The Collaborative International Dictionary of English v.0.48:

Pluteus \Plu"te*us\, n.; pl. L. Plutei, E. Pluteuses. [L., a
   shed.] (Zool.)
   The free-swimming larva of sea urchins and ophiurans, having
   several long stiff processes inclosing calcareous rods.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Pluteus
    n 1: a large genus of fungi belonging to the family Pluteaceae;
         the shape of the cap resembles a roof; often abundant early
         in the summer [syn: Pluteus, genus Pluteus, roof
         mushroom]