Hyperodapedon and Proterosauria. 31 



on each side for the reception of the marginal teeth of the Wall-case, 

 mandible ; these teeth are small and closely arranged, and wear No 8 - 

 by attrition with the upper teeth into a sharp cutting edge. 

 There is also present on the inner side of the mandible a series 

 of large and obtuse teeth. 



The fine specimen of Hyperodapedon Gordoni exhibited from 

 Elgin shows the head, neck, and body region, and some of the 

 limb-bones in fair preservation, but the whole of the caudal 

 region is absent. It was a terrestrial reptile, and attained a 

 length of six or seven feet, and does not appear to have been 

 armed with scutes or spines, but there are traces of wrinkled 

 (skin) markings on the slab near the vertebras. 



A much larger species, named Hyperodapedon Huxleyi, has 

 been obtained from the Triassic deposits of Maleri, India, of 

 which a good series of the jaws is exhibited. It is computed to 

 have attained a length of 17 ft. 



Prof. Huxley remarks ("Quart. Journ. Geol. Soc.," vol. xliii., 

 1887) that this order had already attained its greatest 

 degree of specialization as early as the Trias ; Hyperodapedon 

 being in all respects a more modified form than Sphenodon. It 

 appears therefore to be probable that in the Permian, or perhaps 

 still earlier, there must have existed Lizards differing less from 

 the existing genus than either Hyperodapedon or Rhynchosaurus . 



Aphelosaurus, from the Permian, France, is also placed here. 



From the Trias of Elgin in Scotland, we have the very small 

 Lacertian, the Leptopleuron (Telerpeton) , not exceeding seven 

 inches in length. 



The Saurosternon is another small form of Triassic lizard, 

 from the reptiliferous sandstones of South Africa. 



The Pleurosauridce are typically represented by Pleurosaurus, -wall-case 

 of the Lithographic stone of Bavaria, which is a medium-sized No. 8. 

 Lizard characterized by the extreme elongation of the body (in 

 which there are a great number of presacral vertebras), and the 

 skull is long and narrow, with slit-like nares. Anguisaurus and 

 Acrosaurus, of the same deposits, belong to this family, but 

 it is not certain that they are really distinct from the type 

 genus. 



From the same horizon also we have Sapheosaurus, Ardeo- 

 saurus and Homwosaurus. 



Order VI. PROTEROSAURIA. 



To this order is referred a reptile named Proterosaurus Proterosau- 

 Speneri, from the Permian " Copper-slates " of Thuringia. rus ' 

 Though capable of progression on land, it was evidently of Wall-case, 

 aquatic habits, feeding upon the Palceoniscidce and other fishes, 

 which abounded in the seas of that period. 



