A MONOGRAPH OF THE SKA-SNAKES (HYDROPHflNsE). 



249 



A B C 



Fig. 64. — Hydrus platurtis. 



I have examined 47 specimens besides those in the British Museum. I find the 

 posterior maxillary teeth grooved. 



Description. — Rostral, — the visible portion above one quarter to one half 

 the internasal suture. Prefrontals, — touch the second supralabial (rarely the 

 third also). Front a 1, — sutures subequal, or the fronto-supraocular rather the longest. 

 Post oculars, — one or two. Temporals, — absent, replaced by small scales. 

 Supralabial s, — seven to ten very irregular, the third and succeeding shields very fre- 

 quently divided, two sometimes three touch the eye, viz., the third, fourth or fifth. 

 Inf ralabials, — five or six, the last in contact with three or four scales behind. 

 Marginals, — none. Sublinguals, — small, an anterior pair usually more or less 

 distinct, but widely separated, a posterior pair still less distinct if recognisable at all 

 as such. Costals, — anterior 40 to 54, midbody 45 to 62, posterior 41 to 52 juxta- 

 posed everywhere. Ventrals, — -370 to 440, small but rather larger than the last 

 costal row, very irregular, many being divided. 



Colour*.— Vary variable. I quote from Boulenger's Catalogue (1896). 

 " A. — Yellow, with brown, black edged cross-bands ; black bars between the cross- 

 bands on the sides of the belly (P. ornata, Gray). 



B. — Anterior third of body with a black dorsal stripe ; further back, a series of 

 transverse dorsal rhombs on the back, and black spots on the sides and belly. (Var. 

 metadata, Jan). 



C. — -Dorsal region black ; sides and belly yellow, with a lateral series of black spots, 

 which may be partly confluent into a stripe ; tail with dorsal and lateral spots. 



D. — Dorsal region black, ventral region brown, the two separated by a yellow 

 lateral stripe ; tail spotted as in the preceding.' 



E. — Black above, sides and belly yellow ; tail spotted as in the preceding (H. bi- 

 color, Schn.). 



F. — Yellow, with a black vertebral stripe, broken up into spots posteriorly; no 

 lateral spots on the body or tail. 



G. — Yellow, with a vertebral band and spots on the tail pale brown or olive." 



Habitat. — The tropical area of the Pacific Ocean, and connected waters. In Asia 

 the litoral from the Persian Gulf to Yezo (N. Japan). In Africa the East Coast 



1 A modifier! form of this without the yellow lateral stripe occurs. One such is No. 153 in the Colombo Museum. 



