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sceral cavity of many fishes. It originates in the same way as the lungs of air-breathing vertebrates, and in the adult may retain a tubular connection with the pharynx or esophagus.

The division of Vertebrata in which the embryo develops an allantois. It includes reptiles, birds, and mammals.

That group of vertebrates which develops in its embryonic life the envelope called the amnion. It comprises the reptiles, the birds, and the mammals.

One of the classes of vertebrates.

lancelet. Its body is pointed at both ends. It is the lowest and most generalized of the vertebrates, having neither brain, skull, vertebræ, nor red blood. It forms the type of the group Acrania, Leptocardia, etc.

The division of Vertebrata in which no allantois is developed. It includes amphibians, fishes, and lower forms.

A division of the Invertebrata, nearly equivalent to the Articulata. It includes the Arthoropoda and Anarthropoda. By some zoölogists it is applied to the former only.

from which strata dip in opposite directions, as from the ridge of a roof. -- Anticlinal vertebra (Anat.), one of the dorsal vertebræ, which in many animals has an upright spine toward which the spines of the neighboring vertebræ are inclined.

nimals or plants or their systems of organs are assumed to have been constructed; as, the vertebrate archetype.

A limb, or locomotive or prehensile organ, of an invertebrate animal.

The first vertebra of the neck, articulating immediately with the skull, thus sustaining the globe of the head, whence the name.

The class of Vertebrata that includes the birds.

The second vertebra of the neck, or vertebra dentata.

olumn of bones in the back which sustains and gives firmness to the frame; the spine; the vertebral or spinal column.

Vertebrate.

imals, as the turtles. (c) The long projecting sucking mouth of some insects, and other invertebrates, as in the Hemiptera. (d) The upper or projecting part of the shell, near the hinge of a bivalve. (e) The prolongation of certain univalve shells containing the canal.

A warm-blooded, feathered vertebrate provided with wings. See Aves.

The hard, calcified tissue of the skeleton of vertebrate animals, consisting very largely of calcic carbonate, calcic phosphate, and gelatine; as, blood and bone.

of consciousness and volition) which is inclosed in the cartilaginous or bony cranium of vertebrate animals. It is simply the anterior termination of the spinal cord, and is developed from three embryonic vesicles, whose cavities are connected with the central canal of the cord; the cavities of the vesicles become the…

the central teeth of bivalve shell. See Bivalve. -- Cardinal veins (Anat.), the veins in vertebrate embryos, which run each side of the vertebral column and returm the blood to the heart. They remain through life in some fishes. -- Cardinal virtues, preëminent virtues; among the ancients, prudence, justice, temperanc…