174 MAJOR F. WALL, I.M.S., C.M.Z.S. 
is to be seen in the type-specimen of Hydvophis aspera from Singapore now considered 
by Mr. Boulenger as D. cyanocincta, an opinion with whichIaminaccord. ‘This speci- 
men in this respect, asin all other important ones, is exactly like the large specimens 
labelled grandis in the British Museum, which I cannot separate from cyanocineta. 
I cannot derive any help in distinguishing either species or genera from this condi- 
tion, which appears to me one dependent largely upon age, possibly too upon sex. 
RostrRAL.—This is entire in all the genera except Thalassophis, where it is divided 
in one species. A partial, median vertical suture is seen sometimes as an aberrant 
feature in some species, especially in Platurus schistorhynchus.' In Emydocephalus 
ijimeé it may be furnished with a prominent, sharp spine directed forwards (see fig. 4), 
but this only occurs in certain individuals and has, I believe, no relation to sex. 
The portion of this shield reflected backwards on the snout varies in some species, 
but the ranges of variation met with in individuals of the same species overlap so 
considerably that the point is of very limited importance. In Distiva cantoris and 
D. gracilis the visible portion is from two-thirds to greater than the inter-nasal suture, 
and in two other slender-necked species, viz., obscura and fasciata, but little less. In 
nearly all other forms it is less than two-thirds, or even distinctly less than half. 
The contact with surrounding shields is quite constant. Inthe genus Platurus and 
Thalassophis, owing to the presence of internasals, it touches five or six shields, five in 
P. schistorhynchus, six in the rest ; but in all the other genera it touches four shields only. 
The sutures made with contiguous shields are peculiar in Platuvus, the rostro-labial 
being the longest. In Platurus laticaudatus and P. colubrinus again the height exceeds 
the breadth of this shield, whereas in all the other species in the subfamily the reverse 
condition obtains ; but the degree of breadth relative to height is subject to so much 
variation in individuals of many of the same species that I cannot utilise this feature 
in attempting to separate different forms. 
In Enhydrina the lower margin of the shield is projected downwards to be 
received into the gap in the mental region, and this feature is peculiar to this snake only. 
NASALS.—These are present in every species. Their position is of generic impor- 
tance in Platurus only , owing to the presence in this genus of internasals. Here thenasals 
are lateral and separated, and the nostrils lateral ; but in all other genera, except per- 
haps Thalassophis, the species have nasalsin contact with one another on the snout behind 
the rostral, and the nostrils are superior. Where these shields are superior, sutures 
are frequently seen running from the nostril to adjacent shields. These are very in- 
constant in all the species, but there is a decided tendency for a suture to run outwards 
to the supralabials, backwards to the prafrontals, or inwards towards the opposite 
nasal. Sometimes three such sutures may radiate from the nostril, and in so doing split 
each nasal into three parts. The suture running outward is the one most constantly 
seen, and when present it almost invariably runs to the second supralabial. Exceptions 
| A similar condition is seen in a specimen of D. cerulescens in the British Museum presented by Annandale aud 
Robinson from the Malayan Region, 
