﻿396 DESCRIPTIONS OF NEW SPECIES OF 



except a small space between the umbonal ridge and the beak, leaving a little more 

 than one-third of the basal portion plain, or only marked by lines of growth. 



Dimensions. — Length *3 in., width '6 in., greatest height of valve "2 in. 



Locality. — From the marls and alternating limestone of the Ripley Group, Harde- 

 man Co., Tenn. 



M. ovata. PL 68, fig. 31. Shell wide ; beaks anterior ; cardinal line nearly 

 straight, posteriorly rounded, basal slightly sinuate ; surface marked by obscure, con- 

 centric lines of growth. 



Dimensions. — Greatest length *8 in., width 1*5 in., diameter "6 in. 



Locality. — Yellow Limestone, Timber Creek, N. J. Collection of the Academy. 



TRIGONIA, Brug. 



T. Eufalensis. PI. 68, fig. 32. Subtriangular, resembles T. alwformis, Sow., in 

 outline, not quite so elongate anteriorly; beaks posterior; lunule distinct; surface 

 marked by about fourteen ribs, the more anterior of which proceed from the lunule 

 anteriorly and then cross the shell at right angles with the lunule, exhibiting a 

 tendency to being nodose, especially near the lunule ; lunule marked by ten or twelve 

 transverse ribs ; cardinal margin somewhat incurved, anterior elongate and subbi- 

 angular, basal sinuous and deeply serrate, posterior regularly rounded ; internally, 

 hinge teeth small, muscular impressions deep ; pallial line entire ; a small tooth-like 

 ridge or process extends along the middle of the alation, as in T. aloeformis. 



Dimensions. — The figure is of the natural size. 



Locality. — This is a very distinct species, and I have never seen a specimen larger 

 than the one figured. It is common at Eufala, Ala. Collection of the Academy. 



AXINiEA, Poll. (Pectunculus, Lam.) 



A. rotundata. PI. 68, fig. 33. Subcircular, somewhat convex ; beaks small and 

 central ; surface marked by radiating, impressed and transverse lines ; area narrow ; 

 hinge crenations large, lateral teeth straight and placed obliquely; muscular impres- 

 sions subquadrate, but slightly differing in outline; margin distinctly crenate. 



Dimensions. — Length *8 in., width *9 in., height of valve 3* in. 



Locality. — Eufala, Ala., Ripley Group. Prof. Holmes. 



I have an imperfect specimen before me nearly two inches across. 



NUCULA, Lam. 



N. distorta. PL 68, fig. 34. Triangular, very inequilateral; beaks anterior, 

 marginal; lunule large, cardinal margin nearly straight, posterior subangular, basal 

 regularly rounded, anterior nearly straight; surface marked by obsolete radiating and 

 transverse lines. 



