A MONOGRAPH OF THE SEA-SNAKES (HYDBOPHIINJE) . 193 



Frontal, — touches six shields ; the fronto-parietal sutures are longest, the fronto- 

 praefrontal shortest. Nasals, — touch the first and second supralabials ; sometimes 

 two or more sutures radiate from the nostril and subdivide this shield, forming a 

 pseudo-loreal or other pseudo shields, Prse oculars, — one. Postoculars, — one 

 or two. Temporals, — one, two or three superposed small shields. Supralabi- 

 als, — irregular; the anterior two to five are well developed, the rest small, occasioned 

 by horizontal sub-division, the extent to which this occurs affecting the contact with 

 the eye, and the number of postoculars and temporals ; the third and fourth usually 

 touch the eye, sometimes the fifth also, more rarely the fourth only, or none at all 

 touch the eye. Infralabial s, — the fourth or fifth is the largest of the series, and in 

 contact with three or four scales behind. Marginals , — absent. Sublingual s, — 

 imperfectly developed, but an anterior pair at least can usually be discerned, the fellows 

 of which are widely separated. Costals, — anteriorly 40 to 60, midbody, 50 to 70, 

 posteriorly 50 to 70 ; sub-imbricate, or imbricate. Ventrals, — 230 to 314, little 

 larger, or not as large as the last costal row. Colour, — very variable. The young 

 are bluish or bluish-grey with many well defined, black annuli, often dilated vertebrally. 

 As age advances these bands become more and more obscured, first disappear- 

 ing ventrally, and so converted into dorsal bars, which in old specimens may dis- 

 appear altogether. In old adults the dorsum is frequently a uniform bluish or bluish- 

 grey, merging at midcosta to yellow or yellowish ventrally. Both dorsal and ventral 

 hues again are subject to much modification according to whether the specimen has 

 recently desquamated or is about to do so. In the latter case the yellow on the belly 

 becomes often tinged with brown. 



Habitat. — From the Persian Gulf, through the Indian and Malayan region to New 

 Guinea. 



The post maxillary teeth I find all grooved. 



DISTIRA. 



Having failed to discover a single species in which the posterior maxillary teeth 

 are ungrooved, I have no course open to me but to unite the two genera Hydrophis 

 and Distira (held by Mr. Boulenger to be distinct on this understanding) ; and as 

 Distira is the older title, I retain this name to designate the genus. 



I cannot but think, judging from external characters, that osteological differences 

 will be discovered, to separate the slender-necked species from those of more even 

 relative proportions, and I also expect to discover anatomical grounds for the isola- 

 tion of viperina and jerdoni from the other species herein included in this genus. 

 There seems to me sufficient justification for doing so on external characters alone ; 

 however, I prefer for the present to let them remain as placed by Mr. Boulenger. 



