Key to the species presently recognized in the genus Bathyaethiops

1 4.5 scale rows between lateral line and dorsal fin; 2.5 scale rows between lateral line and ventral fins; squamation always complete................................................................................... B. atercrinis

- 6.5 or more scales between lateral line and dorsal fin; 3.5 scale rows or more between lateral line and ventral fins; or squamation incomplete................................................................................. 2

2 A spot free of any melanophores (red in life, white in preserved specimens) directly in front of dorsal fin........ B. flammeus

- No such spot......................................................................................... 3

3 Humeral spot only slightly smaller as the dark spot on the caudal peduncle; squamation on flanks incomplete; lateral line

incomplete...................................................................................... B. baka - Humeral spot significantly smaller than the dark spot on the caudal peduncle; squamation on flanks complete; lateral line complete or incomplete................................................................................. 4

4 Dark spot on the caudal peduncle more or less rectangular and horizontally elongated hardly extending above midlateral level.......................................................................................... B. breuseghemi

- Dark spot on the caudal peduncle round or irregular with one third or more positioned above midlateral level............. 5

5 6.5 scales between lateral line and dorsal fin; humeral spot smaller than ½ of the pupil (or even absent); caudal peduncle spot horizontally elongated with a more or less irregular outline....................................... B. caudomaculatus

- (7.5) 8.5 scales between lateral line and dorsal fin; humeral spot ¾ of the pupil or more; caudal peduncle spot about as high as wide and more or less rounded..................................................................... B. greeni