ATTACHMENT. 



ponding in size and form with the sohdified base of the tooth. In 

 this case, the inequahties of the opposed surfaces of the tooth and 

 maxillary dental process fit into each other, and for some time 

 they are firmly attached together by a thin layer of ligamentous 

 substance ; but in general, anchylosis takes place to a greater or less 

 extent before the tooth is shed. The small anterior maxillary teeth of 

 the angler {Lophius) are thus attached to the jaw, but the large posterior 

 ones remain always moveably connected by highly elastic, glistening 

 ligaments which pass from the inner side of the base of the tooth to 

 the jaw-bone. These ligaments do not permit the tooth to be bent 

 outwards beyond the vertical position, when the hollow base of 

 the tooth rests upon a circular ridge growing from the alveolar 

 margin of the jaw ; but the ligaments yield to pressure upon the tooth 

 in the contrary direction, and its point may thus be directed towards 

 the back of the mouth ; the instant, however, that the pressure is re- 

 mitted, the tooth flies back, as by the action of a spring, into its usual 

 erect position ; the deglutition of the prey of this voracious fish is 

 thus facihtated, and its escape prevented. The broad and generally 

 bifurcate osseous base of the teeth of sharks is attached by ligaments 

 to the ossified or semi-ossified crust of the cartilaginous jaws. The teeth 

 of the Salarias and of certain Mugiloids are simply attached to the gum. 

 The small and closely-crowded teeth of the rays are also connected by 

 ligaments to the subjacent maxillary membrane. The broad tesselated 

 teeth of the eagle-rays have their attached surface longitudinally 

 grooved, to afford them better holdfast ; and the sides of the contiguous 

 teeth are articulated together by true serrated, or finely-undulating 

 sutures ; which mode of fixation of the dental apparatus is unique in 

 the animal kingdom. 



If the engineer would study the model of a dome of unusual 

 strength, and so supported as to reheve from its pressure the floor 

 of a vaulted chamber beneath, let him make a vertical section of one 

 of the crushing pharyngeal teeth of the wrasse. (1) The base of this 

 tooth is slightly contracted, and is implanted in a shallow, circular 

 cavity, the rounded margin of which is adapted to a circular groove 

 in the contracted part of the base ; the margin of the tooth, which 

 immediately transmits the pressure to the bone, is strengthened by an 



(1) PI. 46. 



