Furrow, a small trench or hollow. Fuscated, darkened, obscured. Fusiform, spindle-shaped, intermediate between the conical and oval. G. Gap, an opening in bivalves when the valves are shut as in the _Pholades_, _Myæ_, &c. Geminated, marked with a double elevated striæ connecting the wreaths. Geniculate, keeled. Genus, an assemblage of species possessing certain characters in common, by which they are distinguished from all others. Genera, the plural of genus. Gibbous, bulged or bulging. Glabrous, smooth, having a smooth surface. Globose, globular. Granulated, beaded, in small grains or beads. Groove, a hollow channel. H. Hemispherical, in the shape of a half globe. Hirsute, rough, beset with strong hairs. Heteroclitical, synonymous with heterostrophe. Heterostrophe, reversed, applied to shells whose spires turn in a contrary direction to the usual way. Hispid, hairy. I & J. Jagged, denticulated, uneven, toothed like a saw. Imbricate, placed like the tiles of a house. Imperforated, not pierced with a hole, wanting an umbilicus. Inequilateral, when the anterior and posterior sides make different angles with the hinge. Inequivalve, where one valve is more convex than the other, or dissimilar in other respects, as in the common oyster. Inarticulate, indistinct, not properly formed. Incumbent, one lying over the other. Incurved, } bent inward, crooked. Incurvated, } Indented, unequally marked, hollowed. Inflated, tumid, swollen, as if blown out. Inflected, bent inward. Indexed, bent towards each other. Intercostal, placed between the ribs. Internode, the space between one knot or joint and another. Interrupted, divided, separated. Interstice, space between one part and another, a crevice. Intortion, the turning or twisting in any particular direction. Involucre, a covering. Involution, that part which involves or inwraps another. Involute, where the exterior lip is turned inward at the margin, as in the Cypræa. Isabella-colour, a brownish yellow with a shade of brownish red. Juncture, the joining of the whorl in univalve shells. K. Keel, the longitudinal prominence in the Argonauta. Knob, a protuberance, any part bluntly arising above the rest. L. Labra, the lips. Laciniate, jagged or cut into irregular segments. Lacunose, having the surface covered with pits. Lamellar, consisting of films on plates. Lamellated, divided into distinct plaits or foliations. Laminæ, thin plates, laid one coat above another. Lanceolate, oblong, and gradually tapering like the head of a lance. Lateral, extending to one side from the centre.