PANAMIC-PACIFIC PELECYPODA 287 



Lamelllconcha circinata Tinacea, new subspecies Plate 48, figures 2-2b 



Dione circinata Reeve, 1863, Conch. Icon., vol. 14, Dione, pi. 7, figs. 25a, b Mazatlan. 

 Not of Born, 1780. 



The shell is small or of medium size (35 mm. or less), ovately cordate, 

 the umbones full and prominent, with the small beaks placed near the 

 anterior one-fourth. The surface sculpture is formed by numerous, fairly 

 strong, narrow and rather harsh concentric riblets, their tops thin and often 

 slightly recurved; interspaces are wider than the riblets, both overrun by 

 fine lines of growth. The anterior lateral tooth in the left valve large. The 

 surface color is usually a violaceous brown or chestnut; more rarely white; 

 the interior white or stained lightly with violet. 



Length 35.6 mm., height 30.1 mm., diameter 10.1 mm. (a left valve). 

 Charapota, Ecuador. Holotype, ANSP 218920. 



Much smaller than L. circinata alternata, more ovate shape and usually 

 of a different color. 



Range — Mexico southward to Ecuador. Mexico: Mazatlan ANSP 

 175468. Panama: Panama City; Bucaro; Pearl Islands; Burica Peninsula. 

 Colombia: Isla del Gallo. Ecuador: Mompiche; Sua; Charapota; Jaramijo; 

 Manta; Puerto Callo; Santa Elena. 



Lamelliconcha concinna (Sowerby) Plate 48, figures 4-4c 



Cytherea concinna Sowerby, 1835, Proc. Zool. Soc. London, p. 23 Panama. 

 Cytheraea concinna Sowerby, 1851, Thes. Conch., vol. 2, p. 630, No. 64, pi. 132, fig3. 



99, 100. 

 Dione concinna (Sowerby), Reeve, 1863, Conch. Icon., vol. 14, Dione, pi. 8, figs. 31a, 31b. 

 Pilar {Lamelliconcha) concinnus (Sowerby), Hertlein and Strong, 1948, Zoologica, vol. 



33, pt. 4, No. 13, pp. 175, 176.— Hertlein and Strong, 1955, Bull. Amer. Mus. 



Nat. Hist, vol. 107, art. 2, p. 192. 



The typical form of L. concinna from Panama is a small shell although 

 specimens may occasionally attain a length of about 40 mm. Shape is 

 oblong ovate, moderately convex, the beaks placed near the anterior one- 

 third, the posterior side narrowed and slightly produced, often with a weak 

 depression extending along the front of the posterior-umbonal angle which 

 thus slightly sinuates the ventral margin; the anterior side is well rounded. 

 Color white or reddish chestnut, often radially rayed. Specimens from Santa 

 Elena, Ecuador, are usually of heavier texture, white or violaceous brown, 

 the lunule and posterior-dorsal area more deeply colored. The concentric 

 riblets form low, rounded, solid ridges which generally extend uniformly 

 over the whole surface except on the somewhat flattened posterior-dorsal 

 submargin where they are reduced in number, the alternate riblet eliminated. 



Length 40.3 mm., height 33.3 mm., diameter 22 mm. Santa Elena, 

 Ecuador. 



L. concinna, L. paytensis, and L. tortuosa have been regarded by some 

 authors as subspecies of the same species. Extremes of the three are 

 distinct and easily recognizable and hence they are dealt with here as 

 separate but closely related species. Because of the confusion noted above, 

 the range of L. concinna to the north of Panama is uncertain. 



Range — Gulf of California ? south to northern Peru. Panama: Panama. 

 Panama Canal Zone: Palo Seco. Ecuador: Santa Elena. Peru: Tumbez. 



