CRASSATELLLD^. 225 



pit is seen posterior to them in both valves, and judging from 

 the general resemblance of the shell to Crassatella, it is probably 

 destined to receive a cartilage. 



Pronoe, Agassiz, 1843. 



Syn. — Yenulites, Schloth. 



Distr. — Liassic; Europe. P. triangularis^ Schloth. 



Shell subtrigonal, like an Astarte Or Cytherea, with slight 

 concentric striation on the surface ; hinge of the right valve 

 with two cardinal teeth, the anterior one extending somewhat 

 below and forming the margin of an elongated pit, above which 

 there is a small sublunular tooth ; a small oblique cartilage-pit 

 is situated just behind the beak and a large remote posterior 

 lateral tooth is also present ; fulcrum strongly thickened. The 

 hinge of the left valve must possess two cardinal and one sub- 

 lunular and one posterior double lateral teeth. If Quenstedt's 

 figure and description of the hinge of P. triangularis^ Schloth., 

 is correct, this would be the oldest form of Crassatellidse, though, 

 as that author remarks, the hinge-teeth of the right valve \&xy 

 much resemble those of a Cyprina ; and should it be proved 

 that the small pit is only an accidental depression in which a 

 part of the external ligament is situated, the generic name would 

 have to be cancelled, and the species referred to Cyprina, with 

 which the shell perfectly agrees in form. 



Crassatellina, Meek, 1811. 



Syn. — Etea, Conrad, 1813. 



Distr. — G. oblonga, Meek (cxxi, 1-9). Cret. ; TJ. S. 



Shell transversel}^ trapezoidal, equivalve, inequilateral, with 

 free margins closed and smooth within ; hinge with two cardinal 

 teeth, and one elongated anterior and one posterior lateral tooth 

 in each valve ; anterior cardinal tooth of the left valve trigonal, 

 and deeply emarginate below ; posterior very much compressed, 

 oblique, and somewhat elongated ; cardinal teeth of right valve 

 diverging, with a triangular pit between for the reception of the 

 larger triangular tooth of the other valve ; anterior one small, 

 oblique, and connected at its upper end with the posterior 

 extremity of the anterior lateral ; posterior larger, obliqvie, 

 longitudinally furrowed, and perhaps emarginated below, while 

 just behind and above it there is a narrow oblique slit or pit, for 

 the reception of the thin anterior cardinal of the other valve ; 

 lateral teeth elongated parallel to the cardinal margins ; the 

 anterior one of the right valve, and the posterior of the left, 

 apparently continued so as to connect with the upper ends of 

 the cardinal teeth ; ligament external ; pallial line simple. 



Eriphyla, Gabb, 1864. 

 Syn. — Dozyia, Bosquet, 1868. Gouldia, C. B. Ad. (in part). 



