natant

Then again, beneath the nearer tumult, this natant, ill rhythm died down to a measured, sinister moan, echoing through the stone corridors in soughing jabs, like sounds marking the visitation of some maimed Hydra.

The Latin sentence appears clearly to end with the word natant, as is not only the case in the St. John's MS., mentioned in MR.

She stood rigid, listening with a natant, sickening consciousness that something terrible hung at her back.