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Concave on both sides; as, biconcave vertebræ.

Having both ends concave; biconcave; -- said of vertebræ.

e of connective tissue. Quain's Anat. Red blood corpuscles (Physiol.), in man, yellowish, biconcave, circular discs varying from 1/3500 to 1/3200 of an inch in diameter and about 1/12400 of an inch thick. They are composed of a colorless stroma filled in with semifluid hæmoglobin and other matters. In most mammals the…

of toothed birds found in the American Cretaceous formation. It is remarkable for having biconcave vertebræ, and sharp, conical teeth set in sockets. Its wings were well developed. It is the type of the order Odontotormæ.

An extinct genus of marine reptiles; -- so named from their short, biconcave vertebræ, resembling those of fishes. Several species, varying in length from ten to thirty feet, are known from the Liassic, Oölitic, and Cretaceous formations.

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.

to Teleosaurus and allied genera. These reptiles are related to the crocodiles, but have biconcave vertebræ.

A group of fossil saurians having biconcave vertebræ and the teeth implanted in sockets.