3. NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN. 

By T. w. STANTON. 

In the San Juan Basin of New Mexico and 

southwestern Colorado the formations that 

have yielded marine Cretaceous faunas are, 

beginning at the base, the Mancos shale, the 

Mesaverde formation, the Lewis shale, and 

the Pictured Cliffs sandstone. The fossils obtained below the middle of the Mancos shale 

belong to the fauna of the Colorado group; 

those obtained above that line belong to the 

fauna of the Montana group. 

East of the mountains, in the Denver Basin 

and more northern areas, the Montana group 

consists of the thick Pierre shale at the base and 

the thinner Fox Hills sandstone above. The 

faunas of these two formations are closely related, but each has its own distinctive species. 

It might naturally be inferred from purely 

stratigraphic and lithologic considerations that 

the Pictured Cliffs sandstone should be correlated with the Fox Hills sandstone, for each is 

the latest marine sandstone in its respective 

section. The direct faunal evidence, however, 

does not support this correlation. Although 

the known fauna of the Pictured Cliffs sandstone 

consists of only a few species and, taken as an 

assemblage, agrees with the known stratigraphy 

in indicating late Montana age, it lacks all the 

strictly characteristic Fox Hills forms and includes some which are not known elsewhere 

above the Pierre shale. The fauna itself, therefore, suggests for the Pictured Cliffs sandstone 

an age slightly older than the Fox Hills. 

Overlying the Pictured Cliffs sandstone with 

apparent conformity in the San Juan Basin 

and underlying the Puerco formation is a group 

of nonmarine sediments, coal bearing in the 

lower part, which in many previous reports 

have been referred more or less doubtfully to 

the Laramie formation. The rocks occupying 

this interval are fully described and a considerable area of them is mapped in the accompanying stratigraphic paper by C. M. Bauer, 1 who 

recognizes in them three formations-the Fruitland formation containing all the coal beds at 

the base, the Kirtland shale in the middle, and 

tl:v3 Ojo Alamo sandstone at the top. The 

vertebrate fauna and the flora of these formations are described and discussed by C. W. Gilmore 2 and F. H. Knowlton/ respectively. The 

invertebrates, which form the subject of the 

present paper, nearly all come from the Fruitland formation. Of the 27 species discussed 

only two, Dnio pyramidatoides and D. baueri, 

were collected in the Kirtland shale, and none 

was found in the Ojo Alamo sandstone. A few 

collections from southern Colorado a short distance north of the area mapped by Mr. Bauer 

have been included in the discussion because 

they are obviously from the equivalent of the 

Fruitland formation. 

The general facts concerning . the stratigraphic range and relationships of the invertebrate species may be most easily presented in 

tabular form, as shown on page 310. 

The list of species shows that the nonmarine 

invertebrates of the Fruitland formation include both a fresh-water fauna and a brackishwater fauna. The latter is mostly confined to 

several thin bands in the lower half of the 

formation, though many of the collections show 

both fresh-water and brackish-water forms commingled. The Corbula and the N eritina especially are found with so many fresh-water 

associates at several localities that the suggestion is justified that they may have ranged 

into fresh waters, like some of their living congeners. The fresh-water fauna is especially 

notable for the greatly varied development of 

the genus Unio and for the abundance and 

considerable variety of the gastropods. 

1 p. S. Geol. Survey Prof. Paper 98-P. 

2 U. S. Geol. Survey Prof. Paper 98-Q. 

aU. S. Geol. Survey Prof. Paper 98-S. 

309 
310 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

Stratigraphic range of nonmarine invertebrates of the San Juan Basin. 

---,---------------------1---------- ------

X 

X 

X 

X 

X 

X X 

X 

Ostrea glabra Meek and Hayden. . . . . . . . . . . . . . . . . . . . . . . x Anomia gryphorhynchus Meek........................ x Anomia gryphreiformis n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . x Modiola laticostata (White).. . . . . . . . . . . . . . . . . . . . . . . . . . . x Unio holmesianus White.............................. x ............................. . Unio amarillensis n. sp ........... :. . . . . . . . . . . . . . . . . . . x ............................. . X 

X 

r 

X 

X 

r Unio pyramidatoides Whitfield? ........................... . 

B~t~ ~~!d~ii:. · 8~- -_ ·_ -_ -_ -_ ·_ -_ ·_ -_ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ _ ••• ______ • _ •• _ ••• __ • __________ •••• _ • __ •• _ 

r 

Un~o brachyopisthus White . . . . . . . . . . . . . . . . . . . . . . . . . . . x ............................. . Un1o bauer1 n. sp .......................................... . Unio neomexicanus n. sp ........ . .................. ." .. x Unio brimhallensis n. sp.............................. x Unio sp. cf. U. primrevus White...................... x Corbicula cytheriformis (Meek and Hayden)............ x Corbula chacoensis n. sp............................... x Panoprea simulatrix Whiteaves?...................... X 

Ter~~ina neom.exicana n. sp. ... . . . . . . . . . . . . . . . . . . . . . . . x N entma bauen n. sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x Neritina (Velatella) sp............................... x Campeloma amarillensis n. sp......................... x Tulotoma _thompsoni White........ . ................... x Melania insculpta Meek? ........................ :.... x Goniobasis? subtortuosa Meek and Hayden. . . . . . . . . . . . x Physa reesidei n. sp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x Physa sp...... ....................................... x Planorbis (Bathyomphalus) chacoensis n. sp........... x 

X 

X 

r 

X 

X 

r 

X 

r 

r 

X 

X 

r 

r 

X 

X 

r 

X 

r 

x? 

X 

r 

r 

r 

r 

X 

X 

X 

r 

r 

X 

r 

r 

r 

r 

N OTE.-In this table "x" indicates the identical species named in the same horizontal-line and "r" ·indicates 

a closely related form. 

The distribution of the species as -exhibited 

in the table may seem at first glance to indicate 

that the Fruitland fauna is about as closely 

related to the Mesaverde and Judith River 

faunas (which are approximately contemporaneous with each other) as it is to the Lance 

and Laramie faunas. A closer analysis of the 

table, however, will show that most of the 

species occurring or represented by related 

forms in the Mesaverde and Judith River are 

long-lived brackish-water species which range 

at least as high as the Laramie. Melania insculpta belongs to this class, for like all the 

other American Cretaceous species referred to 

Melania it is invariably associated with brackishwater forms. The only two Fruitland species 

with an outside distribution which do not elsewhere range into the higher formations are 

Modiola laticostata, from the Mesaverde, and 

Goniobasis? subtortuosa, from the Judith River. 

