The Collaborative International Dictionary of English v.0.48:

Procoelian \Pro*c[oe]"li*an\, a. [See Proc[oe]le.] (Anat &
   Zool.)
   Concave in front; as, proc[oe]lian vertebr[ae], which have
   the anterior end of the centra concave and the posterior
   convex.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Procoelian \Pro*c[oe]"li*an\, n. (Zool.)
   A reptile having proc[oe]lian vertebr[ae]; one of the
   Proc[oe]lia.
   [1913 Webster]