Acraspeda

from The Collaborative International Dictionary of English v.0.48

Acraspeda \A*cras"pe*da\, n. pl. [NL., fr. Gr. 'a priv. + ?
   border.] (Zool.)
   A group of acalephs, including most of the larger
   jellyfishes; the Discophora.
   [1913 Webster]