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

A division of serpents which have some of the posterior maxillary teeth grooved for fangs.

Having the pulmonary sac situated posteriorly; -- said of certain air-breathing Mollusca.

The inferior and posterior of the three elements forming the periotic bone.

. (Opt.) (a) A line drawn through the center of the eye perpendicular to its anterior and posterior surfaces. In a normal eye it is in the direction of the optic axis that objects are most distinctly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial cry…

The posterior nares. See Nares.

by the mantle. -- Pallial sinus (Zoöl.), an inward bending of the pallial line, near the posterior end of certain bivalve shells, to receive the siphon. See Illust. of Bivalve.

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

. The species are very numerous, especially in tropical seas. The outer lip has usually a posterior notch or slit.

Situated behind, or posterior to, the anus.

Situated behind any transverse axis in the body of an animal; caudal; posterior; especially, behind, or on the caudal or posterior (that is, ulnar or fibular) side of, the axis of a vertebrate limb.

A transverse commisure in the posterior part of the roof of the third ventricle of the brain; the posterior cerebral commisure. B. G. Wilder.

The posterior horn of each lateral ventricle of the brain. B. G. Wilder.

- (posterior, back; as, postero-inferior, situated back and below; postero-lateral, situated back and at the side.

Posterior.

The posterior nares. See Nares.

The posterior part of the medulla oblongata. B. G. Wilder.

Situated behind, or posterior to, the mouth.

Of or pertaining to the posterior part of the sphenoid bone.

A posterior zygapophysis.