372 



ANATOMY OF VERTEBRATES. 



Superior pharyngeal hones and 

 teeth (Scarus). v. 



notch on each side of the large middle lobe (Hoops). In the 

 formidable Sea-pike (Sphyrcsna Barracuda) the crown of each 

 tooth, large and small, is produced into a compressed and sharp 

 ■2:>5 point, and resembles a lancet. Sometimes 



the edges of such lancet-shaped teeth are 

 finely serrated, as in Priodon, and the great 

 Sharks of the genus Carcharias, the fossil 

 teeth of which indicate a species ( Carch. 

 Megalodori) sixty or seventy feet in length. 

 The lancetted form is exchanged for the 

 stronger spear-shaped tooth in the Sharks 

 of the genus Lamna, fig. 260 ; and in the 

 allied great extinct Otodus, as in the small 

 Porbeagle, similarly shaped, but sti*onger, 

 piercing and cutting teeth were complicated 

 by one or more accessory compressed cusps on 

 each side of their base, like the Malay crease. 

 With respect to situation, the teeth, in 

 Sharks and Rays, are limited to the bones 

 (maxillary and mandibular), which form the 

 anterior aperture of the mouth : in the 

 Carp and other Cyprinoids the teeth are confined to the bones 

 (pharyngeal and basioccipital) which circumscribe the posterior 

 aperture of the mouth. The Wrasses (Lcibrus) and 

 the Parrot-fishes (Scarus) have teeth on the pre-max- 

 illary and pre-mandibular, as well as on the upper 

 and lower pharyngeals ; both the anterior and 

 posterior apertures of the mouth being thus pro- 

 vided with instruments for seizing, dividing, or com- 

 minuting the food, the grinders beino- situated at 

 the pharynx. In most fishes teeth are developed 

 also in the intermediate parts of the oral cavity, 

 as on the palatines, the vomer, the hyoid bones, 

 the branchial arches ; and, though less commonly, on the pte- 

 rygoids, the entopterygoids and 

 the sphenoids. It is very rare to 

 find teeth developed on the true 

 superior maxillary bones ; but the 

 Herring and Salmon tribes, some 

 of the Ganoid Fishes, and the 

 great S//dis, fig. 86, 21, are ex- 

 amples of this approach to the 

 higher Vertebrates. Among the 

 anomalous positions of teeth may 



256 



Front teeth of Aplo- 

 dactylus. v. 



on of thejnw and teeth <>f the Glol e Qsli 

 i Diod ■>/ '. v. 



