TEETH OF FISHES. 377 



teeth of most of the Chfctodonts are flexible, cL-istic, and composed 

 of a yellowish subtransparent albuminous tissue ; such, likewise, 

 are the labial teeth of the Ilelostome, the premaxillary and 

 mandibular teeth of the Goniodonts, and of tlie percoid genus 

 Trtchiidon. In the Cyclostomes the teeth consist of a denser 

 albuminous sidjstance. The upper pharyngeal molar of the Carj) 

 consists of a peculiar brown arid semitransparcnt tissue, hardened 

 by salts of liine and magnesia. The teeth of the Flying-fish 

 {E.ioca'tus) and Sucking-fish ( Rcmora) consist of osteo-dentine. 

 In many Fislies, e. g. the Acfmtliurus, S'jiki/ircna, and certain 

 Sharks {Lanina, fig. 241), a base, or body of osteo-dentine, is 

 coated l.\y a layer of true dentine, d, but of unusual liardness, like 

 enamel: in Prloiu>doii this hard tissue predominates. In tlic 

 Liihriis the i)haryngeal crushing teeth consist wholly of hard or 

 unvascidar dentine, fig. 240. In most Pyenodonts and Ccstra- 

 ciouts, and many other Fishes, the body of the tooth consists of 

 ordinary unvascular dentine, covered by a modification of gano- 

 dentine. In Sartpix and Baliste-^ the body of the tooth consists 

 of true dentine, and the crown is covered by a thick layer of a 

 denser tissue, differing from the ' enamel ' of Mammalia only in 

 tiic more complicated and organised mode of de})osition of tlie 

 earthy salts. The ossification of the cajisulc of the complex 

 matrix of these teeth covers the enamel vtdth a thin coating of 

 ' cement.' In the pharyngeal teeth of the Scarus a fourth sido- 

 stanee is added by the ossification of the base of the pulji after 

 its smnmit and periphery have been converted into hard dentine ; 

 and the teeth, fig. 262, thus composed of cement, c, enamel, c, 

 dentine, d, and osteo-dentine, are the most complex in regard to 

 their substance that have yet been discovered in the aiumal 

 kingdom. 



The tubes wliich convey the capillary vessels through tlie 

 substance of the osteo- and vaso-dentine of the teeth of Fishes 

 were early recognised, on account of their comparatively large 

 size; as by Andre, e.g. in the teeth of Araiithurus,^ An({ by 

 Cuvier and Von Born in the teeth of the Avolf-fish and other 

 si)eeies. Lecuwenlioek had also detected the much finer tid>es 

 of the peri])heral dentine of the teeth of the haddock.^ These 

 'dentinal tubnli ' are given oft' from the parietes of the vascular 

 canals, and bend, divide, and subdivide rapidly in the hard Ijasis- 

 tissue of the interspaces of those canals in osteo-dentine ; the 

 dentinal tubuli alone are found in true dentine, and they have a 



' cc-XLvn. " cciLVjii., p luO:j. 



