, which seem more 

characteristic of the Great Basin in the strict sense, and 

also exclude the region of large Pleistocene lakes 

(Thompson, 1929, p. 5-7). 

The Mohave Desert is an arid plateau of interior 

drainage lying in the Basin and Range Province in 

easternmost Kern County, northeastern Los Angeles 

County, and San Bernardino County, California, and 

in southernmost Clark County, Nevada. It is characterized by evaporation potentially in excess of rainfall, 

which is approximately three to five inches per year 

over most of the desert and falls almost entirely in the 

winter. Most of the area lies north of the climatically 

significant boundary of 100° F. mean maximum temperature for three months (Russell, 1926). 

Topography is .typical basin and range type. It is· 

controlled chiefly by mechanical, rather than chemical, 

weathering because of the aridity and the cloudburst 

nature of much of the rain. Mountain ranges at. first 

rising from the desert floor gradually become buried in 

. alluvium (see Gilluly, Waters, and Woodford, 1951, 

fig. 15-3). 

The vegetation is characterized by "large woody 

Ethrubs with a sage (half-shrub) understory" (Axelrod, 

1950, p. 262). Annuals flourish briefly after a winter 

of adequate rain. Cottonwoods and other riparian· 

plants grow in the rare spots with permanent water. 

In such an arid region the number of habitats available for mollusks is necessarily restricted. They may 

be divided broadly into two types: mountain slopes with 

rockslides where land snails can remain protected 

through the hot summers, and sites of permanent water 

with attendant vegetation as food and cover for aquatic 

and terrestial mollusks. 

The known Recent molluscan fauna of the Mohave 

Desert is listed below. Excluded from consideration 

are the mollusks of the mountains bordering the desert 

and of Clark Mountain, which seem to be better grouped 

elsewhere. 

Sp haeriidae 

Pisidium casertanum (Poli) 

Musculium truncatum (Linsley) 

Amnicolidae 

H ydrobia sp. 

Lymnaeidae 

Lymnaea bulimoides cassi Baker 

Planorbidae 

Gyraulus parvus williamsoni (Dall) 

Helisoma tenue calijorniense Baker 

H. ammon (Gould) 

Physidae 

· Physa osculans Haldeman 

Ancylidae 

F errissia fragilis (Tryon) 

Limacidae 

Deroceras monentolophus Pilsbry 

Helminthoglyptidae 

Helminthoglypta mohaveana Berry 

H. graniticola Berry 

H. g. arida Pilsbry and Field 

H. crotalina Berry 

H. jaegeri Berry 

H. greggi Willett 

H. fisheri (Bartsch) 

Micrarionta rowelli acus Pilsbry 

M. r. unifasciata Willett 

M. r. bakerensis Pilsbry and Lowe 

M. r. amboiana Willett 

M. argus (Edson) 
70 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Sonorelix rixjordi (Pilsbry) 

S. avawatzica (Berry) 

S. melanopylon (Berry) 

Sonorella micrometalleus (Berry) 

The habitats of these various species are as follows: 

1. Rocky slopes of the mountains. The snails of 

this ecologic niche are generally found among the 

rocks and boulders on the lower slopes of the mountains, 

among the loose detritus in crevices, in rockslides, etc. 

All 'the helminthoglyptid snails have about the same 

habitat. 

2. Among rocks and boulders beside the Mohave 

River. Here a colony of Helminthoglypta mohaveana 

is found under rocks among leaves about six feet from 

the river, among the riparian stand of trees. This 

species also occurs in habitat (1) above. 

3. Damp habitats beside the Mohave River. In 

such places, under logs and stones on damp ground, 

the slug Deroceras occurs. 

4. Edges of the Mohave River. Out of the main 

current of the river, along the edge, in a narrow border 

of slow-moving water, mud bottom, and aquatic 

vegetation, or in marshy patches beside the river, the 

following occur: Pisidium, Musculium, Lymnaea, 

Ferrissia, Gyraulus, Helisoma, and Physa. 

5. Springs. The only permanent springs in the 

desert which have been visited by the writer are just 

nor.th of the San Bernardino Mountains: Rabbit. 

Cottonwood, and Old Woman Springs. All eontain 

Physa, and Old W on1an Springs adds Hydrobia. 

6. Ponds. There are several small ponds, at least 

one of which is natural, in the vicinity of Palmdale and 

Lancaster. In these occur Gyraulus, Helisoma, and 

Physa. 

The significant differences between the Barstow 

fauna and the living mollusks of the Mohave Desert 

appear to be the presence in the Barstow fauna of 

small land snails now found in Southern California 

only in the high mountains (Vallonia, Pristiloma, 

Hawaiia); the relative dominance in the living fauna 

of Helminthoglyptidae; and the presence in the 

Barstow fauna of large aquatic species ( Gonidea, 

Lymnaea), but only small to mediun1-sized forms in 

the living fauna. 

None of the smaller land snails of the Barstow 

formation occurs along the Mohave River, although 

these and other species are living in the San Bernardino 

Mountains. Their absence_ may be due to lack of 

moisture, because only a narrow strip of ground is kept 

damp by the river. It is possibly du~ also to high 

temperature, for in larger damp areas of similar climate 

these small snails are also missing. The amount of 

rainfall in the San Bernardino Mountains and in the 

Mohave River area indicates that these species might 

have survived in a riparian habitat with 15 inches of 

rain annually. 

The present dominance of Helminthoglyptidae is 

probably due to the local extinction of much of the 

Miocene fauna. There may have been as many Miocene 

as Recent species of Helminthoglyptidae in the Mohave 

Desert, but judging from the Barstow fauna they were 

relatively less abundant. The subsequent drier climate 

of the area has presumably eliminated essentially all 

land mollusks but the Helminthoglyptidae. This 

selection may well be connected directly with body size. 

Large aquatic species in the Barstow fauna probably 

indicate a larger volume of habitable water than is now 

present in the desert. This in turn implies greater 

-rainfall. 

Concerning the Miocene vegetation of the southern 

Great Basin, Axelrod (1950, pp. 231, 234) wrote: 

The principal types of vegetation included live oak and 

conifer woodland, chaparral, arid subtropical scrub ('thorn 

forest') coastal sage, and plains grassland * * *· In the more 

southerly parts of the area, where climate was warmer, we may 

infer that woodland and chaparral rose to somewhat higher 

levels as the tropical zone was approached, much as these vegetation types do today. 

According to M. C. McKenna (oral communication) 

the large numbers of species and individuals of the 

grazing animals, such as horses, camels, and antilocaprids, and the variety of carnivores of the Barstow 

fauna are strongly reminiscent of the present fauna of 

the African savannas, with grassy plains and scrub 

forest. 

Axelrod (1950, p. 238) summarized his conClusions 

from Miocene floras for southeastern California as 

follows: 

The Madro-Ter~iary Flora, dominated by live oak woodland, 

chaparral, and thorn forest vegetation, was thriving under a 

semiarid climate of 15 to 25 inches of yearly rain distributed 

biseasonally, hot summers, and mild, frostless winters. 

Faunal evidence is consistent with this picture. 

Mollusks indicate that the area of deposition of the 

Barstow formation included a slow-moving stream or 

pond, in which lived freshwater snails and clams, and 

nearby vegetation furnishing leaf mould habitats for 

land snails. 

AGE AND CORRELATION 

The age of the Barstow formation was determined as 

late Miocene by Merriam (1911, 1919) on the basis of 

the mammalian fauna. The Barstow fauna is used as 

the vertebrate paleontologists' standard for the late 

l\rfiocene Barstovian provincial age of North America 

(Wood and others, 1941, p. 12). Late Tertiary nonmarine mollusks are known too poorly for substantiation or contradiction of this age; thus the Barstow 

mollusks are dated by the associated vertebrates. 

Correlation of late Tertiary nonmarine molluscan 
NONMARINE MOLLUSKS FROM BARSTOW FORMATION 71 

faunas is made difficult by geographic localization of 

species. Of the eleven Barstow mollusks, including 

four living species, only two have been reported previously as fossils. Both Lymnaea megasoma and 

Hawaiia minuscula are Recent species known also from 

the lower Pliocene Laverne fauna of Oklahoma. 

Hawaiia minuscula is a widespread, tolerant form considered not significant in this case; it is also known 

from several Pleistocene faunas in the High Plains. 

L. megasoma lives today under conditions widely 

different from those inferred from the Barstow and 

Laverne faunas, so that its significance is uncertain. 

Axelrod (1950, p. 234) noted a similarity of floras in the 

region~frmn the Mohave Desert to Texas and Oklahoma; 

the presence of Lymnaea megasoma in the two places 

may reflect a similarity of environment. 

