530 Professor R. BurckharcH — On Syperodaijedon Gordoni. 



teeth. Huxley considered that the Indian specimens probably did 

 not differ specifically from the English specimens, but merely 

 exceeded them in point of size. 



As the two fragmentai-y specimens of undoubtedly British origin 

 show exactly the same arrangement in the dentition of the lower 

 jaw, Lydekker's contention as to the specific value of the character 

 of his Indian specimens therefore breaks down. 



The study of the lower jaw of Hyperodapedon minor is particularly 

 instructive in this respect, as the principal row of mandibular teeth 

 extends backward considerably further than in H. Gordoni. 



The dentition of the palate-bones has been accurately described by 

 Huxley, except in the case of the anterior portion of the right side, 

 which he states has three rows, of which the middle one is decayed 

 away, being indicated only by the empty sockets of the teeth. The 

 regularity in distribution of the teeth is somewhat indistinct on the 

 left side of the fore-part of the palate-bone, and it appears to me to 

 depart from the normal plan, a circumstance which I am inclined to 

 attribute to the local displacement already mentioned. In size the 

 teeth increase consecutively from the front backwards. Neither from 

 this fact alone, nor from sections made at a right angle to their 

 longitudinal line of distribution, is information available as regards 

 a succession of teeth. But judging from a fragment of S. minor, 

 containing the germs of the teeth, which have as yet not cut through 

 the bone, I should infer that this does not point to a real change of 

 the teeth, but that it rather suggests the mode of a successive 

 supply of them from the rear, which would continue during the 

 whole of the animal's lifetime. 



Now, therefore, that the purely palatine nature of the dentition has 

 been proved, there is no further occasion for assuming a change of 

 teeth to apply to it in the same manner as that in which it is 

 accomplished in the maxillaries. Whether or not such a change 

 of teeth, in its actual sense, takes place in other palatal bones, is 

 a matter for further examination. Whatever its outcome, it is not 

 likely to furnish direct counter-evidence against Hyperodapedon, 

 the apparatus for prehension in which is so markedly different. 



The peculiar anatomical structure of this appai-atus implies a 

 number of physiological derivations capable of throwing light into 

 the vast abyss which divides its dental arrangement from that 

 of Sphenodon. It would be wrong to imagine the cutting edge of 

 the lower jaw to move backward and forward in the masticating 

 furrows opposing it. This would be an utter impossibility on 

 account of the two furrows converging towards the front. It is more 

 likely that during the process of attrition, they moved obliquely 

 across the upper part of the apparatus, and that the furrows received 

 the lower jaws when at rest, for which purpose they seem to be 

 provided. This is probably the reason too why the tooth-rows 

 which flank them are ground down. In further support of this 

 view of a gradual expansion of the attritive surface in the posterior 

 portion of the lower jaw, is the fact that it was achieved by an 

 increase of the tooth-rows. Another reason why this expansion has 



