PISCES FISHES. 513 



Professor Owen, in his truly splendid work above referred to, 

 thus describes the most important. 



" In the Cod-fish, Wolf-fish, and some other species, in propor- 

 tion as the ossification of the tooth advances towards its base and 

 along the connecting ligamentous substance, the subjacent portion 

 of the jaw-bone receives a stimulus, and developes a process cor- 

 responding in size and form with the solidified base of the tooth. 

 In this case the inequalities 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 teeth of the 

 Angler (Lophtus) are thus attached to the jaw, but the large pos- 

 terior 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 remitted, 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 facilitated, and its escape pre- 

 vented. ' 



" 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 

 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 tesse- 

 lated teeth of the Eagle-Rays have their attached surface longi- 

 tudinally 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 relieve from its pressure the floor 

 of a vaulted chamber beneath, let him make a longitudinal section 

 of one of the pharyngeal teeth of a Wrasse (Labrus). The base 

 of this tooth is slightly contracted, and is implanted in a shallow 



