BETWEEN TYPICAL EEPTILES AND OTHER ANIMALS. 183 



are so similar in Iguana and Emysaura that they might be easily 

 confounded. The distal tarsal bones of Lizards differ in being 

 limited to two. The metatarsals and phalanges of Lizards differ 

 in being elongated, but approximate best to Emysaura and the 

 marine Chelonia, which latter similarly have five digits. 



§ 5. The Chameleon-characters of Chelonians. 



The Chameleon-characters are few. In the head they are seen 

 in the backward prolongation of the supraoccipital and parietal 

 bones, coupled with the high form of the cranium. The pre- 

 maxillaries are similarly narrow in front ; but they do not enter 

 into the lateral perforation of the anterior nares, but into the 

 superior membrane-covered vacuity which I have already spoken 

 of as the middle hole of the skull. 



The palatine bone appears similarly to form the inner floor of 

 the orbit. It may be worth consideration whether the Chelonian 

 terminal hole in the head does not represent the middle hole 

 rather than the true nares, and whether by the prolongation for- 

 ward of the prefronto-nasal, maxillary, and premaxiliary bones, 

 nares in front of these might not be circumscribed which should 

 be more analogous to the nares of Chamceleon — a view which is 

 not unsupported by the existence of long fleshy snouts in some 

 Trionychidse. 



The elongated scapula of the Chameleon approximates to that 

 of the Tortoise ; but the resemblance would seem to be acci- 

 dental. 



§ 6. The Rhynchocephalian Characters of Chelonians. 



The Rhynchocephalian palate has only a resemblance of form 

 to the Chelonian ; for the maxillary and premaxiliary only margin 

 it, there is no similar aperture for the posterior nares, and, although 

 the palatines are parted from each other as in many Chelonians, it 

 is by the pterygoid bones and not by the vomer, which bone is here 

 double and makes the anterior part of the palate. The basioccipi- 

 tal and basisphenoid are exhibited on the underside of the head ; 

 but in the adult they form one bone. The pterygoid gives oflf a 

 strong lateral process into the lateral pterygoid fossa, as in Foclo- 

 cnemis ; and the bones diverge against the basisphenoid to reach 

 the quadrate, as in Ghelo7ie midas ; but there the resemblance 

 ends. 



The oblique orbit is surrounded by much the same bones as in a 



