CONCHIFEKA OR BIVALVES. 77 



Family 6. — Lithophagidce* 



This family comprises a small number of 

 genera, which, like the Tubicolidce and Pho- 

 ladidce, inhabit rocks, stones, &c, into which 

 they bore : they possess an external ligament, 

 and have no tube or shelly pieces uniting the 

 valves, the characteristic mark of the genera 

 mentioned above. The holes they make are 

 tolerably deep, as they conceal nearly the whole 

 of their shell ; the entrance is usually small. 

 There are three genera. 



32. Saxicava. — Shell transverse, inequi- 

 lateral, thick, and solid, 



gaping, rather variable ^^^^^^^ 

 in form ; teeth and ^^^l^^Jj^ 

 bosses obsolete or in- ^^^===^^^^ 

 distinct. Animal, foot 



small, thin, and pointed. — 6 species recent, 

 and 6 fossil. 



The Saxicava perforates and inhabits rocks, 

 oyster-shells, roots of sea-weed, &c, and is 

 known in the South Seas, Mediterranean, 

 Northern Ocean, &c. It appears greatly to 



* Les Litkophages, Lamarck. 



