218 



LACERTILIA. 



coiling round twigs and branches to attach the animal. They are all acrodont, 

 The tympanic membrane is hidden, being covered by the integument. The 

 Charngeleons possess the remarkable power of changing the colour of their skin ; 

 the change is dependent on the light-stimulus of surrounding objects, and is 

 subordinated to the will of the animal. Kecent researches, especially those 

 of Briicke,* have contributed to the explanation of this phenomenon. Two 

 different layers of pigment are placed beneath the thin epidermis a superficial 

 layer of clear, yellow pigment, and a deeper layer of dark-brown to black, the 

 mutual extension and position of which varies. Chamceleon vulgaris Guv., 

 South Spain and Africa. 



Sub-order 3. Crassilinguia. With thick and short fleshy tongue, 

 which is hardly indented at the point ; as a rule it is rather rounded, 

 and cannot be protruded. Eyelids are 

 usually present. The tympanic membrane 

 is usually exposed. In all cases there are 

 four limbs, with digits directed forwards. 

 They live exclusively in the hotter regions 

 of the Old and New Worlds. The eastern 

 and western hemispheres contain types 

 surprisingly alike, which, however (with 

 the exception of the Geckos) can be 

 sharply distinguished by their dentition ; 

 all those found in America are pleurodont, 

 those of the Old World are acrodont. 



Fam. Ascalabotae. Geckos. Lizards of clumsy 

 Salamander-like form, and of small size ; with 

 viscous lobes on the digits for attachment, and 

 with biconcave vertebrae. They are all pleuro- 

 dont, and without palatal teeth. They are shy, 

 nocturnal animals, and their eyes are large and 

 without lids. They climb and run very skilfully 

 oa smooth and steep walls, with the help of their retractile claws and the 

 lobes on their digits. They live for the most part in hot countries ; only a 

 few are found in South Europe. They are harmless, but are erroneously con- 

 sidered as poisonous on account of the acrid fluid of their clinging digits. At 

 night they make a loud cry, sounding like the word " Gecko." Platydactylus 

 mauritanicus L. (fig. 643) ; PI. muralis Dum. Bibr. Mediterranean coasts ; 

 Hemidactylus verruculatvs Cuv. Mediterranean coasts ; Ptycliozon homaloce- 

 plialum Kuhl., Java. 



Fam Iguanidae. Leguana. The body, which is somewhat laterally compressed, 

 is supported by long slender legs, which are pre-eminently adapted for climbing. 

 The head is more or less pyramidal, and often raised like a helmet, and of a 

 peculiar shape, in consequence of the possession of a membranous jugular sac. 



* E. Briicke, " Untersuchungen iiber den Farbenwechsel des afrikanischen 

 Chamaeleons," Denkschr. der k. Aliad. der Wissensch., Wien, 1852. 



FlG. 643.Platyductylus mauri- 

 tanicus. 



