SNAKES OF CEYLON. 135 



muzzle. Body cylindrical, rather short, robust, rough. 

 Belly rounded. Tail moderately long. 



Identification. — The scale rows 19 two heads-lengths behind 

 the head, 19 in midbody, and 17 two heads-lengths before the 

 vent, and a single internasal will establish the genus. 



Habits. — Semiaquatic, diurnal. 



Food. — Chiefly batrachian. 



Breeding. — Oviparous . 



Poison. — ^Non-poisonous . 



Lepidosis. — As detailed under the species schistosus. 



Dentition. — For Indian species. Maxillary : Syncran- 



terian, anododont, coryphodont. Palatine : Anododont, 



isodont. Pterygoid : Anododont, isodont. Mandibular : 

 Anododont, feebly kumatodont. 



Distribution. — America, Tropical Africa, South-east Asia. 



Eleven species have been described, nine of which are 

 American, one African, and one occurs in India, including 

 Ceylon, viz., schistosus. 



Helicops schistosus Daudin. 



(Latin " schistosus" slaty. The name was suggested by 

 the colour shown in Russell's plate.) 



The Olivaceous Keelhack. 



Synonmy. — Coluber schistosus, Pseudoeryx schistosus, Trojd- 

 donotus dimidiatus, T. schistosus, T. maestus, T. s^irgens, 

 Trojddophis schistosus, Atretium schistosum. 



History. — Introduced to scientific notice by Russell in 1801, 

 who figured it in Plate IV. of his second volume. Christened 

 by Daudin in 1803. 



General Characters, — A smallish snake, growing to about 2 J 

 feet. The head is moderate, snout short, subacute, and 



