22 



AMERICAN CORBICULAD^E. 



mid, inclined anteriorly, approximate at apex, somewhat eroded ; striae 



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. 36 ; Diam. 22 mill. 



C. acida. 



Hob. 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 by the 

 great prolongation of the posterior side. 



18. Cyrena mexicana, SOWERBY. Shell small, rounded oval or 

 elliptical, subequilateral ; anterior side a lit- 

 tie the shorter, broader, rounded, posterior 

 side narrower, subangular 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. 



&quot; 32 ; &quot; 28 ; &quot; 29 mill. 



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

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

 York, and Prime.) 



Cyrena mexicana, Sown. Zool. II. 1829, 364. CARP, (pars) Mazatlan 



Shells, 1857, 115. 



Cyrena fraailis, DESHAYES, Mus. Cuming. 

 Cyrena sequilateralis, DESHAYES, Proc. Zool. XXII, 1854, 20. 

 Cyrena varians, CARPENTER, in litt. 



G. mexicana. 



