; class Hydrozoa, order Hydroida)
A suborder of Cnidaria in which the colony is covered by a chitinous perisarc with cup-like extensions, the hydrothecae and gonothecae, which protects the feeding and reproductive polyps respectively. Medusae have gonads on the radial canals. (Obelia is commonly used as an examination specimen.)
Subjects: Zoology and Animal Sciences.