63 OPHIDIAN EEPTILES. 



priately referred. Indeed, it has been erroneously asserted by 

 some authors to be venernous." 



The Homalopsida are an extensive family of Snakes, of tho- 

 roughly aquatic habits, which are only occasionally found on the 

 margins of rivers ; several of them enter the sea, and in some 

 parts of their organization they approximate to the true marine 

 Snakes. They may be easily recognised by the position of the 

 nostrils on the top of the snout, which enables them to breathe by 

 raising only a very small portion of the head out of the water ; an 

 arrangement which is likewise seen in the Hippopotamus, the 

 Crocodile, the Sea Snakes, and other aquatic animals. Many of 

 them have a distinctly prehensile tail, by means of which they 

 hold on to projecting objects. Their food consists either entirely 

 of Fishes, or, in some species, of Crustaceans also. All appear to be 

 viviparous, and the act of parturition is performed in the water. 

 Not any of them attain a large size about three or four feet in 

 length, or considerably less; and in captivity they refuse to feed. 

 All the Asiatic species of this family have a grooved fang at 

 the hinder extremity of the maxillary bone. The species are 

 numerous, and are arranged into many generic divisions. The 

 majority are from the grand Indian region, extending to China 

 and to Australia, but there are also several from the JNew World. 

 The Herpeton tentaculatum, of Siam, is very remarkable from its 

 snout terminating in two flexible, cylindrical, scaly tubercles, which 

 are supposed to be employed as organs of touch under water 

 perhaps to discern its food, which as yet has not been ascertained. 

 The largest known example of this curious Snake is only twenty- 

 five inches long, of which the tail measures six inches. 



We now proceed to the first family of Poisonous Snakes, that of 



THE SEA SNAKES (Hydropkida), 



Which are very distinct from all that follow, though less so from 

 certain of the harmless species appertaining to the two families 

 last treated of. Some of their distinctions have been already 

 noticed (p. 45), but they are especially characterised by their 

 highly compressed tail, indicative of their thoroughly aquatic 

 habits. According to Dr. Giinther, there is no other group of 