DISTRIBUTIONAL RELATIONS OF THE BARSTOW 

FAUNA 

Mollusks of the Barstow fauna may be grouped 

according to their distributional relations as follows: 

1. Southern California element. The following species or their relatives are now living in Southern 

California. 

Gonidea n. sp.? 

Lymnaea mohaveana 

Helisoma? sp. 

Vallonia sp. cf. V. cyclophorella 

Pristiloma chersinellum 

Hawaiia minuscula 

Helminthoglypta alfi 

2. Locally extinct element. The following species 

or their relatives live elsewhere in the United States, but 

occurred in Southern California in Miocene time. 

Lymnaea megasoma 

Planorbula mojavensis 

3. Uncertain element. The following species are of 

uncertain distributional relationship. 

Menetus? micromphalus 

Craterarion pachyostracon 

The above data show that the Barstow fauna is most 

closely related to the one now living in Southern California. This geographic localization, persistent in 

time, helps to explain the difficulties in correlation of 

late Tertiary nonmarine mollusks. 

Other West American molluscan faunas of approximately the same _age as the Barstow fauna may be 

divided into groups as follows: 

1. Northern Great Basin faunas with few if any living 

species and several extinct genera otherwise known only 

from the N eocene of Europe (Orygoceras, Papyrotheca, 

etc.). The faunas are characterized particularly by the 

association of these European forms with the extinct 

American genera Pilsbryus, Pliopholyx, Anculopsis, 

284065-54-2 

Vorticijex, Pompholopsis, Payettia, etc., as well as extinct 

species of Fluminicola, Carinifex, Lanx, etc. Amnicolidae and Planorbidae are relatively abundant. 

a. Malheur Co., Oregon; Pliocene (Henderson and Rodeck, 

1934). 

b. Idaho formation, Idaho; Pliocene (Dall, 1924; Yen, 1944). 

c. Collinston, Utah; Pliocene (Chamberlin and Berry, 1933). 

d. Pliocene assemblage from the-Salt Lake formation, northern 

Utah (Yen, 1947). '~ e. Miocene assemblage from the Salt Lake formation, southeastern Idaho (Yen, 1946). 

f. Truckee formation, Nevada; Pliocene (Yen, 1950). 

2. Western Nevada faunas at least partly from the 

Esmeralda formation. They are characterized by the 

presence of Viviparus and Perrinilla, not surely known 

elsewhere in the western United States, of Lanx and 

species of "Melania" or "Goniobasis" occurring also in 

Group 1, and by the absence (so far as known) of the 

other forms listed under that group. No living species 

occur in the faunas. 

a. Nye and Esmerelda Counties, Nev.; Esmerelda formation, 

Pliocene (Hannibal, 1912; Turner, 1900, p. 203; Buwalda, 1914, 

p. 351). 

b. Tonopah fauna, Miocene, in Esmerelda formation?, north 

of Tonopah, Nev. (Henshaw, 1942, p. 88-89). 

3. John Day Basin faunas, Oregon. The original 

descriptions of most of these species do not reveal 

whether the specimens are·from the Oligocene and Miocene John Day formation, or the upper Miocene Mascall 

formation. For the present purpose they are treated 

as a unit, as listed by Henderson (1935, p. 45). The 

fauna shows no relationship to any other fossil fauna, but 

seems to be related to that now living in the humid 

coastal strip from Washington to Northern California. The fauna is characterized by the presence of 

Monadenia, Vespericola, Polygyrella, Ammonitella, and 

Oreohelix (Pilsbry, 1939, p. 35, 416, 560; 1940, p. 892-

893). 

4. Deep River beds, upper Miocene, Meagher 

County, Mont. This fauna, which consists of 17 terrestrial species, is in process of description by Dr. S. S. 

Berry. It seems to be most closely related to that of 

Idaho and western Montana, but contains a few genera 

now found in the Mississippi Valley. This fauna also 

seems to be unrelated to the contemporary assemblages. 

Of all these faunas only the Barstow has both land 

and freshwater species in any abundance. The other 

Great Basin faunas are entirely freshwater, the Deep 

River fauna wholly terrestrial, and the John Day Basin 

group of species essentially so. This combination of 

geographic localization and incomplete faunal representation effectively prohibits correlation over the western 

United States at the present time, but within an area 

such as the northern Great Basin correlation should be 

practical. 
72 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

LOCALITIES 

Accurate topographic maps of the Barstow Hills have 

not yet been published. Locality descriptions are 

composed of the better-known local names and airline 

distances ta.ken from aerial photographs. 

Locality 1. Three outcrops of whitish volcanic ash in a 

straight line in the northwes~ corner of Rainbow Basin, about 

one hundred yards west of the road. Shell material is mostly 

gone, the snails being chiefly represented by molds, although a 

few are well preserved. 

Locality 2. A stratum of light green volcanic ash exposed 

along the north bank of a westward-trending wash for nearly two 

hundred yards. This locality lies north of the western wall of 

Rainbow Basin, along the first wash north of the cliffs. The 

deposit is apparently fluviatile. The fossils are poorly preserved. 

Locality 3. "Lake Bed Horizon" in the canyon next south 

from Pirie Canyon. The gently dipping stratum is exposed along 

the north canyon wall for about two hundred yards, in the middle 

of theSE 7~ of sec. 15, T. 11 N., R. 2 W. The exposure is straight 

except at the east end, where the bed is sharply upturned and 

truncated. The abundant shells are generally well preserved, 

but some are slightly crushed. 

Locality 4. Gray mudstone northwest of the relatively undissected plain north of Rainbow Basin. One shell, crushed but 

otherwise well preserved, from a nodule, collected by Thane 

McCulloh. 

Locality 5. ''Carnivore Basin," 1.7 miles N. 62 degrees E. of 

the junction of Pirie Canyon and its principal northern tributary. 

Locality 6. 1.63 miles N. 51 degrees E. of the junction of 

Pirie Canyon and its principal northern tributary. 

Locality 7. 1.7 miles N. 57 degrees E. of the junction of Pirie 

Canyon and its principal northern tributary. 

'In addition, there are old localities not yet relocated 

in the field. The type series of Planorbula mojavensis 

with the vague locality designation "near Barstow" 

comes from a place not recognized by the author. The 

University of California collections contain one specimen of Gonidea and two of Helminthoglypta that probably represent at least one more locality. The Stanford 

University collection has a specimen of Afenetus? 

indicating a probably distinct locality. Merriam (1919, 

p. 445) refers to the occurrence of Anodonta? (=Gonidea) 

at rare horizons. 

OcC'urrence of Barstow mollusks 

Locality 

Species 

2 3 4 5 6 7 

-----------------1----------------

Gonidea n. sp.? -------------------------------- ____ ? ____ ____ ____ ____ ____ X 

f~~~;::o~~~~~~~~=========================== Helisoma? _____________________________________ ==== 

____ ==== X _______________________ i -T --~- ==== -x- ==== _ 

Planorbula mojavemis _________________________ ____ X X ________ X ____ X 

Menetus? micromphalus ___ -------------------- ________ X ________________ X 

Vallonia sp. cf. V. cyclophorella ________________ ________ X ___________________ _ 

Craterarion pachyostracon ________ --------~----- ____ ---- X ___________________ _ Hawaiia minuscula ____________________________ ________ X __________________ _ 

Helminthoglypta alfi--------------------------- X ____ X ____ X ________ X 

SYSTEMATIC DESCRIPTIONS 

Class PELECYPODA 

Family UNIONIDAE 

Subfamily ANODONTINAE 

Genus GONIDEA Conrad, 1857 

Gonidea n. sp.1 

Anodonta?, Merriam, 1919, Univ. California Pub. 

BulL Dept. Geology, v. 11, p. 450. 

Diagnosis.-Probably a new species of Gonidea, 

characterized by its long, narrow shape and markedly 

anterior beak. ' 

Description.-Shell long and narrow, suboval at the 

ends, slightly arcuate along the roughly parallel dorsal 

and ventral margins. Beaks about one-fifth the length 

behind the anterior end. A conspicuous, nearly 

straight ridge extending from beaks to ventroposterior 

edge. No sculpture or hinge characters shown on the 

one available mold. 

Measurements.-The complete specimen would probably have measured (in millimeters): length, 75; 

height, 31; width, 24. 

Material.-

!\umber 

Catalog ~ o. of speci- Locality Remarks mens 

uc 34184_--- T 3170 ______ _ 1 "Barstow"_ Described specimen. 

1 2_ _ _ _ _ _ _ _ _ _ Identifiable as unionid 

only. 

Remarks.-Compared with specimens of the recent 

Gonidea angulata (Lea), the Barstow species is narrower 

and more elongate, with the margins more nearly 

parallel and the beaks more anterior. It differs from 

the narrower forms of G. coalingensis Arnold of the 

Tulare formation (Pliocene and Pleistocene) by its 

posteriorly slightly narrower shell and arcuate ventral 

margin. The Barstow species differs from G. hemphilli 

Hannibal of the Orinda formation (Pliocene) by its 

larger size and more elongate shape. 

