Source : Webster's Revised Unabridged Dictionary (1913)

Lancelet \Lance"let\, n. [Lance + -let.] (Zo["o]l.)
   A small fishlike animal ({Amphioxus lanceolatus}), remarkable
   for the rudimentary condition of its organs. It is the type
   of the class Leptocardia. See {Amphioxus}, {Leptocardia}.

Source : WordNet®

lancelet
     n : small translucent lancet-shaped burrowing marine animal;
         primitive forerunner of the vertebrates [syn: {amphioxus}]