A MONOGRAPH OF THE SEA-SNAKES (HYDROPHIINJ'J). 225 



specimens from Burma. I consider the species fairly well differentiated, but it is in 

 most respects extremely like cyanocincta. The prefrontal, however, does not touch 

 the second labial , in which respect it differs from cyanocincta . 



I find the head shields in this species very liable to be broken up, especially the 

 supralabials, and many departures from the type-specimen are, in consequence, to be 

 met with. This I will refer to again 



Fig. 40 — Distira hendersoni. After Boulenger, Joiim. Bomb. Nat. Hist. Soc, vol. xiv, p. 719. 



Distira hendersoni . — This is known from a single specimen from Burma described 

 by Mr. Boulenger. A specimen very like it I referred to under that title in the paper 

 I wrote on the Sea Snakes in the Indian Museum. I remarked at the time upon the 

 very close affinities between this and nigrocinctus (Daudin). Now that I have 

 examined the types of both and the other specimens of nigrocincta in the British 

 Museum. I feel convinced that the two forms are identical, though this view is not 

 borne out by the first glance at the figures I attach herein — the one from Giinther 

 representing one of General Hardwicke's specimens labelled nigrocinctus , and the other 

 reproduced from Boulenger's figure of the type of hendersoni. 



The most important distinction between the two claimed by Mr. Boulenger affects 

 the posterior maxillary teeth, which, he observes, are grooved in hendersoni. I find 

 these teeth also grooved in nigrocincta. In colour and markings the two are peculiar 

 and exactly similar. In the numbers of the scales, ventrals, and in most of the head 

 shields, the two are alike; the apparent differences affecting the latter only, I think, 

 obviously arise from a tendency many of these shields have to division. This same 

 tendency, I may remark, is seen in certain other well defined species, viz., cyanocincta , 

 omata, viperina, etc. It is particularly noticeable in the supralabials and nasals, 

 though by no means confined to these shields. 



The type-specimen of hendersoni has, I consider, the second, third, fourth, fifth 

 and sixth supralabials divided on the left side, and the second, third, fifth and sixth 

 on the right. The upper part of the second Mr. Boulenger considers a loreal, the 

 upper part of the third a prseocular, and the upper parts of the fourth and fifth on 

 the left side suboculars. On the right side the fourth, being undivided, touches the 

 eye; but if my view, which appears to me the obvious one from analogy, is accepted, 

 the third, fourth and fifth labials touch the eye on both sides. Now some of these 

 shields are similarly divided in specimens labelled nigrocinctus in the British Museum , 

 viz., in two out of the three available specimens. (The fourth has been already referred 

 to as a wrongly identified specimen of cyanocincta). In the type, and in Bleeker's 

 specimen, a similarly formed "pseudo loreal" is to be seen on the left side only. 

 In the type-specimen the first supralabial is divided into an upper and a lower part. 