With the fresh-water species, especially those 

belonging to the genus Unio, the case is different. The majority of the identical and closely 

related species are found in the Laramie, the 

so-called "Lower Laramie". ?f southern Wyoming, and the Lance and do not. range below 

these formations. It·is my og~ ... ion, therefore, 

that the invertebrate evidence. as a whole 

favors the assigninep.t of the Fruitland formation to an epoch considerably later than Mesaverde and Judith River and possibly somewhat 

earlier than Lance. If due weight is given to 

the known stratigraphic relations and to the 

faunal evidence from the underlying formal t·>ns, the Fruitland can hardly be older ~han 

Fox Hills, and the sequence from the base of 

the Fruitland up to the top of the Ojo Alamo, 

which is conformable, according to Mr. Bauer, 

may include the equivalents of o;verything from 

the Fox Hills to the Lance inclusive. 
NONMARINE CRETACEOUS INVERTEBRATES OF SAN JUAN BASIN. 311 

Ostrea glabra Meek and Hayden var. 

Plate LXXIX, figures 1-3. 

The New Mexican specimens referred to the 

widespread and long-lived species Ostrea glabra 

show scarcely perceptible differences from the 

variety from the Mesaverde formation at Point 

of Rocks, Wyo., described under the name 0. 

wyomingensis. The species was originally described from the Judith River formation, but it 

also ranges .into the Fox Hills, Laramie, and 

Lance formations. 

Locality and position: The specimens here 

figured are from Bauer's locality 12, in Amarillo 

Canyon, 10 miles south of Jewett (locality 

9279), in the Fruitland formation, 37 feet 

above its base. It was also collected from the 

same horizon 12 miles south of San Juan River 

and 2 miles east of Chaco River. Another lot 

provisionally identified as 0. subtrigonalis Evans 

and Shumard, from Coal Creek, 37 miles south 

of Farmington, N.Mex., may be only young 

specimens of this species. 

Anomia gryphorhynchus Meek. 

Plate LXXIX, figures 7 and 8. 

Anomia? gryphorhynchus Meek, U. S. Geol. Survey Terr. 

Fifth Ann. Rept., p. 375, 1872. 

Anomia gryphorhynchus White, :U. S. Geol. Survey Terr. 

Twelfth Ann. Rept., pt. 1, p. 57, pl. 25, figs. la-c, 

1880; U. S. Geol. Survey Third Ann. Rept., p. 16, 

pl. 12, figs. 12-15, 1883. 

The New Mexican speciJllens of Anomia gryphorhynchus agree very well with the ty!le 

lot from the Mesaverde formation at Point of 

Rocks, Wyo., especially. with those individuals 

which have ery~ fine radiating strire, barely 

visible withou~h~ lens, though many of the 

Wyoming shells have no sculpture other than 

concentric growth lines. The species also occurs 

in the Laramie of Crow Creek, Colo., and in the 

Black Buttes coal group at Black Buttes staAnomia gryphreiformis Stanton, n. sp. 

Plate LXXIX, figures 4-6. 

Shell small, of variable outline, but usually 

much higher than long, very convex and with 

strongly in curved beaks, so that the general 

aspect is that of a small Gryphrea. Surface 

marked by conspicuous, threadlike radiating 

ribs, usually about 30 in number, varying considerably in size but relatively somewhat coarse 

compared with the size of the shell. Lower 

valve not seen. 

The form varies considerably, as in all species 

of this genus, but most of the specimens seen 

resemble the one represented by figures 4 and 

5, which measures 20 millimeters in height, 14 

millimeters in length, and 12 millimeters in 

convexity of single valve. Another specimen 

representing nearly the extreme in variation is 

subcircular in outline, measuring 18 millimeters 

in height and length and 9 millimeters in· convexity of single valve. 

The coarser sculpture, smaller size, more 

slender convex form, and more conspicuous 

beaks distinguish this species from A. micronema Meek, which is probably its nearest relative in the western Cretaceous. 

Locality and position: The types were collected by J. H. Gardner in the SE. l- sec. 19, 

T. 34 N., R. 4 W., in Colorado, from beds that 

are doubtless equivalent to the Fruitland formation. Other specimens came from Beaver 

Creek in T. 35 N., R. 6 W., in a neighboring 

part of southwestern Colorado. 

Modiola laticostata (White). 

Plate LXXIX, figures 9 and 10. 

Volsella (Brachydontes) laticostata White, U. S. Geol. and 

Geog. Survey Terr. Bull., vol. 4, p. 708, 1878; U. S. 

Geol. and Geog. Survey Terr. Twelfth Ann. Rept., 

pt. 1, p. 59, pl. 25, fig. 4a, 1880; U. S. Geol. Survey Third Ann. Rept., p. 423, pl. 13, fig. 2, 1883. 

tion, Wyo. . The type of this species is from the Danforth 

An average specirri n measures 20 milli- Hills, near White River Indian Agency, Colo., 

meters in height and 18 millimeters in length. where it occurs in beds now referred to the 

Local~ty and positi?n: In ~l)_e lower part : !'fesaverde. It is incorr:ple.te at both ends, ~ut 

the Fruitland formatiOn 3 miles northwest ol In form and sculpture It agrees perfectly With 

Fruitland, N. Mex. (locality 3475), where it is some of the largm and much better preserved 

associated with Jfodiola laticostata, Corbicula, specimens from New Mexico here referred to 

and other formt ' the species. The two examples figured show 
312 SHORTER CONTRIBUTIONS TO - GENERAL GEOLOGY, 1916. 

that the species varies in breadth and curvature, but the variation in these particulars is 

even greater than they indicate. 

Locality and position: All the New Mexican 

examples are from the lower part of the Fruitland formation near Fruitland. The two figured were collected by the late Robert Forrester and labeled "Fruitland" (locality 7077). 

Other lots were collected by Schrader and 

Shaler 3 miles northwest of Fruitland, a quarter of a mile southeast of the Bruce mine 

(locality 3475), and by Gardner at Thurling's 

limekiln, 4 miles north of Fruitland (locality 

4002). 

Unio holmesianus White. 

Plate LXXX, figures 1-7. 

Unio holmesianus White, U. S. Geol. and Geog. Survey 

Terr. Bull., vol. 3, p, 604, 1877; U.S. Geol. and Geog. 

Survey Terr. Twelfth Ann. Rept., pt. 1, p. 67, pl. 

22; figs. 4a-e, 1880; U. S. Geol. Survey Third Ann. 

Rept., p. 433, pl. 17, figs. 2-6, 1883. 

The published descriptions and figures of this 

striking species are full and accurate except in 

some minor details of sculpture, which are not 

well presePVed on the types and were slightly 

misinterpreted by the artist, as may be seen by 

comparing the original figures with the photographs of the same specimens as reproduced in 

figures 1 and 2. The radiating ridges on the 

posterior part of the larger specimen are in 

part due to accidental distortion and are not 

conspicuous on any other adult shell in the 

type lot. 

