98 PAL/EOXTOLOGY 



The detached condition of the booklets, and the integrity 

 of the thin border of the basal pulp-cavity, indicate that they 

 have not been broken away from any of those kinds of 

 attachment to a bone which the minute villiform teeth of 

 osseous fishes would show signs of. The Conodonts have 

 been supported upon a soft substance, such as the skin of 

 a mollusk or worm, the mucous membrane of a mouth or 

 throat, or the covering of a proboscis ; but to select the teeth 

 of cyclostomous or plagiostomous fishes as the exclusive illus- 

 tration of the above condition, would be to take a partial and 

 limited view of the subject. 



In comparing the Conodonts with the teeth of fishes, they 

 present most resemblance to the minute conical recurved teeth 

 of the genus Rhinodon of Smith : they more remotely resemble 

 the conical, pointed, horny teeth of Myxinoids and Lampreys 

 in that class : and the absence of any other hard part in the 

 strata containing the Conodonts tallies with the condition of 

 the cartilaginous skeleton ; but not more than it does with 

 the like perishable soft condition of annelidous worms and 

 naked mollusks. Rhinodon has very small teeth, " en brosse," 

 of a simple conical recurved form : there are 12 or 13 teeth 

 in each vertical row, and about 250 such rows in each jaw : 

 so that each fish may have from 6000 to 7000 teeth. But 

 the teeth of Rhinodon have not the basal extensions and 

 processes of many of the Conodonts ; and the teeth of all 

 known Cyclostomes are much less slender and are less varied 

 in form than in the Conodonts. Certain lingual plates 

 of Myxinoids are serrate, but not with a main denticle 

 of much greater length — such as shown in the form of the 

 Conodont called Machairodus by Pander. Most cyclostomous 

 teeth are simple, thick cones, with a subcircular base ; and 

 every known tooth of a cyclostomous fish is much larger than 

 any of the forms of Conodon, which rarely equal half a line in 

 length. This minuteness of size, witli the peculiarities of 



