Introduction
Pleurae with pointed or bluntly rounded spines and oblique or transverse pleural furrows, in some genera represented by row of pits, or effaced. Pygidium with 2 to 4 pairs of pleural ribs and spines; axial rings few. Surface commonly tuberculate, pitted, or both. Appendages only of Ceraurus described; antennae uniramous, other appendages biramous, with gill branches bearing filaments only on distal segments (178, 359). L.Ord.(Tremadoc.)-M.Dev.
 

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