228 



SNAKES. 



(P. colubrinus), with the same distribution, is distinguished by the presence of an 

 unpaired shield on the head, and the arrangement of the scales in from twenty-one 

 to twenty-five rows ; while the third species (P. schistorhynchus), from the China 

 Sea and Western Pacific, differs in having a keel along the hinder half of the 

 lower surface of the body. That the broad-tailed sea-snakes are the direct 

 descendants of terrestrial forms allied to the craits, is proved by their retention of 

 large inferior shields, and by their habits. Xot only are these snakes frequently 

 found at some distance from water, but in Sumatra a specimen was captured 

 nearly a day's march inland. 



Parti-Coloured In common with all the other members of the subfamily, the 



Sea-Snake, parti-coloured sea-snake (Hydrus platyurus) has the nostrils placed 



on the upper surface of the muzzle ; and the under surface of the body and tail 



BLACK-BANDED SEA-SNAKE (f nat. size). 



in this species are scaled like the rest, although in some of the genera traces of 

 enlarged shields still persist. In the skull, the maxilla is considerably longer than 

 the transverse bone, and carries a pair of short fangs, followed, after an interval, 

 by seven or eight solid teeth ; the muzzle is elongated ; the head-shields are large, 

 the nasals being in contact with one another; and the scales on the relatively 

 short body hexagonal in form and with their edges in apposition. This snake 

 attains a length of a yard; and in colour is either yellowish with symmetrical 

 black transverse bands or spots, or uniformly black above, and yellow, with or 

 without black spots below ; the yellow tail being ornamented with either black 

 spots or bars. It is the sole representative of its genus, and has a wider dis- 

 tribution than any other member of the group, ranging over the whole of the 

 Indian Ocean and the tropical and subtropical portions of the Pacific. The 

 tpyical sea-snakes, forming the large genus Hydrophis, differ in having from seven 



