97 St. Maurice and Claiborne Pelecypoda 97 



from Lisbon shows concentric ribbing nearly o\er the whole 

 valve. 



Crassatellites negreetensis, n. sp., PI. 33. Figs. 6-8. 



Specific characteriztion. — Shell squarish, as figured ; when 

 young having very much the appearance of the young of alia, 

 but with concentric lirations less far apart ; becoming in half- 

 grown specimens, ver^^ much of the shape and appearance of the 

 rather uncommon variety of trapaqua?a that has strong concentric 

 lirations over the whole surface ; remaining squarish in form till 

 adult stage, not being contracted posteriorly as in irapaquara ; 

 concentric lirations generally covering the whole surface of the 

 shell, but occasionall}^ becoming more or less smooth basally 

 (see fig. 8). 



This is a short form with strong concentric marking showing 

 as clearl}' on the post-umbonal slope as on the face of the shell. 

 Its ligamental margin, even in adult specimens, remains more or 

 less parallel to the basal margin. This is very different from 

 irapaquara as will be seen b}^ noting the sloping ligamental mar- 

 gin shown b}^ figures i and 3. Nevertheless as there is consider- 

 able variation to be seen in irapaquara in .specimens from Lisbon, 

 Ala., to Smithville, Tex., we predict negreeieiisis v\n\\ approach 

 closely to .some of these forms. 



Types. — Deposited in Paleont. Mus. Cornell Univ. 



Horizon. — St. Maurice Eocene. 



Locality. — Sabine River, La. side, 200 yds. below the mouth 

 of Negreet Baj^ou. Veatch Coll. 



Ca.sts in material from Eutaw Springs, S. C, indicate the 

 presence of a species verj^ closely akin to negreetensis. 



Crassatellites texanus Heilprin, PI. 34- Fig- i- 



Crassatella texana Heilp., Proc. Phila. Acad. Nat. Sci., 1890, p. 407, 



pi. II, fig. 6, 

 Crassatella texana Har. , Idem, 1895, p. 50, pi. 2, fig. i. 



Heilprin" s original description. — Shell irregularly rhomboidal ; 

 valves prominently angulated posteriorly, with the post-umbonal slope 

 broad and slightly concave ; umbones prominent, well incur\'ed ; hinge 



