16 



AMERICAN CORBICULAD^. 



Fis. 9. 



the margins ; epidermis dark brownisli-green ; hinge-margin curved ; car- 

 dinal teeth strong, unequal, divergent ; anterior 

 lateral tooth large, broad, conical ; posterior late- 

 ral tooth situated at a greater distance from the 

 cardinal teeth, narrow, small ; interior of the 

 valves white or pale salmon color, with at times 

 markings of violet on the margins ; sinus very 

 narrow, deep, ascending in a direction oblique to 

 the beaks. 



Long. 1.75 ; Lat. l.'>6 ; Diam. 1.43 inches. 

 " 45 ; " 40 ; " 36 mill. ' 



C. i,,.,,j,,,^. Uah. North America, in the State of California. 



(Cabinets of Cuming and Prime.) 



Cyrena insignis, Desh. Proc. Zool. XXII, 1S54, 20. — II. Conch. IX, 

 1861, 39, pi. 2, f. 2. 



This species, wliich is quite rare, the only specimens known 

 being the one in Mr. Cuming's collection and that in mine, does 

 not present many points of similarity with any others. 



Fig. 10. 



8. Cyreiia arctata, Deshates. — Shell trigonal, inflated, heart- 

 shaped, heavy, inequilateral ; anterior side 

 short, somewhat angular ; posterior side sub- 

 truncated ; beaks large, oblique, generally 

 eroded ; stri?e heavy, regular ; epidermis 

 blackish-green ; interior of the valves white 

 or pale rose- color with at times markings of 

 pale violet on the muscular impressions ; 

 sinus short and broad ; hinge-margin strong ; 

 cardinal teeth small, simple ; lateral teeth 

 subequal, prominent. 



Long. .86 ; Lat. .86 ; Diam. .68 inch. 

 35 ; " 35 ; " 28 mill. 



JSah. South America, in Lake Maracaibo. (Cabinets of Cuming, Smith- 

 sonian Institution, Jay, Swift, Bland and Prime.) 



Cyrena arctata, Desh. Proc. Zool. XXII, 1854, 20. 



This species, though found in great abundance in the waters of 

 Lake Maracaibo, has not to my knowledge been collected in other 

 localities. Compared with G. radiala, to which it bears some re- 

 semblance in marginal outline, it difiFers in being somewhat smaller, 

 very much more vcntricose and more solid ; the beaks are larger 



C. arctata. 



