386 LOWER VERTEBRATES. 



sharks. Specimens of cicrht feet in lensith are eomnuni, ■while there is a sinsle in- 

 stance of one measuring twelve feet, — far too small, it will lie seen, for the sea-serpent 

 of the newspaper. 



The genus Platurus, though found upon the high seas, has so many points of struc- 

 ture in common with the terrestrial, as well as at variance with the marine, serpents, 

 that its position is that of a connecting form vmiting the Elapidse with the Hydroph- 

 idae. The sub-cylindrical body, the smooth, imbricate scales, the well-developed ven- 

 tral scutes, the divided sub-caudals, as well as the general physiognomy, — the cleft 

 of the mouth being horizontal, while other sea-snakes have it turned up posteriorly — 

 are characters which answer equally W'ell for the members of the previous family. 

 The scutellatiou of the head is quite regular ; there are two pairs of frontals, seven 

 labials, no loreal, and the nostril is lateral, a position unique in Hydrophida', and 

 pointing to a partly terrestrial life, though positive information as to this habit has 

 not been obtained. The poison fang is small and generally stands alone, though occa- 

 sionally a small tooth can be found some little distance back. Platurus scutatus 

 inhabits the Indian seas from southern India and Cliiua to Xew Zealand. It some- 

 times reaches a length of five feet. P.Jischeri is a smaller form, having a geographi- 

 cal range of less extent, and is not found on the southern shores of Australia, though 

 it extends further east, having been observed near the New Hebrides. 



The genus Aipi/surus is found around Australia and the neighboring islands. It 

 has the body compressed, the cervical scales divided, the nostrils opening superiorly, 

 and each surrounded by a nasal plate. The scales are of moderate size and may be 

 either smooth or tuberculate ; the ventral scutes are well developed and have a longi- 

 tudinal median ridge ; the sub-caudals are undivided. A. anguiUwfonnis inhabits the 

 Javan seas and reaches a length of two feet. The upper jsarts are brownish, orna- 

 mented with cross-bars of yellow, and the tail is terminated by a large shield-like 

 scale. A. kevis has tlie terminal scale very large, and is of a uniform brown color, 

 inhabiting the seas around Xew Caledonia and Xew Guinea, where it sometimes 

 reaches the length of five feet. Emijdocejjhalus inhabits the Australian seas and is 

 characterized by having the ventral shields large, and with only a slight median ridge, 

 the labials are reduced to six, and the imbricate scales are tuberculate. The tail ends 

 in two large denticulated scales. The tortoise-headed ringed sea-snake, Ernydocepha- 

 lus amiulatus, reaches a length of thirty inches. The head is covered with rounded 

 plates, and the body is encircled by thirty-five black and as many more white rings. 

 -27. tuberculatus, the tortoise-headed brown sea-snake, is about the same size as its con- 

 gener, but differs from it in having a longer head, larger and more tuberculated scales, 

 and in being of a uniform pur])lish brown color, mottled with lighter .spots .along the 

 sides. Of Dit-teira Init a single specimen has been taken, the locality of which is 

 unknown. It has the nasal shields separated by the frontals ; and the ventral shields, 

 though narrow, are distinct. A. cah/ptus is also an extremely rare ophidian, inhabit- 

 ing the southwest Pacific ; only two specimens are known. In length it measures 

 about two feet. 



Much different is the distribution and abundance of Si/drop/iis, a genus character- 

 ized by having the head of moderate length and well provided with shields, and the 

 lower jaw without an anterior notch. There are enumerated of this genus as many 

 as thirty-five species which are easily determined by reference to their general form 

 and armament, the shape of the head, and the arrangement of the cervical plates. 



Sydrophis cyanocincta, the form selected for illustrating the genus, is jaopularly 



