100 REPTILES AND BIRDS. 



the two genera Circosaura and Lepisoma — of which the first com- 

 prises some two or three species only. All of these reptiles have 

 exceedingly long tails, though not so inordinately long as in the 

 Lacertidce of the genus Tachydromus. 



Certain other families have a distinct longitudinal fold, covered 

 with small granular scales on each side. These are the families 

 Chalcidce, Holaspidce, and the more extensive one of Zomiridce. 

 The Chalcidce. have the head covered with regular many-sided 

 shields, and the lateral fold is indistinct ; limbs small and rudi- 

 mentary, and the hind feet are undivided in the genera Chalcis and 

 Bachia, with three tubercles in place of toes in Microdactylias, and 

 with four clawed toes in Brachypus. Each of these genera is 

 founded on a single species, and all are doubtless peculiar to the 

 New World. The Holaspidce is also founded on one species only, 

 the Holaspis Guentheri, which again is supposed to be South 

 American. It has four well-developed limbs, a double row of 

 plates along the back and upper surface of the tail, and the latter 

 organ is curiously serrated laterally. 



The Zonuridce constitute a considerable family, to which some 

 eighteen or twenty genera are assigned, and which present consider- 

 able modification of form. The ears are distinct, whereas, in the 

 Chalcidce they are hidden under the skin. The head is pyramidal, or 

 depressed, and covered with regular many-sided shields ; eyes with 

 two valvular lids. Limbs mostly well-developed, but short in some, 

 and rudimentary, or even wanting, in the so-called Glass Snake which 

 constitute the sub-family Pseudopodince. There is no external 

 trace of them in the North American Glass Snake, Ophisaurus ven r 

 tralis ; and in the Old World genus, Pseudopus, there is only one 

 pair, posterior, rudimentary, and undivided. These Reptiles are long, 

 and serpentiform in shape; whilst in ,other Saurians the whole skin 

 of the belly and of the sides is extensible, the extensibility is limited 

 in the Glass Snakes to a separate part of the skin ; and, as Dr. 

 Gunther remarks, "the scaly covering of the upper and lower parts 

 is so tight that it does not admit of the same extension as in Snakes 

 and other Lizards ; and the Pseicdopus, therefore, could not receive the 

 same quantity of food in its stomach .as those animals, were it not for 

 the expansible fold of the skin running along each side of its trunk." 

 One species of Pseudopus, the P. Pallasii, inhabits Asia Minor and the 

 south-east of Europe ; and there is another, P. gracilis, in the Indo- 

 Chinese countries (or those lying eastward of the Bay of Bengal). A 

 second sub-family, Gerrhonotince is peculiar to America, and consists 

 of more ordinarily-shaped Lizards, which are ranged in four genera. 



