WHITE. | LARAMIE FOSSILS. 75 
CORBICULA OCCIDENTALIS Meek & Hayden. 
Plate 21, Figs. 3a, b, and ec. 
Corbicula ogeldansalis Meek & Hayden, 1856, Proc. Acad. Nat. Sci. Philad., vol viii, 
iG: 
Berticula ( penne) bannistert Meek, 1873, An. Rep. U. 8. Geol. Sur. Terr. for 1872, 
p. 6 
The collections of Dr. Hayden from the Laramie strata of the Judith 
River series contain the type specimens of this species, which are de- 
scribed and figured by Meek in vol. ix U.S. Geol. Sur. Terr. (4to ser.), p. 
521, Pl. 40, Figs. 6a, b, and c. The illustrations on plate 21, figs. 3a, b, 
and ¢c, accompanying this article, are drawn from examples that were 
obtained in the valleys of Bitter Creek and Yampa River, and identified 
with this species. Figures 3b and 3c are drawn from the type specimen 
of C. bannistert Meek, which is regarded as synonymous with C. occi- 
dentalis, because among the numerous examples of the variety of C. oc- 
cidentalis which were obtained at and near the locality which furnished 
the type of C. bannistert are many which show a direct gradation to 
that type from forms which cannot be separated from C. occidentalis. 
Among the collections brought by Professor Powell from Upper Kanab, 
Southern Utah, is a single example which I am unable to distinguish 
from the forms that in the Bitter Creek series I refer to C. occidentalis. - 
Subgenus LEPTESTHES* Meek. 
CORBICULA (LEPTESTHES) FRACTA Meek. 
Plate 23, figs. 2a, b, c, d, and e; and plate 21, fig. 5a. 
Corbicula? fracta Meek, 1871, An. Rep. U.S. Geol. Sur. Terr. for 1870, p..314. 
Corbicula? aes var. crassiuscula Meek, 1873, An. Rep. U. 8. Geol. Sur. Terr. for 1872, 
D. 
The following is Mr. Meek’s original description of the species: 
“Shell attaining a rather large size, longitudinally ovate, wider 
(higher) anteriorly, compressed, very thin and fragile; anterior margin 
rounded; pallial margin semi-ovate in outline; posterior margin nar- 
rower than the other and subtruncate ; dorsal outline sloping gradually, 
with slight convexity behind the beaks, and more abruptly in front; 
beaks rather depressed, oblique, and placed about one-third the length 
of the valves from the anterior extremity; surface only showing very 
obscure lines and somewhat stronger ridges of growth. 
““ Length, 2.24 inches; height at the beaks, 1.48 inches; convexity, 
apparently about 0.40 inch. 
«Specimens of this species are all more or less flattened by accidental 
compression, but show the outline and surface characters perfectly, even 
remains of their epidermis. With considerable difficulty 1 have suc- 
ceeded in clearing away the matrix so far as to see that the hinge-mar- 
gin is comparatively streng for so thin a shell. It shows apparently 
three diverging cardinal teeth in each valve, and a linear anterior 
lateral tooth extending parallel to anterior margin; while the posterior 
lateral teeth are somewhat remote from the cardinal, and rather elon- 
gated. On these posterior lateral teeth I have seen transverse strike, 
which, doubtless, also exist on the anterior lateral, though I have not 
seen a specimen in a condition to show them. Internal casts show the 
*For a diagnosis of this subgenus see vol. ix U. S. Geol. Sur. Terr. (4to ser.) p. 161; 
and also remarks accompanying this description. 
