46 CONCHOLOGY. 



form of a furrow, in consequence of the union of the edges of the 

 mantle, and its continuation with the tubes, which are united and 

 short ; foot small, thickest in front, and issuing through a tolerably 

 large cleft in the mantle. 



Shell. Regular, white, elongated, much compressed, inequi- 

 valved, inequilateral ; right or upper valve quite flat, with a fold ; 

 summits feebly marked ; hinge anomalous, formed by a transverse 

 cardinal tooth on the right ; valve entering a corresponding cavity 

 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, 

 British, and American seas. Four living species, and two fossils, 

 according to Defrance. 



Pandora rostrata. Pandora obtusa. 



P. irilineata.* P. punctata.* 



FAMILY VII. 

 LiTHOPHAGA. Three genera. 

 1. Genus Saxicava. PI. VI. 



^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 laminae free, the external pair much shorter 

 than the internal. 



Lamarck has thought proper to remove this genus from the 

 Mytilus; it possesses the faculty, like the Pholas, of penetrating 

 rocks and substances, and cannot be extracted but by breaking 

 the substance in which it is imbedded. 



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 and 



