540 1HILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



to prove that the Teeth of Cartilaginous Fishes are perpetually renewed. By 



Mr. Urn. Andre, Surgeon, p. '274. 



The amazing variety in the external form of fishes must be obvious to a com- 

 mon observer; and whoever examines will be convinced, that the same variety 

 prevails in their internal structure. No parts perhaps afford a more convincing 

 proof of the last assertion than the teeth of fishes. To adduce a few instances, 

 let us only recollect the tuberculated teeth in the thorn back; the triangular ser- 

 rated teeth in the shark; the slender flexible teeth in the chaetodontes, or angel 

 fishes. There is not only a difference of their form, but also in the substances 

 of which they are composed; some being of a soft horny nature; others made 

 up of bone; others of that substance we call enamel in the teeth of quadrupeds; 

 and some having the apparent hardness and transparency of crystal. We may 

 also notice their uncommon situation; many fishes having teeth not only in their 

 jaws, but on the tongue, the palate, and about the fauces. 



lb illustrate in some degree this part of natural history, Mr. A. describes the 

 teeth of the anarrhichas lupus, or sea wolf, and those of the chastodon nigricans, 

 a species of angel fish. The former have been but imperfectly described, and 

 never represented distinct from the fish, without which it is impossible to have 

 any exact idea of their disposition, number, or form, while the true shape and 

 composition of the latter, from their minuteness, have been entirely overlooked. 

 He then attempts to prove, that a continual renovation of the teeth takes place 

 in cartilaginous fishes. 



The sea wolf, a fierce and ravenous fish, is found in the northern parts of the 

 globe, where at frequently grows to the length of 4 feet and upwards. The jaws 

 of the wolf fish are made up of several bones, to each of which a greater or 

 less number of teeth are affixed. The palate, marked a in fig. 10, pi. 7, is a 

 kind of basis or support to the other bones, to which they are all more or less 

 connected. This is a thick and firm bone united above to the bones of the cra- 

 nium and nose, and ending below in a flat oval surface, on which are incrusted 

 about 12 or 13 strong, blunt, and rather flat teeth of the molar or grinder kind. 

 Their external edges are the most prominent; by which means a hollow is formed 

 in the middle of the palate. 



The upper jaw is composed of 3 bones, 1 of which, b, b, are placed laterally, 

 forming the sides of the upper jaw, and the 3d, c, anteriorly, making the fore 

 part of the jaw. The 3d bone might be divided through its middle into 2 por- 

 tions, firmly connected together. The side bones of the upper jaw have nearly 

 the shape of an italic f. At their posterior ends may be observed a smooth arti- 

 cular surface, for their connection with a similar surface on the posterior extre- 

 mities of the lower jaw; and on their anterior ends there are 1 rows of teeth. 



