The Collaborative International Dictionary of English v.0.48:

Hymenomycetes \Hy`me*no*my*ce"tes\, n. pl. [NL., fr. Gr. ? a
   membrane + ?, ?, a mushroom.] (Bot.)
   One of the great divisions of fungi, containing those species
   in which the hymenium is completely exposed. --M. J. Berkley.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Hymenomycetes
    n 1: used in some classifications; usually coextensive with
         order Agaricales: mushrooms; toadstools; agarics; bracket
         fungi [syn: Hymenomycetes, class Hymenomycetes]