A MONOGRAPH OF THE SEA-SNAKES (HYDROPHIINM). 199 



Again, I do not share Mr. Boulenger's opinion with regard to the snake figured 

 by Schlegel (Phys. Serp., 1837, plate xviii, figs. 6 and 7) which he considers fasciata 

 (Schneider). The specimen is so faithfully depicted that one can count 21 rows of 

 scales in the neck (fasciata has 25 to 31). It appears to me to agree perfectly with 

 gracilis (Shaw). 



I find the posterior maxillary teeth in this species grooved in at least three well- 

 grown specimens. 



gracilis (Shaw) shares with cantoris (Giinther), a combination of characters which 

 occurs in these two species alone amongst Distirce. The portion of the rostral visible 

 above is nearly equal to or even exceeds the length of the internasal suture ; the fourth 

 infralabial touches two scales only behind, and the ventrals in the major part of the 

 posterior half of the body are grooved or divided in the median line, so that each is 

 represented by a pair of pentagons with apposed bases. The commissure of the 

 mouth seen in profile resembles the italic letter /. (Not well shown in figure 10). 

 Some of these characters are suggested or approached in others of the very slender- 

 necked species, viz., obscura (Daudin), fasciata (Schneid.) and neglecta (Wall), but the 

 ventrals are quite peculiar to gracilis and cantoris. 



Description. — Body anteriorly three-tenths to one-fourth the greatest depth. The 

 last measurement was from a gravid female. 



The head shields show great constancy. 



Rostral, — the portion visible above, three-fourths to greater than the internasal 

 suture. Prefrontal s, — touch the second supralabial (five exceptions on one or both 

 sides). Postoculars, — one. Temporals, — one large anterior succeeded by 

 another even larger shield, the anterior' touching the fifth and sixth supralabials. 

 S u p r al ab i al s, — 6, not subject to division. I nf r a 1 ab i al s, — 4, the last 

 touching two scales only behind; the suture between the first longer than that 

 between the anterior sublinguals. Marginal s, — none. Sublingual s, — two pairs, 

 the fellows of each in contact. Costals, — anterior 19 (17 in two, 18 in three, and 

 21 in one), midbody 27 to 31, posterior 27 to 35; the anterior imbricate, the posterior 

 juxtaposed. Ventrals, — 225 to 298; entire anteriorly and about twice the breadth 

 of the last costral, row divided or furrowed in the median line in the posterior half of 

 the body. Colour, — in the young the head is quite black. The body is surrounded 

 with from 42 to 61 annuli, usually dilated, and often more or less confluent vertebrally, 

 and ventrally especially in the forebody. With age the rings may lose definition, 

 or become much obscured especially ventrally, and the head often assumes a much 

 lighter hue. 



Habitat. — All the specimens I have examined were procured from shores between 

 the Persian Gulf and Mergui on the Tenasserim Coast. 



Distira cantoris (Giinther). 



Liopala fasciata, Gray in Zool. Misc., 1842, p. 60. 

 Hydrophis fasciata, Gray , Cat., 1849, P- 5°> s P ec - C. 



,, cantoris, Giinther, Rept. Brit. Ind., 1864, p. 374, pi. xxv, fig. V. 



