&74 



ANATOMY OF VERTEBRATES. 



260 



PorLioli of tlie jaw of Lopliiiis pisratnring, showing the lign- 

 mciitons attaclimcnt of tlic tot'tli. v. 



of tliciv summits (^Sca?-?is, fig. 2,59); in Pimelodus, however, 

 where the tcetli 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- 

 ment; and in the Cod-fish, AYolf-fish, and some other spe- 

 cies, as calcification of tlie tootli })rogresses towards its base, 

 the sul)jacent portion of the jawbone receives a stimulus, and 



developes a process corres- 

 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 pdace to a 

 greater or less extent before 

 the tooth is shed. Most of 



nhriis). \. 



the teeth of the Lophius re- 

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

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

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

 on a conformable alveolar process. The ligaments do not permit 

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

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

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

 tlie instant, however, tliat the jiressnre is remitted, the tootli 

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

 action of a spring, into its usual erect position, h ; tlio deglutition 

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



201 



Tcolh of tho Wrasse (Cr. 



