LIZARDS AND CHAMELEONS. 



37 



Fig. 38. 



fib 



egg-shell being frequently absent. About 400 species are known, 

 which have been grouped in nearly 30 genera. The family attains its 

 greatest development in the Austral- 

 asian region. 



One of the most remarkable types 

 is the Stump-tailed Skink (Trachy- 

 saurus rugosus, 474, fig. 37), recog- 

 nisable by its large and rough scales 

 and short tail. The Australasian Tili- 

 qua (457-458) includes large species 

 with stout button-shaped teeth. The 

 True Skinks have 5-toed limbs with 

 the lateral toes serrated ; the common 

 species (Scincus officinalis, 463), which 

 grows to about 8 inches, has a per- 

 fectly smooth skin, and wedge-like 

 head. It was once esteemed a 

 sovereign remedy for many diseases. 

 Mabuia (456), with about 40 species, 

 is remarkable for including one semi- 

 aquatic form (M. vittata). The Eyed 

 Skink {Chalcides ocellatus, 462) of the 

 Mediterranean countries, which grows 

 to 10 inches, is a member of a genus 

 in which the lower eyelid has a trans- 

 parent "window," the scales are smooth and shiny, and the limbs 

 short or rudimentary (fig. 38). A series of specimens illustrating 

 the degradation of the limbs is shown. 



Hind-legs of Skinks, to show 

 the gradual abortion. 



a, Chalcides ocellatus. 



b, Chalcides mionecton. 



c, Chalcides tridactylus. 



d, Lygosoma lineo-punctulation. 



e, Chalcides gtientheri. 



Sub-order III. — Rhiptoglossa. —Chameleons. 



Chameleons (446—454) constitute by themselves not only the Case 

 family Chamcdeontidce, but also the sub-order Rhiptoglossa — a group 

 of equal value with the Lacertilia. From Lizards Chamaeleons are 

 distinguished by the structure of the tongue, which is club-shaped, 

 and can be extended to a length equal to that of the whole body 

 (fig. 39) ; and by the form of the head, which is somewhat helmet- 

 shaped. There is no tympanum, or drum, to the ear, and no 

 tympanic cavity. The long limbs are also of a peculiar type, having 

 two of the toes opposed to the other three, so as to form an effective 

 grasping foot (fig. 40). Clavicles, or collar-bones, as well as an 



