The Collaborative International Dictionary of English v.0.48:

Allantoic \Al`lan*to"ic\, a. [Cf. F. allanto["i]que.]
   Pertaining to, or contained in, the allantois.
   [1913 Webster]

   Allantoic acid. (Chem.) See Allantoin.
      [1913 Webster] Allantoid

WordNet (r) 3.0 (2006):

allantoic
    adj 1: relating to or characterized by an allantois