HYDROPHIN^L 233 



All the Proteroglyphe Colubrines are included among 

 Thanatophidia, although the bite of all is not, even when 

 untreated, necessarily fatal. There are about 200 species 

 of them, and they are grouped in two subfamilies, namely, 

 Elapince, or poisonous land-colubrines, and Hydrophina, 

 or poisonous sea-snakes. 



(i) Hydrophince. In the poisonous sea-snakes the tail 

 is very strongly compressed like the blade of a paddle : 

 this, and the poison fangs in the front of the upper jaw, 

 distinguishes them from the aquatic snakes that belong 

 to the harmless and " suspicious " groups. There are 

 between fifty and sixty species of Hydrophinae, and they 

 are restricted to the Indian and Pacific oceans in the 



FIG. 99. 



tropical and warmer temperate latitudes : though their 

 range extends from Madagascar to Panama, their head- 

 quarters, where they abound, lie between the Persian 

 Gulf and the seas of China and North Australia. Off 

 the coasts of India they may sometimes be seen in 

 swarms, like shoals of fish. Though they are thoroughly 

 marine they are fond of estuaries, and may travel a long 

 way up tidal rivers into fresh water : one species is 

 confined to a fresh-water lake in the Philippines : a 

 few species may wander ashore, and in these alone the 

 ventral shields are large, and the nostrils are lateral 

 instead of superior. Sea-snakes of this subfamily are, 

 when caught uninjured, very shy and inoffensive ; but 

 the venom of those species in which its properties have 

 been tested is perhaps the most virulent known. 



