GNATHODON. 



Gray in American Journal of Science. 



TESTA subovalis, crassa, seqiiivalvis, inaequi- 

 lateralis, epidermide olivacea induta; umbo- 

 nibus distantibus ; dentibus, alterius valvae, 

 cardinali unico, acuminato, lateralibus duobus, 

 poslico elongate, antico uncinate; alterius, 

 eardinalibus duobus, acuminatis, lateralibus 

 duobus, postico elongato, antico euneiformi; 

 impressionibus muscularibus duabus, lateralibus; 

 impressione muscular i ^SiUu smn parvo. Liga- 

 mentum internum. 



A VERY singular Genus of Bivalves, lately received from 

 New Orleans; as the shell was sent unaccompanied with 

 any particular information, we cannot tell whether it be a 

 marine or fresh-water production ; though judging from 

 the circumstance of the umbones being eroded, we think 

 it fresh-water. It is remarkable for having the general 

 external aspect of a Cyrena, in conjunction with the in- 

 ternal ligament characteristic of a Crassatella. 



Shell nearly oval, thick, equivalve, inequilateral, 

 covered with an olivaceous epidermis ; umbones distant; 

 in one valve there is an acuminated cardinal tooth and 

 two lateral teeth, the posterior of which is elongated, 

 the anterior uncinate ; in the other valve there are also 

 two acuminated cardinal and two lateral teeth, the poste- 

 rior of which is elongated and the anterior wedge-shaped. 



