What is "hymenocaris"

Hymenocaris is a genus of Cambrian crustaceans. Some species originally assigned to Hymenocaris were later transferred to Canadaspis, such as Canadaspis perfecta (Hymenocaris perfecta), leaving only Hymenocaris vermicauda. Differences between Hymenocaris and Canadaspis have been used to justify erecting a separate family, Hymenocarididae and order, Hymenostraca for Hymenocaris, although it is also sometimes placed in the family Canadaspididae and the order Canadaspidida.