Merpersons

[Anton]

I don't know of any fish with slits on the upper parts of their heads like that, do you?

I think it's just an awkward depiction of the jaw (is that the appropriate English word?). You are not allowed to view links. Register or Login to view. is one interesting parallel. The person is also unperturbed, just because he is the Vishnu's avatar.  Diane's post (if you checked the reference above) also shows some similar contexts. What's interesting, they all do not seem to be of European origin.

I'm afraid I can't detect another "eye" shape to the middle of the fish. But I clearly discern two fins in the middle - one upwards, the other downwards (can't make a drawing at the moment, but I can do this later if requested).

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For the two other instances, I don't think those are fish parts, rather some tubes or vessels (note the stuff pouring from the opposite ends of them)