44 CONCHOLOGY. 



in the left ; ligament internal, oblique, triangular, inserted in a 

 somewhat deep pit, with edges a little projecting on each valve ; 

 two round muscular impressions. Inhabits the Mediterranean and 

 British seas. Two Uving species, and two fossils, according to 

 Defrance. 



Pandora rostrata. Pandora obtusa. 



FAMILY VII. 

 LiTHopHAGi. Three genera. 



1. Genus Saxicava. 



Animal. Long, subcylindrical, the mantle closed in all parts, 

 prolonged behind by two long tubes, thick and close together 

 externally, pierced interiorly and in front with a round orifice, for 

 the passage of a very small foot ; mouth very large ; labial appen- 

 dages small ; branchial laminse fre"e, the external pair much shorter 

 than the internal. 



Shell. Thick, with an epidermis, a little irregular, elongated, 

 subcylindrical, obtuse at both ends ; summits feebly marked ; 

 hinge toothless, or with a very small rudimentary tooth ; ligament 

 external, somewhat inflated; two round muscular impressions, 

 distinct, and several others, irregular. Inhabits the British seas, 

 and cavities which they bore in rocks or wood. Five species. 

 Saxicava Rugosa. Saxicava pholadis. 



S. gallicana. S. australis. 



S. veneriformis. 



2. Genus Petricola. 

 Animal. Unknown. 



Shell. Subtrigonal, more or less irregular, transverse, inequi- 

 lateral ; upper side narrowed and a little gaping ; lower side 

 rounded ; hinge with two teeth in each valve, or in one valve 

 only. Inhabits the Australian seas, boring into wood and rocks. 

 Thirteen species. 



Petricola lamellosa. Petricola rocellaria. 



P. Ochrolenca. P. exilis. 



P. Semilamellata. P. ruperella. 



