A MONOGRAPH OF THE SEA-SNAKES (HYDROPHILNJE). 211 



are intermediate forms which unite the three supposed species, and am opposed to the 

 view held by all previous herpetologists that such forms should each rank as species 

 apart. This old view seems to me responsible for much of the extreme confusion 

 into which the subject has fallen, and this is not surprising since the characters made 

 use of to differentiate these pseudo-species are precisely those which I have remarked 

 upon above as very variable in individuals of many well defined species of this genus. 

 subcincta (Gray). — This species was described over 60 years ago from the solitary 

 type in the British Museum which still remains the only specimen known. In Mr. 

 Boulenger's key to the genus Distira (vol. hi, p. 287), it is separated from brugmansii 

 on two points, vi z. } that the neck scales in subcincta are 23 to 25, in brugmansii 27 

 to 31, and that the frontal is hardly as long as its distance to the rostral in subcincta , 

 whereas it is as long or longer in brugmansii . To make any reference to the length 

 of the frontal as a distinction between these two supposed species amounts to an 

 eloquent admission of the extremely close resemblance between them, for the length 

 of this shield in brugmansii by Mr. Boulenger's own showing varies considerably, 

 viz., between its distance to the rostral and its distance to the end of the snout. I 



ABC 

 Fig. 20. — Distira subcincta. After Giinther, Rept. Brit. Ind., pi. xxv, fig. F. 



can find no points of difference in the two species, nor does Mr. Boulenger mention 

 any in his detailed descriptions other than those already referred to, and I cannot doubt 

 that this solitary specimen of subcincta should, therefore, be considered a spiralis vel 

 brugmansii. The 'ow number of neck scales is not by itself sufficient to form the basis 

 of a distinct species, and, moreover, agrees with that of some specimens of melano- 

 cephalus, which I am unable to separate from spiralis. 



The colour of subcincta is unusual, in that there are round costal spots below the 

 dorsal bars, a peculiarity, however, not necessarily opposed to its inclusion with spiralis, 

 since an exactly similar colour variety is included by Mr. Boulenger with his species 

 ornata . a form usually characterised by dorsal bars. 



melanocephalus (Gray), described in 1849 from a single specimen in the British 

 Museum , remained the sole representative till 1901. In that year I saw in Mr. Owston's 

 collection 19 specimens from the Loo Choo Islands which I examined (nine in detail) 

 and identified as D. robusta (Giinther), i.e., brugmansii (Boie). One of these I sent to 

 the British Museum and learnt from Mr. Boulenger he considered H. melanocephalus. 

 This species, in his catalogue description, differs from brugmansii in two points only, 

 viz., that the head and fore-body are smaller and the neck scales fewer in number in 

 melanocephalus . 



I have re-examined the specimen I presented to the British Museum, and find 



