221 



Genus EOPTERIA. (N. gen.) 



Generic Characters. The general form of the species for which this 

 genus is proposed is precisely like that of Pterinea, except that both valves 

 are equally convex, and the hinge appears to have an external ligament 

 like that of Uhio. On this latter point, however, there remains some doubt, 

 as the hinge is only partially seen in one specimen. 



EOPTERIA TYPICA. (1ST. sp.) 



Description. P^'ngj lie straight; anterior wing small, posterior large ; 

 umbones near the anterior extremity. Body of the shell strongly and 

 obliquely convex, sub-cordiform ; ventral margin rounded ; posterior margin 

 descending from the extremity of the hinge line at an angle of about 100, 

 nearly straight or slightly concave, until approaching the posterior ventral 

 angle, where it forms a narrowly-rounded curve to the ventral margin. The 

 posterior wing is not much compressed. The greatest gibbosity is about 

 the middle of the shell, and extends obliquely from the umbones backwards 

 and downwards to the posterior ventral angle. Surface with coarse radia- 

 ting striae, about four in a width of three lines at tti3 ventral margin. 



Length of hinge line about 12 lines ; length from the umbones to the 

 posterior ventral angle about 13 lines. 



Resembles an ordinary form of Pterinea, but is more convex than the 

 generality of the species of that genus. 



Locality and Formation. G-, Port aux Choix, Newfoundland ; Quebec 

 group. 



Collector. J. Richardson. 



CTENODONTA ANGELA. (N. sp.) 



Fig. 203. 

 Fig. 203. Ctenodonta Angela; left valve, interior and exterior. 



Description. Shell small, sub-ovate or sub-rhomboidal ; anterior extre- 

 mity broadly rounded ; posterior narrowly rounded ; ventral margin in the 

 posterior two-thirds somewhat straight, in the anterior third obtusely con- 

 vex ; umbones prominent, situated about the middle of the dorsal margin ; 

 beak small, closely incurved ; a shallow, barely perceptible byssal sinus 

 extending from the umbo obliquely to the posterior half of the ventral 



