modiolus

from WordNet (r) 3.0 (2006)

modiolus
    n 1: the central conical bony pillar of the cochlea

from The Collaborative International Dictionary of English v.0.48

Modiolus \Mo*di"o*lus\, n.; pl. {Modioli}. [L., a small
   measure.] (Anat.)
   The central column in the osseous cochlea of the ear.
   [1913 Webster]