97 St. Maurick and Ci,aiboiine Pelecypoda 97 



from I^isbon shows concentric ribbing nearly over the whole 

 valve. 



Crassatellites negreetensis, n. sp,, PI. .^3- Figs- 6-8. 



Specific characteriztion. — Shell squarish, as figured ; when 

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

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

 grown specimens, very much of the shape and appearance of the 

 rather uncommon variety of trapaqtia'} a that has strong concentric 

 lirations over the whole surface ; remaining squarish in form till 

 adult stage, not being contracted posteriorly as in trapaquara ; 

 concentric lirations generally covering the whole surface of the 

 shell, but occasionally becoming more or less smooth basally 

 (see fig. 8). 



This is a short form with strong concentric marking showing 

 as clearly 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 

 trapaquara as will be seen by noting the sloping ligamental mar- 

 gin shown by figures i and 3. Nevertheless as there is consider- 

 able variation to be seen in trapaquara in specimens from lyisbon, 

 Ala., to Smithville, Tex., we predict negreetensis will approach 

 closel}^ to some of these forms. 



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



Horizon. — St. Maurice Eocene. 



Locality. — Sabine River, I^a. side, 200 yds. below the mouth 

 of Negreet Bayou. Veatch Coll. 



Casts in material from Eutaw Springs, S. C, indicate the 

 presence of a species very 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 incurved ; hinge 



