SERPENTS. 385 



ophidians. The elongated body, though sub-cylindrical anteriorly, is posteriorly com- 

 pressed, the tail often being shaped like a broad paddle. To bring about this struc- 

 ture, the caudal vertebr£e are compressed, and their vertical processes elongated. The 

 head is rather ' indistinct ' in most of the forms, and bears the valvular nostrils, ex- 

 cept in Platurus, on the upper side ; the eyes are small, with a round pupil ; there is 

 no loreal plate, and the general scutellation of the head is regular ; the body scales 

 are small, and may be keeled or tuberculate ; the fangs are of ordinary size, erect and 

 grooved, and followed by other teeth of simple structure. The members of the 

 family inhabit the tropical portions of the Indian and Pacific oceans, and sometimes 

 enter fresh water. All are purely aquatic, spending their whole life in the water, out 

 of which they aj)pear to be blind and soon die {Platurus may be an exception to this 

 statement, as it offers many structural characters opposed to the other Hydrophidse). 

 In their general form the sea-snakes are most admirably adapted for their aquatic life. 

 The compressed body and paddle-like tail not only point to this, but the belly is not 

 rounded as in other ophidians, but sharp, like that of a herring. The ventral scutes, 

 moreover, not being of value for aquatic locomotion, are not Sf)ecialized, oi-, if so, only 

 in a mild degree. The tail, though shaped like that of a fish, is at the same time \>ve- 

 hensile, enabling the animal to rest by winding it about some half-submerged root or 

 piece of coral. The nostrils are so provided with valves, that when the enormous 

 lungs have been inflated, they can be tightly closed, and the animal, with its supjaly of 

 air, can either dive below the surface or rest motionless, being buoyed up by having 

 its specific gravity thus diminished. The position of the nostrils is such as to enable 

 them to breathe without protruding more than the tip of the snout from the water. 

 The armament of scales has been seized upon by the naturalist as offering a means of 

 classifying the several species. While a few have the scales imbricated, like those of 

 terrestrial serpents, the majority have them merely juxtaposed, and often lose their 

 horny covering and become tubei-eular and soft. The shields of the head (exceiDt in 

 JPlaturus, which form is generally exceptional), are so changed as to often lose all 

 resemblance to those of ordinary ophidians. In shedding their epidermis, the sea- 

 snakes resemble the lizards, only a small portion being exuviated at a time. The eye 

 of the sea-snake is so weak that, when the animal is taken from the water, all its at- 

 tempts to strike prove ineffectual. The mouth is so closed by a development of the 

 rostral plate, as to ordinarily prevent the entrance of water, though in some forms there 

 are two small openings for the extrusion of the bif ui'cated tongue. The family pos- 

 sess poison of the most intense virulence, by which they obtain their food, which 

 consists exclusively of fishes. These they seize and sting, the poison affecting the 

 unfortunate animal so that it almost instantly dies, and in a relaxed condition, so that 

 the serpent, in swallowing them, as it does, head first, has no inconvenience from the 

 otherwise erect and rigid spines and barbs with which many pelagic fishes are armed. 

 Though naturally shy, the sea-snake will, when attacked in its native element, dart 

 at the intruder with all the vigor of the indignant terrestrial forms ; but when drawn 

 up in nets they are apparently helpless, the fishermen picking them up and throwing 

 them back into the water with the most surprising unconcern. Many experiments 

 have been made to keep the sea-snakes in aquaria, but they invariably die in a few 

 days. All the forms are viviparous, the young, sometimes to the number of nine, being 

 active swimmers from the first. The adult males may be easily distinguished from 

 the females, as they have on each side of the tail an area which seems to be consider- 

 ably swollen. The natural enemies of the searsnakes are the eagle-rays and rapacious 

 VOL. III. — 25 



