Rathbun.] 250 [December 16, 



curved slope in the moulds, between the beak and the hinge, is very- 

 broad. Inner margin of the valves crenulated. A specimen of me- 

 dium size measures : length, 18 mm.; height, 12 mm.; depth of each 

 valve, 6 mm. 



This form is readily distinguished from all the others at Maria Far- 

 inha by the nearly central beaks. It is moderately abundant, but 

 only internal moulds have so far been obtained ; the exact exterior 

 characters are thus unknown. A single, very small specimen, which 

 I have referred to this species as the young, shows the impressions 

 of nearly all the teeth on the hinge, and the extreme ones are longi- 

 tudinal. The muscular imprints are very indistinct. 



From the Cretaceous limestone bed at Maria Farinha, Prov. of 

 Pernambuco, Brazil, associated with Cucullea Harttii, which it some- 

 what resembles. 



Family ASTARTID^. 



Cardita Morganiana sp. nov. 



Shell above the medium size and ventricose, with the length nearly 

 equal to, or slightly exceeding, the height, and the depth of the two 

 valves about three-fourths the length of the shell. The outline of the 

 internal moulds varies from' subovate-orbicular, when of medium 

 size, to sub trigonal at an older age. Length of hinge line somewhat 

 greater than one-half the length of the valves. 



In the larger specimens the posterior margin is very oblique and 

 nearly straight for about half its length from the hinge ; then it 

 rounds rapidly and regularly to the ventral margin, which curves but 

 moderately. The anterior margin is shorter than the posterior and 

 is quite regularly rounded. The posterior margins of the umbones, 

 together with the upper and larger part of the posterior margin of^ 

 the shell, lie in nearly the same straight line, as do also the anterior 

 margins of the umbones and a small part of the anterior margin of 

 the shell, the two lines so indicated forming a slightly acute angle 

 at the beaks ; while the slightly curving ventral margin completes a 

 rather imperfect triangle. This character of outline is observable in 

 the larger and more perfect internal moulds only; in the smaller spec- 

 imens the outline is frequently nearly circular ; but the various forms 

 so graduate into one another as to make their identification easy. 



The valves are very convex and swell out rapidly from the mar- 

 gins. They are most prominent just above the middle, or in the 



