ORDER RHYNCHOCEPHALIA. 



1135 



nares. The latter probably really formed very small slits on the sides 

 of the palate, as in Chamfisosaurus, and opened between the rows of 

 maxillary and palatine teeth. By far the most remarkable feature 

 is, however, to be found in the upper den- 

 tition. On the palatal surface of the pecu- 

 liar triangular compound bone (fig. 1037), 

 which may be conveniently termed the 

 palato-maxilla, although anteriorly it prob- 

 ably includes the vomer, and posteriorly 

 part of the pterygoid, there are, on the 

 outer or maxillary side, several rows of 

 low pyramidal teeth ; then comes the 

 groove for the reception of the edge of 

 the mandible, on the inner side of which 

 there are two or more rows of similar teeth 

 borne by the palatine and vomer, and prob- 

 ably also by the pterygoid. And it is in- 

 teresting to notice that while in the type 

 species the larger number of rows of teeth 

 occurs on the palatine and vomer, the re- 

 verse condition obtains in the Indian form 

 (fig. 1037). In the type species there 

 appears to be no foramen to the humerus, 

 and the presacral vertebrae are slightly 

 opisthoccelous ; it is, however, not improb- 

 able that the vertebrae of the Indian form 



were amphiccelous. The extremely solid structure of the palato- 

 maxilla causes this part to be the most frequently preserved ; and 

 these bones are very common in the Indian Gondwanas. 



m Fig. 1037.— Oral surface of the 

 right palato-maxilla of Hypero- 

 dapedon Huxleyi ; from the Ma- 

 leri stage of Central India. (After 

 Medlicott and Blanford.) 



Professor Huxley observes that it is very interesting to note that this 

 suborder had attained its greatest degree of specialisation as early as the 

 Trias ; Hyperodapedo?i being in ail 

 respects a more modified form than 

 Sphenodon. It appears therefore to be 

 probable that in the Permian, or per- 

 haps still earlier, there must have ex- 

 isted Lizards differing less from the 

 existing genus than either Hyperoda- 

 pedon or Rhytichosaurus. 



Fig. 1038. — Right lateral aspect of the 

 skull of R. hy nc ho s aunts articeps ; from 

 the Trias of Warwickshire. Reduced. 

 (After Owen.) 



In the typical genus Rhynchosau- 

 rus, from the English Keuper, of 

 which the type skull is represented 



in fig. 1038, there is but a single row of palatine teeth; the orbit 

 is large and lateral ; the infratemporal fossa of considerable size ; 

 and the premaxillary beak long and slender, its form being not 



