SNAKES OF CEYLON. 257 



Cerberus rhyn chops (Schneider). 



(Greek " rhunchos " snout, and " ops " face.) 



The Dog -faced Water Snake. 



Sinhalese : " diyabariya " (Ferguson). 



Synonymy. — Hydrus rhynchops, H. cinereus, Elaps boseformis, 

 Hurria schneideriana, H. bilineata, Coluber Cerberus, C. obtu- 

 satus, Python rhynchops, P. elapiformis, Homalopsis cerberus, 

 H. molurus, H. schneideri, H. rhynchops, H. boasformis, Cerberus 

 cinereus, C. russelii, C. acutus, C. unicolor, C. boseformis. 



History. — Depicted by Russell in his first volume in 1796 on 

 Plate XVII., and again in his second volume in 1801 on Plate 

 XL. Christened by Schneider in 1799. 



General Characters. — As indicated under the genus. 



Identification. — The frontal which is partially, and the 

 parietals which are wholly, broken up furnish an easy means 

 of knowing the snake, but perhaps a more certain method is as 

 follows : A snake which, when laid on its back, reveals well- 

 developed ventrals at least three times the breadth of the last 

 costal row, and at the same time shows three or more rows of 

 costals on each side of the ventrals, will prove to be Cerberus or 

 Gerardia among Ceylon snakes. The former has 23 to 27 scale 

 rows at midbody, and the latter 17. 



Colouration. — The back is bluish gray when the snake is 

 submerged, lightish gray when dry. It is crossed by numerous 

 ill-defined but conspicuous darker bars, involving one to two 

 scales in the length of the snake, the intervals involving five to 

 seven scales. These bars grow less distinct posteriorly, and 

 the foremost are broken up into spots in some specimens. The 

 dorsal colouration ceases abruptly about midcosta, and is 

 replaced by buff subcostally and ventrally. The belly is buff, 

 coarsely spotted, or dappled with deep greenish black. The 

 head is coloured above like the back, and the gray is sharply 

 defined just above the supralabials. The uppei lip and chin 

 are buff. A conspicuous dark postocular streak is prolonged 

 backwards to the side of the forebody. 



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