310 POPULAR CONCHOLOGY. 



to mangrove trees. Considerable clusters are frequently 

 found attached firmly to each other by the byssus. 



Gervillia. Def ranee. — Shell inequi valve, inequi- 

 lateral, oblong, oblique, much elongated ; hinge long, 



Gervillia. 



straight, having small, irregular, transverse, ligamentary 

 pits.* — Fossil. 



In general form resembling Avicula. 



Catillus. Brongn. (Inoceramus 

 Sow.) — Shell thick, inequivalve, 

 subequilateral, triangular, deep, with 

 the umbones incurved ; hinge formed 

 of a series of transverse grooves.* 

 — Fossil. 



Inoceramus. Parkinson. — Shell 

 free, more or less inequilateral, ir- 

 regular ; hinge a marginal, sub- 

 cylindrical, transversely sulcated cal- 

 lus, supporting a ligament; beaks conspicuous, at one 

 end of the hinge.f — Fossil. 



Sowerby depicts several species in his " Mineral Con- 

 chology," some of very large size, which are common in 

 chalk. Dr. Mantell says, these shells vary in size from 

 an inch to three or four feet in diameter. The specimens 



* Sowerby 's Conch. Manual. f Sowerby's Mineral Concb. 



