A MONOGRAPH OF THE SHKA-SNAKES (HYDROPHIIN 1). 235 
specimen agrees with Jan’s in the failure of the prefrontal to meet the second labial, 
which must be considered an abnormal feature. ‘The same abnormality occurs in 12 
of my 36 specimens; in 4 of these, however, only on one side, the usual contact 
with the second labial occurring on the other. In all respects Jan’s description and 
figure accord with ornata, and so apparently does Fischer’s type. 
Fig. 49.—Hydrophis polyodontus. Atter Jan, Icon. Gén., 1872, 4r, pl. 1, fig 1. 
Hydrophis polyodontus.—This is only known from Jan’s original specimen. The 
only apparen tdifferences between this and Distiva ornata are that it has one anterior 
temporal, and only one pair of chin shields. It appears to me in his figure that the 
lower anterior temporal is confluent with the sixth labial, and hence wanting. As 
regards the one pair of chin shields, in some oynata, the posterior pair is so small that it 
may be considered wanting. For instance, I think the type-specimen of ornata in the 
British Museum can hardly be said to have posterior chin shields. ‘This poor develop- 
ment of the posterior pair is in consonance with what one sees in individuals of other 
species, for instance jerdont and cerulescens. 
Distiva andamanica.—Only one specimen is known, which is in the Indian Mu- 
seum. I have examined it, and find it accords perfectly with specimens of ornata. 
The scales in the neck and body, which Dr. Annandale thought too few, come well 
within the range given by my 36 specimens. 
Description.—The neck is about half to two-thirds the extreme body depth. 
The head shields are constant if one excludes the postoculars, temporals and 
labials. 
Rostral,—portion visible above from about half to three-fifths the internasal 
suture. Prefrontals,—touch the second supralabial (12 exceptions, and in four 
of these on one side only). Postoculars,—two (three in six examples, and in 
three of these on one side only). Temporals,—usually broken up, two or three 
superposed scales occurring anteriorly (in five examples a well-developed single anterior 
shield, in two of these on one side only). Supralabials,—seven or eight, the first 
three entire, but any or all of the rest may be divided; the third and fourth, third, 
fourth and fifth, or fourth, fifth and sixth may touch the eye. Infralabials.— 
four, the last in contact with three or four scales behind, the suture between the first 
usually less than that between the anterior sublinguals. Marginals,—none (one 
after the third on one or both sides in three examples only). Sublinguals ,—two 
well-developed pairs, the posterior fellows separated, or the posterior pair ill- 
