THE CnAMJELEONIDA. I99 



character of the absence of the columella, which they share 

 with the preceding group, but by a number of very important 

 positive features. Among these I may mention the soft and 

 tuberculated skin, with its changing hues ; the absence of any 

 tympanum ; the prehensile tail ; and the very peculiarly modi- 

 fied feet. The digits are arranged in bundles of two and three, 

 the manus having the poUex, the index, and the medius, syn- 

 dactylous and turned inward ; while, in the foot, it is the 

 hallux and index only which are thus united and turned in- 

 ward, the three other toes being similarly connected together 

 by integument as far as the ungual phalanges, and directed 

 outward. To these characters may be added the remarkable 

 tongue, capable of protrusion and retraction with almost light- 

 ning rapidity. 



The vertebrae of the Chamoeleons are similar in their char- 

 acters to those of the procoelous K^ionocrania. The sacrum 

 is composed of only two vertebra. Only a few of the anterior 

 ribs are united with the sternum. A large number of the 

 posterior ribs, as we have already seen to be the case in the 

 Gecko, unite together in the mid-line, and form continuous 

 hoops across the ventral wall of the abdomen. 



But it is in the structure of the cranium that the Chamce- 

 leonida depart most completely from the ordinary Lacertilian 

 type. The parietal bone is not movable upon the occipital, 

 the supra-occipital sending up a median ridge, which unites 

 with the base of a corresponding crest or process extending 

 backward for a considerable distance from the middle line of 

 the parietal bone. The summit of this sagittal crest is joined 

 by two curved prolongations of the squamosal, the three 

 giving the occipital region of the Chamreleon its remarkable 

 casque-like form. The frontal bone is comparatively small and 

 single, and the nasals are very narrow, and do not bound any 

 part of the anterior nasal ajDertures. These apertures, in fact, 

 are situated upon the sides of the fore-part of the skull, and are 

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

 stretches outward from the nasal bones ; and external to this 

 by a prolongation forward of the prefrontal bone, which unites 

 with the maxilla, and in some specimens of Chamaeleons is 

 prolonged forward 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 quadrate 

 bone itself is not, as in most other LacertiUa^ movable upon 

 the sides of the skull, but is firmly anchylosed with the bones 



