232 THE ANATOMY OF VEETEBRATED ANIMALS. 



the anterior nasal apertures. These apertures, in fact, are 

 situated upon the sides of the forepart of the skull, and are 

 separated from the nasal bones, in part, by a membrane 

 which stretches outwards from the nasal bones ; and external 

 to this by a prolongation forwards of the prefrontal bone, 

 which unites with the maxilla, and in some specimens of 

 Chameleons is prolonged forwards into a great osseous horn, 

 projecting from the sides of the front part of the snout. 



The orbit is closed behind by the ascending process of 

 the jugal bone, but there is no quadrato-jugal. The quad- 

 rate bone itseK is not, as in most other Lacertilia, move- 

 able upon the sides of the skull, but is iii'mly ankylosed 

 with the bones which lie adjacent to its upper end. The 

 pterygoid bones are produced downwards; and, by a very 

 exceptional peculiartty, do not articulate with the quadrate 

 bones, but are connected 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 portion of the hyoid is represented 

 by a long median cylindrical entoglossal bone, and its pos- 

 terior comua 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 interclavicle is wanting, the 

 sternum being represented only by its rhomboidal ossified 

 cartilage. Again, in the pelvic arch, the ilium is long and 

 naiTOw, and its long axis is directed nearly vertically to 

 that of the trunk — :in which respect the Chamseleons differ 

 veiy much from the ordinary Lacertilia. There is no os 

 cloacce. 



The carpus and the tarsus have a very singular structure. 

 In the carpus there are two proximal bones, articulated with 

 the radius and the iilna respectively. A single spheroidal 

 bone is articulated with these, and with the five proximal 

 constituents of the digits. Besides these, there is an ossicle 

 representing 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 