The strong beak sculpture, which is the 

characteristic feature of the species, covers the 

umbonal region of the shell for a distance of 16 

to 20 millimeters from the apex. It consists 

near the apex of sharp, slightly undulating concentric ridges which are almost parallel with 

the growth lines, but within a short distance 

these ridges become more wavy and develop a 

deep V-shaped sinus with its apex in the broad 

umbonal furrow that lies just in advance of the 

posterior umbonal ridge. Subordinate sinuses 

are developed on the anterior portion of some 

shells. The anterior part of the shell thus 

becomes covered with strong undulating ridges 

which run from the anterior margin obliquely 

backward and downward to the umbonal furrow. The rather narrowly rounded umbonal 

ridge is usually crossed by several short trans-· 

verse ridges that are almost at right angles to 

the main sculpture of the front part of the 

shell, where the continuation of this second 

system of ridges is sometimes faintly shown. 

Small irregular radiating lines with varying 

development on different individuals diverge 

from the umbonal ridge, some passing to the 

posterior margin and others toward or to the 

basal margin, thus extending farther on the 

adult shell than the other elements of beak 

sculpture. Well-preserved shells also show a 

threadlike raised line running from the beak 

down the crest of the umbonal ridge and a 

similar line midway between it and the posterior margin. 

. The dimensions given by White (length 45 

millimeters, height 42 millimetocs) are about 

the average for an adult shell. 

Geographic and stratigraphic distribution: 

The specimen from which this species was 

originally described was found near the base of 

the coal-bearing rocks near Black Buttes station, Wyo. The beds at this locality have at 

different times and by different geologists been 

assigned to the Wasatch, the Laramie, the 

Lance, and a horizon intermediate between the 

Laramie and Lance. My own opinion is that 

the beds should be correlated with the lower 

part of the Lance. Unio holmesianus has also 

been collected from the Lance formation on 

Lance Creek, Wyo., and Fish Creek, Mont., 

from beds of approximately the same age near 

Belfry, Mont., and from the "Lower Laramie" 

as mapped by Veatch 3 miles west of Carbon, 

Wyo. A closely similar if not identical form 

described by Whitfield under the name U. 

browniwasobtainedfrom the'' Hell Creek beds,'' 

now referred to the Lance formation on Snow 

Creek, 130 miles northwest of Miles City, Mont. 

In the San Juan Basin of New Mexico and 

Colorado the species has been found only in the 

Fruitland formation, which in the past has sometimes been tentatively referred to the Laramie. 

It was collected by C. M. Bauer's party from 

his localities 4, 14, 17, 18, and 77, which are, 

respectively, 40 feet above the base of the formation, 1 mile south of Fruitland (locality 9268); 

115 to 140 feet above the base (locality 9270), 

140feetabove the base (locality9271), and 150 

feet above the base (locality 9272) in Amarillo 

Canyon, 10 miles south of Jewett; and 200 feet 

above the base near Hunter's store, 30 miles 

south of San Juan River (locality 9293). One 

broken specimen from locality 9271 showing 
NONMARINE CRETACEOUS INVERTEBRATES OF SAN JUAN BASIN. 313 

beak sculpture is represented by figure 5. The 

material from the above-named localities is 

ample for identification, but the specimens are 

less perfect than those selected for figuring 

from the collection of J. H. Gardner from 

the Ignacio quadrangle, Colo. The specimens 

represented by figures 3 and 4 were collected 

8 feet above "B" coal in sec. 16, T. 35 N., R. 

7 W. (locality 6071), and those shown by figures 

6 and 7, 300 feet below the top of the "Laramie" 

in sec. 19, T. 35 N., R. 8 W. (locality 6063). 

For comparison with these figures new illustrations of White's types are given in figures 1 

and 2. The smaller shell is the original type, 

on which the first description was based. 

Unio amarillensis Stanton, n. sp. 

Plate LXXX, figures 8 and 9. 

Shell small, moderately convex, subquadrangular to subcircular in outline, with height 

and length nearly equal; beaks rather prominent, near middle of hinge line; dorsal margin 

descending rapidly and slightly excavated in 

front of the beak, very gently convex behind 

it; anterior and ventral margins regularly 

rounded; posterior margin subtruncate; surface strongly sculptured for a distance of about 

10 millimeters from the apex of the beak, the 

sculpture consisting at the apex of concentric 

ridges each with a deep V -shaped sinus on the 

urn bonal ridge and a shallower one near the 

middle, but within a short distance these 

sinuses fade out into the smooth surface of the 

shell and only the obliquely descending anterior and posterior portions of the ridges are 

developed. Beyond the distance of 10 millimeters from the beak the shell bears only fine 

lines of growth except on the short posterior 

slope, where there are five to seven rather 

strong plications that descend obliquely from 

the faintly marked umbonal ridge to the posterior margin. Height of type, which may be 

immature, 27 millimeters; length 29 millimeters. 

This specimen belongs in the group of U. 

holmesianus, though in sculpture it shows relationship with U. verrucosif ormis Whitfield and 

U. letsoni Whitfield, both of which differ from 

it in form and in having a line of nodes down 

the middle of the valve. 

Locality and position: The type lot consists 

of three valves from Bauer's locality 14, in 

Amarillo Canyon, 10 miles south of Jewett, N. 

Mex. (locality 9270), 115 to 140 feet above the 

base of the Fruitland formation. Five specimens from the Lance formation on the divide 

between Lance and Lightning creeks, Wyo. 

(U. S. N. M., catalogue No. 23364), are believed 

to belong to this species, though they are 

slightly larger and their beak sculpture is not 

perfectly preserved. 

Unio pyramidatoides Whitfield? 

Plate LXXX, figures 12 and 13. 

Unio pyramidatoides Whitfield, Am: Mus. Nat. Hist. Bull., 

vol. 23 , p. 624, pl. 41, figs. 1-5, 1907. 

The imperfect specimens doubtfully referred 

to Unio pyramidatoides have very nearly the 

same form as U. holmesianus White, but they are 

very much larger and thicker than that species, 

and the beak sculpture, so far as it is still discernible on the eroded beaks, while of the same 

general type is not so strong and does not extend 

over so much of the shell. In all these features 

of size and sculpture they are more like U. 

pyramidatoides, though fuller collections of 

better-preserved material may prove that they 

belong to a distinct species. 

The larger specimen figured measures 70 

millimeters in height and about 72 millimeters 

in length. A slightly crushed specimen from 

Yellow Jacket Creek, Colo., measures 73 millimeters in height and 76 millimeters in length. 

Locality and position: The figured specimens 

were obtained at Bauer's locality 32, 17 miles 

south of San Juan River and 6 miles east of Chaco 

River, N. Mex. (locality 9276), in the Kirtland 

shale 150 feet above its base. Another specimen believed to belong to the same species 

comes from either the Kirtland shale or the 

Fruitland formation on Yellow Jacket Creek in 

T. 34 N., R. 5 W., Colo.; and two small ex.., 

amples, which may be young shells of the 

species, were found 140 feet above the base of 

the Fruitland formation in Amarillo Canyon, 10 

miles south of Jewett, N.Mex. (locality 9271). 