Although the specimen described is sufficiently well 

preserved to name, the author refrains from so doing 

for the following reasons. (1) The exact locality is 

unknown. (2) It is desirable to learn the characters 

of the hinge before description, and therefore waiting 

for more specimens seems the best course. (3) Merriam 

(1919, p. 445) indicated that Gonidea occurs at more 

than one locality. 
NONMARINE MOLLUSKS FROM BARSTOW FORMATION 73 

Class GASTROPODA 

Family LYMN AEIDAE 

Genus LYMNAEA Lamarck, 1799 

Subgenus STAGNICOLA Jeffreys, 1830 

Lymnaea. moha.vea.na. Taylor, n. sp. 

Plate 20, figures 1, 2. 

Diagnosis.-A species of the L. palustris group, distinguished by the wide expansion of the aperture and 

the consequently very broad body whorl. 

Holotype.--S 8077, loc. 3, west end of Barstow Hills, 

7 miles north of Barstow, San Bernardino County, 

California. "Lake Bed Horizon" in the canyon next 

south from Pirie Canyon. Middle of SE }~sec. 15, T. 11 

N., R. 2 W. Barstow formation, upper Miocene. R. 

Tedford and R. Schultz, 1949. Paratypes, T 1785, 

2035, S 8078, USNM 561488, UC 34194-34197. 

Description~--Shell thin, elongate, narrowly conic, 

base strongly expanded; spire acute, approximately 

three-fifths the total shell length; whorls seven, only a 

little convex on the spire; suture slightly constricted; 

body whorl widely expanded, giving an almost obtusely 

rounded appearance. Aperture effuse, elongate-oval; 

outer lip thin, expanded; parietal lip appressed to form a 

heavy callus; columella twisted to form a conspicuous, 

thick plait; umbilical chink generally closed, sometimes· 

narrowly open. Shell smooth except for numerous 

irregular, close growth lines. 

Measurements of holotype (in millimeters).-Length, 

27.3; width, 12.4; length of aperture, 13.2; width of 

aperture, 7.6; whorls 6. It is slightly broken, and 

probably would have measured, whole: length, 28.5; 

width, 13; length of aperture, 13.8; width of aperture, 

8; whorls 7. 

Material.-

Catalog No. ~~umber of 

specimens Locality Remar-ks 

------- ----~-- ~--- ----------------·--·-

s 8077 ·- - - . -- -- - - - - - 1 3 Holot.ype. 

s 8078_--------- - -- H 3 

T 1785 _____________ 2! 3 Poor specimcnA. T 2035 _____________ 6 3 

uc 34194-34h)7---- 4 3? 

u c--- --------·-- --- 11 3? 

U~N:\1 561448_ -···--- 15 3 T 2444 _____________ 2 5 Do. 

T3136 ______________ 3 5 Do. 

The material from locality 3 is composed about 

equally of molds in compacted volcanic ash and specimens in which most of the shell remains. Lymnaea 

mohaveana is the commonest snail at its type locality. 

It is more abundant than the above figures would indicate, but the great majority of specimens collected are 

badly eroded molds, ba.rely identifiable. 

Remarks.-Lymnaea mohaveana appears closest to L. 

palustris (Muller), from which it differs in the broadened 

body whorl and expanded aperture. 

Subgenus BULIMNEA Haldeman, 1841 

Lymnaea. mega.soma. Sa.y 

Plate 20, figure 3. 

Material from the Barstow formation was compared 

with the many Recent specimens in the University of 

Michigan collection, but no differences were found. 

... o/laterial.-

Catalog No. 

T 3171 ____________ _ T 1786 ____________ _ T 2036 ____________ . T 2037 ____________ _ 

uc 34190-34193_--- uc ________________ _ T 2039 ____________ _ 

Nu~ber of Localitv I speCimens · Remarks 

2 

g 

11 

10 

4 

3 

1 

2 Poor specimens. 

3 Do. 

3 

3 Do. 

3? 

3? 

4 Do. 

Remarks.-In studying the Barstow specimens comparison was made with Lymnaea lavernensis Leonard 

and Franzen (1944, p. 22, pl. 4, fig. 11), of the lower 

Pliocene Laverne formation of Oklahoma. This species 

was compared by Leonard and Franzen with the Recent 

L. (Stagnicola) magister Baker, but not with L. (Buhmnea) megasoma Say, with which it appears synonymous. 

L. lavernensis agrees with L. megasoma in several significant respects: The shell is large, ovate-conic, with a 

relatively short spire and convex whorls. The nuclear 

whorl is relatively large, larger than in Stagnicola, 

Fossaria, Pseudosuccinea, etc. Sculpture . consists of 

numerous, irregular, coarse, low, rounded growth lines, 

which on the earlier whorls are cut by subobsolete spiral 

striae. These characters appear to place L. lavernensis 

definitely in Bulimnea. Comparison of the many 

Recent as well as fossil specimens in the University of 

Michigan collections (including paratypes of L. lavernensis) shows their specific identity. 

Lymnaea (Bulimnea) petaluma Hanna (1923, p. 37, 

pl. 2, figs. 3, 7) may or may not be distinct from L. 

megasoma; the material seen is inconclusive. 

Family PLANORBIDAE 

Subfamily HELISOMATINAE 

Genus HELISOMA Swa.inson, 1840 

Subgenus PIEROSOMA Dall, 1905 

Helisoma. t sp. 

A large planorbid from locality 2 (T 3172) may be 

referable to this group. 
74 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Subfamily PLANORBULINAE 

Genus PLANORBULA Haldeman, 1840 

Planorbula mojavensis (Hannibal) 

Plate 20, figures 10-15. 

Planorbis (Segrncntina) Afojavcnsis Hannibal, 1912, Proc· 

Malacol. Soc. London, v. 10, p. 157,200, pl. 8, figs. 2·ia, b (not 27). 

Planorbis mohavens£s Hannibal, Merriam, 1919, Univ. California Pub. Bull. Dept. Geology, Y. 11, p. 450. 

Diagnosis.-A Planorbula characterized by its relatively large upper palatal and small lower palatal 

lamella, and by the apparent absence of a basal lamella. 

Holotype.-UC 34178? (not surely identified). "Rosamond Series, California. Near Barstow, Mojave 

Desert, California (J. C. Merriam, C. L. Baker)." 

-Paratypes, B 8924, S 5460, UC 34179-34182. 

Description.-Shell discoid, biconcave, presumably 

ultra-dextral, of moderate size. Whorls about five, 

convex, regularly rounded; sutures strongly impressed. 

Sculpture of fine, oblique growth lines. Aperture reniform, lamellate. Umbilicus and spirepit wide, shallow, 

about equal in size. Dentition as follows: a large, 

sigmoid, obliquely transverse parietal lamella, about }~ 

mm high along most of its length, sharply descending 

at the ends, highest in the middle, distal end about 1 mm 

from the left suture; a small tubercular sub parietal 

lamella about halfway between distal end of parietal 

lamella and left suture, slightly behind end of lamella; 

a small, elongate suprapalatallamella in the center of 

the right side of the whorl; a medium sized, slightly 

curved upper palatal lamella intermediate between the 

supra palatal and lower palatal lamellae; and a small, 

tubercular lower palatal lamella at the periphery. 

Measurements, in millimeters, without allowance for 

wear.-

:Major 

diameter 

Minor 

diameter Height 

()riginal 

number of 

whorls 

Catalo!! No.~ 

6. 2 

10.0 

Material.-

Catalog No. 

p 12~-------------- T 2040 ____________ _ T 3173 ____________ _ T 1788 ____________ _ 1' 3134 ____________ _ B 8924 ____________ _ 

s 5460 ____________ _ 

uc 34178 --------- uc 34179-34182_---

TJC _______ ---------

5. 5 2. 0 

6. 7 3. 5 

Number 

of speci- Locality 

1nens 

1+ 2 __________ _ 

5 2_ ---- -·---- 2 2 ________ -- 5 3 _________ - 3 6 __ . _______ _ 

1 "Near Barstow". 4 _____ do ____ _ 

1 "Barstow" _ 4 _____ do ____ _ 11 _____ do ____ _ 

4H nc 34178 

5 D 8H24 

He marks 

lu matrix. 

Poor specimens. 

Do. 

Juv{'nile. 

Para type. 

Do. 

Holotype? 

Para types. 

Do. 

Remarks.-Unfortunately the holotype has not yet 

been identified with certainty. A specimen labelled 

"Type" in Hannibal's handwriting (UC 34178) does 

not agree well with the original figures of the specimen 

designated as type (Hannibal, 1912, p. 210). 

