J>74 



ANATOMY OF VERTEBRATES. 



2C0 



of their summits (Scams, fig. 259); in Pimelodus, however, 

 where the teeth are thus attached, the crown is bent down 

 in the upper teeth, and bent up in the lower ones, at right angles 



to the fang, so that they 

 oppose each other by the 

 normal surfaces. Certain 

 teeth of recent and fossil 

 cartilaginous fishes have 

 their base divided into 

 processes like fangs, but 

 these serve for the attach- 

 ment of ligaments, and 

 are not set in bony sockets 

 like the true fangs or 

 roots of the teeth of Mam- 

 mals. 



The base of anchylosed 



teeth is, at first, attached 



to the jawbone by liga- 



Wolf-fish, and some other spe- 



Portion of the jaw of Lophius piscatorius, showing the liga 

 mentons attachment of the teeth, v. 



ment; and in the Cod-fisl 

 cies, as calcification 



of the 



tooth progresses towards its base, 

 the subjacent portion of the jawbone receives a stimulus, and 



developes a process corres- 



261 



Teeth of the Wrasse (Crcnilabrus). v. 



ponding in size and form 

 with the base of the tooth : 

 for some time a thin layer 

 of ligamentous substance 

 intervenes, but anchylosis 

 usually takes place to a 

 greater or less extent before 

 the tooth is shed. Most of 

 the teeth of the Lophius re- 

 tain the primitive connection ; the ligaments, fig. 260, d, of the large 

 internal or posterior teeth of the upper and lower jaws, radiate on 

 the corresponding sides of the bone, the base of the tooth resting 

 on a conformable alveolar process. The ligaments do not permit 

 the tooth to be bent outward beyond the vertical position, but 

 yield to pressure in the contrary direction, by which the point of 

 the tooth may be directed towards the back of the mouth, as at c ; 

 the instant, however, that the pressure is remitted, the tooth 

 returns through the elasticity of the bent ligaments, as by the 

 action of a spring, into its usual erect position, b ; the deglutition 

 of the prey of this voracious fish is thus facilitated, and its escape 



