Sentence:  But the steward of those <WSD>nether regions</WSD> marked him, by the electric lamps, as a lurking passenger to be watched; and wondered who, at that depth in the ship, could be carrying valuables. 
Meaning of the word marked with <WSD> tags:  A place which is subterranean or enclosed beneath a surface, especially one which is dark, dank, or otherwise inhospitable.