HERPETOLOGY OP .TAPAN, 441 



boundary between the two colors being a straight Une until a short dis- 

 tance in front of the vent where it becomes wavy; top of head like 

 back, supralabials like underside, lower labials washed with brown; 

 tail straw-yellow, with a series of about six dark brown roundish 

 blotches along the upper and the lower edge and a median series of 

 smaller ones on the sides. 



IHitiensions. 



mm. 



Total length 609 



Snout to vent 528 



Vent to tip of tail 81 



Width of head across center of eyes 14 



Length of shielded portion of head 31 



Greatest height of body 38 



Greatest height of tail 20 



The males have a somewhat slenderer body, fewer scale rows, and 

 the scales have a central tubercle. 



Variation. — This species is exceedingly variable; especially the 

 shields of the sides of the head are subject to so numerous modifica- 

 tions that it is hardly profitable to enumerate them in view of the 

 striking aj)pearance of this snake, which makes the identification of the 

 species one of the easiest. It may l)e mentioned, however, that the 

 supralabials may vary between 7 and 1 1 ; one or more loreals may be 

 present; suboculars may be present or not; two anterior chin-shields 

 may be sometimes recognized in a pair of enlarged scales never in con- 

 tact, however. In our specimens the number of scale rows varies 

 between 49 and 61, the higher figures belonging to the females, while 

 Boulenger gives 45 to 47 as the normal number. 



The coloration is also very variable, and mention has already been 

 made of the spotted form from the Indian Ocean (p. 440) . In the black- 

 backed form which is the only one found in the eastern waters, the tail 

 is most subject to variation, inasnuich as the spots on the upper and 

 lower edges may join so as to form ])lackish cross-bands, or they may 

 disappear on the lower edge entirely. In many specimens there may 

 be seen on the sides between the blackish color of the back and the 

 more or less dirty clay-color of the l)elly a broad yellow band. 



Habitat. — Probably the most widely distributed species of snake, 

 occurring as it does on all the coasts and islands of the Indian and 

 Pacific oceans within the Tropics ami even extending its range in 

 many places considerably beyond the tropical waters, thus in the 

 southern hemisphere to the Cape of Good Hope and to New Zealand. 

 In the northern hemisphere it has been found on the eastern coasts 

 of Asia as far north as Yezo and the Russian Coast Province 



Beyond the tropics, however, these snakes are only carried occa- 

 sionally by the warm currents. Thus while they are yet of regular 

 occurrence around Formosa, they become gradually scarcer in the 



