The Collaborative International Dictionary of English v.0.48:

Amphicoelian \Am`phi*c[oe]"li*an\, Amphicoelous
\Am`phi*c[oe]"lous\, a. [Gr. ? hollowed all round; 'amfi` + ?
   hollow.] (Zool.)
   Having both ends concave; biconcave; -- said of vertebr[ae].
   [1913 Webster]