The Collaborative International Dictionary of English v.0.48:

Calvatia \Calvatia\ n.
   a genus of puffballs having outer casings whose upper parts
   break at maturity into angular pieces to expose the spores.

   Syn: genus Calvatia.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Calvatia
    n 1: genus of puffballs having outer casings whose upper parts
         break at maturity into angular pieces to expose the spores
         [syn: Calvatia, genus Calvatia]