22 



AMERICAN CORBTCULADJG. 



mid, inclined anteriorly, approximate at apex, soraewiliat eroded ; strire 



heavy, very regular ; epidermis light 



Fig. 17. 



brown ; valves thick, interior variable, 

 pale salmon or dark violet ; hinge-mar- 

 gin curved, moderately broad ; cardi- 

 nal teeth unequal, divergent, simple ; 

 lateral teeth elongated, subequal, pos- 

 terior tooth a little more elongated 

 and depressed and slightly more dis- 

 tant from the cardinal teeth; sinus nar- 

 row, curved and acute at extremity. 



Long. 1.64; Lat. 1.44; Diam. 

 0.88 inches. 



Long. 41 ; Lat. 3G : Diam. 22 mill. 



C. acuta. 



Huh. Central America, 

 of Prime.) 



(Cabinet 



Cyrena acuta, Prime, II. Conch. IX, 1861, 355— X, 1862, 387, pi. xiv, f. 1. 



A rare and fine species, easily distinguished from others bj the 

 great prolongation of the posterior side. 



Fig. 18. 



18. Cyrena mexicana, Sowerby. — Shell small, rounded oval or 

 elliptical, subequilateral ; anterior side a lit- 

 tle the shorter, broader, rounded, posterior 

 side narrower, subaugular at end ; beaks me- 

 dium size, somewhat raised, inclined towards 

 the anterior, generally eroded ; valves mode- 

 rately convex, interior white, with at times 

 purple markings on the margins and on the 

 hinge ; epidermis very variable, rough or 

 smooth, color dingy gray or light yellowish- 

 green ; striae generally light ; hinge thick, 

 three unequal cardinal teeth ; the anterior 

 lateral tooth acute, short, the posterior elon- 

 gated ; sinus long and narrow. 



Long. 1.25 ; Lat. 1.12; Diam. 1.18 inches. 

 " 32 ; " 28 ; " 29 mill. 



Hah. North America, at Mazatlan and Panama. Guyana? (Cabinets 

 of the British Museum, Smithsonian Institution, Cuming, State of New 

 York, and Prime.) 



Cyrena mexicana, Sowb. Zool. II. 1829, 364. — Carp, (pars) Mazatlan 



Shells, 1857, 115. 

 Cyrena fragilis, Deshayes, Mus. Cuming. 

 Cyrena aequUateralis, Dkshayes, Proc. Zool. XXII, 1854, 20. 

 Cyrena varians, Carpenter, in litt. 



mexicana. 



