PANAMIC-PACIFIC PfiLECYPODA 89 



Shell large, broadly subovate or roundly quadrate, ventricose, the 

 umbones being full, wide and placed a little anterior of the middle, the 

 terminating beaks weakly sulcated. The valves are slightly unequal, the 

 ventral margin of the left valve overlapping that of the right but the 

 rounded convexity of each valve is almost the same. The substance of the 

 shell is so light and so thin that the furrows of the external ribs show into 

 the interior almost throughout. Ribs number 33 to 34, of which 8 are found 

 on the posterior slope; these ribs are square or rectangular in section, 

 smooth and flat-topped, almost alike in each valve, their interspaces flat 

 and somewhat narrower. The cardinal area is broadly, obhquely subtrigonal 

 in shape, and of medium height; it is covered completely by the ligament 

 and cut into by three or four transverse grooves. The periostracum is dark 

 in color, usually brown, and a little scaly. Hinge narrow, straight, the 

 teeth small and arranged in a continuous series. 



Length 90 mm., height 85 mm., diameter 77.3 mm. 



South America. Dr. T. B. Wilson, ANSP 4292. 



Length 70 mm., height 60 mm., diameter 46 mm. Panama, Amer. 

 Museum, specimen measured by Maury, 1922. 



There are several specimens of this large species in the collection of 

 the Academy of Natural Sciences in Philadelphia labelled simply South 

 America, Dr. T. B. Wilson. Reeve cited San Miguel, Panama, which is 

 probably the San Miguel, Rey Island of the Pearl Island group. Hertlein 

 and Strong recorded this species from Ceralbo Island, Gulf of California. 



Range — Gulf of California to Panama. Mexico: Ceralbo Island, Gulf 

 of California. Panama: San Miguel, Rey Island, Pearl Islands. 



Anadara (Dllinarca) obesa (Sowerby) Plate 8, figures 8, 8a 



Area obesa Sowerby, 1833, Proc. Zool. Soc. London, p. 21 (Atacames).— Reeve, 1844, 



Conch. Icon., vol. 2, Area, pi. 1. fig. 3- 

 Area (Seapharca) obesa Sowerby, Hertlein and Strong, 1843, Zoologica, vol. 28, pt. 



3, p. 163. 

 Seapharca (Scapharea) obesa (Sowerby), Maury, 1922, Paleont. Amer. vol. 1, No. 4, 



pp. 189, 190, pi. 3, figs. 4, 5 

 Anadara (Seapharca) obesa (Sowerby), Rost, 1955, Allan Hancock Pacific Expeditions, 



vol. 20, No. 2, p. 205, pi. 16, figs. 28 a-b; text-figs. 90 a-c. 



Shell of medium size (length up to about 40 mm.), subequivalve, ovate, 

 with wide, convex, and nearly central umbones. Cardinal area narrow, 

 much longer than high, nearly covered by the ligaments and marked with 

 wide, tent-shaped grooves. Ribs numerous (42 to 44), narrow, rectangular, 

 between flat-bottomed interspaces, their summits smooth or weakly noded. 

 Anterior side obliquely rounded, the posterior slope subtruncate, the um- 

 bonal slope weakly angled, its margin straight, cuneate at its ventral corner. 



Length 39 mm., height 28.7 mm., diameter 25.6 mm. 



Tumbez, Peru. 



This is a relatively common species in northern Peru and along the 

 coast of Ecuador. As noted by Maury, there are no allied species 

 in the Hving Caribbean fauna but several fossil forms are known from the 

 East Coast Miocene. 



Range— Mtxxco to northern Peru. Panama: Bucaro; San Carlos. 

 Ecuador: Sua; Galeras; Charapota; Manta; Punta Blanca; Santa Elena. 

 Peru: Tumbez; Zorritos; Boca Pan; Mancora. 



