In the Decapoda the branchial system is more complex.
It is among the Malacostraca, however, and especially in the Decapoda, that the " gastric mill " reaches its greatest perfection.
In the Decapoda the antennal gland is largely developed and is known as the " green gland."
In the Decapoda three pairs are thus modified, and in the Tanaidacea, Isopoda and Amphipoda only one.
In the higher Decapoda, numerous additional centres are developed in the brain and its structure becomes extremely complex.