40' Dr Grant on a Fossil Tooth found in Red Sandstone 



substance of a recent or fossil tooth. I am well aware that there 

 are many quadrupeds with angular teeth, where the enamel is 

 found only on a small part of the surface, as in the incisors of 

 Rodentia, &c., but none of these could be confounded with the 

 tooth before me, which is obviously destitute of such a coating 

 of enamel. Dr Prout, I understand, on his first inspection of 

 the tooth, declared that it looked more like bone than enamel on 

 the surface ; and I am convinced, after careful examination, that 

 his opinion is correct, and that the tooth belongs to that class of 

 animals where these organs are generally composed throughout 

 of a soft osseous substance, which yields readily, on the surface 

 as well as in the centre, to the point of the knife. In no quad- 

 ruped, recent or fossil, is there a tooth approaching to this in 

 general form, in which a section of the base of the crown pre- 

 sents a series of curves extending round it, as you perceive in 

 this fossil, but such a structure is very common both in reptiles 

 and fishes. There is no tooth of this form in quadrupeds 

 which are destitute of a root to fix it in its alveolus ; but in this 

 fossil you will perceive, by the groove which I have made in the 

 rock at the base of the tooth, that there exists here no trace of 

 a root in connexion with this crown. Would it be more philo- 

 sophical to suppose that this tooth was that of a quadruped and 

 once had a root, and that, before being imbedded in the soft 

 sand which is now so hardened around it, it had been somehow 

 neatly bisected at its thickest and strongest part, and only the 

 crown is handed down to us ; or that it belonged to a class of 

 animals in which the teeth consist only of osseous crowns, with- 

 out a trace of root, or any alveolus to receive it, as is the case 

 with most reptiles, and almost all fishes ? I purposely avoid ad- 

 ducing here any geological reasoning, which would materially 

 support my view of this fossil, and wish to let the tooth speak 

 entirely for itself, as a piece of anatomical structure. There is 

 a great difference in the density both of the osseous substance 

 ' and of the enamel of the teeth of quadrupeds, which is well 

 known to those who are in the habit of cutting these substances 

 to make* artificial teeth, and as we pass through the cold-blooded 

 vertebrata, the texture of both becomes softer, and the propor- 

 tion of enamel becomes less, till it is entirely lost in fishes, where 

 the teeth are often mere osseous spines, anchylosed to the sup- 



