SNAKES 163 



The Proteroglypha, the snakes in which the anterior 

 teeth of the upper jaw are grooved, are all very poisonous, 

 their fangs communicating generally with very large 

 poison glands ; they inhabit Asia, Africa, and America, 

 and form the bulk of the Ophidian fauna of Australia. 



The group is divided into two sub-families — 



1. The HydrophincE (sea-snakes), which are easily 

 recognized by their strongly compressed, oar-shaped tails. 



2. The Elapinte (land-snakes), with cylindrical tails. 

 The Sea-Snakes inhabit the tropical parts of the Indian 



and Pacific Oceans, spending, with one or two exceptions, 

 their entire existence in the sea. Their most striking 

 feature is their compressed paddle-shaped tail, which in 

 some species is prehensile, enabling the serpents to secure 

 a hold by twisting this organ round sea-weeds and other 

 objects. Their nostrils, which are small, crescentic open- 

 ings with a valve interiorly, are placed on the top of the 

 head, and are opened during respiration and closed when 

 the creature dives. In most Sea-Snakes the scales are 

 feebly overlapping, while, with the exception of the snakes 

 of the genus Platurus, which occasionally go on shore, the 

 plates of the under-surface are rudimentary or entirely 

 absent. The head is very small and covered with large 

 shields. The eye, which is also small, has a round pupil, 

 which contracts when the snake is out of the water, the 

 creature, under such circumstances, becoming partially 

 blinded. Sea-Snakes shed their " skin " at frequent in- 

 tervals, the epidermis not coming off entire, but peeling 

 off in pieces as in lizards. Their prey, which consist 

 entirely of fish and Crustacea, are killed by the action of 

 the poison before being swallowed. The greatest size 



