PANAMIC-PACIFIC PELECYPODA 275 



Length 31.7 mm., height 26.5 mm., diameter 19.2 mm. Venado Beach, 

 Panama Canal Zone. 



This small species is known only with certainty from Panama; records 

 from other places are questionable. It is generally a small, rounded or 

 ovate form, the concentric line strong and regular on the anterior slope, 

 much weaker elsewhere. The small lunule is deeply impressed, its inner part 

 under the beaks stained generally a deep brown. Surface coloration is vari- 

 able; sometimes a pure creamy white to other forms with radial rays and 

 arrow-shaped brown lines. 



Range — Panama: Panama City; Pinas Bay (Hertlein and Strong). 

 Panama Canal Zone: Venado Beach. 



Pilar (Pitar) elenensis, new species Plate 45, figures 1-lb 



Shell moderately large, thin to subsolid, trigonal, ventricose, the um- 

 bones wide and full with the small, adjacent beaks curved slightly forward 

 and placed at the anterior one-third. The lunule is large, elliptical cordate, 

 flat-surfaced, defined by a small line, its inner margin long and straight, 

 extending three-fourths or more the length of the anterior side, the extreme 

 anterior end being narrowly rounded. Posterior-dorsal margin is slightly 

 arched and curves evenly into the broadly rounded curve of the posterior 

 end. Outer surface convex, greatest in the middle of the disk, slightly 

 roughened by irregular growth lines, cream-colored, the umbones sometimes 

 marked with four or more brown lines, usually in pairs, but which do not 

 extend beyond the middle of the disk. Cavity of the beaks white or faintly 

 flushed with pink. PaUial sinus not extending to the middle of the shell 

 cavity. 



Length 45.5 mm., height 39 mm., diameter 14.9 mm. (right valve). 

 Holotype, Santa Elena, Ecuador. ANSP 218901. 



A much larger species than P. consanguineus and also distinguished by 

 its more trigonal shape, longer and straighter anterior side, and by its 

 larger lunule which is not impressed in the middle. 



Range — Panama southward to northern Peru. Panama: Bucaro; Puerto 

 Mensabi. Colombia: Isla del Gallo. Ecuador: Jaramijo; Santa Elena. Peru: 

 Boca Pan; Zorritos. 



Pltar (PItar) flnctnatng (Sowerby) Plate 43, figures 7, 7a; 



Plate 45, figures 5, 7 



Cytherea fluctuata Sowerby, 1851, Thes. Conch., vol. 2, p. 634, No. 79, pi. 136, figs. 



185, 186 Santa Elena. — Romer, 1867, Mongr. Molluskengattung Venus, Linn^, 



bd. 1, p. 122. 

 Circe fluctuata (Sowerby), Reeve, 1863, Conch. Icon., vol. 14, Circe, pi. 9, fig. 36. 

 Pitar (Pitar) fluctuatus (Sowerby), Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. 



Hist, vol. 107, art. 2, pp. 189, 190, pi. 2, figures 10, 15, 19. 



Shell small or medium-sized (length about 33 mm.), rounded, ovate 

 in form, cordate, with high, convex, full umbones ending in small, adjacent 

 beaks placed near the anterior one-third. The lunule is large, more deeply 

 impressed in the middle, and outlined by a faintly incised line. Anterior end 

 is widely rounded, its outline accentuated by the deep lunule, the posterior 

 end more narrowly rounded to crudely subquadrate in shape. Surface 

 marked with fairly coarse, concentric threads; the color in our specimens 