A paratype of Ptanorbis mojavensis (S 8080) is 

referred to Menetus? micromphalus. 

Planorbula mojavensis differs from other species of the 

genus by its relatively large upper palatal lamella and 

relatively small lower palatal lamella, and by the apparent absence of a basal lamella. In the original description Hannibal indicates the presence of a supraparietal 

lamella, but none of the speci1nens available sh9w it. 

Segmentina durhami Hanna and Hertlein (1938, 

p. 109, pl. 21, figs. 3-5), from the Oligocene of Washington, was considered to be related to S. armigera (Say), 

now called Planorbula. P. mojavensis differs from 

P. durhami by its smaller size, lesser height, and 

biconcavity. The lamellae of P. durhami were not 

preserved well enough for comparison. 

Genus MENETUS H. and A. Adams, 1855 

Menetus1 micromphalus 1 Taylor, n. sp. 

Plate 20, figures 4-9. 

Diagnosis.-A medium sized Menetus-like planorbid 

with rapidly increasing whorls and a peripheral subangulation. 

Holotype.-T 2038a, loc. 3, west end of Barstow Hills, 

7 miles north of Barstow, San Bernardino County, 

California. "Lake Bed Horizon" in the canyon next 

south from Pirie Canyon. Middle of SE 1/4, sec. 15, 

T. 11 N., R. 2 W. Barstow formation, upper Miocene. 

D. W. Taylor and M. C. McKenna, 1-II-1950. Paratypes, T 2038, S 8079, USNM 561451. 

Description.-Shell moderately large, discoid, biconcave, presumably ultradextral. Whorls about 4~~, 

the last rapidly expanding, rounded at the aperture but 

variably angular from about the second to the fourth 

whorl. Aperture semicircular, oblique, slightly expanded; lip thickened. c Umbilicus small and shallow; 

spire pit deep and broad. The slightly imperfect 

material shows no sculpture. 

Afeasurements (in millimeters, with allowance for 

damage), of holotype.-Major diameter, 12; minor 

diameter, 8.5; height, 4; whorls 4 1/2. 

111aterial.-

Catalog No. 

s 807fl------- -·------------ s 80~0--- -·----- ·-------- --- T 2038 __________________ _ 

· T 2038a _ - _______ ·-------- - FSNM fi6145L __________ _ 

Number 

of RpecimAns 

1 Gr. micros, small, and omphalns, umbilicus. 

r.oealit.y 

5 3 

1 "Near Barstow." 

6 3 

1 3 

8 ~ 
NONMARINE MOLLUSKS FROM BARSTOW FORMATION 75 

Remarks.--The paratype of Planorbis mojavensis 

here referred to J\,Jenetus? micromphalus (S 8080) has a 

series of low, broad grooves on the periphery of the 

third whorl, giving it an undulatory appearance. They 

become less prominent coarse growth lines on the left 

side of the body whorl The specimen is a mold, and 

thus it is uncertain whether these lines are coarse growth 

striae or a series of internal shell thickenings only. The 

holotype of M.? micromphalus does not show coarse 

striae on the preserved parts of the shell 

Family V ALLONllDAE 

Genus VALLONIA Risso, 1826 

Vallonia sp. cf. V. cyclophorella Sterki 

Plate 20, figures 24-26. 

One specimen (T 1792) with the lip absent con1pares 

favorably with this recent species in size, excentricity 

of body whorl, and sculpture. The chief difference 

noted is that the fossil has a relatively gradual increase 

of whorls, while in recent Vallonia cyclophorella the last 

whorl expands more rapidly. 

Material.--

C t l N Number of 1 11.t a ,a og ~ 0 · specimens Joca Y 

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

Tl792 __________ . _______ . ____________ _ 

Family ARIONIDAE 

Subfamily BINNEYINAE 

Genus CRATERARION 2 Taylor, n. g. 

3 

Characters those of the type and only known species. 

Craterarion pachyostracon. s Taylor, n. sp. 

Plate 20, figures 16-20. 

Diagnosis-A very thick, convex subspiral, longoval slug plate. 

Holotype.-S 8073, loc. 3, west end of Barstow Hills, 

7 miles north of Barstow, San Bernardino County, 

. California. "Lake Bed Horizon" in the canyon next 

south from Pirie Canyon. Middle of SE }~, sec. 15, 

T. 11 N., R. 2 W._ Barstow formation, upper Miocene. 

D. W. Taylor, Xl-1950. Paratypes, T. 1791, S 8074, 

B 19936, G 5924, UC 34183, USNM 561449. 

Description.-Shelllong-oval, thick and heavy, convex. Nucleus hemispherical, situated nearly at the 

posterior margin and slightly to the right of the median 

line; deflected to the right so that the shell has about 

one-tenth of a whorl. Right posterior margin bearing 

a small projection, often slightly curved to the left. 

Left posterior margin in larger specimens also showing 

a small tubercle. Edges thickened, with later growth 

2 Gr. crater, a basin, and Arion, type genus of the tamily. Named for its occmrence 

in the Great Basin. 

a Gr. pachy, thick, and ostracon, shell. 

apparently taking place only dextrally and anteriorly. 

Dorsal surface roughened by irregular growth wrinkles; 

a few faint raised longitudinal lines are visible toward 

the anterior margin of the best specimens. Ventral 

surface without growth lines or any sort of SC\Upture, 

irregularly concave, callused slightly at the po::;terior 

end. 

J\,Jeasurements, in millimeters.-

Catalog No. Length Width Thickness 

-------------·-----------------

s 8073- - - - . - - - - - -- - - - - - .. 8.5 5. 3 3. 5 

T 1791A ________________ 8.0 5. 1 1.4 

T 1791B __ ·- - - - - - - - - -- - - - 7. 4 4. 6 1.9 

B 19936_-------- -- . - --- 6. 8 4. 2 2. 0 

"A1aterial.-

Catalog No. Number of Locality Remarks specimens 

B 19936 ________________ 1 3 Para types. 

G 5924 ___________ .. _____ 2 3 Do. 

s 8073 __________________ 1 3 Holotype. A 8074 __________________ 6 3 Para types. 

T 1791 _________________ 11 3 Do. 

uc 34183 _______________ 1 3? Do. 

l"TSNM 561449 __________ 6 3 Do. 

Remarks.-Craterarion has characters of the two 

recent genera Binneya and Hemphillia but is close to 

neither. Its shell shows a tendency toward spiral 

coiling, as in Binneya, and the weak raised spiral lines 

are reminiscent of the embryonic sculpture of Binneya. 

The coiling is however, not strong, and in this respect 

approaches Hemphillia. Craterarion differs radically 

from both in the extreme thickness of the shell, the 

degree of coiling, and the possession of the posterior 

"hook" in young specimens. In this character it is 

similar to some species of Deroceras. 

Slugs are known from the Miocene of Europe, but 

this is apparently the earliest record for any slug in 

North America. The only other pre-Pleistocene slug 

known from America is Deroceras aenigma Leonard 

(1950, p. 38), described from the type section of the 

upper Pliocene Rexroad formation of Smith, 1940, 

revised by Hibbard, 1950, in Meade County, Kansas. 

Family ZONITIDAE 

Subfamily ZONITINAE 

Genus PRISTILOMA Ancey, 1887 

Subgenus PRISCOVITREA H. B. Baker, 1931 

Pristiloma chersinellum (Dall) 

Plate 20, figures 27-29. 

Comparison of the Barstow specimens was made with 

a lot of P. chersinellum from Cottonwood Camp, 
76 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Elizabeth Lake Canyon, Los Angeles County, California. Neither W. 0. Gregg nor the writer could find 

any differences between the two sets. 

Material.-

Genus HAWAIIA Gude, 1911 

Hawaiia minuscula (Binney) 

Pla.te 20, figures 21--23. 

One slightly imperfect specimen is referred to this 

living species. Characters shown by the fossil agree 

with recent specimens, but better material might show 

differences. 

Material.-

Catalog No. Number of L . 

specimens ocauty 

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

T 1792a---------------------~------

Family HELMINTHOGLYPTIDAE 

Subfamily HELMINTHOGLYPTINAE 

Genus HELMINTHOGLYPTA Ancey, 1887 

Helminthoglypta al:fi Taylor, n. sp. 

Plate 20, figures 30-32. 

3 

Diagnosis.-One of Pilsbry's "Mohave Desert Series" 

of Helminthoglypta, closely related to H. graniticola and 

H. g. arida. It differs from these in its smaller size, 

intermediate height of the spire, and subcircular 

aperture. 

Holotype.~S 8075, loc. 1, Barstow Hills, 7 miles 

north of Barstow, San Bernardino County, California. 

