biramous

The name, meaning "cleft-footed," applies to the appendages of the thorax, which are once-branched (biramous).

The sixth segment of the abdomen has a pair of biramous appendages, which, with the telson, form a swimming-fan.

There are always six pairs; each biramous and multiarticulated, supported on a pedicel formed of two segments.

At the end of the last thoracic segment, there is a minute abdomen, bearing three pairs of biramous cirri.

There are four pairs of biramous cephalic appendages, which differ only very slightly from the appendages of the thorax.