56 SYNOPSIS OF THE CHARACTERS OF THE 



DoNAX PRiMiGENius. M'Coy. (PI. X. fig. 7). 



Sp_ cii. — Transversely trigonal, gibbous; anterior end short, obliquely tmncated, beaked; posterior side 

 elongate, rounded ; a deep, angular sinus in the palleal impression. 



This curious fossil is a perfectly formed Donax ; the anterior end is truncated near the beak, but produced 

 into a sliort pointed beak inferiorly; there is a very deep, angular sinus in the palleal impression, which, in the 

 specimen figured, is well preserved. Length four lines, width seven lines. 



Cardium orbiculare. M'Coy. (PI. XII. fig. 7). 



Sp. Ch. Shell depressed, orbicidar; posterior side a Httle longer than the anterior; anterior and posterior 



ends subtruncate, rounded, equal ; beaks prominent, subcentral ; surface smooth, with a few concentric striis. 



To most of the species of Cardium this species is extremely dissimilar, from the thinness of the substance 

 of the shell, the concentric markings, and general form. I think, however, it bears a closer resemblance to 

 the Cardium Grcenlandicum, forming the genus Aphrodita and Acardo of different authors, than any other 

 shell with which I am acquainted, nor do I see any thing to discountenance the idea of their generic affinity. 

 Length two inches four lines, breadth two inches six lines. 



Cardiomorpha axineformis. Phil. SP. 



Isocardia axiniformis. Phil. Geol. York. 

 Sp. C7(.— Transversely ovate, depressed, smooth; beaks prominent, incurved; anterior side very short, 

 rounded; front margin much curved, sharp; posterior side compressed, obliquely truncated, defined by a ridge 



from the beak. 



This species much resembles an Axinus in its depressed, hatchet-like form, and obliquely truncated, com- 

 pressed, posterior side ; the large, incurved beaks, however, approximate it more to Isocardia or Cardiomorpha. 

 Length one inch, width one inch six lines. 



Cardiomorpha corrugata. M'Coy. (PI. VIII. fig. 15). 



Sp. 67/ .—Transversely oblong, outline ovate in the adult, orbicular in the young shell; anterior side very 

 small; posterior side lengthened, rounded; anterior and posterior sides deeply corrugated; ruga; obsolete in the 



middle. 



This handsome shell is a much larger species than the /. ohloncja. Sow., frequently attaining a size of 

 six or seven inches in its greatest diameter. The deep, concentric rugaj distinguish it from the other species : 

 there are about twelve on a moderate sized specimen, but only four or five on a young orbicular one. Length 

 two and a half inches, width three inches eleven lines. (Small specimen). 



Cardiomorpha oblonga. Sow. sp. 



Isocardia oblonga. Sow. Min. Con.— Isocardia oblonga. Phil. Geol. York.— Cardiomorpha oblonga. Koninck. Fos. Bel. 



Sp. Ch. Transversely ovate, diagonally gibbous, smooth; beaks large, prominent, incurved; anterior end 



very small, rounded ; posterior side large, subquadrate, hi]ige-line straight. Length one inch eight lines, width 

 two inches eight lines. 



Cardiomorpha vENTRicosA. M'Coy. (PI. XIII. fig. 3). 



Sp. CVt.— Transversely oblong, subquadrangular, diagonally gibbous, very ventricose, the depth being 

 equal to the length ; anterior side small, the beaks curved into it ; posterior end subtruncate ; dorsal and ventral 

 margins parallel ; surface smooth. 