A series of three outcrops of a stratum of whitish 

volcanic ash lying in a straight line in the northwest 

corner of~Rainbow Basin. Barstow formation, upper 

Miocene. D. W. Taylor, 8-II-1948. Paratypes, B 

15373, 19935, G 5925, S 8076, T 1107, 1108, 1417, 1439, 

3137, 3138, USNM 561450. 

Description.-Shell helicoid, small for the genus, 

slightly to moderately elevated; whorls four to five, 

evenly rounded, regularly increasing; suture slightly 

impressed; body whorl conspicuously descending to the 

lip in approximately the last twelfth of its turn. Aperture oblique, and, except for the excision made by the 

preceding whorl, oval, though nearly circular; lip' 

somewhat thickened and slightly reflected. Umbilicus 

small, contained five to six times in the diameter of the 

shell, steep-sided, permeable to the apex, but little if at 

all covered by the reflection of the lip. Later whorls 

smooth except for the irregular, oblique growth lines; 

no spiral sculpture. 

Measurements (in millimeters) of adult specimens.-

Diameter Number 

Catalog No. Height Diameter of urn- of 

bilicus whorls 

---------------------1-------------

s 8075 ___________ _ s 8076 ___________ _ 

s 8076-- - .. - -- --·--- s 8076 ___________ _ 

USNM 561450 ____ _ U~NM 561450 ____ _ 

'A1aterial.-

Catalog No. 

5. 8 

6.4 

6.4 

6.4 

6. 0 

5. 3 

B 15373 _____________________ ---

B G 5925 19935-----------------------~ ________________________ _ 

s 8075 __ ---------------------- 8 8076 ________________________ _ 

T 1107 ________ ~---------------- T 1108 ________________________ _ T 1417 ________________________ _ T 1439 _______ ~ ______________ . __ T 3.137 __________ ...... ___________ _ T.3138 ________________________ _ 

USNM 561450 ______ ---·--------· __ 

T T 2445 1789----~-------------------- ________________________ _ T 3135 _________________________ _ 

uc 34185-34189---- -~---- -.------

10. 6 2. 4 

11.4 1.9 

11. 5 2. 0 

11. 9 2. 0 

10. 1 2. 0 

9. 3 1. 7 

Number of I 

specimens 

1 1. 

4 1. 

2 1. 

1 1. 

8 1. 

1 1. 

8 1. 

-1: 1. 

5 1. 

2-1: 1. 

84 1. 

6 1. 

7 3. 

6 5. 

2 5. 

4-. 1 

5. 0 

4. 5 

4. 6 

4. 2 

4. 2 

Locality 

5 "Barstow." 

Remarks.-ln general shape immature (3%-4 whorls) 

specimens of Helminthoglypta alfi and H. graniticola 

arida are the same, except that the body whorl of the 

latter is higher, relative to the width of the shell. Adult 

shells of H. g. arida are larger, more depressed, have a 

lower spire, a more oval aperture, and a proportionately 

broader body whorl. In addition H. alfi has the very 

last portion of the body whorl strongly deflected, 

whereas in H. g. arida the deflection of the body whorl 

is more gradual, and takes up about an eighth of the 

whorl. H. alji differs from H. graniticola sensu stricto 

in being more depressed, although it can be matched by· 

a few specimens of the latter in this respect, and in 

being smaller. It also has a proportionally higher body 

whorl and a more nearly circular aperture. The deflection of the body whorl is more conspicuous than in 

H. graniticola. 

Only one specimen (T 3135) shows clearly the embryonic sculptUre. The first half-whorl has numerous 
NONMARINE MOLLUSKS FROM BARSTOW FORMATION 77 

oval or tear-drop-shaped papillae arranged radially on 

a backgronnd of irregular, fine radial wrinkles. These 

wrinkles alone are present on the second half-whorl, and 

thereafter become fine, irregular growth lines. This 

sculpture shows that the specimen cannot belong to 

Micrarionta (Eremarionta), but must be placed in 

Helminthoglypta. 

LITERATURE CITED 

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and Kings Counties, California: U. S. Geol. Survey Bull. 

396. 

Axelrod, D. I., 1950, Evolution of desert vegetation in western 

North America: Carnegie Inst. Washington Pub. 590, 

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Baker, F. C., 1911, The Lymnaeidae of North and Middle 

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xvi, 539 p., 58 pl. 

--- 1928, The fresh water Mollusca of Wisconsin, Part I, 

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xx, 507 p., 28 pl. 

--- 1945, The molluscan family Planorbidae: Illinois. Univ. 

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Dall, W. H., 1924, Discovery of a Balkan fresh-water fauna in 

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from western North America: Jour. Paleontology, v. 12, 

p. 106-110, pl. 21. 

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v. 10, p. 112-211, pl. 5-8. 

Hemphill, H., 1891, A collector's notes on variation in shells, 

with some new~varieties: Zoe, v. 1, p. 321-337, pl. 10. 

Henderson, J., 1935, Fossil non-marine Mollusca of North 

America: Geol. Soc. America, Spec. Paper. 3 vii, 313 p. 

\ 

Henderson, J., and Rodeck, H. G., 1934, New species of Pliocene 

Mollusca from eastern Oregon: Jour. Paleontology, v. 8, 

p. 264-269, pl. 37, figs. 1-10. 

Henshaw, P. C., 1942, A Tertiary mammalian fauna from the 

San Antonio Mountains near Tonopah, Nevada: Carnegie 

Inst. Washington Pub. 530, p. 77-168, pl. 1-11. 

Hibbard, C. W., 1950, Mammals of the Rexroad formation from 

Fox Canyon, Kansas: Mich. Univ. Mus. Paleont., Contr., 

v. 8, p. 113-192, pl. 1-5. 

Leonard, A. B., 1950, A Yarmouthian molluscan fauna in the 

midcontinent region of the United States: Kans. Univ. 

Paleont. Contr., Mollusca, art. 3. 48 p., 6 pl. 

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Laverne formation (lower Pliocene) of Beaver County, 

Oklahoma: Kans. Univ. Sci. Bull., v. 30, part 1, p. 15-39. 

Merriam, J. C., 1911, A collection of mammalian remains from 

Tertiary beds on the Mohave Desert: Calif. Univ. Pub., Bull. 

Dept. Geology, v. 6, p. 167-169, pl. 29. 

--- 1919, Tertiary mammalian faunas of the Mohave Desert: 

ibid., v. 11, p. 437a-437e, 438-585. 

Pilsbry, H. A., 1934, Mollusks of the fresh-water Pliocene beds 

of the Kettleman Hills and neighboring oil fields, California: 

Acad. Nat. Sci. Philadelphia, Proc., v. 86, p. 541-570, pl. 

18-23. 

--- 1939, Land Mollusca of North America (north of Mexico): 

Acad. Nat. Sci. P:Qj.ladelphia, Mono. 3, v. 1, part 1. 

xvii+1-573+ix p. 

--- 1940, ld.: ibid., v. 1, part 2. viii+575-994+ix p. 

--- 1946, ld.: ibid., v. 2, part 1. viii+ 1-520 p. 

--- 1948, ld.: ibid., v. 2, part 2. xlvii+521-1113 p. 

Russell, R. J., 1926, Climates of California: Calif. Univ. Pub. 

Geog., v. 2, p. 73-84, 1 map. 

Smith, H. T. U, 1940, Geologic studies in southwestern Kansas: 

Kans. Geol. Surv. Bull. 34. 212 p., 34 pl. 

Thompson, D. G., 1929, The Mohave Desert region, California; 

a geographic, geologic, and hydrologic reconnaissance: U. S, 

Geol. Survey Water-Supply Paper 578. xi+759 p., 34 pl. 

Turner, H. W., 1900, The Esmerelda formation, a fresh-water 

lake deposit: U. S. Geol. Survey Ann. Rep. 21, part 2, p. 

191-208, pl. 24-29. 

Wood, H. E., 2d, and others, 1941, Nomenclature and correlation of the North American continental Tertiary: Geol. Soc. 

America, Bull., v. 52, p. 1-48, pl. 1. 

Woodring, W. P., Stewart, R. and Richards, R. W., 1940, Geology 

of the Kettleman Hills Oil Field, California; stratigraphy, 

paleontology, and structure: U.S. Geol. Survey Prof. Paper 

195. v+ 170 p., 57 pl. 

Yen, T.-C., 1944, Notes on fresh-water mollusks of Idaho forma~ -

tion at Hammett, Idaho: Jour. Paleontology, v. 18, p. 101-

108. 

--- 1946, Late Tertiary fresh-water mollusks from southeastern Idaho: Ibid., v. 20, p. 485-494, pl. 76. 

--- 1947, Pliocene fresh-water mollusks from northern Utah: 

Ibid., v. 21, p. 268-277, pl. 43. 

