9 
valve; with an oblong, marginal, adjoining pit, divided in two by a contraction. 
Ligament internal, inserted in the pits. 
Plate IV. Fig. 7. (a) U. transversa. Natural size. [Brit. Mus.] 
(b) Magnified view of the Hinge. 
Sorenrmya.—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. 
AmPHIDEsSMA.—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. 
Corsuta.—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. poreina. 
(6) Hinge of ditto. 
Panpora.—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.) 
(6) 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.) 
(6) Inside of ditto. 
Perricota.—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. pholadiformis, 
(b) Hinge of ditto, 
