262 AXEL A. OLSSON 



Colombia: Isla del Gallo; Gorgona Island. Ecuador: Esmeraldas; Manta; 

 Santa Elena. Peru: Tumbez; Zorritos; Sechura. 



Dosinia (Dosinidia) annae Carpenter Plate 42, figures 2-2b 



Dosinia annae Carpenter, 1855, Cat. Mazatlan Shells, Brit. Mus., p. 61. — Romer, 1862, 

 Mon. Molluskengattung Dosinia Scopoli, p. 18, taf. 4, fig. 1. 



The shell is generally a little larger than D. dunkeri, higher, less 

 circular, the posterior side subtruncated and with weaker sculpture; the 

 concentrics are best developed on the sides and smoother over the middle. 

 Pallial sinus is smaller, not extending to the middle of the shell cavity. 



Length 51.5 mm., height 50.5 mm., diameter 25.8 mm. Cojimenes, 

 Ecuador. 



A much rarer species than D. dunkeri but easily distinguished by the 

 characters mentioned above. 



Range — Mexico southward to Ecuador. Panama: Bucaro. Ecuador: 

 Mompiche; Cojimenes. 



Genus CYCLDfELLA Ball, 1902 

 Type species by original designation, Artemis tenuis Recluiz. Recent, 

 West Indies. 



Shell dosinoid, discoidal to suborbicular, depressed or convex, moder- 

 ately thin, white, often chalky. Hinge as in Dosinia with three cardinal 

 teeth in each valve, the right posterior tooth large and bifid, no laterals. 

 Resilial scar as in Dosinia. Posterior adductor scar large, placed a distance 

 below the end of the hinge line. Pallial sinus large, deep, pointed at the 

 end. Sculpture formed by fine, crowded threadlike concentrics. Lunule 

 large and defined by a weak line only, its surface not depressed. Valve 

 margin smooth. 



Cyclinella differs from Dosinia by its hinge which lacks the small, 

 pimple-like anterior lateral tooth of the right valve; also by the texture of 

 the shell which is usually thinner and by its surface markings formed by 

 close, concentric growth threads which are irregular and do not form the 

 flat, ribbon-like bands so commonly seen on Dosinia. The posterior adductor 

 scar is placed low and separated from the end of the hinge plate by a wide 

 space. 



Key to Panamic-Pacific Cyclinella 



I. Shell quite large (60 to 100 mm. in length). 



A. Shell with subrhomboidal to subquadrate form, the posterior side ex- 

 panded. Greatest inflation of the valves lies obhquely along the um- 

 bonal slope. 



1. Shell often large. Posterior side with its ventral margin directed 

 inward. Ecuador and Peru. 



C. subquadrata 



2. Shell smaller. Posterior-dorsal margin shorter, the whole posterior mar- 

 gin more evenly rounded. Panama northward. 



C. saccata 



B. Shell with more circular outline. Inflation of the valves more centrally 

 located. 



