122 FISHES. 



teeth being the largest. It is impossible, however, to give 

 in this place any further exemplification of the great variety 

 of form exhibited by these singular bodies. As regards 

 their texture, the Conodonts have shining enamelled surfaces, 

 and they appear to consist of a translucent horn-like mate- 

 rial. In microscojnc structure they are seen to consist of 

 concentric layers of a minutely punctate tissue, which close- 

 ly resembles the structure of tlie shell of many Crustaceans, 

 though not absolutely incompatible with the theory that we 

 may be dealing here with a peculiar form of dentinal tissue. 

 Lastly, in chemical composition, they consist of carbonate of 

 lime, with a notable proportion of phosphate of lime. 



The above being the general characters of the "Conodonts," 

 it remains briefly to consider what their true nature may 

 be. By Pander, who first discovered them, and who gave 

 a most careful and minute account of their peculiarities, 

 they were regarded as being the teeth of Fishes, though he 

 does not positively decide to what group of this class they 

 should be referred. He compares them with the palatal 

 teeth of certain Percoid fishes ; and though he recognises 

 their general likeness to the minute teeth of Cyclostomatous 

 fishes, he rejects this view of their affinities upon the ground 

 that they cannot be shown to possess the microscopic denti- 

 nal tubes which occur in these teeth. Owinsf to their great 

 antiquity, much difficulty was felt by scientific men in ac- 

 cepting Pander's view that the " Conodonts " were the teeth 

 of Pishes ; and, after due examination, the high authority of 

 Professor Owen was cast in favour of their belonging to 

 Invertebrates, and having " most analogy with the spines, or 

 booklets, or denticles, of naked Molluscs and Annelides." 

 On the other hand, Dr Harley, after examining microscopi- 

 cally a number of supposed " Conodonts " from the " Bone- 

 bed " of the Ludlow formation (Upper Silurian), came to the 

 conclusion that all these little bodies really belonged to 

 Crustaceans, probably principally to Ceratiocaris. It is to 

 be noticed, however, that almost all of the forms figured by 

 this observer under the name of " Conodonts " have little or 

 no likeness to the typical forms of these bodies as described 

 and figured by Pander, and are probably not really " Cono- 



