9 
valve; with an oblong, marginal, adjoining pit, divided in two by a contraction. 
Ligament internal, inserted in the pits. 
Plate IV. Fig. 7. («) U. transversa. Natural size. [Brit. Mus.] 
( b ) Magnified view of the Hinge. 
Solenimya. — Shell inequilateral, equivalve, transversely oblong, the extremities obtuse; 
the epidermis shining, and extending beyond the margin. Beaks not prominent, 
scarcely distinct. One cardinal tooth in each valve, dilated, compressed, and ve- 
ry oblique ; rather concave above, to receive the ligament, which is partly internal, 
and partly external. 
Plate IV. Fig. 8. (a) S. Mediterranea. [Mrs. Mawe’s Cabinet.] 
( b ) Inside of ditto. 
Amphidesma. — Shell transverse, inequilateral, subovate or rounded, sometimes gaping a 
little at the sides : hinge having one or two teeth, and a narrow pit for the internal 
ligament. Ligament double; one external, short; the other internal, fixed in the 
cardinal pits. 
Plate IV. Fig. 9. (a) A. reticulatum. (Sowerby’s Genera.) (Tellina reticulata. — Linn.) 
( b ) Inside of ditto. 
CORBULEA — 2 Genera. 
Shell inequivalve. Ligament interior. 
Corbula. — Shell regular, inequivalve, inequilateral, closed, or very slightly gaping. One 
large conical, curved, ascending tooth in each valve, with a pit beside it : no late- 
ral teeth. Ligament internal, inserted in the pits. 
Plate V. Fig. 1. (a) C. porcina. 
(6) Hinge of ditto. 
Pandora. — Shell regular, inequivalve, inequilateral, transversely oblong; upper valve 
flat, and the lower convex. Two oblong, diverging, unequal, cardinal teeth in the 
upper valve; two oblong pits in the other. Ligament internal. 
Plate V. Fig. 2. (a) P. rostrata. .(Tellina inequivalvis. — Linn.) 
( h ) Inside of ditto. 
LITHOPHAGA. 3 Genera. 
Boring Shells, without accessory pieces or sheath, and more or less gaping at their anterior side. 
Ligament of the valves external. 
Saxicava. — Shell bivalve, transverse, inequilateral; gaping anteriorly at the superior 
margin: hinge almost without teeth. Ligament external. 
Plate V. Fig. 3. (a) S. rugosa. (Mytilus rugosa. — Linn.) 
(J) Inside of ditto. 
Petricola.— Shell bivalve, subtriangular, transverse, inequilateral ; the posterior side 
rounded, the anterior attenuated ; slightly gaping. Hinge having two teeth in 
each valve, or in one only. 
Plate V. Fig. 4. (a) P. plioladiformis, 
( h ) Hinge of ditto. 
C 
