The Amphipod Functional Model and Its Bearing upon Systematics and Phylogeny

The peculiar habitus of Amphipods with lateral compression, deep coxal plates 1‐4, broad bases of peraeopods 5‐7, and enlarged pleura (epimeral plates) of abdominal segments 1‐3 is seen as a functional system closely dependent upon the currents produced by the incessant beating of the pleopods. The derivation and position of branchiae and oostegites is discussed. The morphology of more or less aberrant groups, including the suborders Caprellidea and Ingolfiellidea, and its correlations with the mode of life and the basic functional model is analyzed. The possible bearing of the functional model system upon the position of the Amphipoda among the Peracarida is briefly dealt with.