i8 Journal of the F.M.S. Museums. [Vol. X, 



I therefore group all these together under forma 

 caerulescens (type locality, Vizagapatam) . 



Hydrophis caerulescens caerulescens. 



33 to 43 scales round the neck, 42 to 53 ^ round the 

 body ; ventrals, 253 to 337 ; parietals usually not in contact 

 with the postocular. 



Colour. — Greyish above, yellowish-white below, with 

 from 40 to 60 dark bands which may be incomplete ven- 

 trally. The young have the bands very clearly defined, but 

 with age the markings lose definition, and in some adults 

 are scarcely recognizable, the back being almost uniform 

 grey. Head blackish in the young, darkish grey in the 

 adult, sometimes with a light streak behind the eye -. 



Habitat. — Shores of India and Burma and west coast 

 of the Malay Peninsula, 



Number of specimens examined, 65. Coast of India, 

 9 ; Mergui Archipelago, 2 ; Straits of Malacca, 54. 



The actual variation between my series from the Indian 

 coast and the Straits of Malacca is as follows :— 



India. 35 to 43 scales round the neck, 45 to 51 round 

 the body ; ventrals, 269 to 332. 



Straits of Malacca. 33 to 42 (usually 37 to 39) scales 

 round the neck ; 45 to 51 (usually 45 to 48) round the body ; 

 ventrals, 253 to 319 (average, 290). 



Variation. — The frontal shield in 11 examples is as 

 long- as its distance from the rostral. In 3 examples the 

 posterior chin-shields are absent. The parietal shield 

 touches the postocular on both sides in 3 examples only, 

 and on 1 side in 7 more. 



Specimens from the Gulf of Siam I distinguish as 



Hydrophis caerulescens thai ', subsp. nov. 



Dift'ers from the tj'^pical form in having fewer scale 

 rows round the neck and body, and in the parietals usually 

 being in contact with the postocular. 



31 to 38 (usually 33 to 36) scales round the neck, 38 

 to 49 (usually 41 to 45) round the body ; ventrals, 262 to 

 334. 



Colour. — The dark bands upon the body, although not 

 so conspicuous in adults as in juveniles, do not shew that 

 tendency to become entirely lost with advancing age as in 

 the preceding form. 



Habitat. — Coasts of Siam and Cochin China. 



Number of specimens examined, 42 (Gulf of Siam, 40, 

 Cap St. Jacques, 2) . 



Type. — Adult male, author's number, 1353, collected 

 at Hua Hin, Gulf of Siam, in June 1917. 



^53 is recorded by Wall (Monograph). 



^The presence of this streak is not mentioned by any author, 

 although Giinther very clearly figures it. It occurs in about 30% 

 of my specimens. 



'Thai = Siamese, pronounced tai, 



