430 AXEL A. OLSSON 



Aloidis {Caryocorbula) nasuta (Sowerby), Hertlein and Strong, 1950, Zoologica, vol. 

 35, pt. 4, p. 240.— Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist., vol. 

 107, art. 2, pp. 205, 206. 



Shell elongate-elliptical, Nuculana-Vike, the average length about 15 

 mm., subequivalve, the right valve somewhat larger, its posterior-ventral 

 margin overlapping and clasping the left. Valves relatively thin or of 

 moderate weight only. Posterior-dorsal area distinct, of equal size in both 

 valves, generally somewhat excavated, and defined externally by a low 

 angle. Valves similarly sculptured with concentrics fairly regular on the 

 umbones, coarser and crowded on the ventral side, their interspaces usually 

 marked with minute radial threadlets, often producing a fine reticulated 

 pattern. Posterior end bluntly pointed, often produced into a snout by 

 secondary growth. Color white, with periostracum yellow, or rusty brown. 



Length 15 mm., height 9.1 mm., diameter 7.1 mm. Zorritos, Peru. 



C. jragilis appears to be merely a thin-shelled form but has been con- 

 sidered a separate species by some authors. Specimens in good condition 

 show fine radial striae between the concentrics, which according to Hertlein 

 and Strong are formed by lines of minute pustules and it was to such a 

 specimen that Carpenter gave the name C. pustulosa. Such lines of pustules 

 are to be seen on many different species of Corbula. 



Range — Lower California to northern Peru. Panama: Bucaro. Panama 

 Canal Zone: Amador; Venado Beach. Colombia: Isla del Gallo. Ecuador: 

 Manta; Santa Elena. Peru: Tumbez; Zorritos. 



Caryocorbula (Caryocorbula) nuclformis (Sowerby) Plate 75, figures 7-8; 



Plate 76, figure 7 



Corbula nuciformis Sowerby, 1833, Proc. Zool. Soc. London, p. 35 Real Llejos. — Reeve, 



1843, Conch. Icon., vol. 2, Corbula, pi. 2, fig. 9. — Maxwell Smith, 1944, Panamic 



Marine Shells, p. 68, fig. 869. 

 Aloidis (Caryocorbula) nuciformis (Sowerby), Hertlein and Strong, 1950, Zoologica, 



vol. 35, pt. 4, p. 241, pi. 2, fig. 1. 

 Corbula obesa Hinds, 1843, Proc. Zool. Soc. London, p. 57.— Hinds, 1844, Vol. Sulphur, 



Moll., pt. 3, p. 68, pi. 20, fig. 12. — Reeve, 1844, Conch. Icon., vol. 2, Corbula, 



pi. 5, fig. 38. 



Shell generally small (length 12 to 14 mm., or less), elongate, trigonal- 

 ovate, both valves strongly convex and solid, the right valve somewhat 

 larger and clasping the left valve along the posterior-ventral margin. The 

 umbones are wide, with the beaks close, touching, the anterior side de- 

 pressed below the beaki and prolonged a little into a well-rounded end, 

 the posterior side generally a little shorter, contracted, with a wide rostrum 

 in each valve, flattened or depressed, setoff by an angle along the side of 

 ithe umbone and often terminating in a long, narrow, upturned snout, that 

 of the left valve formed of shelly, accessory growth. Sculpture over the 

 disk is formed by medium to coarse, concentric riblets, usually overrun 

 (by lines of fine, pustulated, radial riblets, pronounced on the umbones and 

 disk, absent nearer the ventral margin; near the ventral margin the shell 

 is often sharply inflected, forming a flattened surface sculptured with 

 large and coarse concentrics. Color white except along the ventral side and 

 the posterior snout which is brown. 



Length 11.3 mm., height 5.6 mm., diameter 6.3 mm. Zorritos, Peru. 



Often found with C. nasuta and at times may appear to grade into it 

 but typically smaller, of more solid build, the ventral side is more strongly 



