TROPIDONOTUS. 259 



ha-ving seized it, they at once commence to swallow it. They are excellent swimmers, but 

 more frequently live near water than in it ; in agreement with which habit, the position of 

 their nostrils is not on the upper surface of the head, as in the true freshwater snakes, but 

 on the side. 



However, this type of snakes passes into other groups : whilst the species with a stout 

 body approach the Ilomalopsides, others, of a more slender make, show a transition to an 

 aberrant species, Tropidonotas platijceps, which at first sight might be taken for a Herpeto- 

 dryas, having a remarkably slender body and very feeble keels of the scales ; the ventrals, 

 however, are rounded, without any trace of a keel. 



The Tropidonoti are found in North America, Europe, Asia, the East Indian archipelago, 

 and North-western Australia : a single species has lately been received from tropical Africa. 

 The species are very numerous, and some of them extremely rich in individuals. The fol- 

 lowing occur in British India : — 



I. The teeth form one continuous series, gradually increasing in length, the last tooth being not much 



larger than the preceding. 

 Each ventral with blackish anterior margin ; two labials entering the 



orbit T. quincunciatus, p. 260. 



Belly with black cross bands T. annularis, p. 261. 



Three labial sliields entering tlie orbit T. trianguUgerus, Tp. 26\. 



II. The last tooth is much larger than the one preceding, and enveloped in a separate membranaceous 

 pouch : Tropidonotus. 



A. The last tooth is scarcely separated from the others by an interval. 

 Scales in nineteen rows ; subcaudals ca. 78 ; eye large ; anterior part of 



the belly with large quachangnlar blackish-browTi spots .... 7". macropfithalmus, p. 262. 

 Scales in seventeen rows; subcaudals ca. 52; eye large; anterior part 



of the belly with subquadrangnlar blackish-brown spots . . . . T. dorsalis, p. 263. 



(*) Scales in seventeen rows ; subcaudals 124-146 ; eye large T. macrops, p. 263. 



B. The last tooth is separated from the others by a distinct interval: Amphiesma, D. & B. 

 Scales in nineteen rows; one (two) prse-, two post-oculars. Rostral 



shield with a black vertical streak T. platyceps, p. 264. 



Scales in nineteen rows; one prseocular; the third, fourth, and fifth 

 labials enter the orbit ; an oblique triangular black spot below the 

 eye; no dorsal bands T. subminiatus, -p. 2(\h. 



Scales in nineteen rows; one praeocuiar; the fourth and fifth labials 

 enter the orbit. Upper labials edged with black behind ; two dorsal 



series of small yellow spots T. himalay anus, p. 265. 



(*) Scales in seventeen rows ; 2-4 praj-, 4-5 post-oculars T. angusticeps, p. 266. 



Scales in nineteen rows ; anterior frontals pointed in front ; back with 



black transverse bands and with two yellowish longitudinal bands . T. stolatus, p. 266. 



Scales in nineteen rows; anterior frontals truncated in front. Body 



with black cross bauds, each divided into three square spots ... 7". monticola, p. 267. 



Scales in nineteen rows; one prseocular ; nine upper labials, the fourth, 

 fifth, and sixth entering the orbit ; a V-Uke yellow marking on the 

 neck T.junceus,^.2Q%. 



* The species marked (*) were not examined by myself. 



o T 9 



^ Li .J 



