Key to the species of Chikila

The following key serves to identify the four nominal species of Chikila based on specimens in our examined sample.

1. Eye visible; head pointed; fewer VPs than PMs; maximum adult size generally less than 200 mm; northeast India north of Brahmaputra river......................................................................... Chikila darlong

- Eye generally not clearly visible; head more broadly rounded anteriorly or moderately pointed; similar numbers of VPs and PMs or fewer PMs; maximum adult size generally greater than 200 mm; south of Brahmaputra river....................2

2. Chin, throat and underside of anteriormost primary annuli with pale blotches; pale eye-tentacle patch extensive, generally encircling and extending posterior to position of eye; disc surrounding vent partly pigmented; no unpigmented patch immediately anterior of disc surrounding vent; annular grooves very strongly marked............................ Chikila fulleri

- Chin, throat and underside of anteriormost primary annuli without pale blotches; pale eye-tentacle patch restricted, generally not extending back to or beyond position of eye; disc surrounding vent unpigmented; unpigmented patch immediately anterior of disc surrounding vent; annular grooves weakly or moderately marked.......................................... 3

3. Strongly bicoloured; relatively large, narrowly separated choanae (interchoanal gap <1.25 x width of each choana)............................................................................................... Chikila gaiduwani

- Weakly bicoloured, almost unicoloured; narrow, widely separated choanae (interchoanal gap> 2.25 x width of each choana).......................................................................................... Chikila alcocki