45-i Systematic Paleontology 



in the better preserved individuals are equal and opposite, broad and 

 gibbous, and are curved inward and forward over the hinge-line and placed 

 considerably anterior to the middle. Surface of both valves marked by 

 moderately strong radiating costa3. The costse are low, rounded, and 

 simple, six or seven occupying the space of 5 mm. in the umbonal region, 

 the costas are indistinct toward the base in the individuals at hand, but 

 the general appearance indicates that they become wider toward the base. 

 Shell varying in size from small individuals to quite large ones for this 

 genus. 



This species most closely resembles Amphicoelia costata (Hall and 

 Whitfield) of the Niagara of Ohio. It differs, however, in being less 

 ventricose, the beaks are more nearly central, and the costse are more 

 numerous. 



Occurrence. — Helderbeeg Formatiox, Iveyser Member. Iveyser, 

 West Virginia. 



Collection. — U. S. National Museum. 



[]\Iaynard.] 



Family PINNID/E 



Genus PALEOPINNA Hall 

 Paleopinna lata n. sp. 

 Plate LXXVI, Fig. 1 



Description. — Shell large, very oblique, axis and hinge-line making an 

 angle of about 23°; greatest length to greatest height as about 3 to 4 : 

 anterior margin truncate and emarginate, ventral margin broadly and 

 regularly curving, posterior margin more rapidly rounding and recurving 

 to meet the hinge-line; left valve gibbous in middle and anteriorly, de- 

 pressed posteriorly and dorso-posteriorly ; right valve not known. Umbo 

 wide, beak probably extending to posterior limit of body; a narrow ridge 

 extending from beak ( ?) along hinge-line to posterior end of dorsal 

 margin. Interior marked by broad obsolete growth lines. Exterior un- 

 known. 



Length 8.75 cm.; height 6 cm. 



The description is from the cast of the interior of the left valve of a 

 single specimen. It has all the marks of this genus and is readily separable 



