HYDEOPHIS GRACILIS. 373 



Htdrophis diadema. (Plate XXV. fig. S.) 



Head very small and narrow, more than twice as long as broad ; neck very slender, its 

 length being rather more than one-third of the total. Rostral shield of moderate size, much 

 broader than long ; two postoculars ; the third upper labial is not in contact Avith the nasal. 

 Two large temporals on the side of each occipital. Two pairs of chin-shields, which are in 

 contact with each other. Thirty-three seiies of scales round the neck. Scales slightly 

 imbricate, with the apex truncated, and with a small central tubercle. Ventral shields 

 distinct, but only those on the thin portion of the body are twice as large as the scales of the 

 adjoining: series; they are 318 in number. Four anal shields, the outer of which are very 

 large. Trunk with sixty-two blackish rings, which are broader than the interspaces between 

 them, broadest on the back, and narrow and much paler on the belly. Head blackish above, 

 with a yellow band over each superciliary and the temple ; the two bands convergent ante- 

 riorly, and meeting on the frontal shields. Lower jaw and belly yellowish ; tail with from 

 seven to nine blackish cross bars. 



The three specimens which I have examined are in the British Museum ; it is not known 

 where they were captured ; the largest is 32 inches long, the cleft of the mouth measuring 

 5 lines, the tail 3f inches. 



Htdrophis gracilis. 



Russell, ii. tab. 8. 



Hydrus gracilis^ Shaio, Zool. iii. p. 560. 



Hydrophis obscurus, Daud. Kept. vii. p. 375. 



? Microcephalophis gracilis, Less., in Belang. Voy. Ind. Orient. All. Rept. pi. 3. 



Microcephalophis gracilis, Gray, Viper. Snakes, p. 46. 



Thalassopliis microcepliala, Schmidt, Abhandl. Naturw. Hamb. ii. p. 78. taf. 2. 



Hydrophis microcepliala, Fischer, ibid. iii. p. 52. 



Head very small, narrow ; neck very slender. Rostral shield cutting in front ; one post- 

 ocular ; the third upper labial not in contact with the nasal ; two large temporal shields along 

 the side of the occipital. Two pairs of chin-shields, in contact with each other. Nineteen 

 to twenty-one series of scales round the neck ; scales provided with central tubercles. The 

 ventral shields are twice as large as the scales of the adjoining series on the slender anterior 

 part of the body ; the ventral shields of the compressed part are split into two, both halves 

 being first opposite to each other, and alternate posteriorly. They are 228-(247-254-)294 

 in number ; six small anal shields. Anterior part of the body surrounded by blackish rings, 

 which become very indistinct posteriorly. The hinder half of the body is greenish olive 

 above and whitish below ; sometimes traces of darker cross bands extending downwards to 

 the belly are visible. Throat, anterior ventral shields, and crown of the head blackish, sides 

 of the head and snout lighter. 



A young specimen has forty-one rhombic black cross bands, continued on to the belly, but 

 subinterrupted on the sides ; head, ventral shields, and posterior part of the tail black. 



