P. rostrata. The beaked Pandora. Pl. [6], fig. 3.
Shell white, regular, elongated, inequivalve, inequilateral; right or upper valve entirely flat, with a plait or fold; much produced towards the beak; hinge anomalous, formed by a transverse cardinal tooth on the right valve, entering into a corresponding cavity on the left; ligament internal, oblique, triangular, inserted in a pit rather deep, with edges a little projecting on each valve; two rounded muscular impressions.
FAMILY VII.
Lithophagi. Three genera.
1. Saxicava. Five species.
This genus is taken from the Mytilus, and, like the Pholas, possesses the faculty of penetrating calcareous rocks, from which it cannot be extracted without breaking the substance in which it is imbedded.
Shell bivalve, thick, covered with epidermis, rather irregular, elongated, sub-cylindrical, obtuse at the two extremities; summits little marked; hinge toothless, or with a very small rudimentary tooth; ligament external, a little inflated.
Saxicava rugosa.
S. Gallicana.
S. pholadis.
S. Australis.