One pair of filaments arising in many Anostraca from bases of antennae but independent of them; may be ramified [Moore and McCormick, 1969].
(Order Diplostraca):
Frontal organ [Stachowitsch, 1992].
(Order Anostraca):
Paired filaments arising from bases of antennae but independent of them [McLaughlin, 1980].
(Order Anostraca):
Unpaired median process projecting from head between antennae. (unbranched, branched; with two terminal branches, with three terminal branches; shorter/longer than antenna) [Stachowitsch, 1992].
Crustacea glossary. Natural History Museum of Los Angeles County. 2011.