--- 1950, A molluscan fauna from the type section of the 

'Truckee formation: Am. Jour. Sci., v. 248, p. 18Q-193, pl. 1. 

INDEX 

[Italic numbers indicate descriptions] 

A hp 

Abstract______________________________________________________________________ 67 

acus, Micrarionta rowellL _ _ ___ _ _ __ _ __ _ ____ _ ____ _ _____ _ ___ _ _ __ _ _ _ _ _ ___ _ ___ _ _ __ _ 69 

aenigma, Deroceras_____ __ ____ _ ___ __ _ _ ____ ___ _ ___ ___ ___ _ ___ _ _ __ _ _ __ _ ___ _ __ _ _ ___ 75 

Age of Barstow formation _____________________________________________________ 70-71 

alfi, Helminthoglypta _________________________________ _______ 67, 68, 69, 71, 72, 76, pl. 20 

amboiana, Micrarionta rowellL _________ -------------------- ________ ____ _______ 69 

ammon, Helisoma ___________ _______ -------------------------- ___ _____________ _ 69 

Ammonitella___ _ _ _ ___ _ ___ ___ _ ___ _ __ _ __ _ _ ___ _ _ __ ___ _ _ ___ ____ _ _ __ _ ___ _ __ _ ___ _ __ _ 71 

Amnicolidae __________________________________________________________________ 69, 71 

Anculopsis______ _ _ ___ _ ___ _ __ _ ___ _ ___ _ ___ _ ____ ___ _ __ _ ___ _ ___ _ _ __ _ __ _ ___ _ __ _ __ _ _ 71 

Ancylidae. _ ____ __ _ __ _ _ __ _ ___ ___ _ ___ _ ___ _ _______ ___ ____ _ ____ _ __ _ ___ _ ______ _ __ _ 69 

angulata, Gonidea_ _ ___ _ ___ ___ _ __ _ ___ _ _ _ _ __ _ _ _ __ ____ __ ____ _ _ __ _ _ ______ ____ _ ___ _ 72 

subangulata, Anodonta_____________________ ____________ _______________ ____ 67 

Anodonta__ _ _ __ _ ___ __ ______ _ _ __ ____ _ _____ ___ _ ___ _ __ __ _______ _ ___ __ _ ______ _ __ _ _ . 72 

angulata subangulata ______ _______ ------------------------------------- ____ 67 

Aquatic species_______________________________________________________________ 69 

argus, Micrarionta_ __ ___ ___ __ _ _ _ __ _ _ ___ _ __ ___ _ _ ______ _ ___ __ __ ____ ____ _ ___ ____ _ 69 

arida, Helminthoglypta granticola _ ____________________________________________ 69, 76 

armigera, Planorbula____ _ _ __ _ __ _ _ __ _ ____ __ __ _ ___ _ __ _ _ ___ __ ___ ___ _ _ ______ _ _ __ _ _ 68 

Segmentina_ __ ___ _ ___ _ ___ _ ___ ___ _ ____ ___ _ ___ _ __ _ ___ _ __ __ _ __ _ _ ___ _ __ _ _ _ _ _ _ _ 74 

avawatzica, Sonorelix_ __ _ __ _ _ ___ _ __ _ _ __ _ _ __ _ _ ___ _ ___ _ ___ _ __ _ _ _ __ _ _ ___ _ _ _ _ _ _ _ _ _ _ 70 

B' 

bakerensis, Micrarionta rowelli_________ _ ____ ________ ____ ________ ____ ____ ____ ___ 69 

Bibliography_________________________________________________________________ 77 

Binneya _____ _____________ --------------- _________________ -------------------- 68, 75 

bulimoides cassi, Lymnaea_____________________________________________________ 69 

c 

Cache formation______________________________________________________________ 68 

Cache Lake bed______________________________________________________________ 67 

californiense, Helisoma tenue ________ ----------------------------------------- _ 69 Carinifex_____ _ ___ ______ ___ ___ ___ _ __ _ _ __ _ _____ ___ _____ __ _ _ ___ _ ___ _ _ __ _ _ _ ______ _ 71 

casertanum, Pisidium__ ____ ____ ___ ____ _ ____ ____________ ___________ ____ ________ 69 

cassi, Lymnaea bulimoides _________ ---------------------------------- _______ ___ 69 

chersinellum, Pristiloma ________________________________________ 67, 68, 69, 71,75 pl. 20 

Climate of Mohave Desert____________________________________________________ 69 

coalingensis, Gonidea ___ _______________________________________________________ 67, 72 

Contra Costa Lake beds, CaliL______________________________________________ 68 

cooperi, Gonidea____ ____________ __ _ __ _ _ _ ___ _ ____ __ _ _ _ _ _ __ _ ____ _ ______ _ __ _ _ _ _ _ _ _ 67 

Correlation of Barstow formation _____________________________________________ 7Q-71 

Craterarion pachyostracon. __________________________________ 67, 68, 69, 71, 72, 75, pl. 20 

crotalina, Helminthoglypta__ _ __ _ _ _ _ _ ___ _ _ ___ _ ___ _ _ __ _ ___ _ ___ __ ___ _ __ ____ ____ _ _ _ 69 

cyclophorella, Vallonia ____________________________________________ 67, 68, 69, 71, 72, 75 

D 

Deep River beds, Mont______________________________________________________ 71 

Deroceras _________ --------- ___________________________________________________ 70, 75 

aenigma_ _ _ _ _ __ ____ ____ ___ _ __ _ _ __ _ _ ____ __ _ ____ ___ ________ ___ _ ___ _ ___ _ __ __ _ 75 

monentolophus_______ _____ __ ___ _ _ ___ _ _ _ ___ ____ _ _ ___ ____ _ __ _ _ ______ _ ___ ____ 69 

Distributional relations offauna ____________________ -------------------------- 71 

durhami, Planorbulo_ _ _ _ _ __ _ __ _ ____ _ ___ _ ___ ___ ____ _ ___ _ _______ ____ ___ _ __ __ _ __ _ 74 

Segmentina_ _ __ __ __ _ _ __ _ _ _ _ _ _ _ _ _ __ _ _ __ ____ _ ___ _ __ _ _ ____ __ _ ___ _ ___ _ __ _ __ __ _ 74 

E 

(Eremarionta), Micrarionta ___________ ---------------------------------------- 77 

Esmeralda formation ________________________________ -------------------______ 71 

F 

Ferrissia _____ _________________________________________________ --..------ _ _ _____ 70 

fragilis_____________ _ _ _ _ _ _ __ ____ _ __ _ _ ___ ___ _ __ _ ___ _ _ _ ___ ____ ___ _ ____ _ ___ ___ 69 

fisheri, Helminthoglypta ____ --------·------------------------------------------ 69 Fluminicola_____ _______ _ ___ _ ______ _ ____ _ __ _ ___ _ __ _ _ __ __ _ _ _ _ __ _ ___ ____ __ _ ___ ___ 71 

Fossaria_ _ ___ _ ___ ____ __ _ _ _ _ _ __ _ ___ __ _ _ _ ___ _ ___ ___ __ _ ___ ____ _ ___________ _ ______ 73 

fragilis, Ferrissia. _ ___ _ _ __ _ _ __ __ __ _ _ __ __ _ _ _ _ ___ _ __ _ _ ___ _ _ __ _ ___ _ ___ ____ _ ___ _ ___ 69 

G Page 

Gonidea __ ______________________ -------- _________________________ -_______ --- __ _ 70 

angulata ______ ______________________________________ --- ______ -_ _ _ __ _ _ _ _ _ _ __ 72 

coolingensis ___________________________ ------------------------- ___________ 67, 72 

cooperi___ ____ _ _ ____ _ ___________ ___ _ ___ ____ _____ _______ _________ ________ ___ 67 

hemphilli_ _____________________________________ --------------------------- 68, 72 

n. SP--------------- ---------------------------- _c __ - ---------------- 67, 69, 71,72 Goniobasis_ _ __ _ _ _ _ _ __ _ ___ _ _ ___ _ __ _ _ __ _ _ _ _ _ _ __ _ _ _ __ _ _ __ _ _ __ _ _ __ _ _ _ __ _ __ _ _ ___ _ __ 71 

graniticola, Helminthoglypta ___________________________________________________ 69, 76 

arida, Helminthoglypta. ____________________________________ -------- _______ 69, 76 

Great Basin, northern, faunas. ____________________ --------------------------- 71 

greggi, Helminthoglypta_______ ___ _ ___ ____ _ ___ _ ____ ____ ____ ____ _____ _ __________ _ 69 

Gyraulus ________________________________________________ --------- _ ______ ____ _ 70 

parvus williamsonL _ _ ____ ____ __ _ ___ _ ___ _ ____ ____ ________ ____ ________ _____ 69 

