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A plane for shaving or dressing the concave or inside faces of barrel staves.

A concave metallic mirror attached to the object-glass end of a microscope, to throw down light on opaque objects; a reflector.

crystal which is more than ordinarily flattened in the center; also, a species of convexoconcave lens for spectacles.

A lens convex on one side and concave on the other.

are normally converged so as to produce a distinct image. It is corrected by the use of a concave lens.

ence the popular name. Called also dancing girls. -- Opera glass, a short telescope with concave eye lenses of low power, usually made double, that is, with a tube and set of glasses for each eye; a lorgnette; -- so called because adapted for use at the opera, theater, etc. -- Opera hat, a gentleman's folding hat. -…

or of the eye, particularly the retina. Light is thrown into the eye by a mirror (usually concave) and the interior is then examined with or without the aid of a lens. -- Oph*thal`mo*scop"ic, a.

Concave behind; -- applied especially to vertebræ in which the anterior end of the centrum is convex and the posterior concave.

The inner and somewhat concave part of the hand between the bases of the fingers and the wrist. Clench'd her fingers till they bit the palm. Tennyson.

r on all sides. Periscopic spectacles (Opt.), spectacles having concavo-convex or convexo-concave lenses with a considerable curvature corresponding to that of the eye, to increase the distinctness of objects viewed obliquely.

Combining forms signifying flat, level, plane; as planifolious, planimetry, plano-concave.

Flat at the anterior and concave at the posterior end; -- said of the centra of the vertebræ of some extinct dinouaurs.

rocodilia, including the true crocodiles and alligators, in which the dorsal vertebræ are concave in front.

Concave in front; as, procoelian vertebræ, which have the anterior end of the centra concave and the posterior convex.

An order of reptiles having biconcave vertebræ, immovable quadrate bones, and many other peculiar osteological characters. Hatteria is the only living genus, but numerous fossil genera are known, some of which are among the earliest of reptiles. See Hatteria. Called also Rhynchocephalia.

Having a back like that of roach; -- said of a horse whose back a convex instead of a concave curve.

Having the outline of the upper part concave like the seat of a saddle.

Anything saddle-backed; esp., a hill or ridge having a concave outline at the top.

A concave molding used especially in classical architecture.

is not tightly fastened upon the handle, but may be reversed. Knight. (b) A hammer with a concave face which forms a die for shaping anything, as the end of a bolt, rivet, etc. -- Set line, a line to which a number of baited hooks are attached, and which, supported by floats and properly secured, may be left unguarded…