100 
NATURAL HISTORY. 
[N. ZOOL. GAL. 
the tail is compressed and with a double keel above. In Hydrosaura y 
the nostrils are apical, and in Odatria the scales of the tail are sub- 
spinose. 
The family of Heloderms ( HELODERMiDiE, Case 3) have their body 
and head covered with large convex scales. Unlike other lizards, their 
teeth have a groove behind, like the fangs of serpents; they are said 
to be poisonous, but this may be a mistake, for ignorant persons are in¬ 
clined to believe that all reptiles are dangerous. They come from 
Mexico, and having been seen in a dried state only, the form of their 
tongue is not known. 
The following lizards have an equally lengthened and deeply 
forked tongue, but it only contracts its length, and is not furnished 
with any sheath. 
The family of Safeguards, (Teldje, Case 4,) which have the head 
covered with large shields, and the back and limbs with small scales, are 
confined to the warmer part of the New World. Some have two cross 
folds on the throat with six-sided scales between them; the ventral shields 
are small and longer than broad in Teius; larger and broader than long- 
in Ameiva. Others have a collar of large shields like the Lizards ; in 
Acanthopyga and Centropyx the ventral and collar shields are 
lanceolate and keeled, and the tail is round ; in the former the scales of 
the back are large and in the latter small. The genera Ada and 
Crocodilurus , have a compressed tail with two ridges of scales, and the 
ventral shield is small and long, like the Teii. 
The family of True Lizards, (Lacertidje, Case 4,) which are 
peculiar to the Old World, chiefly differ from the former in their eye¬ 
lids being protected by a bony plate. Many species are found in Europe. 
One species, Zootoca crocea, found on our heaths, is said to hatch its 
young in the body of the mother, if it be kept in a dry place; but to 
deposit eggs, if in a moist one. Some have a distinct collar and granular 
scales on the back, and erect apical nostrils on the side of the nose, 
broad smooth ventral shields, and simple toes, as the Zootoca , which 
have the nostrils in a suture between two scales, and square abdominal 
shield, and Lacerta , which has the nostrils between three scales, and 
the central series of abdominal shields with oblique sides. Teira 
only differs from the former in the central series of abdominal shields 
being square, and in Eremias they are oblique on the sides, and there 
are several preanal scales one behind the other. Others have a distinct 
collar, rather granular dorsal scales, horizontal nostrils in the keel on the 
side of the muzzle, the toes fringed, and the ventral shields oblique, as the 
Scapterice, with the nostrils on the upper edge of the first lateral shield, 
with two small shields above and behind it, and Mesoles , which have 
them between two plates. The Masulince have no collar, but only a 
small axillary p 1 # on each side, lanceolate, keeled dorsal scales, and 
superior subapical nostrils; and lastly, Calrita , Algira and Psamrno- 
dromus have an indistinct collar united to the breast in the middle with 
distinct plaits on the sides and keeled rhombic scales. 
Most of these animals have the faculty of forming a new tail when 
it has been broken off, an accident which often happens in the mere 
exertion of the animal to escape from danger. The new formed tail 
has only a central cartilage in the place of the bones, and is often 
covered with scales different from those of the rest of the tail. If the 
