^^8 AXEL A. OLSSON 



Key to species of Caryocorbula 



I. Surface of valve sculptured principally with fine or coarse, growth- 

 like concentrics; with or without radial lineation. 



Subgenus Caryocorbula, s.s. 



A. Shell fairly large (length 22 mm. or more, solid). No radial lineation. 



1. Shell elongately ovate, the posterior end produced and rostrated, 

 generally twisted and snoutlike. Color white, tinged with brown; the 

 umbones sometimes rose-red. 



C. ovulata 



2. Shell higher, ovate-trigonal, the posterior end obliquely truncated and 

 pointed, not twisted. Color usually white tinted with rose-pink or red. 



C. amethystina 



B. Shell smaller (length 16 mm. or less). Sculpture formed by growth line 

 concentrics, usually with fine radial threads or pustules showing on some 

 part of the surface. 



a. Posterior end extended into a twisted or upturned siphonal snout, 

 usually with accessory, shelly plates. 



3. Shell elongated to elliptical, thin, or thick. Average length about 15 mm. 



C. nasuta 



4. Shell smaller, shorter, and more convex, ovate-trigonal in shape. 

 Average length about 12 mm. 



C. nucijormis 



C. Without radial striation or lines of minute pustules, or if present, 

 they are largely confined to the rostral area. 



5. Shell small, flattened, solid, with a marble-like surface mottled faintly 

 with white. 



C. marmorata 



6. Shell small (length 7.5 mm.), with short convex valves and strong 

 concentric sculpture. Microscopic granulation is present on the surface 

 of the rostrum. 



C. porcella 



7. Shell larger (length 13 mm.), with high, median umbones, and strong 

 sculpture. Rostral area plain. 



C. ventricosa 

 II. Surface with strong sculpture consisting of large, deep, wavelike, con- 

 centric riblets. 



Subgenus H exacorbula 



8. Shell large (length about 22 mm.), coarse, solid, elongated ovate in 

 shape, the posterior end pointed. 



C. esmeralda 



Caryocorbula (Caryocorbula) orulata (Sowerby) Plate 75, figures 2-2c 



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



Icon., vol. 2, Corbula, pi. 1, fig. 7.— Hanley, 1843, Cat. R-^c. Bivalve Sh-lls, p. 



47, suppl. pi. 10, fig. 52. — Maxwell Smith, 1944, Panamic Marine Shells, p. 



68, fig. 866. 



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



35, pt. 4, p. 241.— Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist., vol. 



107, art. 2, p. 206. 



Shell large for the genus, solid, elongate-elliptical, generally white, and 

 in life covered with a thin, light brown to rusty colored periostracum. 

 Sculpture of coarse concentrics, similar in both valves. Adult shells become 

 thickened, porcellaneous, the visceral cavity rounded and deeply excavated, 

 surrounded by wide thickened margin. Adductor scars distinct, the pos- 



