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with Amphioxus in which the backbone is represented by a simple undivided notochord. The Vertebrata always have a dorsal, or neural, cavity above the notochord or backbone, and a ventral, or visceral, cavity below it. The subdivisions or classes of Vertebrata are Mammalia, Aves, Reptilia, Amphibia, Pisces, Marsipobran…

A comprehensive division of the animal kingdom, including all except the Vertebrata.

The lowest group of Vertebrata, including the amphioxus, in which no skull exists.

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

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.

The class of Vertebrata that includes the birds.

A comprehensive division of animals including all Vertebrata together with the Tunicata, or all those having a dorsal nervous cord.

A comprehensive group of Invertebrata, mostly marine, comprising the Anthozoa, Hydrozoa, and Ctenophora. The name implies that the stomach and body cavities are one. The group is sometimes enlarged so as to include the sponges.

A comprehensive division of the Vertebrata, including all those that have a skull.

A grand division of the Vertebrata, including the Amphibia and Fishes.

Destitute of a backbone; having no vertebræ; of or pertaining to the Invertebrata. -- n.

The lowest class of Vertebrata, including only the Amphioxus. The heart is represented only by a simple pulsating vessel. The blood is colorless; the brain, renal organs, and limbs are wanting, and the backbone is represented only by a simple, unsegmented notochord. See Amphioxus. [Written also Leptocardii.]…

An extensive group of Invertebrata, including the Mollusca, Brachiopoda, and Bryozoa. Called also Malacozoaria.

The highest class of Vertebrata. The young are nourished for a time by milk, or an analogous fluid, secreted by the mammary glands of the mother.

A class of Vertebrata, lower than fishes, characterized by their purselike gill cavities, cartilaginous skeletons, absence of limbs, and a suckerlike mouth destitute of jaws. It includes the lampreys and hagfishes. See Cyclostoma, and Lamprey. Called also Marsipobranchiata, and Marsipobranchii.

A division of Invertebrata which includes the classes Brachiopoda and Bryozoa; -- called also Anthoid Mollusca.

Same as Vertebrata.

The Vertebrata.

Same as Vertebrata.