PANAMIC-PACIFIC PELECYPODA 91 



Shell elongate-subrectangular, flat or moderately convex, generally 

 with the dorsal-posterior side somewhat depressed, often more or less 

 aviculoid or emarginate, especially in the young. Umbones wide, full, passing 

 over gradually into the normal inflation of the valves, the beaks small, and 

 prosogryrate. The cardinal area is long and narrow, covered entirely by 

 the ligament, and marked with numerous V-shaped or chevron-like grooves. 

 Sculpture formed by numerous, flattened ribs between narrower inter- 

 spaces, the anterior set of ribs noded or divided mesially. Hinge formed by 

 numerous, small teeth continuous along the entire hinge line. 



Cara Gray, 1857 is considered to be a synonym of Rasia since its 

 type species, the Area aviculoides of Reeve is but the young form of Area 

 formosa Sowerby. 



Anadara (RasIa) forniosa (Sowerby) Plate 7, figure 4 



Area formosa Sowerby, 1833, Proc. Zool. Soc. London, p. 20 Gulf of Tehuantepec. — 



Reeve, 1844, Conch. Icon., vol. 2, Area pi. 2, fig. 10. 

 Area (Anadara) formosa Sowerby, Hertlein and Strong, 1943, Zoologica, vol. 28, pt. 



3, p. 156. 



Seapharca (Seapharea) formosa (Sowerby), Maury, 1922, Paleont. Amer., vol. 1, 



No. 4, pp. 28, 29, pi. 2, fig. 11. 

 Anadara (Anadara) formosa (Sowerby), Reinhart, 1943, Special Paper, Geol. Soc. 



America, No. 47, p. 62, pi. IS, figs. 4-6. 

 Area aviculoides Reeve, 1844, Conch. Icon., vol. 2, Area, pi. 10 fig. 63. 

 Seapharca (Seapharea) aviculoides (Reeve), Maury, 1922, Paleont. Amer., vol. 1, No. 



4, pp. 24, 25, pi. 2, fig. 2. 



Shell large, oblong, rectangular, the hinge line and ventral margin 

 straight but not quite parallel, divergent slightly on the posterior side. 

 Color white but fresh specimens are covered with a dense, pilose, brown 

 periostracum. Ribs strong, numerous, generally about 33 in number, the 

 anterior set narrow and with a medial groove, the posterior ones wider 

 and simple. 



Length 102 mm., height 58 mm., diameter 52.7 mm. 



Pearl Islands. 



This is a widely distributed species, seldom common at any locality. 

 Young shells are more strongly auriculated than the adult; a specimen of 

 this kind from Santa Elena was named avieuloides by Reeve. 



Range — Lower California to northern Peru. Panama: Pearl Islands; 

 Bucaro. Ecuador: Manta; Isla la Plata; Santa Elena. Peru: Zorritos; 

 Mancora; Yasila near Paita. 



Anadara (Rasia) emarginata (Sowerby) Plate 8, figures 6, 6a 



Area emarginata Sowerby, 1833, Proc. Zool. Soc. London, P. 20. — Reeve, 1844, Conch. 

 Icon., vol. 2, Area, pi. 4, fig. 26. 



Seapharea (Seapharea) emarginata (Sowerby), Maury, 1922, Paleont. Amer., vol. 1, 

 No. 4, p. 23, pi. 2, fig. 5. 



Area (Cara) emarginata (Sowerby), Hertlein and Strong, 1943, Zoologica, vol. 28, pt. 

 3, p. 159. 



Anadara (Seapharea) emarginata (Sowerby), Rost, 1955, Allan Hancock Pacific Ex- 

 peditions, vol. 20, No. 2, pp. 203, 204, pi. 14, fig. 22; text-figs. 89 a-c. 



Shell of medium size (up to 50 mm.), thin, often irregular, subequi- 

 valve, elongate, subquadrate, the dorsal and ventral sides straight, sub- 

 parallel, the anterior end slightly narrower. Anterior side short, rounded, 

 the posterior side much longer, emarginate or with a deep notch below the 



