208 NEW-YORK FAUNA MOLLUSCA. 



FAMILY CHAMWM. 



Animal with the mantle opened beneath, merely for the passage of the foot ; the edges adherent and minutely 

 fringed, united behind by a transverse band, pierced by two orifices, one for breathing and the other for 

 the excretions. Marine or fresh water. Shell often attached: lateral teeth on the posterior side only ; 

 cardinal teeth variable. 



Genus Chama, Linn. Shell irregular, attached hy the lower valve ; a single lengthened tooth in one 



valve, and a corresponding groove in the other. 

 C. arcinella. (Lam. Vol. 3, p. 683.) Shell suhcordate, with the ribs armed with very long spines; 



the spaces between punctated : posterior area large, heart-shaped and verrucose; margin crenulated. 



Color, white, occasionally tinged with rose-red; within, yellowish. Length, 1-5; width, 1*8. 



Florida. 



SECTION 3. CONCHIFERA. 



Animal with the mantle closed: one opening beneath and in front, for the passage of the 



foot, and in the rear exhibiting two extensible, more or less elongated tubes, united or 



distinct ; one beneath for respiration, and the other above for the excrementitious 



dejections. Shell subcordiform, equivalve, with radiated sides : hinge of four teeth in 



each valve ; ligament very short. 



FAMILY TELLmiDM. 



Not more than two cardinal teeth on the same valve. Nymphce in general externally promi- 

 nent, and covered by a ligament. 



GENUS TELLINA. Lamarck. 



Mantle bordered with tentacular appendages. Gills unequal on each side. Foot much 

 compressed, trenchant, and pointed in front. Tubes much elongated, distinct, and entering 

 into a fold of the mantle. Shell transverse, subequivalve, compressed, angular and 

 somewhat rostrated at the posterior end, where there is an irregular wave-like fold : two 

 small cardinal teeth, and generally two lateral teeth in each valve. 



