200 THE ANATOMY OF VERTEBRA TED ANIMALS. 



which lie adjacent to its upper end. The pterygoid bones 

 are produced downward ; and, by a very exceptional peculiar- 

 ity, do not articulate with the quadrate bones, but are con- 

 nected with them only by fibrous tissue. In the lower jaw, 

 the dentary piece takes up a very much larger proportion of 

 the ramus than is the case in other Lacertilia. The basal por- 

 tion of the hyoid is represented by a long median cylindrical 

 entoglossal bone, and its posterior cornua are much stronger 

 and longer than the anterior pair. In the pectoral arch the 

 scapula and coracoid are remarkably longer and narrower than 

 in other Lacertilia. There are no clavicles, and the inter- 

 clavicle is wanting, the sternum being represented only by its 

 rhomboidal ossified cartilage. Again, in the pelvic arch, the 

 ilium is long and narrow, and its long axis is directed nearly 

 vertically to that of the trunk — in which respect the Chamae- 

 leons differ very much from the ordinary Lacertilia. There is 

 no OS cloac<e. 



The carpus and the tarsus have a very singular structure. 

 In the carpus there are two proximal bones, articulated with 

 the radius and the ulna respectively. A single spheroidal bone 

 is articulated with these, and with the five proximal constit- 

 uents of the digits. Besides these, there is an ossicle repre- 

 senting the pisiform. In the tarsus there are also four bones, 

 two articulated with the tibia and fibula respectively, a third 

 below and between them, and a fourth distal bone articulating 

 with the five proximal bones of the digits. In both manus 

 and pes the number of the phalanges, counting from the pre- 

 axial to the postaxial side, is 2, 3, 4, 4, 3. 



IV. The Ophidia. — This order of Reptiles has been divided 

 as follows : 



A. The palatine bones widely separated, and their long axes longitudi- 



nal ; a transverse bone ; the pterygoids united with the quadrate 

 bones. 



a. None of the maxillary teeth grooved or canaliculated. 



1. Aglt/phodontia. 



b. Some of the posterior maxillary teeth grooved. 



2. Opis/hoffli/^ihia. 



t. Grooved anterior maxillary teeth succeeded by solid teeth. 



3. Proierorjlyphia, 



d. Maxillary teeth few, canaliculated, and fanglike. 



4. '%/ri/f>r////phia. 



B. The palatine bones -neet, or nearly meet, in the base of the skull, and 



their long axes are transverse ; no transverse bone ; the pterygoids 

 are not connected with the quadrate bone. 

 5. TijphlopidiB. 