Whitfield's types came from beds now referred 

to the Lance formation on Snow Creek, 130 

miles northwest of Miles City, Mont~ The 

species has also been recognized in the Lance 

on Fish Creek, Mont. 
314 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

Unio gardneri Stanton, n. sp. 

Plate LXXX, figures 10 and 11. 

Shell s;mall, subcircular in outline, very con .. 

vex; beaks prominent, strongly in curved, 

somewhat flattened, situated near the middle of 

the hinge line; anterior, ventral, and posterior 

margins forming a nearly regular curve~ dorsal 

margin straighter. Surface strongly sculptured 

for a distance of about 20 millimeters from the 

apex of the beak, the sculpture consisting primarily of concentric ridges on which two deep 

V -shaped sinuses develop-one on the posterior 

umbonal ridge and the other near the median 

line of the shell. Within a short distance these 

ridges break up into oblique, more or less curved 

lines of nodes, and there are also developed two 

radiating lines of irregular tubercles, one down 

the middle of the shell and the other on the 

posterior umbonal ridge, and behind this ridge a 

number of small irregular curved ribs that extend from it toward but not to the posterior 

margin. The rest of the surface shows only 

lines of growth. 

Height of type specimen 38 millimeters; 

length 43 ;millimeters; convexity of single valve 

14 millimeters. 

This species belongs to the group of Unio 

letsoni Whitfield, of the Lance formation, from 

which it differs in being more convex, in having 

two lines of tubercles instead of one, and in 

having much less conspicuous sculpture on the 

posterior portion of the shell. 

The species is named for Mr. James H. 

Gardner, who collected the type. 

Locality and position: Sec. 19, T. 35 N., R. 

8 W., Ignacio quadrangle, Colo. (locality 6063), 

about 300 feet below the top of the" Laramie," 

probably in the upper part of the Fruitland 

formation. 

Unio reesidei Stanton, n. sp. 

Plate LXXXI, figure 1. 

Shell rather small, broadly subelliptical in 

outline, strongly convex; beaks very inconspicuous, situated about one-third the length 

of the shell behind the front; anterior margin 

forming a regular curve from the beak to the 

ventral ;margin, which is more broadly curved; 

dorsal margin behind the beak gently convex, 

and posterior margin slightly subtruncate. 

Beak sculpture not preserved on the specimens 

studied. Surface in advance of the inconspicuous u;mbonal ridge ;marked only by fine lines 

of growth; posterior portion, comprising about 

two-fifths of the total surface, marked by 8 or 

9 distinct but somewhat irregular radiating 

plications decreasing in size from the umbonal 

ridge backward and upward. 

Height of figured type 46 millimeters; length 

(restored) 62 millimeters. A small specimen 

measures 39 millimeters in height, 49 millimeters in length, and 33 millimeters in greatest 

convexity of both valves united. 

The species is named for Mr. J. B. Reeside, jr., 

of the United States Geological Survey. 

In general features of-form and sculpture 

this species suggests U. gonionotus White, from 

the "Laramie" of Sevier Cliffs, 10 miles above 

Panguitch, Utah, but it is easily distinguishable 

by its stouter form and the smaller size and 

different shape of the posterior plications. 

Locality and position: The type specimen was 

obtained at Bauer's locality 48, 25 ;miles south 

of San Juan River and 6 miles east of Chaco 

River, N. Mex. (locality 9288), about 150 feet 

above the base of the Fruitland formation. 

Other specimens were collected at Bauer's 

locality 21, 12 miles south of the San Juan and 

2 miles east of the Chaco (locality 9281) at 

about the same horizon. 

Unio brachyopisthus White. 

Plate LXXXI, figures 2 and 3. 

Unio brachyopisthus White, in Powell, Geology of the east-

- ern portion of the Uinta Mountains, p. 126, U. S. 

Geol. and Geog. Survey Terr., 2d div., 1876; U. S. 

Geol. and Geog. Survey Terr. Twelfth Ann. Rept., 

pt. 1, p. 64, pl. 22, figs. 2 a, b, 1880; U. S. Geol. 

Survey Third Ann. Rept., p. 433, pl. 16, figs. 7, 8, 

1883. 

This species, originally described from specimens found in the coal-bearing rocks at Black 

Buttes station, Wyo., is widely distributed in 

the so-called "Lower Laramie" of southern 

Wyoming and in the Lance formation in the 

eastern part of the State. It varies considerably in outline, even at the original locality, and 

the small type specimen is relatively shorter and 

higher than the average. In the San Juan 

Basin it. is represented by the typical form (fig. 

3) at Yellow Jacket Creek, Colo. (locality 7079), 

and by a more elongate form (fig. 2) at Bauer's 

locality 18, in Amarillo Canyon, 10 miles south 

of Jewett, N. Mex. (locality 9272), 150 feet 

above the base of the Fruitland formation. 
NONMARINE CRETACEOUS INVERTEBRATES OF SAN JUAN BASIN. 315 

Unio baueri Stanton, n. sp. 

Plate LXXXI, figure 6. 

Shdl of medium size, subovate in outline, 

convex and thick; beaks prominent, situated in 

the anterior third of the shell; dorsal margin in 

front of the beak descending steeply into the 

broadly rounded front margin; postero-dorsal 

margin nearly straight and forming an obtuse 

angle with the subtruncate posterior margin; 

ventral margin very bro.adly convex. Beak 

sculpture not preserved on the type. The rest 

of the shell marked by irregular broad, rounded 

radiating plications which are strongest just 

behind the umbonal ridge and are separated 

by much narrower shallow furrows. 

Height of type 57 millimeters; length 89 

millimeters; convexity of single valve about 35 

millimeters. · 

The species is nanied for Mr. C. Max Bauer. 

Locality and position: At Bauer's locality 

32, about 17 miles south of San Juan River 

and 6 miles east of Chaco River, N. Mex. 

(locality 9276), 150 feet above the base of the 

Kirtland shale. 

Unio neomexicanus Stanton, n. sp. 

Plate LXXXI, figures 4 and 5. 

Shell small to medium, obliquely ovate in 

outline, moderately convex; beaks moderately 

prominent, at anterior end of shell; front margin descending abruptly with very slight curvature from the beaks for three-fourths of the 

height and then curving backward more rapidly 

to join the nearly straight (slightly convex) 

ventral margin; posterior end obliquely subtruncate above and broadly rounded below. 

A rather prominent rounded umbonal ridge extends obliquely from the beak to the posteroventral margin, and in front of this is a broad, 

shallow depressed area. Beak sculpture not 

well preserved but apparently confined to a 

small area and consisting of irregular concentric ridges. The crest of the umbonal ridge 

bears a threadlike elevated line, especially in 

the umbonal region, and a similar line is midway between this and the postero-dorsal margin. The rest of the shell shows only fine lines 

of growth. 

