312 AXEL A. OLSSON 



teriorly the costals are coarser and more riblike. Color white, sometimes 

 with faint brownish mottling along the posterior-dorsal margin. 



Length 49 mm., height 41.2 mm., diameter 14 mm. a right valve 

 Holotype, ANSP 218898. 



Length 52.7 mm., height 43.5 mm., diameter 16.4 mm. a left valve. 

 Paratype. 



This interesting species is known to me only from some loose valves 

 picked from shell heaps at Palmar, a fishing village and the port of the 

 small, inland town of Colonche in Ecuador. At this place, this species was 

 sufficiently plentiful that it was gathered along with other clams as a 

 sea food. Its surface usually chalky and weathered suggests that it is a 

 mud dweller, probably in somewhat brackish waters. 



Genus PAPHONOTIA Hertlein and Strong, 1948 



Type species by original designation, Petricola elliptica Sowerby. 



Shell variable in shape, sometimes distorted, usually suborbicular to 

 oblong, the beaks placed near the anterior one-third, strongly convex and 

 sculptured with large, widely spaced, high concentric lamellae with radial 

 riblets in their interspaces except on the posterior slope where they are 

 lacking. Hinge with three cardinal teeth in each valve, the middle and 

 posterior right cardinal teeth and the middle left cardinal tooth being 

 bifid. Lunule defined by an incised line and sculptured with strong con- 

 centrics; the escutcheon narrow, flattened, restricted to the left valve. Area 

 of the ligament small and immersed. Pallial sinus strong, rounded at the 

 end, reaching to about the middle of the shell cavity. 



These shells are rock borers or nestlers, their valves often distorted, 

 sometimes nearly circular to narrowly produced. The color is usually a 

 dirty white or cream, the interior colored brown at the ends and over the 

 adductor scars. From Petricola, the genus is distinguished by its venerid 

 hinge and well-defined lunule. 



Paphonotla elliptica (Sowerby) Plate 41, figure 3 



Plate 55, figure 10 



Petricola elliptica Sowerby, 1834, Proc. Zool. Soc. London, p. 46.— Sowerby, 1854, Thes. 



Conch., vol. 2, Petricola p. 774, No. 10, pi. 166, fig. 10 Paita.— Sowerby, 1874, 



Conch. Icon., vol. 19, Petricola, pi. 2, fig. 12. 

 Venerupsis elliptica (Sowerby), Lamy, 1922, Jour, de Conchy., vol. 67, pp. 306-308. 

 Petricola solida Sowerby, 1834, Proc. Zool. Soc. London, p. 46 Lambeyeque.— Sowerby, 



1834, Thes. Conch., vol. 2, Petricola, p. 774, No. 11, pi. 166, fig. 9.— Sowerby, 



1874, Conch. Icon., vol. 19, Petricola, pi. 2, fig. 15. 

 Petricola oblonga Sowerby, 1834, Proc. Zool. Soc. London, p. 46 Pacosmayo. — Sowerby, 



1834, Thes. Conch., vol. 2, Venerupsis, p. 765, No. 10, pi. 165, fig. 21. 

 Irus {Paphonotia) ellipticus (Sowerby), Hertlein and Strong, 1948, Zoologica, vol. 33, 



pt. 4, p. 193. 



Shell highly variable in shape from nearly circular to elliptical or 

 oblong. Common along the southern coast of Ecuador and northern Peru, 

 occasionally attains a length of about 40 mm. 



Length 35.7 mm., height 32.9 mm., diameter 26.8 mm. Negritos, Peru. 



Length 38.6 mm., height 28.5 mm., diameter 22.2 mm. Mancora, Peru. 



Range — Mexico to northern Chile. Panama: Burica Peninsula; Bucaro. 

 Ecuador: San Francisco; Puerto Callo; Santa Elena. Peru: Tumbez; Man- 

 cora; Negritos; Paita; Yasila; Lambayaque. 



