622 REPTILIA. 
DESCRIPTION OF A LIZARD AS A TYPE OF REPTILES 
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 agz/is) and 
to the viviparous lizard (Lacerta vivipara) :— 
Form and external features.—The depressed head is 
separated from the body by a distinct 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 fur- 
nished 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 cloacal. aperture is 
a considerable transverse opening placed at the root of the 
tail. There is no external ear, but the tympanic membrane 
at either side is slightly depressed below the level of the 
skin of the head. The eyes are furnished with both upper 
and lower eyelids, and also with a nictitating membrane. 
Skin.—As contrasted with that of the frog, the skin has 
a distinct exoskeleton of epidermic scales, the external 
covering of which is shed from time to time. In the head 
region these exhibit a definite arrangement characteristic 
of the species. With the presence of an exoskeleton we 
must associate the absence of the numerous cutaneous 
glands of the frog. Peculiar tubular ingrowths of epidermis 
form a row of so-called “femoral glands,” which open by 
pores on the ventral surface of the thigh. Their product 
{débris of epidermic cells) is most obvious in the male at 
pairing time. The structure of the skin is very similar to 
that of the frog. Pigment is deposited here also in two 
layers, of which the outer is greenish, the inner black. 
Over the parietal foramen on the top of the skull the black 
pigment is absent, the green only feebly represented ; in 
this region, therefore, the skin is almost transparent. In 
moulting—which means casting off the outermost portions 
of the scales—there is a distension of the blood vessels and 
a great increase of blood pressure. 
Many lizards, such as the Chameeleons, exhibit in a remarkable degree 
the power of rapidly changing the colour of their skin, This is due to 