Height 39 millimeters; length 60 millimeters; 

convexity of single valve 19 millimeters. 

Vnio neomexicanus is related to V. proavitus 

White, which is found in the coal-bearing 

30830°--17----21 

rocks at Black Buttes, Wyo., and in the Lance 

formation on Lance Creek, eastern Wyoming. 

The Wyoming species differs in details of outline and has much more prominent beaks. 

Locality and position: Represented by two 

left valves from the Fruitland formation, 150 

feet above its base, at Bauer's locality 48, 25 

miles south of the San Juan and 6 miles east 

of Chaco River, N. Mex. (locality 9288). 

Unio brimhallensis Stanton, n. sp. 

Plate LXXXI, figure 7; Plate LXXXII, figure 1. 

Shell large, transversely broad ovate, gently 

convex; beaks prominent, situated about onefourth the length of the shell from the front; 

dorsal margin deeply excavated in front of the 

beaks and almost straight behind them; anterior and posterior margins broadly and almost 

equally rounded; ventral margin more broadly 

rounded. Surface marked only by ordinary 

lines of growth on the anterior half of the valve. 

The rest of the surface not preserved except 

traces of faint radial sculpture near the dorsal 

margin behind the beaks. , 

The types are two imperfect valves, one of 

which shows the front part of the shell and 

the other preserves the outline of the posterior 

part. The better specimen measures 93 millimeters in height and has a convexity of about 

30 millimeters and an estimated length of 

about 130 millimeters. 

This species or a closely similar form is represented by a cast retaining part of the shell from 

the Lance formation between Lance and Lightning creeks, eastern Wyoming. The specimen 

measures 102 millimeters in height and 140 

millimeters in length. 

Locality and position: On Brimhalls Wash 

at Bauer's locality 48, about 25 miles south of 

San Juan River and 6 miles east of Chaco River, 

N.Mex. (locality 9288), 150 feet above the bt;tse 

o(the Fruitland formation. 

Unio sp. 

Plate LXXXII, figure~ 2 and 3. 

cf. Unio primrevus White, U. S. Geol. and Geog. Survey 

Terr. Bull. , vol. 3, p. 599, 1877; U. S. Geol. and 

Geog. Survey Terr. Twelfth Ann. Rept., pt. 1, p, 

70, pl. 29, figs. 3 a, b, 1880; U. S. Geol. Survey 

Third Ann. Rept., p. 432, pl. 14, figs. 4, 5, 1883. 

Several small, poorly preserved specimens 

evidently represent a distinct species of Unio 

that may be compared with the Judith River 

.. 
316 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

form U. prirru£vus ·White, from which it differs 

in its more anterior beaks, more angular and 

prominent posterior umbonal ridge, and probably in details of sculpture. These differences 

are probably of specific value, but on account 

of distortion and other accidents of preservation 

it is impossible to give a full, accurate specific 

description or even to decide whether ·all the 

specimens here grouped·together belong to a 

single species. For similar reasons U. prirru£vus, 

with which these specimens are compared, is in 

the same uncertain status. 

Of the two specimens figured the smaller one, 

which is only an ·exfoliated fragment showing the umbonal region, is.' b~lieved to represent nearly the normal form. The larger one 

is obliquely compressed so that the posterior 

area behind the umbonal ridge is much 

shortened. 

Locality and position: The smaller specimen 

was obtained from the Fruitland formation 

about 150 feet above its base at Bauer's locality 48, 25 miles south of San Ju_an River and 6 

miles east of Chaco River (locality 9288); the 

larger one 40 feet above the base of the same 

formation at Bauer's locality 4, 1 mile south 

of Fruitland, N.Mex. (locality 9268). Another 

specimen was found 140 feet above the base of 

the Fruitland formation at Bauer's locality 21, 

12 miles south of San Juan River and 2 miles 

east of the Chaco. 

Corbicula cytheriformis Meek and Hayden. 

Plate LXXXII, figure 4. 

Cyrena ( Corbicula?) cytheriformis Meek and Hayden, A cad. 

Nat. Sci. Philadelphia Proc. for 1860, p. 176, 1860. 

Gorbicula cytheriformis Meek, U. S. Geol. Survey Terr. 

Rept., vol. 9, p. 520, pl. 40, figs. 5a-c, 1876; White, 

U. S. Geol. Survey Terr. Twelfth Ann. Rept., pt. 1, 

p. 74, pl. 21, figs. 4a-d, 1880; U. S. Geol. Survey 

Third Ann. Rept., p. 437, pl. 22, figs. 1-6, 1883. 

In the brackish-water fauna that is found in 

the lower part of the Fruitland formation the 

genus Corbicula is .abundant at certain localities, especially in the neighborhood of Fruitland. Several species may be represented by 

more or less distorted and imperfect material. 

The form here figured, however, agrees in every 

particular with the types of 0. cytheriformis 

from the Judith River forma;tion of Montana. 

The species is widely . distributed in the Mesaverde formation and also ranges up into th~ 

Lance formation. 

Locality and position: The specimen figured 

came from Bauer's locality 36, 120 feet above 

the base of the Fruitland formation, 18 miles 

south of San Juan River and 3 miles east of 

Chaco River, N. Mex. (locality 9286), where it 

is associated with Oorbula chacoensis, Neritina 

baueri, Viviparus, Oampeloma amarillensis, and 

Tulotoma thompsoni. 

Corbula chacoensis Stanton, n. sp. 

Plate LXXXII, figures 5 and 6. 

Shell of medium size, sub triangular in outline, 

moderately convex; beaks prominent, situated 

slightly in advance of the middle of the hinge 

line; dorsal margin descending steeply before 

and behind, the two portions making an angle 

of about 110°; anterior end and ventral margin 

broadly rounded; posterior end narrowed and 

obliquely subtruncate; surface marked only by 

numerous fine concentric growth lines until the 

shell has attained about three-fourths the dimensions of a full-grown individual, after which 

strollg concentric corrugations are developed on 

the ventral part of the shell and the convexity 

becomes relatively greater. 

Height 16 millimeters; length 22 millimeters; 

convexity of the two valves 12 mi)..limeters. 

The species is related to Oorbula subtrigonalis 

Meek and Hayden, from which it differs in its 

more nearly equilateral form and other details 

of outline and in the much stronger corrugations at the later stages of growth. 

·Locality and position: The type came from 

the lower part of the Fruitland . formation at 

Bauer's locality 25, about 13 miles south of San 

Juan River and 1 mile east of Chaco River, 

N. Mex. (locality 9284). The collection from 

this place contains 18 individuals in addition to 

the figured type. The species is abundantly 

represented, mostly by immature individuals, 

half a mile north of this locality, and it was 

collected at several other localities ranging from 

18 to 28 miles south of San Juan River. 

Panoprea simulatrix Whiteaves? 

Panoprea simulatrix Whiteaves, Contr. Canadian Paleontology, vol. 1, p. 11, pl. 2, figs. 2, 2a, 1885. 

