资料来源 : pyDict

二道体区

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Bivium \Biv"i*um\, n. [L., a place with two ways. See
   {Bivious}.] (Zo["o]l.)
   One side of an echinoderm, including a pair of ambulacra, in
   distinction from the opposite side (trivium), which includes
   three ambulacra.