Source : Webster's Revised Unabridged Dictionary (1913)

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