ZOOLOGICAL GARDENS. 
US 
and they have generally triangular heads, very broad be¬ 
hind, and covered only with scales. The Cobra has the 
power of dilating its neck into what is called the hood, 
and this is brought about by its expanding the long ribs 
of its neck. The other large snake, Ophiophagiis elaps or 
the Snake-eating Cobra, the largest of all the poisonous 
snakes, attaining to about 15 feet in length, has also the 
power of partially dilating its neck. One harmless snake 
can expand its neck, but the expansion is more vertical 
than lateral and is not produced, as in the cobra, by elong¬ 
ated ribs. These bones play a very important part in the 
economy of snakes as these reptiles walk on their ribs 
which are very numerous, occurring from the neck to 
the vent. In each pair, in the higher terrestrial snakes, 
the points are connected below with a ventral plate, the 
posterior margin of which is more or less free, an arrange¬ 
ment which facilitates the climbing of very much inclined 
surfaces. 
All serpents cast their skins, and as the eye of a serpent 
differs from the eye of other animals in having a thin 
pellicle of skin, continuous with the cuticle of the head, 
extended over it, vision, during the process of skin 
casting, becomes much impaired. In a healthy serpent, 
the skin is generally cast entire, but in the Marine Snakes 
it appears to peel off in shreds. This process of shedding 
the skin is frequently repeated, even in one year ; but 
snakes in this habit are not peculiar, as it occurs also 
in the next group to be examined. 
The great division of Lizards or Sauria includes some 
animals very remarkable both in structure and appearance ; 
some being practically without limbs, and so resembling 
snakes, whilst the majority have well-developed limbs. 
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