18 



PRISODON. 



II. SUBGENUS PRISODON. 



f 



TRIANGULAR. 



*truncatus. Schum. 



Oast, ambigua. Lam. D' Orb. Ouv. 



Sow. G-uerin. Pot. Sehom. 

 Oast, quadrilatera. D' Orb. 1 

 Oast, inflata. D'Orb. 

 TJnio ambigua. Blain. Desk. Soiv. 

 Mya ambigua. Wood. 

 Tetraplodon peetinatum. Sjnx. 



w 



' 



m 



H 





55 





O 





n 





o 





w 









Pi 





Ph 



a 



s 





H " 





o 





55 





tx 









Ph 













>H 





CQ 





55 





O 





55 





TRIANGULAR. 



Duprei. Recluz 



1 Schumacher, in his Nouveau Si/sthne, 1817, p. 138, formed the genus Prisodon, in which he included the 

 two now well known shells Hyria syrmatophorus and Castalia ambigua. His name for the first cannot be 

 applied, as Klein, in 175S, preoccupied this genus by naming it Triquetra. Therefore it must be applied to Cas- 

 talia, which name was given to the same shell by Lamarck in 1819. Mr. Gray, in his "Genera," gives Schumacher 

 priority in the name of Prisodon, in which he is perfectly correct. 



2 I owe to the kindness of M. D'Orbigny specimens of this and inflata. I regret, however, that I am com- 

 pelled to differ in opinion with this distinguished naturalist, believing, as I do, that there have been as yet observed 

 but two species of Prisodon (Lamarck's Castalia). The second by Recluz, the Duprei. 



