The Collaborative International Dictionary of English v.0.48:

Valvelet \Valve"let\, n.
   A little valve; a valvule; especially, one of the pieces
   which compose the outer covering of a pericarp.
   [1913 Webster]

WordNet (r) 3.0 (2006):

valvelet
    n 1: a small valve [syn: valvule, valvelet, valvula]