A MONOGRAPH OF THE SEA-SNAKES (HYDROFHIINjE). 



235 



specimen agrees with Jan's in the failure of the preefrontal 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. After Jan, Icon. Gen., 1872, 41, pi. 1, fig 1. 



Hydrophis polyodontus. — This is only known from Jan's original specimen. The 

 only apparen tdifferences between this and Distira 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 ornata, 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 jerdoni and ecerulescens. 



Distira 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. Prsef rontals , — 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). Supral abials , — 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- 



