114 SAURIANS. 



square, in cross bands. Tail long, and generally more or less- 

 compressed. The feet are well developed, with five toes on each, 

 which are armed with strong claws. Most of them live near 

 water, and they are excellent swimmers, their long and com- 

 pressed tail serving as a propeller. Their movements on land 

 are not much less rapid than in the water. Several of the species 

 climb trees, and they are more or less nocturnal in their time of 

 action, though also about by day. They are exclusively carni- 

 vorous, feeding on the different water animals, and on the eggs 

 of birds, and likewise on those of other large reptiles ; some of 

 them are also destructive to ducklings, and to various Snakes. 

 Dr. Giinther remarks that "their external nasal opening leads 

 into a spacious cavity situated in the snout ; when the animal 

 dives, it closes the nasal aperture, and retaining a certain quantity 

 of air in that pouch, or rather in the two pouches, it is enabled 

 to remain under water for a prolonged period without the neces- 

 sity of rising to the surface in order to breathe. It is the same 

 plan of structure -as that with which a large northern Seal 

 (Cystophora borealis) is provided." In like manner, the air-bag- 

 connected with the one developed lung of the Ophidians retains 

 the necessary supply of air during the tedious process of degluti- 

 tion or swallowing. The nostrils are variously placed, either mid- 

 way between the eye and muzzle, or nearer to one or to the other ; 

 and according to this and some other differences, Dr. Gray divides 

 the VaranidcB into as many as seven genera, but Dr. Giinther would 

 seem to admit not more than two genera. When the tail of these 

 Lizards is mutilated, the lost portion is never renewed ; whereas 

 in the preceding families of the Zonuridte, Lacertida, and Teidce 

 a new tail or portion of -one soon sprouts forth but this renewed 

 portion contains no bony vertebrae, and it remains smooth exter- 

 nally ; when the fracture is cleft, -as sometimes happens, two 

 new tails are put forth. Another family of Lizards in which the 

 tail is thus commonly renewed is that of the Geckos ; but never 

 in the IguanidcB^ the Agamidce, and the Chameleonidce, any more 

 than in the Varanidw. The species of this family defend them- 

 selves vigorously, when attacked, by lashing forth smart blows 

 with the tail, as do also the Crocodiles and the larger Iguanidce. 

 In the genus Varanus, the nasal apertures form an oblique 



