Bivium
Pronunciation : Biv"i*um
Part of Speech : n.
Etymology : [L., a place with two ways. See Bivious.] (Zo?l.)
Definition : Defn: One side of an echinoderm, including a pair of ambulacra, in distinction from the opposite side (trivium), which includes three ambulacra.
Source : Webster's Unabridged Dictionary, 1913