Several casts obtained at Bauer's locality 51, 

in the Fruitland formation 120 feet above its 

base/ 28 miles south of San Juan River, and 6 

miles·' east ·of Chaco River, N. Mex. (locality 

9290), represent either this species or one closely 
NONMARINE CRETACEOUS INVERTEBRATES OF SAN JUAN BASIN. 317 

related to it. Whiteaves's species occurs in 

Canada and Montana in the Judith River formation, and a closely similar if not identical 

form is found near the top of the Fox Hills 

sandstone in South Dakota. 

Teredina neomexicana Stanton, n. sp. 

Plate LXXXII, figures 7-10. 

cf. Xylophomya laramiensis Whitfield, Am. Mus. Nat. Hist. 

Bull., vol. 16, pp. 73-76, pis. 28, 29, 1902. 

Shell small, subglobose, broadly gaping in 

front and behind and with the posterior ends 

of the valves prolonged into a tapering, somewhat tortuous shelly tube several times the 

len~th .of the valves themselves; anterior gape, 

whiCh 1s formed by a rectangular notch in each 

valve, closed by a shield-shaped plate or callus 

with median furrow or suture; posterior end of 

valve broadly subangular. Surface marked by 

distinct growth lines parallel to the margins, by 

a narrow umbonal furrow corresponding in position to an internal rib or thickening, extending 

from the beak to the ventral margin, and by 

a less conspicuous furrow extendjng from the 

beak to the lateral angle of the anterior gape. 

One of the types shows fragments of an umbonal accessory valve. 

Height of best-preserved type, 12 millimeters; 

length of valve, 12 millimeters; convexity of 

united valves, 12 millimeters. 

A tube associated with the types and believed 

to belong to the same species indicates dimensions nearly twice as great. 

This burrowing shell seems to be referable to 

the g~nus Teredina Lamarck, though it is also 

certainly congeneric with the Lance species for 

which Whitfield proposed the new name Xylophomya. Through the courtesy of the American Museum of Natural History it has been 

possible to make direct comparisons with the 

type specimens of X ylophomya laramiensis on 

which the genus was based. The study of these 

specimens, which came from the Lance formation near Alkali Creek,! eastern Wyoming, and 

of large collections, apparently belonging to 

the same species, from the "Lower Laramie" 

opposite the mouth of Medicine Bow River 

Carbon County, Wyo., shows that they hav~ 

1 Mr. Barnum Bro\vn, who collected these fossils, states in a personal 

letter that the locality is on the "east side of Alkali Creek, 3 miles from 

the mouth and not more than 50 feet above the Fox Hi1ls or marine 

Cretaceous." 

all the generic characters of Teredina and that 

they differ from the New Mexico shell here 

described only in their larger size and in slight 

differences in the outline of the posterior end 

of the valve. Whitfield described the hinge of 

Xylophomya as having "four minute toothlike 

denticles on the right valve anterior to the 

beaks," and the figure as well as the fragment 

itself suggests taxodont teeth at first glance, 

but a oloser examination shows that they can 

not be hinge teeth, for they are strictly marginal 

and connected with the outer surface, and the 

shell was doubtless edentulous like other members of its family. 

Locality and position: At Bauer's locality 22, 

n~ar the base of the Fruitland formation, 12-! 

miles south of San Juan River and 1 mile east 

of Chaco River, N. Mex. (locality 9283), associated with Oorbula chacoensis, with several 

species of Unio, and with Tulotoma thompsoni 

and other fresh-water gastropods. 

N eritina baueri Stanton, n. sp. 

Plate LXXXIII, figures 1-4. 

Shell large, subglobose, consisting of about 

three very rapidly increasing volutions; spire so 

much depressed that it scarcely projects above 

the general curved surface of the shell; aperture 

nearly semicircular, with sharp outer lip and 

broadly flattened, simple inner lip; surface polished and without sculpture except numerous 

very fine growth lines but on well-preserved 

specimens retainin,g the color pattern, which 

consists of numerous irregular dark-brown 

spots and bands, some of which tend to have 

a spiral arrangement, while others run in zigzag fashion nearly parallel with the growth 

lines. The color pattern varies in different, 

individuals. 

The largest specimen collected, which is figured as the type, measures 38 millimeters in 

height and 37 millimeters in greatest breadth .. 

The smaller figured specimen is believed to Le 

a young individual of the same species. 

This species is much larger than any other 

American Cretaceous Neritina that has been 

described, and it is also distinct in form and 

proportions. 

~ocalities and position: The type was obtained at Bauer's locality 21, about 140 feet 

above the base of the Fruitland formation 12 ' miles south of San Juan River and 2 miles east 
318 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

of Chaco River (locality 9281), where six other 

specimens were collected. The other ·figured 

specimen came from about the same horizon 

in Amarillo Canyon, 10 miles south of Jewett, 

N. Mex. (locality 9270), and others were collected in the same neighborhood (locality 9271). 

One lot of nine small specimens referred to this 

species was found near the base of the Fruitland 

formation, 12! miles south of San Juan River, 

and 1 mile east of the Chaco (locality 9283), 

and one imperfect cast 200 feet above :the base 

of the Fruitland formation, 17 miles south of 

the San Juan (locality 9285). 

N eritina (V elatella) sp. 

A. single small, imperfect specimen belonging 

to Meek's subgenus Velatella was collected in 

the Fruitland formation, 120 feet above the 

bas~, at Bauer's locality 36, 18 miles south of 

San Juan River and 3 miles east of Chaco 

River, N. Mex. (locality 9286). In size and 

form it does not differ greatly from Neritina 

(Velatella) baptista White, which was originally 

described from specimens obtained in the lower 

part of the coal-bearing formation at Black 

Buttes station, Wyo., and which has also been 

found in the Laramie of northeastern Colorado. 

Campelorna amarillensis Stanton, n. sp. 

Plate LXXXIII, figures 5 and 6. 

Shell small, rather slender, consisting of about 

6 moderately convex whorls that are slightly 

compressed above; suture distinctly impressed; 

surface nearly smooth but showing when magnified fine, slightly sinuous growth lines and, 

especially on the upper part of the last whorl, 

fine raised revolving lines; aperture ovate, with 

length a little less than half the height of shell. 

Height of larger figured type, 22 millimeters; 

greatest breadth, 13 millimeters; height of 

aperture, 10 millimeters; breadth of aperture, 

7 millimeters. Apical angle about 40°. 

In size, general form, and other external 

features this species, is intermediate between 

Campeloma vetula Meek and Hayden, from the 

Judith River formation, and C. prod1fcta White, 

from the Fort Union. 

Locality and position: The types came from 

Bauer's locality 14, in Amarillo Canyon, 10 

miles south of Jewett, N.Mex. (locality 9270), 

in the Fruitland formation, 115 to 140 feet 

above its base. The species was .collected at 

several other localities, ranging from 12 to 25 

miles south of San Juan Rtver and from 50 

to 300 feet above the base of the Fruitland 

formation. 

