400 BULLETIN 58, UNITED STATES NATIONAL MUSEUM. 



The high, compressed tail, shaped Hke the blade of an oar, dis- 

 tinguishes these snakes at once from all others and stamps them as 

 inhabitants of the water. As a matter of fact these snakes are not 

 only aquatic, but truly marine, some of them to an extent that 

 renders it correct to designate them as pelagic. 



Not only has the shape of the tail become specialized in these 

 snakes, ])ut the whole body is strongly compressed in some; in others 

 the general shape has been greatly modified, so that the whole posterior 

 portion of the body is abnormally enlarged while the front part is 

 drawn out into an excessively elongated and narrow neck finished 

 off with a small head not wider than the neck. Owing to the com- 

 pressed form of the body the ventrals have been reduced in most 

 of the forms to an extent which makes it difficult to recognize them 

 as such. Even the scales of the body have become highly altered in 

 many forms, being polygonal and juxtaposed with short keels or 

 knobs or spines, sometimes in pairs, and totally unlike the scales of 

 other snakes. That the nostrils are placed on top of the snout and 

 provided with valves it is scarcely necessary to mention. 



Not all the species are as greatly differentiated as above mentioned. 

 A small group, the habits of wliich are still partly terrestrial, live 

 near the shores and occasionally and temporarily climb among the 

 rocks or even sometimes venture farther inland. These have still 

 fairly well-developed ventrals to some extent fit for terrestrial 

 locomotion, and their scales are imbricate. To this group belong 

 the genera Laticauda and Emydocephalus. 



Being ''proteroglyph, " all these marine snakes are poisonous. 

 Nevertheless, several forms are perfectly harmless to man, such as 

 the Laticauda occurring so frequently around the Riu Kiu Islands 

 wliich the fishermen handle without fear and without accident. 



The sea snakes, broadly speaking, inhabit all the tropical and sub- 

 tropical seas outside of the Atlantic Ocean. In spite of much good 

 work of late in this group, the species and their distribution are as 

 yet but poorly understood. The lack of definite boundaries to their 

 habitat and their liability to be carried beyond their natural limits 

 by currents make it difficult to decide how many species to include 

 in the present work. It has therefore been thought best to take 

 cognizance of a few more species than have actually been recorded 

 from the coasts of the territory covered by this work, when they are 

 known to occur in the adjacent seas. Such species, however, have 

 been included in brackets. 



Doctor Boettger, in 1888 (Zool. Anz., pp. 395 seq.), published a 

 paper on the external sexual characters of the sea snakes based upon 

 an examination of 46 specimens belonging to two genera {Disteira 

 and Lapemis), all from the Philippine Islands. He came to the coji- 



