neencephalon

from WordNet (r) 3.0 (2006)

neencephalon
    n 1: the part of the brain having the most recent phylogenetic
         origin; the cerebral cortex and related parts [syn:
         {neencephalon}, {neoencephalon}]

from The Collaborative International Dictionary of English v.0.48

neencephalon \ne`en*ceph"a*lon\
   (n[=e]`[e^]n*s[e^]f"[.a]*l[o^]n), (Anat.)
   The most recently evolved part of the brain of higher
   animals. It includes the cerebral cortex and related
   structures.
   [PJC]