CONCHIFERA. 



277 



and on the coasts of Guinea and New Holland. They 

 bore into soft stones. 



Opis. Defrance. — Like Trigonia, but having the bosses 

 subspiral, with a large striated tooth on the hinge. — 

 Many fossil species. 



Myoconcha. Soiv. — Shell oval, inequilateral, equi- 

 valve, oblique, umbones terminal ; ventral margin rounded ; 

 hinge with an external ligament, and one oblique, elongated 

 tooth in the left valve ; impression of the mantle not 

 sinuated. * — Fossil. 



Family 1 5. — S OLE NO MY A CEA. 



The* animal has the mantle entire, with a third of the 

 front cloven ; behind a small circular opening beset with 

 cirrhi for the gills and other ducts ; somewhat beyond are 

 a couple of cirrhi, which Deshayes erroneously took to be a 

 second opening ; the foot is cylindrical, when it protrudes 

 it is truncated, disk-shaped, and there beset with papilli, 

 when it is withdrawn the disk folds together; on each 

 side is a single gill, formed like a feather of uprightly- 

 placed, divided lamilla ; the mouth is very small, with- 

 out lip-feelers, instead, are found on each side of the 

 base of the foot, two small sickle-shaped appendages. 

 The shell is equivalve, linear, or cylindrical, inequi- 

 lateral, rounded at each end, and gaping ; with a thick 

 brown glistening epidermis covering the shell in rayed 

 stripes, and projecting beyond the edge ; the bosses 

 scarcely distinct, the hinge without teeth, an oblique rib 

 bearing the inner ligament ; two muscular, but no pallial 

 impression. — Marine. 



* Sowerby's Conch. Manual. 



x 3 



