SNAKES OF CEYLON 79 



Lepidosis. — Costals broader than long, small, numerous, 

 and juxtaposed ; with claw-like keels ; larger dorsally than 

 ventrally. Ventrals longer than broad, curved, imbricate, 

 in four or five series along a raised ridge. Head covered with 

 granular scales, and no enlarged shields. 



Dentition. — Maxillary : Anododont and feebly kumato- 

 dont. Palatine : Anododont and scaphiodont. Pterygoid : 

 Anododont and scaphiodont. Mandibular : Anododont and 

 feebly kumatodont. 



Distribution. — The genus includes but one species which 

 inhabits the coasts from Bombay to Indo -China, and the 

 Malayan Archipelago to New Guinea. 



Chersydrus granulatus Schneider. 



(Latin: Adjectival form of " granus "grain, and ' : ulus " 

 diminutive, in allusion to the small scales.) 



The Ghersydrus or Rasp-Skinned Water Snake. 



History. — First referred to by Schneider in 1799- 

 Synonymy. — Hydrus granulatus, Acrochordus fasciatus, A. 

 granulatus, Pelamis granulatus, Potamophis fasciata, Chersy- 

 drus fasciatus. 



General Characters. — As indicated under the genus- 

 Identification. — So different from all other snakes as to be 

 unmistakable. The small scales with harsh chaffy keels, 

 the median ventral ridge formed of four or five transverse 

 rows of scales, and the ring-like closely approximated 

 nostrils are all peculiar to this snake. The top of the head 

 has no enlarged shields- 



Colouration. — Alternately banded with deep brown, and 

 pale buff: rings which are subequal at midcosta. The dark 

 rings are confluent vertebrally. In the young these bands 

 are very strongly Contrasted and conspicuous, and the dark 

 bands black, so that the young snake bears a very zebra -like 

 appearance. There are also light, symmetrically-arranged, 

 small spots on the back of the head, and a larger spot on the 

 temporal region- As age advances the yellow bands become 

 more and more obscure. Many old specimens are uniform, 

 or nearly uniform deep brown- 



