CETACEA; Gr. xvrn, &XCpcvos, Aristotle; Eng. Whale tribe, Cetaceans ; Fr. Cetacgs ; Germ. Waltfische.
[An order of mammiferous animals, distin guished, as regards outward characters, by the absence of hinder extremities, neck, hair, and external ears; and by the presence of a. large horizontal caudal fin, and the fin-like form of the anterior extremities, the bones of which are shortened, flattened, and enveloped in a thick unyielding smooth integument. With this con figuration the Cetaceans are fitted only for aquatic life, and reside habitually in the waters of the sea or of large rivers : their resemblance to the true Fishes is so close that many natu ralists, since the revival of literature, and the vulgarin all ages, have regarded them as mem bers of the same class. Aristotle, from his anatomical knowledge, was aware of the essen tial differences between the Whales and Fishes, but it is not absolutely necessary to seek for internal characters to establish the real distinc tion which subsists between these different de nizens of the deep; the horizontal position of the tail-fin at once distinguishes the cetacean from the fish, in which that fin is vertical. This difference relates to the different., nature of the respiration of the Whale, which is by lungs, and consequently necessitates a frequent rising to the surface of the water to breathe the air, and a corresponding modification of the chief organ of locoinotion.
With the lungs are also associated the pre sence of warm blood, a double circulation, an epiglottis, and a diaphragm, a true viviparous creneration, a nourishment of the young by a mammary secretion, and in short all the essen tial parts of a mammiferous organization.
The order is subdivided as follows : Tribe I. PHYTOPHAGA.
Char. Teeth of different kinds ; molars with flattened crowns, corresponding to the vegetable nature of their food. Mammx, two, pectoral. Lips provided with stiff bristles. External nostrils, always two, situated at the extremity or upper part of the rostrum, which is ob tuse.
Genus MA N ATUS, Cuv.
Char. Incisors g (two superior, deciduous in the fcetus, not replaced). Molars g grinding surface with tri-tuberculate transverse ridges. Body with a few scattered bristles. Anterior extremities each provided with four nails. Tail:fin oval.
Species 1. Manatus .Americanus, Cuv.
Richcchus Manatus, Linn. : the Ma natee. Lamantin d'Amerique, Cuv. 2. Manatus .Africanus, Lamantin du Senegal, Cuv.
Genus HALicoitE, Cuv.
Char. incisors S. (In the young animal the two superior permanent incisors are preceded by two deciduous ones ; six or eight deciduous incisors in the lower jaw which have no permanent succes sors). Molars n; (in the young ani mal g ; the grinding surface exhibits a rim of enamel at the circumference and a slightly excavated centre of ivory. Body, with a few scattered bristles. Upper lip with bristly mustaches. An terior extremities without nails. Tail fin very broad, crescentic.
Species 1. Halicore Indicus, Cuv. The Indian Dugong, or, more properly, Duyong.
2. Halicore Tabernaculi, Ruppel. Du gong of the Red Sea.
Genus RYTINA) Illiger. Incisors none. Molars large, lamelliform, of a fibrous structure, with the triturating surface roughened by tortuous furrows. Body, without hairs, but covered by a rough and thick fibrous epidermis. An ieri01' extremities terminated by an un guiform callosity. Caudal-fin crescent shaped, each angle terminated by a horny plate.
Species. Rytina Stelleri, Le Stellere, Cuv. This species inhabits the seas of Kamt schatka. It was discovered by the Russian naturalist, Steller, after whom it is named ; and is described by him with much zoological and anatomical detail in the Nova Comment. Petrop. t. p. 294, (1751,) under the name of the Manati or Vacca marina.
Tribe II. ZOOPHAGA.
Char. Teeth of one kind or wanting, not adapted for mastication. Mammx, two, pudendal. External nostrils, double or single, situated on the top of the head.