193 St, Maurice and Claibokne Pelecypoda 193 



flated, very corrugate form so well known in this species. Oc- 

 casionally the early shell cleaves off ; sometimes the exterior of 

 the great right valve scales away, leaving a strange looking, 

 smooth specimen. 



Type. — Lea's figured tj'pes seem to be those we have cata- 

 logued as 5061 and 5062 in the Phila. Acad. Coll. 



Horizon. — Claiborne sand. 



Locality. — Claiborne, Ala. 



Corbula murchisoni var. fossata, Meyer & Aid. PI. 58, Figs. II, 16-20 



C. murchisoni v^x. fossata Meyer and Aldrich, Jr. Cinn. Soc. Nat. 



Hist., vol. 9, p. 45. pi. 2, fig. 22, 1886. 

 C. fossata Dall, Trans. Wag., Ill, p. 844, 1898. 



Meyer and Aldrich' s original description. — Like Corbula murchisoni 

 Lea, from Claiborne, but the concentric ribs terminate rather abruptly at a 

 depressed line along the carina. Between this line and the carina there are 

 double the number of small concentric ribs. The form, besides, is smaller 

 than in Claiborne. 



Newton, Wautubbee ; Lisbon, Ala. 



The type specimen is from Newton. The sharp and well defined de- 

 pression along the carina of the umbonial slope is so striking and seems to 

 be so characteristic for the horizon, Newton-Wautubbee-Lisbon, that some 

 might consider it more practical to give to the form a new specific name. 

 This however would not show its close relation to Corb. murchisoni. 



Dall seems to regard this as a separate species and adds 

 Vaughan's locality, Mt. Lebanon, La. 



We now hesitate to follow the same course for there are now 

 a«id then to be found in the Claiborne sand, specimens of murchi- 

 soni of transitional form, some even quite tj'pical fossata as shown 

 by fig. II. 



Type. — Johns Hopkins Univ. Mus. 



Horizon. — St. Maurice and occasionally Claiborne. 



Specimens figured. — Mus. Cornell Univ. 



Localities. — Mt. Lebanon, La. Johnson's place ; 8 miles W. 

 of Enterprise ; Hickory ; Newton ; Wautubbee, Miss. Clai- 

 borne, Ala. 



