127 St. Maurice^^and Claiborne Pelecypoda 127 



Specimens showing interior characteristics are very rare, 

 and we have found none showing in a satisfactory manner the 

 characteristics of the muscular scars. The more robust develop- 

 ment of the teeth in this species, as compared with the specimens 

 Conrad studied suggest the modifying of his generic description 

 so as to include the strong, sickle-shaped anterior in the right 

 valve and the decidedly bifid or twinned anterior cardinal in the 

 left valve. The long, posterior cardinals are remarkable in their 

 greatly developed, practically^ free, posterior extension and inter- 

 locking character. Conrad's Miocene "tyi:)e" form unfortunate- 

 l}' represents a decadent and senile strain of this virile genus. 

 This fact has doubtless led to such statements as : "It is evident, 

 therefore, that Sphcerella can be regarded at most as a section of 

 Diplodonta, closely allied to the typical form of that genus." 

 Again, regarding the species in question : "This remarkable 

 globular species is not a Sphcerella, but simply a turgid Diplo- 

 dontar (Trans. Wag., Ill, p. 1182). 



This species is well distributed in Texas, but perhaps no 

 other locality can well compare for abundance and size and var- 

 iety of specimens with St. Maurice, La. 



7)'/^.— Singley's Collection, Tex. 



Horizon. — St. Maurice Eocene. 



Specimens fgjired. — Deposited in Paleont. Coll. Cornell 

 Univ., from St. Maurice, La. 



Localities. — Texas : Cedar Creek, Wheelock League, Robert- 

 son Co., cutting on Tyler and S. E. R. R., 400 5^ds. S. of mile 

 post No. 23, Cherokee Co. ; Dr. Collard's farm. Sparks Head- 

 right, Brazos Co.; Elm Creek, Lee Co.; Smithville. La.: 

 St. Maurice, Natchitoches, Vivian, Marble Q'y, ? Cedar Bluff, 

 Sabine R. Miss. : McLeod's Mill, Suwanlovey Cr., Clark Co. 



Diplotlonta ungulina, PL 4°. Figs. 10-14. 



Astartc unglina Con., Am. Jr. Sci., vol. 23, 1833, p. 342. 

 Egeria rotunda Lea, Cont. to GeoL, 1833, p. 50, pi. r, fig. i7- 

 Diptodonta astartiformis Con., Jr. Phila. Ac. Nat. Sci., i860, vol. 4, 



296. 

 Diptodonta dettoidea Con. Jr. Phila &c., vol. 4, p. 296. 



