PANAMIC-PACIFIC PELECYPODA 429 



terior one large and seated on the thickened margin above a small bend or 

 sinuosity in the pallial line. Posterior end of the shell twisted or bent to 

 the left. Generally pure white but occasionally brown in the visceral cavity 

 and along the margins, sometimes rose-pink with the tip of the beak re- 

 maining white. 



Average shell: length 27 mm,, height 15 mm., diameter 12.2 mm. Zor- 

 ritos, Peru. 



This is a common and widely distributed species. The shell is usually 

 white or gray with the rostral area, posterior end and the ventral margin 

 colored brown. Occasional specimen may have the middle of the disk and 

 the umbone painted with deep, purplish red but with the beaks remaining 

 white; such shells resemble C. amethystina but will be separated easily by 

 their longer Leda-Vike form. This Corbula occurs as fossil in the Pliocene of 

 Ecuador. 



Range — Gulf of California to northern Peru. Panama: several places, 

 Bucaro. Panama Canal Zone: Venado Beach. Ecuador: Mompiche; Manta; 

 Santa Elena; Ancon. Peru: Zorritos; Tumbez; Mancora, 



Carjocorbnla (Caryocorbula) amethystina, new species Plate 75, figures 1-lc 



The shell is large or of medium size, solid, obliquely elongate-ovate, 

 with nearly median beaks and low, flattened, inconspicuous umbones. The 

 anterior side is somewhat impressed in front of the beaks but shows no true 

 lunule, its end widely rounded and passing evenly into the curve of the 

 ventral margin so that the contour of the shell as a whole is strongly oblique. 

 The posterior side is strongly contracted and narrowed, its upper and lower 

 margins approaching to form a bluntly pointed end. Valves are nearly 

 equal in size, the right is a trifle larger and more convex so that its posterior- 

 ventral margin overlaps or clasps that of the left slightly. Rostral area is 

 narrow, flattened, and defined by an angle. Surface covered with coarse, 

 wrinkled, concentrics, and much finer, growth incrementals. Color white, 

 more or less deeply suffused with violet or rose-purple, heaviest on the 

 umbones. Interior white, often bordered by pink or brown. The substance 

 of the shell is usually solid, the visceral cavity deep, the adductor scars 

 distinct. 



Length 27.4 mm., height 18.2 mm., diameter 14 mm. Tortutilla, Panama, 

 Coll. H. B. Johnson. Holotype, ANSP 218902. 



This is a large, solid shell, often confused with C. ovulata but from 

 which it differs by its more rectangular form, pink, violet or rose-purple 

 color, and by its shorter posterior side, the end of which is not twisted. 



Range — Panama south to Ecuador. Panama: Pearl Islands at numerous 

 places; Puerto Mensabi; San Carlos; El Lagartillo. Panama Canal Zone: 

 Yenado Beach; Taboquilla. Ecuador: Puerto Callo; Santa Elena. 



Caryocorbula (Caryocorbula) nasuta (Sowerby) Plate 75, figures 3-3e 



Corbula nasuta Sowerby, 1833, Proc. Zool. Soc. London, p. 35. — Reeve, 18+3, Conch. 



Icon., vol. 2, Corbula, pi. 1, fig. 1. — Maxwell Smith, 1944, Panamic Marine 



Shells, p. 68, fig. 868. 

 Corbula pustulosa Carpenter, 1855, Cat. Mazatlan Shells, Brit. Mus., p. 22. 

 Corbula fragilis Hinds, 1843, Proc. Zool. Soc. London, p. 56.— Hinds. 1844, Zool. Voy. 



Sulphur, Moll., pt. 3, pi. 68, pi. 20, fig. 11.— Reeve, 1843, Conch. Icon., vol. 2, 



Corbula, pi. 3, fig. 19. 



