FROM THE TERTIARY OF VIRGINIA. 245 



This little shell is interesting from its singular spinous appendages. No other Mo- 

 diola, that I have met with, has them. Indeed, the only shell I have ever seen with 

 spines similarly posited, is the Cardium aviculare, Lam., from the Paris Basin. 



FAMILY MALLEUm 



GENUS AVICULA. 



A. MULTANGITLA, PL. 35. FlG. 31. 



A. testa valde transversd, sub-inaquilaterali, antice acute rostratd, postice truncatd, compressd, undulatd, crossa, striata; 

 striis radiantibus minimis, raris; clivo umboniali elevato; margine basali flexuoso; margine dorsali recto; natibus compressis; 

 cardinis area triangulari, transversd; sulco ligamentifero, triangulari, prof undo; testae parte anticd interne valde incrassatd. 



Shell very transverse, sub-inaequilatera], acutely rostrate anteriorly, truncate posteriorly, compressed, undulate, 

 thick, striate; strise few, radiating, very small; umbonial slope elevated; basal margin flexuose; dorsal margin straight; 

 beaks compressed; area of the beaks triangular, transverse; ligamentiferous sulcation triangular, deep; anterior part 

 of the shell, very much incrassated within. 



Diam. .18. Length .20. Breadth .45 of an inch. 



Remarks. There are numerous exceedingly minute lines of growth over the surface. 

 The radiating striae are plainest where they terminate at an angle in the basal margin. 

 The cavity of the beaks is very deep and small. It is abruptly cut off by the incrassa- 

 tion of the anterior end, which is perfectly flat and on a level with the dorsal and basal 

 margins. As all of rny specimens are very much worn, I cannot perceive any trace of 

 the muscular impressions. 



This curious little shell differs from the genus Avicula somewhat in the hinge. The 

 fosset is more conspicuous than in general with that genus, while the tooth is almost or 

 entirely obsolete. I had at first intended erecting a new genus for it, but the characters 

 of the hinge in this family are so variable and so little to be depended on, that I have 

 thought it best to leave it in this genus. It can hardly be confounded with any of its 

 congeners. 



FAMILY PECTENID.E. 



GENUS PECTEN. 



P. MICROPLEURA, PL. 35. FlG. 32. 



P. testa longitudinaliter ovatd, sub-inflatd, crassd, radiatim costatd; costis parvis, crebris, regularibus, planis, lavibus; 

 margine basali circulari; auribus CBqualibus, costatis; natibus compressis. acutis. 



Shell longitudinally ovate, somewhat inflated, thick, radiately costate ; costae small, numerous, regular, flat, smooth; 

 basal margin circular; auricles equal, costate; beaks compressed, acute. 



Diam. .30. Length .60. Breadth .58 of an inch. 



Remarks. The whole surface, from one auricle to the other, is covered with small, 

 regular, smooth ribs, distant from each other about their own width. They are between 

 thirty and forty in number, besides about ten on each auricle. 

 VOL. ix. 65 



