362 AXEL A. OLSSON 



Length 91.8 mm., height 84.2 mm., diameter 17.7 mm. (a left valve, 

 Mompiche, Ecuador). 



As fossil, this species is represented by closely related forms in the 

 Zorritos Miocene of Peru and in the Miocene of northwestern Costa Rica 

 (subsp. costaricensis Olsson). It occurs as a Pliocene fossil in Ecuador and 

 in the Pleistocene of Panama. 



Range — Guatemala to northern Peru. Guatemala: El Salvador and 

 Costa Rica, recorded by Hertlein and Strong. Panama: Bucaro; Guanico; 

 Bahia Honda near Las Tablas; San Carlos. Panama Canal Zone: Fort 

 Amador beach. Colombia: Choco (0. L. Haught, USNM). Ecuador: Sua; 

 Mompiche; Charapota; Jamaijo. Peru: Tumbez; Zorritos. 



Semele elllptica (Sowerby) Plate 64, figure 5 



Amphidesma ellipticum Sowerby, 1833, Proc. Zool. Soc. London for 1832, p. 200 Monte 

 Christe. — Sowerby, 1833, Conch. Illust., No. 6, fig. 17 (no figure given). — 

 Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, pi. 5, fig. 31. 



Semele elliptica (Sowerby), Maxwell Smith, 19++, Panamic Marine Shells, p. 62, fig. 808. 



This species much like S. laevis but consistently smaller, higher, the 

 anterior side shorter, more widely rounded at the end. The posterior side 

 is quite short, with a well-marked, depressed, posterior-dorsal area, more 

 or less flexed, and widely truncated at the end. Surface white under a gray 

 periostracum, the surface smooth but frequently ringed or banded, the 

 umbones smooth and with fine, low, concentrics below. Inside white, often 

 with slight yellow or pink staining in the middle. 



An average shell measures: length 47.3 mm., height 42.7 mm., diameter 

 21 mm. 



A common species in Panama at several places. 



Range — Panama. Panama: Cathedral Rocks; Panama City; Concepcion 

 beach near Poicri; Las Tablas; Puerto Chame. Panama Canala Zone: Venado 

 Beach. 



Semele flarescens (Gould) Plate 64, figures 4-4b 



Amphidesma flavescens Gould, 1851, Proc. Boston Soc. Nat. Hist, vol. 4, p. 89. — Gould, 



1853, Boston Jour. Nat. Hist., vol. 6, p. 392 San Diego. 

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



5, pp. 513, 5+7, No. 487.— Turner, 1956, Occas. Paper on Mollusks, Mus. Comp. 



Zool., vol. 2, No. 20, pp. 76, 77, pi. 18, figs. 14, 15. 

 Amphidesma proxima C. B. Adams, Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, 



pi. 3, fig. 20. 

 Semele proxima (C. B. Adams) Maxwell Smith, 1944, Panamic Marine Shells, p. 62, 



fig. 805. 

 Semele catifornica A. Adams, 1853, Proc. Zool. Soc. p. 96. — Lamy, 1914, Jour, de 



Conchyl., vol. 61, No. 3, pp. 359, 360. 

 Amphidesma catifornica (A. Adams), Reeve, 1853, Conch. Icon., vol. 8, Amphidesma, pi. 



3, fig. 19. 

 Semele flavescens (Gould), Hertlein and Strong, 19+9, Zoologica, vol. 34, pt. 4, No. 



19, pp. 2+2, 2+3. 



Shell of medium size to large, (length 62.4 mm.), orbicular to nearly 

 circular, slightly longer than high, thick, the beaks median. Surface with 

 irregularly spaced, concentric groovings, marking stages of growth and fine 

 radial striae. On close examination under a lens, the texture of the surface 

 Is seen to be finely granulose as if built up of small, closely packed grains. 

 External color a dull white, overlain by a thin, gray periostracum retaining 

 the fine, granulose textured surface of the shell beneath. Interior of shell 



