PANAMIC-PACIFIC PELECYPODA 183 



The beaks are small but prominent, pointed, and turned sharply backwards 

 to face a long, excavated dorsal margin terminating in a pronouncedly point- 

 ed end. The anterior-dorsal margin mildly convex. Because of the obliquity 

 of the axis of the shell, the ventral margin has a bulge in the posterior 

 half while its anterior portion is slightly convex to insinuated with a de- 

 pressed zone extending upwards across the disk to the beak. Surface slightly 

 convex to depressed, sculptured by 10 or more, stout, concentric riblets be- 

 tween wide, wavelike depressions; in addition the whole surface is covered 

 by fine, submicroscopic radial lineation. Color pure white to various shades 

 of brown and Ulac, often rayed with lines of purple-pink or brown. Interior 

 glossy, white or stained. Hinge strong. 



Length 2.9 mm., height 2.5 mm., diameter 1.4 mm. Puerto Callo. 

 Holotype, ANSP 218934. 



A small species, easily recognizable by its shape, its posterior side with 

 its margin deeply concave or indented and ending in a short, snoutlike point. 



Range — Coasts of Ecuador and western Colombia. Colombia: Isla del 

 Gallo. Ecuador: Esmeraldas; Puerto Callo. 



Crassinella rarians (Carpenter) Plate 25, figures 7-7b 



Gouldia vartans Carpenter, 185f, Cat. Mazatlan Shell, Brit. Mus., pp. 83, 84, No. 117. 

 Crassinella vartans (Carpenter) Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 3, 

 No. 8, p. 104. 



The shell is generally small, subtrigonal, rather solid, moderately con- 

 vex, subequilateral, the popterior side usually slightly longer, the dorsal 

 margins quite straight, descending, the ventral margin widely rounded. 

 Surface sculpture is often quite smooth except for growth incrementals or 

 concentric riblets may be present, usually strongest on the umbones. Color 

 plain white or blotched with brown, especially on the posterior side. 



Length 3.5 mm., height 3 mm., diameter 1.7 mm. Punta Blanca, 

 Ecuador. 



This is a small, moderately convex, trigonal species, its shape that of 

 a narrow, equilateral triangle with sharply pointed beak, the surface smooth 

 or variably ribbed. 



Range — Gulf of California to Ecuador. Mexico: Mazatlan (Carpenter). 

 Nicaragua: Corinto (Hertlein and Strong). Ecuador: Punta Blanca. 



Crassinella adamsi, new species Plate 25, figures 3-3c 



Shell small, moderately convex, solid, subtrigonal but with the anterior 

 side longer, rounded at the end, the posterior side short, its margin rapidly 

 descending, excavated by a narrow, linear, sunken escutcheon. Beaks small, 

 pointed, opisthogyrate. Surface sculptured by small, strong, rounded con- 

 centric riblets which number from 10 to 14 depending upon the size of 

 the shell; these riblets are close-set. Color commonly white or glassy, occa- 

 sionallv stained irregularly with brown. Length 22 mm., height 2 mm. Punta 

 Blanca, Ecuador, Holotype, ANSP 218933. 



In shape, this small shell recalls a venerid but its hinge and other 

 characteristics show it to be a Crassinella. It differs from the other Pacific 

 species of the genus by its longer anterior side. A closely similar species is 

 found along the Caribbean coast of Panama which differs only in having 

 the concentric riblets between deeper interspaces. 



Range — Panama. Ecuador: Punta Blanca. 



