476 REPTILES. 



There is a urinary bladder and a double penis. 



Most are oviparous, but in a few the eggs are hatched 

 within the body. 



They are usually active agile animals, beautifully and often 

 protectively coloured. 



The caudal region is often very brittle ; lost tails and even 

 legs may be regenerated. 



The food generally consists of insects, worms, and other 

 small animals, but some prey upon larger animals, and 

 others are vegetarian. 



Most are terrestrial, some arboreal, a few semi-aquatic, and 

 there is one marine form. 



Lizards are most abundant in the tropics, and are absent 

 from very cold regions. 



Some Peculiarities in the Skeleton of Lizards (mostly quoted 

 from Huxley). 



The epidermic exoskeleton of scales is sometimes, as in Cycloiius, 

 associated with scutes or ossifications in the dermis. In Geckos and 

 Amphisbsenas there is hardly any exoskeleton. 



Except fhe Geckos, all living Lizards have proccelous vertebrae. The 

 sacral vertebrae, two or rarely three in number, are not fused. Under- 

 neath the vertebrte, in the anterior part of the tail, there are usually 

 special " chevron " bones. In many cases there is an unossified septum 

 across the middle of each caudal vertebrae, and it is across this that the 

 tail so readily breaks. 



In the skull, there is an interorbital septum except in Amphisbaenas, 

 there are no alisphenoids nor completely ossified presphenoid or orbito- 

 sphenoids, there is usually an unossified parietal foramen on the roof of 

 the skull, in most an epipterygoid (or " columella") runs from the parietal 

 to the pterygoid, in most there are prominent parotic processes formed 

 from prolongations of the opisthotics, pro-otics and ex-occipitals, with 

 the outer end of one of these processes the quadrate articulates, and is 

 usually movable, the fronto-parietal region is often slightly movable on 

 the occipito-sphenoidal part, the quadrato-jugal is usually represented 

 by ligament only, from the union of the palatine and pterygoid a trans- 

 verse bone extends to the maxilla, the two rami of the lower jaw are in 

 most cases firmly connected. 



Teeth occur on the premaxillae, maxillae, and dentaries, and sometimes 

 also on palatines and pterygoids. They generally become fused to the 

 bones which bear them. When they are attached by their bases to the 

 ridge of the jaw, the dentition is described as acrodont ; when they are 

 attached by their sides to the side of the jaw, the dentition is described 

 as pleurodont. 



