22 INTRODUCTION 



Key to the Identification of the European 

 Snakes from External Characters only 



I. Eyes minute, under the head-shields; mouth 

 small, inferior ; body vermiform, covered with 

 uniform scales above and beneath ; vent close to 

 the end of the body, ■ the extremely short tail 

 ending in a small spine Typhlops vermicular is. 



II. Eyes very small, with vertical pupil; upper 

 surface of head covered with small scales ; 

 ventral shields much narrower than the body ; 

 tail short, ending obtusely ; subcaudals single, or 

 mostly single ; scales smooth or feebly keeled, in 

 40 to 50 rows Eryx jaculus. 



III. Eyes small, moderate, or large; ventral shields 

 at least nearly as broad as the body ; tail taper- 

 ing to a point ; subcaudals paired. 

 A. Pupil round; upper surface of head with nine 

 large shields ; no upper labial in contact with 

 the parietal ; anal shield usually divided. 

 1. Dorsal scales strongly keeled, with paired 

 apical pits ; a single anterior temporal. 

 a. Nostrils lateral ; internasals broadly trun- 

 cate in front. 

 Scales in 19 rows ; normally 1 pre- and 3 post- 

 oculars ; usually 7 upper labials, third and fourth 

 entering the eye; ventrals 157-181 ; subcaudals 

 50-88 Tropidonotus natrix. 



