BETWEEN TYPICAL REPTILES AND OTHER ANIMALS. 165 



produces this modification may be presumed to depend the high 

 form of the head, the vertical quadrate bone, the absence of a 

 quadrato-jugal (ifit be absent), the lateral aspect and large size of 

 the orbits and nares. The external nostril in Ghamceleon is not 

 enclosed by the premaxillary as in a Crocodile, but has that bone 

 and the nasal dividing it, so that the nares look outward and 

 are double. To bring the premaxillaries into harmony with the 

 Crocodile's, it would be necessary to suppose that the Crocodilian 

 bones had been turned round through nearly half a circle by 

 having their anterior termination drawn backwards through the 

 nares. This view would account for their narrowness in the 

 dental border, the few premaxillary teeth (which do not exceed 

 two, and those obliterated in old age), the divided nostril, &c. 



The teeth, instead of being conical and in sockets, are flattened, 

 serrated, and anchylosed with the jaw. Neither the maxillaries, 

 palatines, nor pterygoids meet mesially on the palate, but are 

 divided by a groove. The middle holes of the skull, covered by 

 membrane, are large, between the orbits and nares, look upward, 

 and are divided by the premaxillary and frontal bones ; in living 

 Crocodiles these perforations have no representative. The occi- 

 pital condyle is chiefly made by the exoccipital bones, which meet 

 mesially, as in Chelonians ; in Crocodiles the condyle is chiefly 

 made by the basioccipital. In the Chameleon the lower jaw does 

 not extend backward behind the articulation with the quadrate 

 bone. 



Throughout the vertebral column there runs a transverse plat- 

 form, which is made by the zygapophyses extending outward, be- 

 yond and above the small flat single facet on the lower part of 

 the side of the centrum to which the rib is attac^hed ; in Croco- 

 diles the wide platform is made by the transverse process which 

 carries the rib. 



The cervical vertebrae are short from front to back, and have a 

 hypapophysis. The last two of the five have long ribs, which are 

 free at their distal ends. The dorsal vertebrae have the centrum 

 somewhat elongated ; and the neural arch is long, especially in the 

 early part of the back. All the vertebrae, except the last two, 

 appear to have ribs, which, relatively are enormously long, cylin- 

 drical, and in the dry state only consist of a dorsal and sternal 

 part, though in a fresh specimen the latter joints into four 

 parts. In the tail, though transverse processes are developed, 

 they are directed down\\ard and outward from the hinder corners 



12* 



