. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. TEETH 315 are wanting in Cyclostomes, and are represented functionally by a number of conical horny teeth, the morphological nature of which has been variously interpreted. Amongst cartilaginious Ganoids teeth are absent in the adult Sturgeon, though present in the embryo. Amongst Teleostei they are wanting in the Lophobranchii, and, except in very early stages, in Coregonus. In bony Ganoids and Teleosts, teeth may be present on all the bones bounding the oral cavity, as well as on the hyoid arid the branchial arches (&qu
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. TEETH 315 are wanting in Cyclostomes, and are represented functionally by a number of conical horny teeth, the morphological nature of which has been variously interpreted. Amongst cartilaginious Ganoids teeth are absent in the adult Sturgeon, though present in the embryo. Amongst Teleostei they are wanting in the Lophobranchii, and, except in very early stages, in Coregonus. In bony Ganoids and Teleosts, teeth may be present on all the bones bounding the oral cavity, as well as on the hyoid arid the branchial arches (" pharyngeal ;) In the latter position, as well as on the parasphenoid, they often form brush-like groups. In form the teeth may be cylindrical, conical, hooked, or chisel- shaped (Scarus, Sarginae) ; in some forms they give rise to a definite pavement, are rounded in form, and serve to crush the food ; in others, again, they are delicate and bristle-like (Cha?todon), or sabre- shaped (Chauliodus). In the Dipnoi (Fig. 71) the teeth, which are wanting in enamel (though an enamel organ is present in the embryo Lepidosiren), are exceedingly massive, presenting sharp edges and points : they have probably arisen by the concrescence of a number of individual More particularly in Ceratodus, the origin of the vomer, palatopterygoid, and dental plates of the mandible from a fusion of the bony basal portions of the teeth is FIG. 230.— SKULL OF very evident, and the same has been shown in the case of the Amphibia. In the Amphibia there is in general a considerable diminution in the number of teeth as compared with Fishes ; and at the same time a much more uniform character is noticeable in their form through- out (Fig. 231. A, B). They are conical, enlarged below, and rest on a definite base, while above they become narrower and slightly curved, ending either in a double (Myctodera, Anura), or a single apex (Perennibranchiata, Derotremata, Gymnophiona) ; the latter
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