At the end of the last thoracic segment, there is a minute abdomen, bearing three pairs of biramous cirri.
The name, meaning "cleft-footed," applies to the appendages of the thorax, which are once-branched (biramous).
As figured, some of the appendages have the form of exopodites, others of endopodites, indicating that they were biramous.
The sixth segment of the abdomen has a pair of biramous appendages, which, with the telson, form a swimming-fan.
They are all biramous, though the two rami are not as yet jointed.
This form is retained, with little alteration in some adult Copepoda, where the biramous “palp” still aids in locomotion.
While highly diversified, these appendages are very trilobite-like, and some Ostracoda even have biramous antenn.
The antennas are also locomotor organs, and in most orders are biramous.
The mandibles are biramous and usually with, but sometimes without, a gnathobase.
There are four pairs of biramous cephalic appendages, which differ only very slightly from the appendages of the thorax.
biramous bi·ra·mous (bī-rā'məs)
Consisting of or having two branches, as the appendages of an arthropod.