In cirripeds (e.g., scalpellids), small unpaired plate below rostrum [Moore and McCormick, 1969].
(Subclass Cirripedia):
Barnacle shell plate: in stalked form, relatively small, unpaired plate below rostrum [Stachowitsch, 1992].
(Subclass Cirripedia):
Unpaired plate below rostrum [McLaughlin, 1980].
Crustacea glossary. Natural History Museum of Los Angeles County. 2011.