H 

Habitats, damp _________________________________________________ ---------____ 70 

of Recent species in Mohave Desert_ __ ----------------------------------- 70 Hawoiia ___ _____________________ --- __________ -- __ -- ______ -- _____ ---------- _ __ _ 70 

minuscula __ _________ -------------- _____________________ 67, 68, 69, 71, 72, 76, pl. 20 

Helisoma. ______________________________________ ------------------------------ 70,72 

ammon _____________________________________________________ ---___________ 69 

sp _______________________________________________________________ 67, 68, 69, 71,79 

tenue californiense ___ ______________________________ -________ ---- _ ------- ___ 69 

Helminthaglypta alfi __ ----------------------- _ ------------ __ 67, 68, 69, 71, 72, 76, pl. 20 crotalina~- __________________________________________________ -- _____ ------ _ 69 

fisheri ____ ___________________________________________ ---- __ ------------ _ ___ 69 

graniticola ________________________________________________________________ 69, 76 

arida _____ _______________________________________________ -- ___ ---- _____ 69, 76 

greggi_ _____________________________________________________ ------ _ --- _ __ __ 69 

jaegeri_ _____________________________________________ ------------------ _ ___ 69 

mohaveana ___ _______________________________________________ --- ___ ---- ____ 69, 70 

Helminthoglyptidae ________________________________________ ------- _ ------ ____ 69, 70 

hemphilli, Gonidea _______ ----------------------------------------------------- 68 

Hemphillia ___ __________________________________ ------------ __ ---------------- _ 68, 75 

Hydrobia sp ____________________________________________ ----- _____ ---------- ___ 69 

I 

Idaho formation. _______________________________________ -- ____ ---- ____ -_- ____ _ 

J 

jaegeri, Helminthoglypta __ _ ------- ______ ---- _____ --------~---------------------

John Day Basin faunas ________ ----------- ____ --------------------------------

L 

71 

69 

71 

Land snails, damp habitat____________________________________________________ 69 

dry habitaL ________ ----------- ____________ ----- __ ----------------------- 69 

Lanx ___________________________________ -_______ --- ___ ------------------------ 71 

Laverne formation ___________________________________ ------------------------- 68,73 

lavernensis, Lymnaea __________________________________ -___ ------------------__ 73 

Lirnacidae _______________________________________ ---------------------------- _ 69 

Localities of collection _________________ --------_--- ________ ------------------- 72 

Location of Mohave Desert _______________________________________________ ---- 69 

Lymnaea __ ------------------ ____________________________ -----------------____ 70 

(Bulimnea) megasoma _____ ___________________ ---------------------------- _ 73 

petaluma ___ ---------- ____ ---------------_-------------------------------- 73 bulimoides cassL ________________________________ -------------------------- 69 

lavernensis _________ ________________________ ------------------------------- 73 

megasoma __ --------------------------------------- _____ 67, 68, 69, 71, 72, 73, pl. 20 mohaveana ______________________________________________ 67, 68, 69, 71, 72, 79, pl. 20 

palustris ___________________________________ ------------------------------ _ 68, 73 

nutalliana __________________________________ ------------------------------ 68 

(Stagnicola) magister ____ -----------_--- __ --------------------------------- 73 Lymnaeidae _____________________________________________________ --------- _ __ _ 69 

79 
80 INDEX 

M Page Page 

magister, Lymnaea (Stagnicola) _____ _ ___ ______ _ ___ __ ____ ___ _ _ ___ _ __ ____ ___ _ ___ 73 Planorbula armigera ___________________________________________________ -- ___ -- . 68 

Margaritana subangulata__ __ ___ ___ _ __ _ _ __ _ ___ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ ___ _ __ _ _ _ _ _ _ _ _ 67 durhamL _ ----------------- ______________________________ ----------------- 74 

megasoma, Lymnaea ________________________________________ 67, 68, 69, 71, 72, 73, pl. 20 mojavensis _______________________________________________ 67, 68, 69, 72, 74, pl. 20 

Lymnaea (Bulimnea) _ __ _____ _ ___ _ _ _ ___ _ __ _ _ _ _ _ __ _ _ _ _ __ _ _ __ _ _ __ _ _ __ _ _ _ _ _ _ _ 73 (Segmentina) mojavensis _____ _______________________ ----------------------- 74 

Melania_-------------- ____ ----- ___ ---________________________________________ 71 Pliopholyx_ _ _ ___ _ _ __ _ __ _ _ _ ___ ___ _ _ __ _ _ _ __ _ ___ __ __ _ ___ _ _ ___ _______ _ ___ ________ _ 71 

melanopylon, Sonorelix __ ______________________________________________________ · 70 Polyggrella ______ ___________________________________________________________ --- 71 

Menetus micromphalus __ -----~-------------------- ______ 67, 68, 69, 71, 72, 74, 75, pl. 20 Pompholopsis ____ ________________________________________________________ ----- 71 

Micrarionta argus_____________________________________________________________ 69 Pristiloma __ ____________________ ----- __ . _ --------- _ --------------------------- 70 

(Eremarionta) _ _ _ _ __ _ ___ _ __ _ _ __ _ __ _ _ __ _ __ _ _ __ _ _ __ _ _ __ ____ _ ___ _ __ _ __ _ __ _ _ _ _ 77 chersinellum _______________ _______ --------------------- __ 67, 68, 69, 71, 76, pl. 20 

rowelli acus_ -------- _ __ _ _ __ _ __ _ ___ _ _ __ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ __ _ __ _ _ _ _ _ __ _ __ _ _ _ _ 69 Pseudosuccinea ______ --------------------------- ______ ----------------------- 73 

amboiana_ ----- ___ _ __ _ _ __ _ _ _ _ _ __ _ _ ___ _ ___ _ _ _ _ ______ __ __ _ _ _ _ ___ _ ___ ___ _ __ _ _ 69 

bakerensis_______ _ _ _ _ ___ _ _ ____ ____ _ __ _ __ _ ___ _ _ _ _ _ __ _ _ _ _ _ _ __ _ ___ _ _ _ _ _ __ _ 69 R 

unifasciata_ ____ _ __ _ ___ _ _ _ _ _ __ _ ____ _ __ _ _ _ _ _ __ _ _ _ _ _ _ ___ _ _ _ _ _ __ ___ __ __ _ _ _ 69 Recent molluscan fauna, Mohave Desert.------------ ----------------------- 69,70 

micromphalus, Menetus ________________________________ 67, 68, 69, 71, 72, 74, 75, pl. 20 

micrometalleus, Sonorella____ _ _ __ _ _ _ _ _ ____ _ ___ _ _ _ _ _ _ _ _ __ _ _ _ ___ _ __ _ __ _ ____ ___ _ _ _ 70 

rixfordi, Sonoreli:J;_ _ _ _ __ _ ___ __ __ _ ___ _ ____ _____ __ _ _ __ __ __ __ __ _ _ _ _ _ _ __ _ _ __ _ __ _ _ _ _ 70 

Rexroad formation __________ -------------------------------------------------- 75 

minuscula, Hawaiia ______________________________________ 67, 68, 69, 71, 72,-78, pl. 20 

Mohave Desert_ ______________________________________________________________ 68, 69 

habitat of Recent species in_______________________________________________ 70 

"Rosamond Series," CaliL ________________________ --------------------------- 74 

rowelli acus, Micrarionta _______________________________________________ ------- 69 

amboiana, Micrarionta _____________________________________________ ------- 69 

Mohave Desert Series ________________________________________________________ 68, 76 

mohaveana, Helminthoglgpta ___ __ --------------------------------------------- 69,70 

bakerensis, Micrarionta ___ ___________________________________________ ------ 69 

unifasciata, Micrarionta __ _ --------------- __ __ _ _ __ __ __ ___ _ ____ __ ____ _ ___ ___ 69 

Lymnaea _____________________________________________ 67, 68, 69, 71, 72, 73, pl. 20 

mojm•ensis, Planorbis__________________________________________________________ 67 

Planorbis (Segmentina) __ ------------------------------------------------- 74 

Planorbula ___________________ • _______________________ 67, 68, 69, 71, 72, 74, pl. 20 

monentolophus, Deroceras _ _ ______ ____ _____ ___ _ ___ ____ _ ___ ________ ____ ____ _____ 69 

Monadenia ___ ----------------------------------------------------- ___________ 71 

J.fusculium_ ___ ____ __ _ _ _ _ __ _ _______ __ _ _ _ __ _ _ __ ___ _ _ ___ _ ____ _ __ _ _ ___ __ _ _ __ __ ___ 70 

truncatum_ _ __ ___ __ __ __ __ _ __ _ _ __ _ _ ___ _ _ __ _ __ _ _ __ _ _ _ _ _ ___ _ _ _ _ _ __ _ __ _ _ __ _ ___ 69 

s 

Salt Lake formation ____________________________________________________ ------- 71 

