The Collaborative International Dictionary of English v.0.48:

Utriculus \U*tric"u*lus\, n. [L., a little womb or matrix, a
   calycle.] (Anat.)
   A little sac, or bag; a utricle; especially, a part of the
   membranous labyrinth of the ear. See the Note under Ear.
   [1913 Webster]

WordNet (r) 3.0 (2006):

utriculus
    n 1: a small pouch into which the semicircular canals open [syn:
         utricle, utriculus]