PANAMIC-PACIFIC PELECYPODA 371 



under rocks, hence variable in shape and often much distorted. Sculpture 

 is produced principally by concentric growth lines, often lamellose, their 

 interspaces flat and wide, and finely striated with submicroscopic radial 

 lines. Ligament with both external and internal elements, the resilium at- 

 tached to a large, prominent, cup-shaped chondrophore developed equally 

 in both valves. Hinge plate wide and stout, bearing the median chondro- 

 phore and bordered by strong, lateral teeth developed principally in the 

 right valve. The cardinal teeth are small and weak (there is a small lamellar 

 tooth (or its socket) on the anterior side of the chondrophore). There is 

 a small, smooth lunule and an escutcheon (largest in the left valve). Pallial 

 sinus large, confluent with the pallial line below. 



Some species of Cumingia are nestlers and live in confined or crowded 

 quarters, hence, their shells are commonly distorted and irregular in shape; 

 other species with more normal shells, lived in open situations as buried 

 in mud or attached by their byssus to worm tubes and the like. Three 

 species of the genus are noted in this work, but the status of some named 

 forms is not well understood. 



Key to Panamic-Pacific species of Cumingia 



I. Valves coarse, generally distorted and with strong, concentric surface 

 sculpture. 



C. lamellosa 



II. Valves thinner, normal in shape. Surface lamellae rather fine, their in- 

 terspaces with minute, radial striae. 



a. Shell large (20 mm., or more), depressed, or convex. Peruvian. 



C. mutica 



b. Valves smaller and generally convex. Panamic. 



C. adamsi 



Cumingia lamellosa Sowerby Plate 66, fgures 10, 10a ; 



Plate 67, fgures 3, 3a 



Cumingia lamellosa Sowerby, 1833, Proc. Zool. Soc. London, p. 34. Found at Payta 

 in hard clay at low water; and at Panama in deep water. — Sowerby, 1873, 

 Conch. Icon., vol. 19, Cumingia, pi. 1, fig. 5. — Hertlein and Strong, 1949, 

 Zoologica, vol. 34, pt. 4, No. 19, pp. 250, 251. 



Cumingia coarctata Sowerby, 1833, Proc. Zool. Soc. London, p. 34. Hab. ad Sinura 

 Caraccensem. 



Cumingia trigonularis Sowerby, 1833, Proc. Zool. Soc. London, p. 35. Hab. ad Sanctam 

 Elenam. — Sowerby, 1873, Conch. Icon., vol. 19, Cumingia, pi. 1, fig. 4. 



Shell white, moderately coarse and heavy, oblong but often distorted, 

 length to about 22 mm., but generally smaller. The umbones and beaks are 

 nearly median, the anterior side rounded and expanded; on the posterior 

 side, the dorsal margin descends forming an obliquely angled or obtuse 

 end at the ventral corner. Sculpture is produced by raised, concentric 

 lamellae or lines which when well formed are regular and widely spaced. 

 Hinge coarse, the lateral teeth prominent. 



Similar to C. calif ornica Conrad (Plate 40, figs. 3, 3a) but has a smaller 

 and thinner shell. C. lamellosa is found living buried in sand, clay or along 

 fissures in rock; hence the shape of the shell may be irregular and the 

 strength of the concentric lamellae variable. 



Range — Gulf of California to northern Peru. For some northern records 

 see Hertlein and Strong. Panama: Panama City; Pedro Gonzales Is. (Pearl 



