Wikipedia has a disambiguation page that tells us this can refer to:
- a species of eagle ray
- a name applied to the manta ray
- the venomous fish Inimicus didactylus
- an alternative and rather obsolete name for the octopus
- Gray whales, once called devil fish because of their self-defensive behavior when hunted
- one of two Australian fishes
- purported Jenny Haniver cryptid (amazing)
There was not a mark of dignity or pride upon his bestial countenance, while his enormous bulk spread itself out upon the platform where he squatted like some huge devil fish, his six limbs accentuating the similarity in a horrible and startling manner.
Given the “squatting” and the “six limbs”, I guess we can go with… octopus? Although, if you’d checked your facts, Mr. Burroughs, I think you would’ve found that they have eight.