CYPRIXA O'EXILICARDIA ?) ABEIHEXSIS. 47 



Although both our specimens allowed the separation of their valves, only 

 part of the internal characters were brought to light. The cardinal teeth are 

 completely silicified, and instead of separating were cleft, in the larger and 

 liner specimen (the one figured) leaving a surfiice so irregularly fractured 

 that the natui-e of this portion of the hinge is not discernible. From the 

 left valve of the smaller enough can be distinguished to make it tolerably 

 certain that tlic hinge was longer and more complicated than the short and 

 simple hinge of Asiarte. In the right valve of both specimens a very distinct, 

 but peculiar, long, straight, remote, posterior lateral tooth is present, a char- 

 acter never found in Astarte. The lateral tooth of the left valve is not well 

 preserved in either case. Being thinner than that of the right, and over- 

 lapping it externally, the tooth was injured in separating the valves. The 

 pallial line could not be freed from hard stony deposit, and remains unknown. 

 The muscular impressions are shallow, and with the thin and smooth inner 

 margins of the valves, which show no traces of crenulation but have a sharp 

 chisel-edge, they coincide closely with Ci/jniua Mandka Linn. Such a mar- 

 ginal edge is exceptional in Astarte. 



Calling in the aid of external characters in the determination, it will be 

 observed that the shells of all recent, as well as of all fossil species of Astarte 

 to which doubt in respect to their classification does not attach, are consider- 

 ably flattened, while the specimens in question are decidedly ventricose. 

 And though their umbonal wrinkles or varices are very like those of Astarte, 

 yet instead of covering the whole surface of the shell and growing stronger 

 towards the ventral margin, as in most species of that genus, in these fossils 

 the wrinkles are found only upon the beaks. But for the conspicuous ex- 

 ternal ligament, the Avrinkles would suggest rather that the species belongs 

 to CrassatcUa, in some recent species of which, as 0. Kiiiijicola Lam. and C. nn- 

 dulata Sow., a few strong wrinkles similar to those of our fossils appear upon 

 the beaks and are confined to them. 



Comparing the present species with C//prina ( Vcnihcardia) Ligeriensis d'Orb. 

 (Paleont. Franc., Terr. Cret., Ill, p. 103, PI. cclxxv), one of the most charac- 

 teristic species of the subgenus Vmihcanlia, it will be found that the two 

 have lunules, areas, umbonal slopes, and in fact most of their parts, strikingly 

 similar, the chief external difference, aside from the umbonal plaits, being 

 that the posterior dorsal slope of Ligeriensis is less rapid, producing a hinder 

 extremity higher than thai of the subcaudate Abeihensis. 



Tj'pical specimens of Cz/prina rostruta Sow. (Ti'ans. Geol. Soc. Lond., [2,] 



