PANAMIC-PACIFIC PELECYPODA ,S39 



Donax obesula Reeve, 1854, Conch. Icon., vol. 8, Donax, pi. 5, fig. 30 Peru. — Deshave?, 



1855, Proc. Zool. Soc. London, p. 352. 

 Donax obesulus Deshayes, Sowerby, 1866, Thes. Conch., vol. 3, Donax, p. 308, No. 



23, pi. 280, fig. IS. 



Shell small or medium-sized, convex, thin to moderately solid, tri- 

 gonal-ovate, the umbones wide, prominent, submedian, the posterior side 

 obliquely truncated, flattened, except for a small impressed or concave 

 area under the beak, the somewhat longer but still short anterior side de- 

 pressed and rounded at the end. The posterior keel is sharply angled. Sculp- 

 ture is formed by fine, crowded, flattened, smooth, radial riblets on the 

 anterior surface, somewhat larger and neatly cancellated by cross con- 

 centrics in a band just behind the posterior keel; and more finely can- 

 cellated on the flattened posterior surface. Interradial lines are not pitted. 

 Color white, yellow, gray or salmon-brown, the umbones often darker 

 and sometimes showing a short, purple ray on each side. Interior white 

 or blotched with purple. Inner margin of valve coarsely crenulated along 

 the whole ventral side; much finer along the posterior margin. 



Length 34.2 mm., height 19 mm., diameter 13.2 mm. Puerto Mensabi. 



Length 16.1 mm., height 13 mm., diameter 8.8 mm. Cojimenes. 



D. rostratus was described from a single valve which measured, length 

 40.6 mm., height 29.2 mm., diameter 20 mm. The type is lost but its identi- 

 fication seems fairly certain. Adams compared it to D. carinatus, but it is 

 more closely allied to D. asper and possibly is merely the young form of 

 that species. At Cojimenes, this shell was found in considerable abundance, 

 all specimens of the same size. 



Range — Panama to Peru. Panama: Panama City (C. B. Adams); 

 Puerto Mensabi. Ecuador: Cojimenes; Sua. Peru: Tumbez. 



Donax panamensis Philippi Plate 59, figures 3, 3a 



Donax cayennensis Lamarck, Reeve, Conch. Icon., vol. 8, Donax, pi. 4, figs. 22a, 22b. 

 Hab. Panama and Santa Elena, West Colombia; Cuming. — Sowerby, 1866, 

 Thes. Conch., vol. 3, Donax, p. 308, No. 19, pi. 281, figs. 46, 47, 48, gives same 

 habitat as Reeve. Not D. caianensis Lamarck, 1818, Anim. s. Vert., vol. 5, p. 550. 

 Habite I'Ocean de la Guyane (for a figure see Delessert, 1841, Rec. Coq. 

 decrites par Lamarck et non encore figures, pi. 6, figs. 13a, 13b). See also 

 Hanley, 1842, Recent Bivalve Shells, p. 82. Gave Guiana as habitat and re- 

 marked that it is less tumid but akin to the last (D. striata I.inne). 



Donax panamensis Philippi, 1848, Zeit. f. Malakozool., Jahrg. 5, No. 10, p. 145. — 

 Reeve, 1854, op. cit., pi. 9, fig. 63. 



Donax assimilis Hanley, Hertiein and Strong, 1949, Zoologica, vol. 34, pt. 4, p. 252. 

 Not. D. assimilis Hanley, 1845. 



Shell trigonal, subquadrate, the anterior side much longer than the 

 posterior, with the beaks placed at the posterior one-third. Posterior side 

 flattened and truncated along the margin. The sculpture is formed by small, 

 radial riblets, heaviest over the posterior section and along the umbonal 

 angle, much finer and smoother elsewhere, the riblets and their interspaces 

 beaded or cancellated. On the posterior slope, the ribbed sculpture is 

 divided into a finer and a coarser section but the dividing line is not 

 produced into a tooth at the margin (as in D. dentijerus). Color is usually 

 a grayish white, shading to yellow, brown, or violet, the umbones usually 

 darker and often marked with a white ray at the beaks. Interior generally 

 purple around the margins, the cavity itself thickened and white. 



Length 34 mm., height 22.4 mm., diameter of a left valve 7.7 mm. 

 Panama City, Panama. 



