Source : Webster's Revised Unabridged Dictionary (1913)

Tethyodea \Te`thy*o"de*a\, n. pl. [NL., fr. Tethys + Gr. ?
   form.] (Zo["o]l.)
   A division of Tunicata including the common attached
   ascidians, both simple and compound. Called also
   {Tethioidea}.