1869.] HUXLEY nrPERODAPEDON. 147 



With respect to the affinities of Hyperodapedon, there can be no 

 doubt that it is very closely allied to the genus BhyncJiosauruSy 

 established by Prof. Owen upon a fossil skeleton from the Trias of 

 Shropshire. But Rhynchosaurus has shown no trace of teeth in 

 either upper or under jaw, and seems to differ from Hypey^odapedon 

 as Oudenodon does from Dicynodon. There is a certain analogy 

 with another Triassic genus, Placodus, in the dentigerous roof of the 

 palate of Hyperodapedon ; but too little is known of the rest of the 

 organization of Placodus to test the value of this analogy. 



I do not find grounds for assuming any special affinity between 

 Hyperodapedon and Telerpeton ; nor has Hyperodapedon anything to 

 do with the Thecodonts, Crocodilian or otherwise, which abound in 

 the Trias. 



But it is a very remarkable circumstance that it is nearly allied 

 to an anomalous lizard, Sphenodon {Hatteria), which still lives in 

 New Zealand. Professor Owen first directed attention to some simi- 

 larities in the construction of the skull between Sphenodon (under 

 the name of Rhynchocephalus) and RhyneJiosaurus. A short time 

 since, however, the iS'ew-Zealand lizard furnished to Dr. Giinther, 

 F.R.S., the subject for an excellent memoir now published in the 

 ' Philosophical Transactions,' in which the many anatomical pecu- 

 liarities of this singular saurian were first indicated; and on perusing 

 this memoir, I was at once struck with the resemblance in the 

 arrangement and wear of the teeth, as described by Dr. Giinther 

 in Sphenodon, to that which I had become acquainted with in the 

 fossil lizard. 



I have since had the opportunity, by Dr. Giinther's kindness, of 

 inspecting his osteological and other preparations, and I have satis- 

 fied myself that Sphenodon is the nearest ally to Hyperodapedon of 

 all recent or fossil reptilia, except Rhynchosaurus. 



Both Sphenodon and Hyperodapedon have amphiccelous vertebrae 

 (those of the ancient reptile being far less fish-like than those of 

 the modern one, be it noted); both have beak-like praemaxiUae, not 

 anchylosed together ; both have the inferior zygoma complete ; both 

 have similarly formed lower jaws; in each, a single row of teeth in 

 the mandible bites between two rows of teeth fixed to a plate 

 which is formed by a union of the maxilla with the palatine bone — 

 a structure which is quite anomalous among Lacertians ; and, finally, 

 in both, these teeth wear down to the bone of the jaw by the effect 

 of masticatory attrition. 



I now proceed to offer to the notice of the Society a few general 

 considerations which arise out of the facts just detailed. 



With respect to the habits of life of Hyperodapedon, I see no 

 reason to doubt that it may have been a purely terrestrial animal— 

 though it is a very hard matter, from the structure of a Lacertian, 

 to say whether it is entirely terrestrial or largely aquatic. Consider, 

 for example, how nearly the aquatic and terrestrial Varani resemble 

 one another, and how slight is the difference between that species 

 of Amblyrhynchus in the Galapagos Islands which cannot be driven 



VOL. XXV. PART I. M 



