CONCHIFEBA. 



321 



inequivalve, inequilateral, 

 attached ; umbones spirally 

 curved to one side; hinge 

 pit curved, nearly linear; 

 an obtuse tooth in the flat 

 free valve, fits into a cavity 

 parallel with the hinge pit 

 in the convex attached 

 valve ; one muscular impression in each valve. 



Exogyra. 



* — Fossil. 



Carolia. Cantraine. — Shell not attached, slightly 

 irregular, almost equilateral, inequivalve; the one valve 

 flat, the other somewhat convex, with a distinct boss ; the 

 hinge in the flat valve with a large irregular tooth, in the 

 convex valve there are two diverging supports; the ligament 

 is short and strong, placed inwardly and under the bosses ; 

 only one deep central muscular impression. Animal not 

 known. 



Pododesmus. Philippi. — Shell attached, inequivalve, 

 irregular, with unequal bosses, that of the under attached 

 valve is spirally formed ; the hinge is toothless ; the liga- 

 ment is entirely internal, and situated on a projecting 

 plate ; one single oval muscular impression. Animal un- 

 known. — 1 species. 



P. decipiens from Cuba is the only living species. 



Placuna. Solander. (Placenta, Retz.) — Shell nearly 

 equivalve, irregular, very much 

 compressed, iridescent ; two 

 internal cardinal teeth in one 

 valve, shaped like a V, and in 

 the other valve impressions to 

 receive them ; shell thin, and 



Placuna placentia. 



Sowerby's Conch. Manual, 

 y 



