The Collaborative International Dictionary of English v.0.48:

Ephyra \Eph"y*ra\, n. [NL., fr. Gr. ?, an old name of Corinth.]
   (Zo["o]l.)
   A stage in the development of discophorous medus[ae], when
   they first begin to swim about after being detached from the
   strobila. See Strobila.
   [1913 Webster]