n. [ See Tethys. ] (Zool.) A tunicate. [ 1913 Webster ]

‖n. pl. [ NL., fr. Tethys + Gr. e'i^dos form. ] (Zool.) A division of Tunicata including the common attached ascidians, both simple and compound. Called also Tethioidea. [ 1913 Webster ]

n. [ NL., fr. Gr. &unr_; an oyster, or &unr_; a kind of ascidian. ] (Zool.) A genus of a large naked mollusks having a very large, broad, fringed cephalic disk, and branched dorsal gills. Some of the species become a foot long and are brilliantly colored. [ 1913 Webster ]