inframedian

from The Collaborative International Dictionary of English v.0.48

Inframedian \In`fra*me"di*an\, a. [Infra + median.] (Zoological
   Geog.)
   Of or pertaining to the interval or zone along the sea
   bottom, at the depth of between fifty and one hundred
   fathoms. --E. Forbes.
   [1913 Webster]