SNAKES. 183 
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(3) The Tree Snakes are extremely active, wonderful climbers, 
and spend the greater part of their time in trees. They are the 
most strikingly coloured of all the Ophidians, their colouring 
frequently closely resembling that of their surroundings. Their 
body, which is often very slender, is seldom cylindrical, but 
frequently compressed, Their eyes, with exceptions, are beauti- 
ful and large, and for their size these creatures generally possess 
an enormous gape of mouth. Their food, asa rule, consists of 
those animals which lead an arboreal life, such as tree-frogs and 
birds. The members of this group are both poisonous and non- 
poisonous ; the latter being more numerous than the former. 
(4) The Freshwater Snakes are naturally good swimmers and 
divers. Their nostrils are arranged to suit their manner of life, 
being placed on the top of the nose, and possessing the power of 
closing at will, or when the animal is under water. Their 
cylindrical and rather long body is provided with a tapering tail 
and ventral scutes, which are narrow. Their head is short and 
rather flat, and the eyes are small. These Snakes, which do not 
often leave the water, are natives of the tropical and sub-tropical 
parts of the world. They are non-poisonous, and bring forth 
their young in the water. 
(5) The Sea Snakes are beautifully adapted for their mode of 
life. Their valvular nostrils are placed on the top of the snout ; 
and their prehensile tail is so strongly compressed as to resemble 
a kind of vertical fin. As the creatures, with one exception, 
according to Dr. Giinther, never leave the sea, they need no 
ventral scutes, and therefore possess none. The lower part of 
their body is shaped somewhat like the keel of a boat. Their 
eyes are very small, and their scales are not tiled or only slightly 
so. This arrangement of the scaling, of course, assists their 
movements in the water. All these snakes are poisonous, and 
cannot be kept in captivity. They belong to the tropical part of the 
world, and of that, the Eastern Hemisphere. They feed on 
marine animals and are viviparous. 
Most Snakes lead a diurnal life ; those which are active during 
the night may generally be known by the pupils of their eyes 
being contracted into a vertical slit ; sometimes this slit is hori- 
zontal in position. Some snakes are ovoviviparous, others are 
