DIVISIONS OF SNAKES. 39 



as deer and goats. In the Bird class, the famous Serpent-eater, or 

 Secretary-bird of South Africa, is one of their chief destroyers ; and 

 there are various other snake-devouring birds of prey, besides the great 

 African Ground Hornbill — even the Peafowl, sundry Storks, and other 

 waders, seldom fail to attack them when opportunity offers. Compara- 

 tively large birds of the Kingfisher family prey chiefly upon Snakes and 

 Lizards in Australia ; and of Reptiles, besides those Snakes which prey 

 upon others, the Monitor Lizards frequently seize and devour them. 



The series of Ophidians is arranged by our most eminent herpe- 

 tologist, Dr. A. Gunther, into five subordinate groups, which he 

 characterises as follows : — 



I. — Burrowing Snakes, living under ground, only occasionally 

 appearing above the surface. They are distinguished by a rigid 

 cylindrical body, short tail, narrow mouth, small head not distinct 

 from the neck, little teeth in small number, and by the absence or 

 feeble development of the ventral shields. They feed chiefly on 

 small invertebrate animals. Not any of them are venomous. 



II. — Ground Snakes, or species which live above ground, and 

 only occasionally climb bushes or enter the water; their body is 

 more or less cylindrical, very flexible in every part, and of moderate 

 proportions. Their ventral shields are broad. They feed chiefly on 

 terrestrial vertebrate animals. By far the greater number of Snakes 

 belong to this category, and it is represented by many variations in 

 all of the three sub-orders to be noticed presently. 



III. — Tree Snakes, or species passing the greater part of their life 

 on bushes and trees, which they traverse with the utmost facility. 

 They are distinguished either by an exceedingly slender body, with 

 broad, sometimes carinated, ventral shields, or by a prehensile tail, 

 Many of the species are characterised by their vivid colouring, of 

 which green forms the principal part. We shall see, in the sequel, 

 that the first and third sub-orders offer numerous instances of Tree 

 Snakes ; the Tree Snakes of the second sub-order being confined to 

 tropical Africa. They feed on animals which have a mode of life 

 similar to their own ; only a few species on eggs. 



IV. — Fresh-water Snakes, distinguished by the position of the 

 nostrils, which are placed on the top of the snout, and by a tapering 

 tail. They inhabit fresh waters, and are, therefore, excellent swim- 

 mers and divers ; only a few species (which also in external characters 

 approach the following group, that of the true Sea Snakes) venture 

 out to sea. They feed on fishes, frogs, crustaceans, and other water 

 animals, and are viviparous. Not any of them are venomous. 



