it AXEL A. OLSSON 



covered by a heavy, brown to black, strongly wrinkled periostracum, the 

 umbones often corroded and showing the white shell. Ribs are numerous, 

 (33 to 37 in number), relatively large, rounded, close set and separated 

 merely by a groove or narrowly lined interspaces, usually with a scattering 

 of nodes or tubercles along their summits. Umbones wide and prominent, 

 often weakly sulcated. Cardinal area is narrow in the shape of a depressed or 

 flattened triangle and engraved with three or more tent-shaped grooves, 

 the whole area covered by the ligament. 



Length 54.6 mm., height 39.6 mm., diameter 32.4 mm. 



Guayaquil, Ecuador (market). 



This is a common and widely distributed species, living buried in the 

 soft mud amongst the roots of mangrove trees. "As reported by Coker 

 (Dall, 1909, p. 154), among the first phenomena to catch one's attention 

 on entering the mangrove swamps is a sound heard repeatedly on every 

 side, as of nuts falling into the water or soft mud. Tracing the sound with 

 some care, it is found to come from the watery hollows in the mud occupied 

 by the concha prieta, and is presumably made by the sudden closing or 

 opening of its valves under water by the mollusks". The common name 

 of this ark is "Concha Prieta", in allusion to its black color. It is a common 

 article of shell food, and on sale in market places throughout its range. 



Range — Lower California to Peru. Numerous records. Peru: Tumbez, 

 (its most southerly occurrence). 



inadara (Dilnvarca) simills (C. B. Adams) Plate 7, figures 2, 2a 



Area stmilts C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New York, vol. 5, pp. 485, 486, 

 545, No. 422 Panama. — Turner, 1956, Occas. Papers on Mollusks, Mus. Comp. 

 Zool., vol. 2, No. 20, pp. 85, 86, pi. 20, figs. 1, 2. 



Area (Anadara) similis C. B. Adams, Hertlein and Strong, 1943, Zoologica, vol. 28, 

 pt. 3, p. 157, pi. 1, figs. 2, 5. 



The shell is ellipsoidal, slightly oblique posteriorly, relatively thin. 

 Surface covered by a brown or black, wrinkled periostracum, often scaley 

 and when worn away showing a white-colored shell beneath. Ribs numerous 

 (40 to 44), small, narrow, separated by rather wide interspaces, the ribs 

 more or less strongly tuberculated, especially near the ventral margin. 

 Hinge is narrow and straight, the teeth small and numerous, arranged in 

 an uninterrupted series. 



Length 51 mm., height 33.5 mm., diameter 27.8 mm. 



Limones, Ecuador. 



Similar in shape to the common A. tuberculosa but with a more elliptical 

 shape, more numerous ribs, and thinner shell. 



Range — Nicaragua to the Gulf of Guayaquil. Costa Rica: Punta Arenas 

 (Hertlein and Strong). Panama: vicinity of Panama City. Ecuador: 

 Limones; Guayaquil (market). 



Anadara (Dllnyarca) cepoides (Reeve) Plate 9, figures 7, 7a 



Area eepotdes Reeve, 1844, Proc. Zool. Soc. London, p. 47. — Reeve, 1844, Conch. Icon., 



vol. 2, Area, pi. 10, fig. 66. 

 Scapharea (Scapharea) cepoides (Reeve), Maury, 1922, Paleont. Amer., vol. 1, No. 4, 



p. 193, pi. 3, fig. 6. 

 Area (Seapharea) eepotdes Reeve, Hertlein and Strong, 1943, Zoologica, vol. 28, pt 



3, No. 19, p. 162. 



