In the higher Decapoda the male is generally larger than the female and has stronger chelae.
Orders: Decapoda (Sub-orders: Brachyura, Macrura), Schizopoda (including Anaspides), Stomatopoda, Sympoda (Cumacea), Isopoda (including Tanaidacea), Amphipoda.
In the Decapoda (fig.
In the Decapoda the branchial system is more complex.
In most of the Decapoda the eggs are carried by the female, attached to the abdominal appendages (fig.
In the Malacostraca it is absent in the adult, or persists only in a vestigial condition, as in some Decapoda and Schizopoda.
A minute entosternite having the above-described structure is found in the Crustacean Apus between the bases of the mandibles, and also in the Decapoda in a similar position, but in no Crustacean does it attain to any size or importance.
In the Decapoda three pairs are thus modified, and in the Tanaidacea, Isopoda and Amphipoda only one.
Orders: Decapoda and Stomopoda.
Among the Malacostraca the nauplius is less commonly found, but it occurs in the Euphausiidae among the Schizopoda and in a few of the more primitive Decapoda (Penaeidea) (fig.