The Branchiopoda have a very variable number of body-segments, with or without a shield, simple or bivalved, and some of the postoral appendages normally branchial.

The group may be defined as follows: Sessile solitary Coelomata with bivalved shells usually of unequal size and arranged dorso-ventrally.

The C. sophera, L., is characterized by 10 stamens, all fertile and a smooth, linear, bivalved pod full of seeds separated by false partitions.