12 AMERICAN CORBICULAD^B. 







made to include several genera which have since been diverted 

 from it Corbicula, Batissa and Velorita. The genus, as now 

 most generally received, embraces only the species of Cyrena with 

 simple lateral teeth. 



Cyrena in a living state are found in all tropical countries. 

 The genus is represented at the present time in North America but 

 by one species ; in Central and in South America the species are 

 numerous and bountifully distributed. I am not aware that, out 

 side of America, any of the so-called Marine Cyrena have been 

 found. A peculiarity of the Cyrena of this continent lies in the 

 fact that the palleal impression is always terminated in a sinus, 

 whereas in those from other parts of the world it is simple. 



proper. 



1. Cyrena caroliniensis, LAMARCK. Shell orbicular-trigonal, 



inequilateral ; margins generally round- 

 Fig. 6. ed ; beaks obtuse, oblique, often eroded ; 

 strise very fine ; epidermis rough, of a 

 grayish olive-green ; valves moderately 

 full, not heavy ; interior white in adult, 

 pale bluish in young, occasionally with 

 markings of light violet on the margins 

 and on the hinge ; hinge-margin nar 

 row ; cardinal teeth small ; lateral teeth 

 short, obtuse ; sinus very narrow, acute 

 at extremity. 



Lon - L44 ; LaL l - l -&amp;gt; Diam - 94 inch - 



38; &quot; 33; &quot; 25 mill. 



Hab. North America, in the States of Alabama and Georgia. (Cabinets 

 of the British Museum, Smithsonian Institution, Cuming, Jay, Prime and 

 others.) 



Cydas carolimensis, Bosc, Fer. Cat. Meth. 1807. 



Cyclas caroliniana, Bosc, III, 37, pi. xxiii, f. 4. 



Cyrena caroliniensis, LAM. An. s. vert. V, 1818, 558. SAY, pi. 52. 



This, our most common species of Cyrena, is not very liable to 

 be confounded with any other ; in exterior it bears some resem 

 blance to C. mexicana, it differs, however, in being larger, 

 more trigonal, the beaks are less prominent and the sinus is nar 

 rower and more acute. The young shell is less elongated trans 

 versely and more quadrangular than the adult. 



