81 



ISOCARDIA. ^ S0 



CHAMA COR. — Linnceus. 

 Sowerbfs Genera, No. 7, pi. %fiy. 1, 2. 

 The shells constituting this genus have been separat- 

 ed from the G. Chama of Linnaeus, and the G. Cypri- 

 cardia and G. Cardita of La Marck; not only on ac- 

 count of the peculiar shape of the cardinal teeth, but 

 also of the singular and graceful curvature of the um- 

 bones, which are spirally turned on either side, in the 

 form of a fool's cap ; from whence is derived the fami- 

 liar English name of the type of this genus. Shell 

 equi valve, heart-shaped, globose; the umbones distant 

 and spirally recurved to the side of each valve; two 

 flat primary teeth, one of which is bent and inserted 

 under the umbo; a lateral prolonged callosity or length- 

 ened tooth ; ligament external and forked on one side. 



The Isocardia Moltkiana, (Sowerby's Genera, No. 7, 

 plate %fig. 3 J, may be mentioned as the most elegant 

 and illustrative species of this genus; it is also a very 

 rare shell. 



Isocardia cor Isocardia semisulcata 

 Isocardia Moltkiana. [ A nd one fossil species.] 



