The Collaborative International Dictionary of English v.0.48:

Phalangoidea \Phal`an*goi"de*a\, n. pl. [NL., from Phalangium
   the daddy longlegs (see Phalangious) + Gr. e'i^dos form.]
   (Zool.)
   A division of Arachnoidea, including the daddy longlegs or
   harvestman (Phalangium) and many similar kinds. They have
   long, slender, many-jointed legs; usually a rounded,
   segmented abdomen; and chelate jaws. They breathe by
   trache[ae]. Called also Phalangides, Phalangidea,
   Phalangiida, and Opilionea.
   [1913 Webster]