APPEARANCE OF VERTEBRATE ANIMALS. 119 



calcium phosphate, and the structures are more like those of 

 teeth of Sharks than of Lampreys, so that there can be no doubt 

 that they are really teeth of fishes, and probably of fishes of 

 somewhat higher grade than the Lampreys. The Cambrian 

 and Silurian specimens are said to be composed of calcium 

 carbonate, which would render it more probable that, as has 

 been suggested by Prof. Owen, they may have been teeth of some 

 species of Sea-snail destitute of shell. It is, however, possible 

 that they may have originally been horny, and that the animal 

 matter has been replaced by ca bonate of lime. The structures 

 which Pander has figured are certainly very like those of true 

 fish teeth, and would give some countenance to this last 

 supposition.^ 



Fig. 103 — Lower Carboniferous Conodont. Magnified.— After Newberry. 



If these curious objects were really teeth of fishes, they carry 

 the introduction of these nearly as far back as that of the 

 MoUusks and Crustaceans. If they were not, then the earliest 

 known representatives of this class belong to a much later age, 

 that of the Upper Silurian. Here we have undoubted remains 

 of fishes belonging to two of the higher orders of the class ; 

 and in the succeeding Devonian these became multiplied and 

 extended exceedingly. 



^ Dr. Newberry has kindly furnished me with specimens, and Dr. Har- 

 rington has submitted to analysis portions of shale filled with these little 

 teeth, the result giving 2*58 of calcium phosphate for the whole, which 

 indicates that the Conodonts are really bone. Their microscopic structure 

 approaches to that of tbe dentine of such Carboniferous fishes as Diplodus. 

 Hinde has described Conodonts from the Lower ijilurian of Canada, since 

 the above was wiitten. 



