PANAMIC-PACIFIC PELECYPODA 363 



cavity white, often tinted with light yellow. Both valves have an elongate, 

 flattened escutcheon setoff sharply from the shell disk by angled borders. 

 Lunule small, deeply sunken. 



Length 52.8 mm., height 47 mm., diameter 25.3 mm. Santa Elena. 



Gould's original specimens of S. flavescens have never been figured, and 

 hence, some doubt may exist as to its real identity but an escutcheon was 

 mentioned in the original description which appears to indicate the shell 

 here under consideration. The name "■proximuin' was given to the same 

 shell by C. B. Adams the following year. 



Semele flavescens is similar to S. corrugata in shape but is smaller, its 

 dorsal side is higher and more trigonal in shape. It is best distinguished by 

 the presence of a small escutcheon in both valves and by its submicroscopic 

 granulose surface. The species is common over a wide range. 



Range — California to northern Peru. Panama: Panama City; Bucaro. 

 Panama Canal Zone: Venado Beach. Ecuador: Sua; Punta Blance; Palmar; 

 Manglaralto; Santa Elena. Peru: Zorritos; Boca Pan. 



Semele sparsilineata Dall Plate 66, f'gure 7 



Semele sparsilineata Dall, 1915, Proc. Acad. Nat. Sci. Philadelphia, vol. 67, p. 26 

 "Panama". — Hertlein and Strong, 1949, Zoologica, vol. 3+, pt. 4, pp. 247, 248, 

 pi. 1, fig. 8. 



Shell ovately elliptical, of moderate convexity, the beaks placed a 

 little behind the middle, the anterior side hence longer, somewhat narrower 

 and well rounded, the posterior side higher. Surface marked with small, 

 even and widely spaced threadlike, concentric ridges which begin on the 

 posterior slope and pass obliquely across the midzone onto the anterior 

 slope. Surface usually white or light-colored, blotched with brown or purple, 

 heaviest on the umbones and as finer zigzag markings elsewhere. 



Length of a specimen 33.2 mm., height 27.6 mm., diameter of a left 

 valve 7.2 mm. Santa Elena. 



Gosely resembles the Atlantic S. -purpurascens (Gmelin) but usually 

 smaller, heavier, and less convex. 



Range — Nicaragua to Ecuador. Nicaragua: Corinto (Hertlein and 

 Strong); San Juan del Sur (Lowe). Panama: Taboga Island (Lowe); 

 Ecuador: Santa Elena; Punta Blanca; Esmeraldas. 



Semele lentlculare (Sowerby) Plate 65. figures 8-8b: 



Plate 66, figures 9-9a 



Amphidesma lenticular e Sowerby, 1832, Proc. Zool. Soc. London, p. 200 "Sanctam 



Elenam. — Sowerby, 1833, Conch. Illust. fig. 9. 

 Amphidesma lenticularis Sowerby, Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, pi. 



6, fig. 39. 

 Amphidesma bicolor C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New York, vol. 5, 



pp. 512, 547, No. 485. — Turner, 1956, Occas. Papers on Mollusks, Mus. Comp. 



Zool., vol. 2, No. 20, p. 35, pi. 18, figs. 7, 8. 

 Amphidesma ventricosum C. B. Adams, 1852, op. cit., pp. 516, 547, No. 491. — Turner, 1956, 



op. cit., p. 97, pi. 19, figs. 9, 10. 

 Amphidesma striosum C. B. Adams, 1852, op. cit., pp. 515, 547, No. 489. Not A. striosum 



Turner, 1956, op. cit., p. 90 (pulchra Sowerby). 



The shell is small or of medium size (average length 23 to 25 mm.), 

 subcircular, thin or heavy, white, but often with the beaks and the interior 



