Search Result for "arcella": 
Wordnet 3.0

NOUN (1)

1. an amoeba-like protozoan with a chitinous shell resembling an umbrella; 



The Collaborative International Dictionary of English v.0.48:

arcella \arcella\ n.
   An amoebalike protozoan with a chitinous shell resembling an
   umbrella.
   [WordNet 1.5]


WordNet (r) 3.0 (2006):

arcella
    n 1: an amoeba-like protozoan with a chitinous shell resembling
         an umbrella