HERPETOLOGY OF JAPAN, 257 



ARTIFICIAL KEY TO THE GENERA OF SNAKES OCCURRING IN JAPAN AND ADJACENT 



TERRITORY. 



(In two instances reference is only had to the family or subfamily names, in which 

 cases the genera may be found in the key or synopsis on the page quoted.) 



«' Tail laterally compressed Hydrinse, p. 400. 



a^ Tail cylindric. 



6' Body covered with nearly uniform cycloid scales, above and below, 



Typhlops. p. 260. 

 b^ Body covered above with scales, below with transverse plates. 



c' A deep hole or pit between nostril and eye Crotalidse, p. 448. 



(? No hole between nostril and eye. 



d^ Snout covered with small scales Coluber, p. 443. 



dr Snout covered with regular shields. 



e^ No internasal shields Calamaria. p. 375. 



e'^ Internasal shield or shields present. 



/' Parietals broken up into minor shields Hurria, p. 304. 



f^ Parietals normal. 



g^ A single internasal shield Enhydris, p. 300. 



g^ Two or more internasal shields. 



h^ No postocular shield, temporals joining eye Achalinus, p. 294. 



K^ One or more postocular shields separating temporals from eye. 



i^ Subcaudals undivided Bunqarus, p. 397. 



i^ Subcaudals in pairs. CalHophis, p. 391. 



y Scale rows 13 \Hemibungarus, ^y. 387. 



j- More than 13 scale rows. 



Ic^ Neck dilatable; more scale rows around neck than around 



middle of body Naja, p. 394. 



¥• Neck not dilatable; scale rows around neck not more numer- 

 ous than around middle of body. 



l^ Vertebral scale row enlarged Boiga, p. 381. 



P Vertebral scale row not enlarged. 

 tn^ Pupil vertically elliptic. 

 n^ Nostril in a single nasal; three pairs of chin-shields, 



Psammodynastes , p. 383. 

 n^ Nostril between two scales; two pairs of chin-shields, 



Dinodon, p. 356. 

 m- Pupil round. 



n' More than one loreal Ptyas. p. 345. 



n^ Not more than one loreal. 



o' Portion of rostral Aisible from above as great as its 



distance from frontal Holarchus, p. 353. 



o- Portion of rostral visible from above less than its dis- 

 tance from frontal. 

 p^ Posterior chin-shields considerably longer than 



anterior Natrix, p. 263. 



p- Posterior chin-shields equal to or shorter than 

 anterior. 



9' No scale pores Liopfltis. p. 337. 



q^ Scale pores present. 



/■' Tail more than one-fourth of total length, 



Zamenis, p. 349. 

 r'^ Tail less than one-fourth of total length, 



Elaphe, p. 307. 

 26485— No. 58—07 17 



