SNAKES. 43 



absence or feeble development of the ventral shields. They feed 

 chiefly on small invertebrate animals. Not any of them are 

 venemous. 



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 mode- 

 rate 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 taU.. Many of the species are characterised by their 

 vivid coloration, of which green forms the principal part. "We 

 shall see, in the sequel, that the first and third sub-orders ofier 

 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-rcater Snakes, distinguished by the position of the 

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

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

 swimmers 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 venem.ous. 



V. Sea Snakes, distinguished by a strongly compressed tail, 

 and by the position of the nostrils, which are placed as in the last 

 group. They live in the sea, only occasionally approaching the 

 land feed on marine fishes, are viviparous and venemous. One 

 genus only {Platurus) has the ventral shields so much developed 

 as to be able to move on land. No Oceanic Serpent is known of 

 gigantic dimensions, such as is currently alleged to have been 

 seen by unscientific observers. 



