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, trilineata.* P. punctata.* 
FAMILY VII. 
LiruorHaca. Three genera. 
1. Genus Saxicava. Pl. VI. 
Animal. T.ong, 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 lamine 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. 
Sheil. 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 
