trachymedusæ

from The Century Dictionary.

• noun In Haeckel's system of classification, an order of acalephs whose marginal bodies or sense-organs are tentaculicysts, and whose genitals are situated in the course of the radial canals.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) A division of acalephs in which the development is direct from the eggs, without a hydroid stage. Some of the species are parasitic on other medusæ.