Tulotoma thompsoni White. 

Plate LXXXIII, figures 9-11. 

Tulotoma thompsoni White, in Powell, Geology. of the 

eastern portion of the Uinta Mountains, p. 134, 

U. S. Geol. and Geog. Survey Terr. , 2d div. , 1876; 

U.S. Geol. and Geog. Survey Terr. Twelfth Ann. 

Rept. , pt. 1, p. 100, pl. 28, figs. 2a-h, 1880; U . S. 

Geol. SurveyThird Ann. Rept., p.467, pl. 24, figs. 

17-22, 1883. 

This well-characterized and easily recognized 

species was first found at Black Buttes station, 

Wyo., in the lower part of the Black Buttes 

coal group, which, in my opinion, should be 

correlated with the "Lower Laramie" of Carbon County, Wyo., and with the Lance formation. The species has a wide distribution 

in the Lance formation in Wyoming and Montana and is abundant in the Laramie on Crow 

Creek, Colo., where a number of the specimens 

figured by White were obtained. It has also 

been found abundantly and typically develpped in the Mesaverde formation of northwestern . Colorado, especially in the upper part 

of the formation near Axial, Colo. 

~ocality and position: The specimens figured 

came from Bauer's locality 14, in Amarillo 

Canyon, 10 miles north of Jewett, N. Mex. 

(locality 9~70), in the Fruitland formation 115 

to 140 feet above its base. The species ranges 

through the entire thickness of the Fruitland 

and has been collooted--at many localities. 

Melania insculpta Meek? 

Melania insculpta Meek, U. S. Geol. Survey Terr. Sixth 

Ann. Rept., for 1872, p. 515, 1873. 

White, U. S. Geol. and Geog. Survey Terr. Twelfth Ann. 

Rept., pt. 1, p. 94, pl. 20, fig. 4a, 1880; U. S. 

Geol. Survey Third Ann. Rept., p. 54, pl. 26, figs. 

4, 5, 1883. 

Two collections obtained near the base of 

the Fruitland formation at Bauer's localities 

22 and 25, 12! and 13 miles. south of San Juan 

River, N. Mex. (localities 9283 and 9284), and 

one collection obtained near the middle of the 

same formation at Bauer's locality 51, 15 miles 

farther south (locality 9290), contain imperfect 

specimens of a Melania which in form and 

sculpture seems to agree very well with M. 

insculpta Meek. The specimen from which 

this species was first described was found in 

rocks now referred to the Mesaverde formation 
NONMARINE CR.ETACEOUS INVERTEBRATES OF SAN JUAN BASIN. 319 

near Rock Springs, Wyo., and it also oocurs in 

the Laramie of northeastern Colorado. 

Goniobasis? subtortuosa (Meek and Hayden) Meek. 

Plate LXXXIII, figures 7 and 8. 

Melania subtortuosa Meek and Hayden, Acad. Nat. Sci. 

Philadelphia Proc., vol. 9, p. 136, 1857. 

Goniobasis? subtortuosa Meek, U. S. Geol. Survey Terr. 

Rept., vol. 9, p. 569, pl. 42, figs. 17a, b, text figs. 75, 

76, 1876. 

White, U. S. Geol. Survey Third Ann. Rept., p. 57, 

pl. 27, fig. 34, 1883. ' 

Whiteaves, Contr. Canadian Paleontology, vol. 1, p. 

74, pl. 10, fig. 7, 1885. 

Meek's description based on specimens from 

the Judith River formation near the mouth of 

Judith River, Mont., is as follows: 

Shell conoid-screw-shaped, thin; spire rather low; volutions about five, very convex, and strongly carinate 

around the middle, increasing rather rapidly in size from 

the apex; suture deep in consequence of the prominence of 

the angular whorls; surface with moderately distinct lines 

of growth; aperture rhombic-suboval, about as long as 

wide. Length 0.39 inch; breadth 0.21 inch; slopes of spire 

nearly straight, with a divergence of 47°. Some crushed 

specimens show that it attained nearly twice the linear 

dimensions of that from which the above measurements 

were taken. 

Better material than Meek had, from both 

Montana and Alberta, shows that adult shells 

consist of six or seven whorls and that they 

vary considerably in proportions. A few specimens which retain part of the surface of the 

shell when magnified show very faint revolving lines on the last whorl, especially above the 

carina, and agree in this feature, as well as in 

form, with the well-preserved specimens from 

New Mexico that are referred to the species. 

The larger specimen figured measures 20 millimeters in height and 12 millimeters in breadth. 

Locality and position: At Bauer's localities 

14, 15, and 17, in Amarillo Canyon, 10 miles 

south of Jewett, N. Mex. (localities 9269, 

9270, 9271), 115 to 140 feet above the base of 

the Fruitland formation. It is noteworthy 

that the species has not been recorded from 

any locality between Montana and New Mexico. 

Physa reesidei Stanton, n. sp. 

Plate LXXXIII, figures 12 and 13. 

Shell large, stout, with very small depressed 

spire; surface sculpture not preserved. 

Height 44 millimeters; greatest breadth 

about 32 millimeters; height of aperture almost equal to length of shell, and breadth 

about half the breadth of the shell. 

This species seems to be sufficiently distinct 

to justify its description, even from the imperfect material at hand-eight more or less 

distorted casts, of which the best-preserved one 

is selected as type. Its nearest relative among 

An1erican fossil forms appears to be Physa 

fel1:x White, from the Laramie of Crow Creek, 

Colo. 

Locality and position: About 200 feet above 

the base of the Fruitland formation at Bauer's 

locality 27, 17 miles south of San Juan River 

and 4 miles east of Chaco River, N. Mex. (locality 9285) 

Physa sp. 

.Another species of Physa, smaller and much 

more slender than P. reesidei, is represented 

by two fragmentary specimens from Bauer's 

locality 22, near the base of the Fruitland formation, 12! miles south of San Juan River and 

1 n1ile east of Chaco River, N.Mex. (locality 

9283). 

Planorbis (Bathyomphalus) chacoensis Stanton, n. sp. 

Plate LXXXIII, figures 14-16. 

Shell small, consisting of about five very 

gradually increasing whorls; spire flat; whorls 

slightly rounded above, carinate on the periphery, broadly rounded from the carina to 

the margin of the umbilicus, which is nearly 

as broad as the last whorl; surface marked by 

relatively coarse lines of growth. 

Greatest diameter 7 millimeters; height 3 

millimeters; breadth of last whorl2 millimeters. 

This little species is evidently congeneric 

with Planorbis (Bathyomphalus) kanabensis 

White, from the so-called Laramie of the 

Kanab Valley, Utah. It appears to differ 

frmn White's species in its somewhat more 

rapidly increasing whorls and its more distinetly carinate periphery. 

