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—eyven 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. Giinther, into five subordinate groups, which he 
characterises as follows :— 
l.— 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.—7Zree 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. 
1V.—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. 
