A Descriptive List of the Sea Snakes (Hydrophiidse) in the Indian. Museum, Calcutta. 



(With two plates). 

 By Captain F. Wall, I. M.S., C.M.Z.S. Cormnumcated by N. Annandale. 



[Read March 7th, 1906.] 



The classification of the sea snakes has proved to all observers a most difficult task, 

 in fact has given more trouble than that of any other Ophidian family. No two authors 

 have expressed similar opinions, and some idea of the confusion which has, in conse- 

 quence, arisen, may be gained by taking a single example, viz., Distira cyanocincta. This 

 species, as now regarded by our greatest living authority Mr. Boulenger, comprises no 

 fewer than 16 forms, all of which have been deemed by one authority or another distinct 

 species. 



Naturally the confusion existing in the minds of experts, whose views have appeared 

 in print, has been transmitted to those of humbler attainments seeking information, and 

 many of these with whom I have been personally acquainted, declare the task of identifi- 

 cation from the books at present available quite hopeless, and this is very decidedly my 

 own opinion. This argues either a very considerable degree of variation in individuals 

 of the same species, or badly arranged methods of identification. 



Now individuals of the species in this family are not subject to any greater variation, 

 in their essential features, than those of other families, so that I feel sure it is the keys 

 that are at fault. They, undoubtedly, require amplification and simplification. 



I have lately had opportunities of examining all the sea snakes in the Bombay 

 Natural History Society's Museum, as well as some 30 odd specimens collected by Mr. 

 J. R. Henderson in Madras. More recently the kindness of Colonel A. Alcock, I. M.S., 

 F.R.S., and Dr. Annandale, has given me access to the very large collection in the Indian 

 Museum, and, as a result, my recent observations, grafted upon those made upon other 

 collections in the past, lead me to think I can very materially elucidate this perplexed 

 subject. 



I am decidedly of opinion that the descriptions given in the works of our best-known 

 authors, with one solitary exception, viz., Mr. Boulenger, are too imperfect and too in- 

 definite to hint at, much less indicate, the species under reference in many cases, and for 

 this reason I adopt Mr. Boulenger's terminology in the present paper. 



Even this great authority, I venture to think, has not been very happy in his choice of 

 distinguishing characters, at any rate from the ordinary inquirer's point of view, for his 

 most important guides are precisely those which are most difficult and troublesome to 

 investigate, viz., the counting of the costal scales and the ventrals. The latter some- 

 times exceed 500. Again, in adopting the same routine method of description which he 

 applies to the land snakes, he reiterates with each species many characters (in relation 

 to head-shields particularly) which have no weight in separating the species of this 

 large family, and, whilst giving these undue prominence, fails to make mention of many 

 others which are most striking and of the greatest value. In some instances a character 



Mem. A.S.B. 4.6-06 



