402 



MANUAL OF ZOOLOGY 



SECT. 



number of other bones in the wall of the mouth. In most 

 of the Teleostei the maxilla is devoid of teeth, and does not 

 enter into the upper boundary of the mouth opening. In 

 the great majority the teeth are small and very numerous, 

 adapted for preventing the struggling prey from slipping out 

 of the mouth, but quite unfitted for either tearing or crush- 

 ing ; but in many instances teeth are comparatively large and 

 few in number, and in some (Fig. 242) there is a marked 

 differentiation of the teeth, those in. front of the jaws being 



Fig. 242. — Premaxillse of Sargus, showing teeth. (After Owen.) 



pointed or chisel-shaped, and adapted for seizing or cutting, 

 while the back teeth have rounded surfaces adapted for 

 crushing. The teeth may be either simply embedded in the 

 mucous membrane so as to be detached when the bones 

 are macerated or boiled, or they may be implanted in the 

 sockets of the bone or ankylosed to it. Their succession 

 is perpetual, i.e., injured or worn-out teeth are replaced at 

 all ages. The Ganoids have a spiral valve in the intestine ; 

 this is absent in the Teleostei. Coeca (the pyloric caeca) 

 are commonly developed at the junction of the stomach and 

 small intestine. The anus is always distinct from, and in 

 front of, the urogenital apparatus, there being no cloaca 

 such as occurs in Elasmobranchs. The gills are usually 



