PANAMIC-PACIFIC PELECYPODA 295 



10), narrow, raised, concentric ridges, the spaces between them wide and 

 flat, both the ridges and interspaces marked with strong, generally paired, 

 cordlike, radial riblets. The escutcheon is large and elliptical in shape, nearly 

 as long as the dorsal-posterior margin, flattened and setoff by a sharp 

 angle; the lunule is narrowly cordate, sculptured with fine radials and 

 coarse, growth incrementals. Color white or cream and variegated with fme, 

 brown lines. 



Length 52.3 mm., height 49.4 mm., diameter 27.3 mm.; length 58.6 mm., 

 height 54.7 mm., diameter of a left valve 15 mm. Both specimens from 

 Bayovar, Sechura Bay, Peru. 



In its typical form, Chione compta is a large, thick-shelled, compressed 

 species, strongly sculptured with widely spaced, erect concentric lidges which 

 are finely crenulated on their sides by the radials. It is a common species 

 around the shores of Sechura Bay but rare elsewhere. The species resembles 

 Chione californiensis (Broderip) {succincta Valenciennes) in its large size 

 and shape but is typically more compressed and the concentrics are more 

 widely spaced and not recurved on top as well as differing by its radial 

 sculpture. It is possible that records of C. californiensis from the Panama 

 region may represent C. compta. Hertlein and Strong recorded this species 

 from Costa Rica. It is a common fossil in the Peruvian tablazos. 



Range — Gulf of California.? to northern Peru. Panama: Guanico; San 

 Jose Id., Pearl Islands (USNM 603334). Ecuador: Jaramijo; Manta. Peru: 

 Bayovar, and shores of Sechura Bay; Paita; Lobos de Tierra. 



Chione (Chione) snhlmbricata (Sowerby) Plate 55, figures 4-4b 



Venus subimbricata Sowerby, 1835, Proc. Acad. Nat. Sci. Philadelphia, p. 21 Puerto 

 Portrero.— Sowerby, 1853, Thes. Conch., vol. 2, p. 711, pi. 154, figs. 35-38.— 

 Reeve, 1863, Conch. Icon., vol. 14, Venus, pi. 19, figs. 85a, b, c. 



Venus neglecta Sowerby, 1839, Zool. Beechey's Voyage, p. 151, pi. 41, fig. 8. 



Venus bilineata Reeve, 1863, Conch. Icon., vol. 14, Venus, pi. 22, figs. 105 a, b. 



Anomalocardia subimbricata (Sowerby), Hertlein and Strong, 1948, Zoologica, vol. 

 33, pt. 4, No. 13, pp. 189, 190. 



Chione {Anomalocardia) subimbricata (Sowerby), Parker, 1949, Jour. Paleont, vol. 

 23, No. 6, p. 587, pi. 92, fig. 5. 



Shell unusually solid and heavy, subtrigonal, moderately convex, the 

 beaks elevated, trigonal, flattened, pointed or coiled slightly forward. The 

 sculpture is produced by a variable number of low, flattened, concentric 

 riblets forming ledges or steps over much of the disk except on the umbones 

 and beaks, where they rise in the shape of narrow, elevated ridges; in addi- 

 tion, the surface is overrun by strong, radial cords producing a cancellate 

 sculpture. The color is variable, usually a white base mottled with rays, 

 blotches and veinlets of brown, the lunule and escutcheon more deeply 

 colored; in some cases, the rays are reduced to narrow, paired, brown lines 

 (bilineata Reeve). Interior of the valves is usually white or flushed faintly 

 with brown or violet. 



Length 45.5 mm., height 40.3 mm., diameter 26.1 mm. Puerto Chame, 

 Panama. 



Authors have generally followed Dall (1909) in referring this species 

 to Anomalocardia which its mature sculpture somewhat resembles; how- 

 ever, the pattern on the umbones is more regular and finely cancellate and 

 its close relationship with Chione is apparent. 



