570 REPTILES. 



Some Peculiarities in the Skeleton of Lizards (mostly quoted 

 from Huxley). 



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

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

 Amphisbsenas there is hardly any exoskeleton. 



Except the Geckos, all living Lizards have procoelous vertebrae. The 

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

 neath the vertebrae, 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 vertebra, and it is across this that the 

 tail so readily breaks. 



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

 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 pterygoicl, 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 premaxillas, maxilke 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. 



DESCRIPTION OF A LIZARD. 



The following description applies especially to the long- 

 tailed green lizard (Lacerta viridis\ found abundantly in 

 Jersey, but, except in minor points, it will be found to apply 

 equally to the small British grey lizard (Lacerta agilis) and 

 to the viviparous lizard (Zootoca vivipara). 



Form and External Features. 



The depressed head is separated from the body by a dis- 

 tinct neck, but the posterior region of the body passes 

 gradually into the long tail, which is often mutilated in 

 captured specimens. Both fore and hind limbs are present, 

 and both are furnished with five clawed digits. Of the 

 apertures of the body, the large mouth is terminal, the 

 external nares are close to the end of the snout, and the 



