τήθυον · tēthyon — LSJ
an animal of the kind called ascidia or sea-squirt, Arist. HA 531a18 (v.l. τηθέου), PA 680a5, al.; once in Hom., τηθεα διφῶν Il. 16.747 (= εἶδος θαλασσίων ὀστρέων, Sch.), cf. Arist. Fr. 304. (For the variation τήθυον: τήθεον, cf. πτύον: πτέον, etc.; tethea is pl. in Plin. HN 32.117, nom. sg. fem. ib. 151.)
τηθύα· τενάγη, ἃ προχέουσιν οἱ ποταμοί, Hsch.