PANAMIC-PACIFIC PELECYPODA 361 



fb. Concentric elements of the sculpture dominant, the radials restricted 

 to groovings on one or both ends. 



fba. Concentrics small and fine. 



19. With radial groovings on the anterior slope only. 



S. pulchra and S. quentinensis 



20. With radial groovings on both ends. 



S. jaramija 



fbb. Concentric elements coarse. 



21. Radial groovings mostly on the anterior slope, sometimes also on the 

 posterior but much weaker. 



S. guaymasensis 



Semele corrngata (Sowerby) Plate 64, figures 1, la, lb 



Amphidesma corrugata Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 200 (in 

 Peruvia et ad Iquiqui). — Sowerby, 1833, Conch. Illust, p. 7, No. 8. — Reeve, 

 1853, Conch. Icon., vol. 8, Amphidesma, pi. 1, fig. 4. 



Semele corrugata (Sowerby), Dall, 1910, Proc. U.S. Nat. Museum, vol. 37, No. 1704, 

 p. 271. 



Shell large, subcircular to suborbicular, thick, the right valve larger 

 and more convex, the left valve flattened to slightly convex. Surface marked 

 with small, wrinkled, concentric corrugations and weak to subobsolete 

 radial lines and striations, often so arranged as to form radial rays. Ex- 

 ternal color white, the interior white or a deep apricot, the teeth generally 

 stained with violet or purple. Adductor scars large and subequal, the pallial 

 sinus deep, well rounded at the end. 



Length 96 mm., height 85.5 mm., diameter 40 mm. Specimen from 

 Bahia de la Independencia, Peru. 



This is a large, white shell often with an apricot-colored interior, the 

 teeth stained deep red or violet. It is quite common at many places along 

 the middle and south Peruvian coast where it is used both for food and bait 

 by the natives. It has been reported as ranging as far northward as the 

 Gulf of California but I have seen no authentic specimens north of the 

 Santa Elena peninsula. 



Range — Southern Ecuador to Chile. Ecuador: Santa Elena. Peru: 

 Negritos; Baj'^ of Sechura; Paracas; Bahia de la Independencia. 



Semele laeris (Sowerby) Plate 64, figure 6 



Amphidesma laeve Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 199. XIpixapi. — 



Sowerby, 1833, Conch. Illust., No. 22, pi. 18, fig. 6. 

 Amphidesma laevis Sowerby, Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, pi. 7, fig. 



50. 

 Semele laevis (Sowerby), Hertlein and Strong, 1948, Zoologica, vol. 34, pt. 4, No. 19, 



p. 245. 



Shell medium or large (to about 90 mm.), subsolid, ovately elliptical 

 in shape, equivalve, and with slight or moderate convexity. The beaks are 

 placed a little behind the middle, the posterior side being shorter and higher, 

 its dorsal margin weakly arched. The posterior dorsal area is barely defined, 

 not flexed. Anterior dorsal margin descends with a slight curve towards 

 the end, the whole anterior side appears as if drawnout slightly. The beaks 

 are small and overhang a small, elongate lunule found only in the left 

 valve; there is also a narrow escutcheon in the same valve. Surface smooth, 

 polished, especially over the umbones, the growth lines showing best but 

 somewhat irregular towards the ventral side. A large pallial sinus extends 

 to about the middle of the shell cavity. 



