410 WHALES, SEALS, AND SEA-SERPENTS 



virulently poisonous, and fierce in their attack ; and my 

 old master, Sir Wyville Thomson, used to tell comical 

 tales of the panic they sometimes caused among the 

 naturalists of the " Challenger/' when he and his col- 

 leagues were wading among the coral reefs. They are 

 adapted in various ways for their aquatic life. The 

 head is small and pointed ; the belly is not flattened 

 like that of an ordinary snake, but sharp or keeled 

 like that of a herring ; the tail is flattened like that of a 

 fish, but is at the same time prehensile, and the snake 

 clings by means of it , like a little sea-horse, to weed or 

 coral. The lungs are of great size, and the nostrils have 

 valves which can be tightly closed, so that, on the one 

 hand, the creature can dive with safety, and on the 

 other hand it may float motionless on the surface, 

 buoyed up by its store of air. They are all viviparous. 

 They feed on fishes, and it is said that the instant effect 

 of their poison is to relax the whole body of the fish, 

 so that it may be safely swallowed head foremost, its 

 spiny fins offering no obstacle in their relaxed condi- 

 tion. There are many kinds of sea-snakes, belonging 

 to several different genera. They are in most cases 

 brilliantly coloured, often in alternate rings of black and 

 white, sometimes adorned with green and yellow. In 

 Indian and other eastern harbours the passenger may 

 at times recognize their slender and gaudy shapes, 

 swimming in the clear water. The widely distributed 

 Hydrus platurus (or Pelamys bicolor), a rather small 

 species, conspicuous with its yellow belly, and the 

 much larger Distira cyanocincta, more or less annulated 

 with black, are perhaps the oftenest seen. Many 

 species are over a yard long, and the largest, D. grandis 

 (from Malay and North Australia), is about 8 feet long. 

 Specimens 12 feet long are said to have occurred. 

 The sea-serpents of Aristotle and of Pliny seem to 





