Title: Text book of zoology
Identifier: cu31924000397905 (find matches)
Year: 1896 (1890s)
Authors: Boas, J. E. V. (Johan Erik Vesti), 1855-1935; Boas, J. E. V. (Johan Erik Vesti), 1855-1935. Lehrbuch der Zoologie
Subjects: Zoology
Publisher: London, Sampson Low, Marston
Contributing Library: Cornell University Library
Digitizing Sponsor: MSN

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Glass 2. Pisces. 371 pterygoid, the branchial bars (especially tlie superior and inferior pharyngeal bones), the basibranchials of the visceral skeleton, and the vomer; they may, however, be wanting from one or other of these bones. The teeth are of somewhat diverse form: most often pointed, conical, slightly curved, and more or less powerful; in other cases they are low, rounded, grinding teeth (Rajidse, certain Teleostei); or compressed and triangular (Squalidse); or chisel-shaped, resem- bling the incisors of Man (teeth on the premaxilla and mandible of certain Teleosteans). Very often they are extremely numerous, covering the bones like a mosaic; on the jaw there is frequently only a single row of teeth, or a row of larger, outside a row of smaller, denticles. They are either attached to the subjacent bone by connective tissue, and then often partly movable, or they are implanted in bony sockets. They are renewed throughout the whole life, the old teeth fall out as the connection between them and the cartilage or bone gives way, or if a socket is present this is absorbed. The usual conical, piscine teeth are chiefly prehensile, and the points are therefore turned backwards and inwards; they are movable so that the point may assume another position. Teeth of other forms are used for biting or masticating the food. The CBSophagus is so short and wide that the mouth passes almost directly into the stomach. In most Teleosteans a varying number of short, blind, glandular sacs (1â100), the appendices pyloricce, open into the anterior part of the small intestine, close to the stomach. In Cyclostomes, Selachians, and Ganoids, there is a spiral valve in the small intestine, a large projecting fold, attached to the inner side of the gut, and almost filling up its cavity ;* it is absent from the Teleosteans. The large intestine is quite a short tube.
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