PANAMIC-PACIFIC PELECYPODA 265 



Cyclinella singleyl Dall Plate 43, figures 5, 5a 



Cyclinella singleyi Dall, 1902, Proc. U.S. Nat. Museum, vol. 26, No. 1312, p. 404, pi. 15, 

 fig. 3. 



Shell of small or medium size (length 42 mm.), suborbicular to sub- 

 circular, strongly convex, the umbones wide and full with the small beaks 

 placed near the anterior one-quarter, curved, and pointed over a small 

 lanceolate lunule defined by a faintly incised line. Surface white or faintly 

 ochraceous, covered by fine, sharp, concentric striation and sometimes an 

 obscure, radial Hneation. Interior white, sometimes with a faint flush of 

 apricot pink in the middle and with a deep, angular paUial sinus reaching 

 to about the middle of the cavity. Hinge plate stout, the right valve with 

 three cardinal teeth of which the posterior one is bifid, the ligament long, 

 straight, and deeply inset. 



Length 41.8 mm., height 39.3 mm., diameter 28.4 mm. Tumbez, Peru. 



Recognized by its relatively small size, rounded, convex valves. Most 

 common on mud flats and similar situations. 



Range — Gulf of California to northern Peru. El Salvador: La Union 

 (ANSP Lowe). Panama: Panama City; Rey Island; Pearl Islands. Colom- 

 bia: Isla del Gallo. Peru: Tumbez. 



Subfamily CLEMEJfTimAE Frizzell, 1936 

 (Clementiidae Frizzell). 

 Type genus, dementia Gray, 1842. 



Shell subovate, convex, generally thin, the surface marked with con- 

 centric, wavelike undulations, strongest on the umbones but usually fading 

 out below, but more or less distinctly transmitted through the substance 

 of the valve into the interior. Hinge carrying three cardinal teeth in each 

 valve, the right, posterior cardinal tooth bifid and more or less joined above 

 with the anterior tooth, the middle cardinal tooth below it standing free. 

 There are no lateral teeth, but the lunular margin within the hinge plate 

 is deeply grooved. Lunular area is impressed but not set apart by a line; 

 there is no escutcheon. PaUial sinus deep, the ventral margins of the valves 

 smooth. 



Genus CLEMENTIA Gray, 1842 



The genus at first proposed without species; the type species sub- 

 sequently designated by Gray, 1847, Venus papyracea Gray. Australia. 



Having the principal characters of the family. 



Subgenus EGESTA Conrad, 1845 

 Type species by monotypy, Venus inoceriformis Wagner. Miocene of 

 Maryland. 



Similar to dementia, s.s. but larger and heavier, the posterior side is 

 longer and at its end assumes a crudely truncated form. The pallial sinus 

 is long and narrow. 



Clementia (Eg-esta) solida Dall Plate 50, figures 5, 5a 



dementia solida Dall, 1902, Proc. U.S. Nat. Museum, vol. 16, No. 1312, p. 401, pi. 14, 



fig. 4 Topolobampo, Mexico. 

 Clementia {Egesta) solida Dall, Woodring, 1926, Prof. Paper, U.S. Geol. Survey, No. 



147, p. 37, pi. 16, figs. 7, 8. 



