22 GENERA OF SHELLS. 



band, and from tellina, by wanting the irregular fold 

 on the anterior margin. 



C. fimbriata — (Fossil) lamellosa, petunculus. 



LuciNA. Shell suborbicular, inequilateral, 

 beaks small, pointed oblique. Hinge variable ; 

 two cardinal teeth, of which one is bifid, dis- 

 appearing by age ; two lateral teeth, the pos- 

 terior nearest the cardinal ; two muscular im- 

 pressions distant, the posterior produced into 

 a long band ; ligament exterior. 



L. Jamaicensis, Pennsylvanica, edentula, mutabilis, radula, 

 concentrica, divaricata, carnaria, scabra, reticulata, squamosa, 

 lactea, undata, circinaria, columbeila, sinuata, pecten, lutea, 

 digitalis, globularis. 



DoNAx. Shell transverse, equivalve, inequi- 

 lateral, anterior side very short, very obtuse ; 

 two cardinal teeth, either on one or both 

 valves ; one or two lateral teeth, more or less 

 remote ; ligament exterior, short, in the place 

 of the lunule. 



This genus is characterised by its rather flattened 

 and almost triangular shell, and by having one or two 

 rather distant lateral teeth, separated from the cardinal 

 teeth, and analogous to the lateral teeth of lucina, 

 corbis, cyclas, mactra and tellina. They are marine 

 shore shells, smooth or finely striated, and often deco- 

 rated with lively colors. 



(a.) Internal margin entire, or nearly so. 



D. scortum, pubescens, cuneata, compressa, radians, abbre- 

 viata, granosa, columbella,veneriformis, australis, epidermia 

 bicolor, vittata, triquetra. 



