SNAKES. 59 



with large quadrangular black spots, towards the tail marbled 

 with brown. From the back edge of eye to the angle of mouth 

 a dark streak ; in half-grown individuals some yellow spots on 

 the neck ; in young ones a broad, yellow, black-edged collar. 

 Posterior maxillary teeth longest, not channeled, separated from 

 the anterior ones by an interval. Length of cleft of mouth § " ; 

 leDgth of tail 7" ; total length 39". 



4. Tropidonotus, Kuhl. 



Body moderate, rather stout (in one species slender) ; belly 

 rounded; tail moderate, not distinct from trunk, tapering; head 

 moderate, with flat crown, rather distinct from neck; snout 

 pointed, rounded. Eyes moderate, pupil round; nostrils near 

 the tip of the muzzle, small, between two shields ; cleft of mouth 

 deep and curved. Shields of head regular ; two small anterior 

 frontals, acute-angled in front, and forming together an isosceles ; 

 occipital plates often with a pair of yellow spots. Anal divided 

 (in one species entire). Scales keeled, rhombic or sublanceolate, 

 moderate, generally in nineteen rows, sometimes in more, in one 

 species in fifteen. Teeth smooth, equal, except the posterior in 

 the upper jaw, which is longest. In one species all the teeth 

 equal. Almost every part of the globe. 



Tropidonotus, Kuhl, Ms, 1826, p. 205; Boie, Isis, 1827, 

 p. 518; Wagl. Syst. p. 1/9; Schleg. Ess. p. 296. Tropidonotus 

 et Amphiesma, Dum. §• Bibr. vii. p. 549, 724. Hydrophis, Hy- 

 dras, Enhydris, Natrix, Coluber, sp., auct. prior. 



Instead of dividing this very natural genus into several, I 

 separate the species in ten groups, showing at once their close 

 relationship and their geographical distribution. 



A. Group with the type of Natrix. Europe ; North Africa. 



1. natrix. 



Var. natrix, colchica, atra, bilineata, persa. 



2. viperinus. 



Var. viperina, chersoides. 



B. Group with the type of Hydrus. From South Europe through 



the continent of Asia, to the East Indian Islands. 



3. hydrus. 



4. quincunciatus. 



Var. quincunciata, melanozosta.funebris, hydroides(var. 

 C and D), umbrata, ceylonensis. 



5. spilogaster. 



6. annularis. 



