434 



LOWER VERTEBRATES. 



like, the quadrangular scales arranged in transverse series, and the limbs absent or 

 represented by a single pair of appendages, unprovided with toes and placed at the 

 posterior portion of the abdomen. P. pcdlasi, a timid animal inhabiting the more cen- 

 tral portions of Europe and Asia, seldom wanders far from its retreat, to which it 

 quickly retires on the slightest apprehension of danger. It is said to be especially 

 fond of dark, wooded glens, where it can find the nests of smaller birds, feeding to a 

 considerable extent on their young. In its marking it is dull brown, a shade which 

 well harmonizes with its usual surroundings. P. gracilis, the Khasya glass-snake, is a 

 closely allied form inhabiting the Khasya Hills of India, but differs in being unpro- 

 vided with even the rudiments of limbs. Like other lizards having a longitudinal fold 

 of skin running along the sides, the scaly covering of the back and abdomen is so 

 rigid that it prevents the general distention of the body so characteristic of serpents 



yiJ:^itj^^Sy.% 



Fig. 250. — Ckirotes canaliculatus. 



and some lizards ; food, however, of considerable size is allowed to enter the body 

 through the elasticity of these lateral folds, extensibility being here limited to a special 

 area, like that of Opheosaurus. 



The genus Lacerta is abundantly found in the warmer portions of the Old Woi-ld. 

 These lizards are diurnal in their habits, the eyes being provided with connivant lids ; 

 and they run about over rocks and prostrate logs, seldom or never attempting to lead 

 an arboreal life. The scales are non-imbricate, simply appressed, and the limbs are 

 four in number and well developed. 



L. agilis is a most familiar object of the country in England, as well as on the 

 continent, being popularly known as the gray or sand-lizard. In the warmer portions 

 of Europe these inoffensive creatures are very abundant ; and, though of fair size, 

 being sometimes ten inches in length, they are extremely agile, their movements being 

 so rapid that the eye can with difficulty follow them, as they scamper away over the 



