648 PISCES. 



(1771.) We will not enlarge further upon this portion of our subject ; 

 enough has been said for our present purpose, and the reader will find 

 elsewhere abundant information*. 



(1772.) The teeth of osseous fishes are generally firmly anchylosed 

 to the bones that support them, although in a few instances they are 

 found fixed in sockets, as in the rostral teeth of the Saw-fish (Pristis), 

 and in the mouth of Sphyrcena, Acanihurus, Dictyodus, &c. t But there 

 are other modes of attachment only met with among fishes, some of 

 which are not a little curious ; and 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 proportion as 

 the ossification of the tooth advances- towards its base and along the con- 

 necting ligamentous substance, the subjacent portion of the jaw-bone 

 receives a stimulus, and developes a process corresponding 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 (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 mar- 

 gin 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 faci- 

 litated and its escape prevented. 



" The broad and generally bifurcate osseous base of the teeth of Sharks 

 is attached by ligaments to the ossified or semiossified crust of the carti- 

 laginous 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 tessellated 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 relieve from its pressure the floor of a vaulted 

 chamber beneath, let him make a longitudinal section of one of the 



* Vide Yarrell's British Fishes. 8vo. 2 vols. t Owen, Odontography, p. 6. 