Locality and position: At Bauer's locality 

22, near the base of the Fruitland formation, 

12! miles south of San Juan River and 1 mile 

east of Chaco River, N. Mex. (locality 9283). 

PLATES LXXI=K-LXXXIII. 

321 
PLATE LXXIX. 

Ostrea glabra Meek and Hayden var. (p. 311 ). 

FIGURES 1, 2. Upper valves. 

3. Lower valve. 

U.S.N. M., catalogue No. 32026. 

Anomia gryphreiforrnis Stanton (p. 311 ). 

FIGURES 4, 5. Side and profile views of typical form. 

6. Side view of broader, less convex specimen. 

U.S.N. M., catalogue No. 32027 . 

. Anomia gryphorhynchus Meek (p. 311). 

FIGURES 7, 8. Side views of two specimens varying in outline and convexity. 

U.S.N. M., catalogue No. 32028. 

Modiola laticostata (White) (p. 311). 

FIGURES 9, 10. Left valves of two specimens varying in form and sculpture. 

U.S.N. M., catalogue No. 32029. 

322 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 98 PLATE LXXIX· 

4 

5 

3 

1 

6 

7 

8 

2 

9 

NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN. 
U. S. GEOLOGICAL SURVEY 

2 

1 

5 

4 

6 

10 12 

11 

_______ I 

PROFESSIONAL PAPER 98 PLATE LXXX 

3 

7 

8 

9 

I 

I 

NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN. 
PLATE LXXX. 

Unio holmesianus White (p. 312). 

FIGURES 1, 2. Type specimens from Black Buttes, Wyo., figured by White. 

U. S. N. M., catalogue No. 9041. 

3, 4. Specimens from T. 35 N., R . 7 W., Ignacio quadrangle, COlo. 

U.S.N. M., catalogue No. 32030. . . . .. 

5. Fragmentary specimen, showing beak sculpture, from Amarillo Canyon, N. Mex. 

U. S. N. M., catalogue No. 32031. 

6, 7. Immature specimens, showing details of beak sculpture, from T. 35 N., R. 8·W., Ignaeio quadrangle, 

Colo. Figure 6 is enlarged 2 diameters. 

U.S.N. M., catalogue No. 32032. 

Unio amarillensis Stanton (p,,31.3). 

FIGURES 8, 9. Side and profile views of type. 

U.S.N. M., catalogue No. 32033. 

Unio gardneri Stanton (p. 314). 

FIGURE 10. Left valve. 

11. Right valve. Both from Ignacio quadrangle, Colo. 

U. S. N. M., catalogue No. 32034. 

Unio pyramidatoides Whitfield? (p. 313). 

FIGURE 12. Small right valve. . 

13. Larger right valve with surface partly exfoliated. 

U.S.N. M., catalogue No. 32035. 

323 
PLATE LXXXI. 

Unio reesidei Stanton (p. 314). 

FIGURE 1. Type specimen. 

U.S.N. M., catalogue No. 32036. 

Unio brachyopisthus White (p. 314). 

FIGURE 2. Left valve of an elongate specimen from Amarillo Canyon, N. Mex. 

, U.S.N. M., catalogue No. 32037. 

3. Right valve of typical form from Yellow Jacket Creek, Colo. 

U.S.N. M., catalogue No. 32038. 

Unio neomexicanus Stanton (p. 315). 

FIGURE 4. Left yalve, slightly distorted by crushing. 

5. Smaller left valve. 

U. S. N. M., catalogue No. 32039. 

Unio baueri·Stanton (p. 315). 

FIGURE 6. Type specimen, left valve. 

U.S.N. M., catalogue No. 32040. 

Unio brimhallensis Stanton (p. 315). 

FIGURE 7. An imperfect right valve. Outline restored from specimen represented by Pl. LXXXII, fig. 1. 

U.S.N. M., catalogue No. 32041. 

324 ' 
U. S. GEOLOGICAL SURVEY 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

\\\ 

\ 

' ',, 

',, 

4 

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

PROFESSIONAL PAPER 98 PLATE LXXXI 

2 

3 

6 

.... _ 

--, _____ , _____________ _ 

7 

NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 98 PLATE LXXXI~ 

4 

1 

5 

3 6 

7 

8 9 

11 

NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN. 
PLATE LXXXII. 

Unio brimhallensis Stanton (p. 315). 

FIGURE L An exfoliated left valve. 

U.S.N. M., catalogue No. 32041. 

Unio sp. cf. U. primmvus White (p. 315). 

FIGURE 2. Imperfect left valve, distorted by crushing. 

U.S.N. M., catalogue No. 32042. 

3. Fragment showing umbonal portion of right va1.ve. 

U.S.N. M., catalogue No. 32043. 

Corbicula cytheriformis Meek and Hayden (p. 316). 

FIGURE 4. Small left valve. 

U.S.N. M., catalogue No. 32044. 

Corbula chacoensis Stanton (p. 316). 

FIGURES 5, 6. Left side and profile views of type. 

U.S.N. M., catalogue No. 32045. 

Teredina neomexicana Stanton (p. 317). 

FIGURE 7. Left side of specimen retaining p~rt of tube. 

8, 9. Right side and front views of another specimen, >< 2. 

10, 11. Casts of tubes believed to belon15 to this species. U. S. ~. M., catalogue No. 32046. 

325 
PLATE LXXXIII. 

Neritina baueri Stanton (p. 317)o 

FIGURES 1, 2. Front and back views of type. 

U. S. N. M., catalogue No. 32047. 

3, 4. Front and back views of smaller specimen. • 

U. S. N. M., catalogue No. 32048. 

Campeloma amarillensis Stanton ·(p. 318). 

FrGtJRE 5. Front view of large type. 

6. Back view of smaller specimen. 

U. S. N. M., catalogue No. 32049. 

Goniobasis? subtortuosa (Meek and Hayden) (p. 319)o 

FIGURE 7. Front view of large specimen. 

8. Back view of smaller specimen; 

U. S. N. M.; catalogue No. 32050. 

Tulotoma thompsoni White (p. 318). 

F IGURES 9, 10. Back views of two specimens. 

11. Front view of another specimen. 

· U. S. N. M., catalogue No. 32051. 

Physa reesidei Stanton (p. 319). 

F IGURES 12, 13. Back and front views of slightly distorted cast. 

U.S.N. M., catalogue No. 32052. 

· Planorbis (Bathyomphalus) chacoensis Stanton (p. 319)o 

FIGURES 14-16. Top, bottom, and front views of the type, X 2. 

U. S. N. M., catalogue No: 32053. 

326 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 98 PLATE LXXX!Ii 

3 

1 2 

4 

5 6 

8 9 

7 

10 

12 13 

14 15 

16 11 

NONMARINE CRETACEOUS INVERTEBRATES OF THE SAN JUAN BASIN,