EHMAINS OF REPTILES AND FISHES. 101 



say, in addition to what has been previously stated, that it is 

 most frequently absent from teeth attached to the jaws, and that 

 by far the greater number of our specimens are deprived of it, 

 (as we are inclined to believe) from the effect of erosion. Be 

 this, however, as it may, the fact remains unchanged. Authen- 

 ticated PalcEoniscus teeth in connexion with the jaws agree in all 

 respects with the tooth of Ganacrodus, even to the absence of 

 enamel on the crown of the tooth. 



PalcBoniscus, however, is not the only genus in which this 

 beautiful enamel-cap exists. Although Prof. Owen is pleased 

 to ignore what is stated in the previous "Criticism" on the 

 subject, we here venture to assert that the teeth of Pygopteriis, 

 Amblypterus, Gyrolejns, and Cycloptychius have a perfectly simi-. 

 lar tip of enamel. This we have determined by our own inde- 

 pendent research, and can prove the fact by numerous sections 

 of the teeth of all these genera. 



Considerable importance, however, appears to be attached to 

 the supposed novelty of this peculiar tooth structure in the paper 

 so often referred to. Prof. Owen therein states, on this subject, 

 " that he had not before met with any similar tooth in the whole 

 range of his odontological researches."* Betwen twenty and 

 thirty years ago, however, M. Agassiz described and figured the 

 very same structure in the teeth of PygojJterus,^ 8aurichthys,\ 

 Polypterus, and Lepidosteus,^ the last two being recent sauroid 

 fishes. 



After giving a full description of the general characters of the 

 tooth of PygojJterus, M. Agassiz says, " Un cone de dentine en- 

 toure cette cavite pulpaire de tons cotes ; il est plus massif au 

 milieu, la oil se voit le renflement exterieur, plus mince vers 

 la base et vers le sommet, et reconvert en haut d'un capuchon 

 en email, qui occupe a-peu-pres le tiers de la dent et forme a 

 lui-seul toute la pointe. En examinant la dent a la loupe, on 



* Pamphlet reprinted from the " Transactions of the Odontolog-ical Society," p. 29. 



f'Poissons Fossiles," Vol. II., Part II., p. 102. 



tibid, Vol. II., Part II., p. 153, tab. H., figs. 2-5. 



§ Ibid, Vol. II., Part 11., pp. 27, 4.3, tab. G., figs. 9-12. 



