Cymbiform, boat-shaped. D. Decorticated, worn, divested of epidermis or skin. Decussated, generally applied to striæ or lines which are crossed, or which intersect each other perpendicularly or horizontally. Deflexed, bent aside. Dentary, of or belonging to the teeth. Dentile, a small tooth, such as the tooth of a saw. Denticulated, set with small teeth, as in the Arca. Depressed, pressed down horizontally, low, shallow, flat. Dexter valve, is the right valve. Diaphanous, transparent, clear, pellucid. Digitated, fingered or clawed, as in the lobes of the outer lip of the Strombi, &c. Disk, the middle part of the valves, or that which lies between the umbo and the margin. Divaricated, straddling, spreading out widely. Divergent, tending to various parts or directions from one point. Dorsum, the back; it generally means the upper surface of the body of the shell, when laid upon the aperture or opening. In the genera of Patella and Haliotis, the back means the upper convex surface. Dotted, punctured like a thimble. Duplicated, divided into plaits or folds. Duplicature, a fold, anything doubled. E. Echinated, bristled like a hog, set with spines. Effuse, spread out. Elliptical, having the form of an ellipsis, oval. Elongated, lengthened, drawn out. Emarginate, } with the edge or margin notched. Emarginated, } Ensiform, sabre-shaped. Entire, whole, uninterrupted, not divided. Epidermis, the outer coating or scarfskin of the shell. Equidistant, being at the same distance. Equilateral, having all sides alike. Equivalve, having both valves of equal dimensions. Exolete, worn or faded. Exserted, standing out, protruding. Extraneous, not belonging to a particular thing. F. Falcated, bent or hooked like a scythe. Fasciated, filleted, or covered with bands. Fascicled, clustered together as in a bundle. Fasciculated, consisting of little bundles. Fastigate, flat and even at top. Faux, what can be seen of the cavity of the first chamber of the shell, by looking in at the aperture. Ferruginous, of an iron colour, or rust coloured. Filament, a slender threadlike process. Filiform, thread-shaped, slender, and of equal thickness. Fimbriated, fringed. Fissure, a cleft, a little slit, or narrow chasm. Flexuous, zigzag, with angles gently winding. Flexure, a bending. Fluviatic, of or belonging to a river. Fluviatile, belonging to fresh water. Foliaceous, consisting of laminæ or leaves. Foliated, bent into laminæ or leaves. Fornix, the excavated part under the _umbo_. It likewise signifies the upper, or convex shell in the _Ostrea_. Fragile, brittle, easily broken. Front, in univalves, when the aperture is turned towards the observer. Furcated, forked.