XXIII] LACERTA VIVIPARA 569 



by very few species ; in North America the last three are well 

 represented. 



As type we may select the common lizard, Lacerta vivipara, 



which may be seen on very warm days disporting 



LaceiS! 1 ^self sandy and stony places in the south of 



England. On the Continent it and allied species 



are far more abundant : in the south of Europe in summer the 



whole country is alive with lizards. Almost every step in the 



country causes two or three specimens to rush rapidly away into 



some retreat, either a hole under a stone or a cleft in the bark of 



a tree. 



The English lizard has roughly the shape of a Newt, but there 

 is a distinct neck region in front of the fore-limb, and the limbs are 

 sufficiently powerful to completely raise the belly well above the 

 ground and also to run at a comparatively rapid rate. Both manus 

 and pes have five digits which end in sharp claws. The body is 

 covered all over with minute scales (Fig. 279), of which the prevail- 

 ing colour is reddish-brown above, and orange passing into yellow 

 beneath. On the ventral surface and the top of the head the scales 

 are larger and arranged in pairs. The ear-drum is situated at the 

 bottom of a slight pit, which is the first appearance of the outer 

 ear. It is not developed in all Reptiles. 



The anal opening is a transverse slit at the root of the tail 

 behind the hind pair of legs. In front of the thigh the scales are 

 perforated by a row of pores, the openings of the only dermal glands 

 which the lizard possesses. 



Turning at once to the skeleton, we find that the vertebral 

 column consists of procoelous vertebrae. All the 



Skeleton. 



vertebrae articulate with one another by overlapping 

 facets called pre- and postzygapophyses as in Amphibia. 

 Although externally similar to the vertebrae of Amphibia, the 

 vertebrae of the lizard and of Reptiles generally are formed of 

 different elements, as has been explained in the section dealing with 

 Amniota. It is a characteristic of the lizard that the basiventral 

 arch-pieces, which form the cartilaginous intervertebral pads in all 

 Amniota, are partly ossified, and therefore appear in the dried 

 skeleton. In the region of the neck they are termed sub- 

 vertebral wedge bones or intercentra. In the region of the 

 tail they form definite haemal arches and are known as chevrons. 

 The rib has shifted its position so that the capitulum. is attached 



