676 



PROF. T. H. HUXLEY OBSEE\ r ATIOXS 



I am glad to be able to say that, so far as it goes, the account 

 of the structure of the skeleton of Hyperodapedon which I gave in 

 1869 needs no correction ; but the new material enables me to 

 make large and important additions. Moreover , several specimens 

 of Hhynchosaurus articeps in the Palaeontologies! Collection of the 

 British Museum render it possible to make a full comparison of 

 Hhynchosaurus with Hyperodapedon, and to put an end to any doubts 

 which may have been entertained as to the generic distinction of 

 the two. Finally, the full evidence now accessible permits us to 

 obtain a clear view of the relations of both these extinct genera 

 with the recent Sphenodon, a point to which I drew particular 

 attention in 1869 *. These relations, both of resemblance and of 

 difference, are so interesting and important, in fact, that I shall give 

 my account of Hyperodapedon mainly in the form of a comparison 

 between that genus and Sphenodon. 



The present specimen of Hyperodapedon Gordoni has been exposed 

 by the splitting of a large block of sandstone into two slabs, along a 

 plane which corresponds roughly with that of the imbedded skeleton. 

 I have no information respecting the relative position of these slabs 

 in the rock before it was quarried ; but, supposing that slab which 

 contains the larger part of the skeleton and the entire skull to have 

 been uppermost, the animal laj T flat upon its belly with its limbs 

 standing out, yery much as those of a dead Lizard ordinarily do, when 

 it was buried in the sands of the Elgin shore. The skull, the verte- 

 bral column as far as the root of the tail, slightly curved towards 

 the right side, almost the whole of the bones of the left (and part 

 of the right) fore limb, with those of the right hind limb, are pre- 

 served in almost their natural relations. 



The following table gives a view of the actual dimensions of 

 Hyperodapedon and of the proportions of its parts compared with a 

 specimen of Sphenodon : — 



Measurements, in millimetres. 



Hyperodapedon. 



Total length (Probably over 2000) 



End of premaxilla to end of 



second sacral vertebra 900 



Skull, end of premaxilla to edge 



of occiput 160 



Skull, greatest breadth of the 



occipital region 210 



Total length of humerus + 



radius 210 



Total length of femur + tibia . . 200 



Supposing the tail of Hyperodapedon to have been as long in pro- 

 portion as that of Sphenodon, this specimen will have had a length 

 of between six and seven feet, or rather more than four times as long 

 as the specimen of Sphenodon. Hence it would appear that the 



* Loc. cit. p. 147. 



Sphenodon. 

 460 



208 =(4-5 : 1) 



55=(3:1) 



34=(7: 1) 



56=(4: 1) 

 66=(3:1) 



