The Collaborative International Dictionary of English v.0.48:

Leucosoid \Leu"co*soid\ (-soid), a. [NL. Leucosia, the typical
   genus (fr. Gr. leyko`s white) + -oid.] (Zool.)
   Like or pertaining to the Leucosoidea, a tribe of marine
   crabs including the box crab or Calappa.
   [1913 Webster]