CONCHIFERA. 



235 



in one valve, shutting between two cardinal and two 

 lateral teeth in the other; liga- 

 ment internal, inserted in a deep 

 pit situated between the cardinal 

 and posterior lateral teeth; the 

 impression of the mantle exhibits 

 a small sinus.* Animal with the 

 mantle divided from one to two 

 thirds of its length ; two short ap- 

 proaching siphons partly united ; 

 foot compressed, oblique, nearly 

 four cornered or hatchet shaped ; 

 gills like those of Galatea, namely 

 the outer one fastened by its centre to the upper edge of 

 the inner one, so that it looks as if there were three gills 

 on each side ; the lip tentacles are large, triangular, 

 elongated, very pointed ; mouth small. — 2 species. 



One species G. cuneatus, from New Orleans, is found in 

 Lake Pontchartrain and is used as food. Phillippi alludes 

 to another, but does not give its specific name. 



Gnathodon cuneatus. 



Family 2. — LITHOPHA GA. 



The mantle of the animal is more or less cloven in front ; 

 the siphons behind more or less grown together ; on each 

 side are two leaf-shaped unequal gills ; the foot bears a 

 byssus and is small. The shell is oval, often somewhat ir- 

 regular, equivalved ; the hinge teeth are variable, lateral 

 teeth none; the ligament external. The animals bore 

 into rocks, balani, roots of sea weed, &c, and are found in 

 all seas. 



* Reeve's Conch. Systematica. 



