The mouthparts and associated structures and the feeding mechanism of two small atyid prawns, Caridina africana and C. nilotica, are described in detail. Both species collect fine particles of food with the chelipeds, which for this purpose are armed with greatly modified spines and setæ, and transfer them rapidly to the mouthparts. Here the food is removed from the chelipeds by a grid-like arrangement of setse on the first maxillipeds and combed from these by the highly modified and teasel-like distal portions of the maxillæ which operate in conjunction with the first maxillipeds as a single functional unit. From these it is passed to the maxillules and thence to the mandibles.

An attempt is made to reconstruct on a functional basis the route by which primitive malacostracans could reach the condition now found in Caridina, and the evolution of chelipeds is discussed.