Sand Draw fauna ____ --------------------------------- _________ --------------- 68 

San Joaquin formation. ___________________________________________________ --__ 68 

Santa Clara formation ______ ------------______________________________________ 68 

Santa Clara Lake beds. _________________________________________________ ------ 67 

Segment ina arwigera. _ ___ _____ _ ___ _ ___ _ __ __ ____ ____ ___ _ __ _ _ __ _ _ __ _ _ __ ____ _ _ ___ 74 

durhamL ___________ ------- _________ --------------- __ -------- _ --- _ -------- 74 

(Segmentina) mojavensis, Planorbis _____________ ----_------- ____________ ------- 74 

N Sonorelix avawatzica _________ ______________________ ------------- _________ ------ 70 

N eocene _______ ----------_____________________________________________________ 71 melanopylon __ ______________________ - __ -- _ ----- _- -- _- ------ _ --- ___ -------- 70 

Nevada faunas, western __ ---------------------------------------------------- 71 rixf()rdi______ ___ _ __ _ ____ _ ___ _ __ _ ___ _ _ __ ____ _ _ __ _ ____ __ _ __ _ _ ______ _ ___ _ __ _ __ 70 

Northern Great Basin faunas_________________________________________________ 71 Sonorella micrometalleus ____ ____________________________________________ ------- 70 

nutalliana, Lymnaea palustris___ _ __ __ _ __ _ ___ _ ___ _ ____ _ __ _ ___ _ ___ _ __ _ _ _ _ ____ _ _ _ 68 Sphaeriidae ____________________________________________________________ ------- 69 

Stagnicola ______ _________________________ - __ -------- _- ------ ____ ------ __ ------- 73 

0 

Occurrence of Barstow mollusks______________________________________________ 72 

subangulata, Anodonta angulata _____ _______ -_______ -___ --- _ __ _ ____ ____ _ ________ 67 

Margaritana __ ________ . __________________ --- _- ___ -___ --- ___ ----- ____ ------- 67 

Oreoheli:J; ___________ ___ ------------- ________ ------------- _ ___ _____ ________ _ _ _ _ _ 71 ·r Orinda formation _______________________________ ------------------____________ 68 

Orygoceras__ ______ _ __ ____ _ _ ___ _ __ _ __ _ _ __ _ _ _ __ _ ___ _ ___ ____ __ ________ ______ _____ 71 

osculans, Physa________ ____ ________ _____ _ __ _ _ __ ____ __ _ _ ___ _ _______ ____ ____ ___ 69 

Telegraph Canon, Calif_ ________________________________ ---------------------- 68 

tenue californiense, Helisoma. _ ------------------------------------------------ 69 

Tonopah fauna ______________________________________________ -------·--------- 71 

Topography of Mohave Desert __________________________________ -______ --_---- 69 

p Truckee formation ______________________________________________________ -----_ 71 

pachyostracon, Craterarion ________________________________ 67, 68, 69, 71, 72, 75, pl. 20 

palustris, Lymnaea ____________________________________________________________ 68, 72 

truncatum, Musc·ulium_____ _ _ __ _ _ __ _ _ __ __ __ __ __ _ _ ___ _ ____ ___ _ __ _ _ _ __ _ _ __ _ __ __ _ 159 

Tnlare formation ______________________________________________________ ------ 67, 68 

nutalliana, Lymnaea______________________________________________________ 68 

Papyrotheca ______ _ -------------- _ _ ___ ____ _ __ __ __ _ _ __ _ __ _ _ __ _ _ _ __ _ _ __ __ __ _ _ _ _ _ _ 71 

parvus williamsoni, Gyraulus___ __ __ ____ _ _ ___ _ __ _ _ __ _ _ _ _ _ _ ___ _ ___ _ _ __ __ __ _ _ _ _ _ _ 69 

u, unifas~iata, Micrarionta rowellL ______________________ _________ --------------- 69 

Payettia. ___ ----------- _ ___ ____ _ ____ ___ __ __ _ _ __ _ __ _ _ _ _ _ __ __ _ ______ _ _ _ _ _ _ _ _ _ _ _ _ 71 v Perrinilla __ -------------------- __ _ ___ __ ___ _ _ _ _ _ __ _ _ __ _ _ __ __ _ __ _ ___ _ __ _ _ __ _ _ _ __ 71 Vallonia ________________________________ -_____________________________ ----____ 70 

petaluma, Lymnaea (Bulimnea)____ _ _ __ __ __ _ ___ _ __ _ _ ___ ____ _ _ __ _ __ _ _ ___ _ __ _ _ _ _ 73 

Physa ___ ---------------------------------- _ ____________________ ___________ _ __ 70 

osculans _ _ _ _ ___ _ ___ _ __ _ ___ _ ___ _ _ __ _ _ ____ __ _ _ __ ____ _ _ ___ _ __ _ _ ___ _ __ __ __ _ _ _ 69 

Physidae. _ ___ _ __ _ __ _ _ ___ _ ___ __ _ _ ____________ _ _ __ _ __ _ ___ _ __ __ _ _ _ _ _ __ _ _ __ _ __ _ _ _ 69 

Pilsbryus _____________________________ :__ _ _ __ _ _ _ _ _ __ _ _ __ _ _ _ __ _ _ _ _ _ _ __ _ ___ _ __ _ _ 71 

Pisiliium_ _ _ __ _ ____ ____ __ _ _ ____ __ __ __ _ _ ____ _ _ _ _ __ _ _ __ _ _ __ _ _ __ _ _ __ _ _ __ _ _ __ _ ___ _ 70 

casertanum. _ _ __ ____ ______ _ ___ _ __ __ _ ___ _ __ _ __ _ _ _ _ _ _ __ _ _ _ __ _ _ __ _ _ __ _ ___ _ ___ 69 

Planorbidae __________________________________________________________________ 69, 71 

cyclophorella _____________ --------------------------- __________ 67, 68, 69, 71, 72, 75 

SP------------------------------------------------------ 67, 68, 69, 71, 72, 76, pl. 20 

Vegetation of Mohave Desert_________________________________________________ 69 

Vespericola. __ --- _ ---- ________________ ---------------------------------------- 71 

Victorville, Calif______________________________________________________________ 68 

Viviparus ___ ____________________________ --- _ --- _ --- _- _- ---- ____________ ------- 71 

Vorticifex _______________________________ -_ _ _ _ __ _ _ __ _ _ __ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ __ _ ___ _ 71 

Planorbis (Segment ina) mojaiJensis_____ _ _ _ __ _ __ _ _ __ _ _ _ _ __ _ _ __ _ _ __ _ _ __ ____ _ ___ _ 74 w 

Planorbis mojavensis. __ _ _ _ _ ___ _ ____ __ _ _ _ __ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ __ _ _ __ _ _ __ _ __ _ ___ _ _ 67 williamsoni, Gyraulus parvus ________ _____ ------------------------------------- 69 
' 

PLATE 20 
FIGURES 1, 2. Lymnaea mohaveana Taylor, n. sp. (p. 73) 

Holotype. X 1. S 8077. 

3. Lymnaea megasoma Say. (p. 73) 

Figured specimen. X 1. T 2036A. 

PLATE 20 

4-9. Menetus? micromphalus Taylor, n. sp. (p. 74) 

4-6. Holotype, adult. X2. T 2038A. 

7-9. Paratype, juvenile. X2. S 8079. 

10-15. Planorbula mojavensis Hannibal. (p. 74) 

10-12. Paratype, adult. X3. B 8924. 

13-15. Figured specimen, juvenile. X 3. T 1788A. 

16-20. Craterarion pachyostracon Taylor, n. gen. and sp. (p. 75) 

16. Paratype. X 2. T 1791A. ' 

17. Paratype. X 2. T 1791B. 

18-20. Holotype. X 2. S 8073. 

21-23. Hawaiia minuscula (Binney). (p. 76) 

Figured specimen. X 4. T 1792A. 

24-26. Vallonia sp. cf. V. cycloph01·ella Sterki. (p. 75) 

Figured specimen. X 4. T 1792. 

27-29. Pristiloma chersinellum (Dall). (p. 75) 

Figured specimen. X 4. T 1790A. 

30-32 Helminthoglypta alfi Taylor, n. sp. (p. 76) 

Holotype. X 2. S 8075. 

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U.S GOVERNMENT PRINTING OFFICE: 19!4 
<iEOI.OG!CAL >;I"RYEY PROn~SSIONAL PAPER 254 PLATE 20 

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NONMARINE MOLLUSKS FROM THE BARSTOW FORMATfON