﻿AMERICAN TERTIARY AND CRETACEOUS FOSSILS. 387 



Dimensions. — Length '09 in., width •OS in. 



Locality. — More common than the preceding, from Caldwell Co. My collection. 



HELCION, Montfort. 



H. Leanus. PI. 67, fig. 48. Subcircular, apex sub-marginal, inclined anteriorly; 

 surface marked by numerous, irregular, radiating ribs, crossed by undulating lines of 

 growth. Rare. 



Dimensions. — Diameter "06 in., height '03 in. 



CORBULA, Drug. 



v C. Texana. PI. 67, fig. 54. Inflated, subtriangular, thick, umbones large ; right 

 valve marked by numerous large, transverse ribs ; umbonal slope rather abrupt ; 

 basal margin regularly rounded; left valve? 



Dimensions. — Length - 3 in., width '38 in., depth of right valve "15 in. 



Common. I have seen numerous specimens of the right valve, but no left valves. 



TELLINA, Drug. 



*■ T. Mooreana. PI. 67, fig. 56. Wide, flattened, nearly equilateral ; beaks small, 

 inclined internally ; hinge line in advance of the beaks, straight, posterior slightly 

 curved ; surface smooth, or covered only by obsolete lines of growth. 



Dimensions. — Length *5 in., width - 9 in., thickness '2 in. 



Locality. — Caldwell Co. One specimen, in my collection. 



CIBOTA, Brown. (Byssoarcq, Swains.) 



""^C. Mississippiensis. PI. 67, 'fig. 58. 



Byssoarca Mississippiensis, Con., Jour. Acad. Nat. Sci., 1st series, Yol. 1, pi. 13. 



Inequilateral, equivalve ; beaks small, incurved, situated in advance of the middle ; 

 basal margin, below and in advance of the beaks, deeply emarginate ; surface marked 

 by numerous dichotomous radiating folds, crossed by imbricating lines, presenting a 

 reticulated or granulated appearance; area very narrow; hinge narrow, almost linear 

 in the middle, anteriorly and posteriorly, the crenulations are oblique, sometimes 

 angulated. 



Dimensions. — Length '7 in., width 1*6 in. 



Common. 



LEDA, Solium. 



L. compsa. PI. 67, fig. 57. Inequilateral; beaks very small, incurved; shell 

 rounded anteriorly, acuminate posteriorly; basal margin very regularly curved ; hinge 

 teeth very small, fosset triangular ; surface marked by numerous transverse ribs, 



