14 The order Amphipoda is distinctly divisible into four suborders: Gam- 

 maridea, Hyperiidea, Lemodipoda (Caprellidea), and Ingolfiellidea. The 

 suborder Gammaridea is the richest in terms of absolute numbers and 

 species composition. Its members inhabit benthic and pelagic domains 

 of the ocean from the littoral zone to maximum depths of the ocean 

 basins, enter fresh waters, and live on land. Members of the suborder 

 Lemodipoda, depauperate in species composition, inhabit outgrowths of 

 dendroid algae, hydroids, and bryozoans, or lead a parasitic mode of life 

 (family Cyamidae — whale-lice). The Ingolfiellidea is an aberrant group. 

 Only three of its representatives are known: two oceanic (Davis Strait 

 and Gulf of Tonkin) and one from cavernous fresh-water reservoirs. 



The suborder Hyperiidea includes purely pelagic marine forms. None 

 of its species is benthic, but many are, to some extent, obligate commen- 

 sals or parasites of coelenterates or salps and other gelatinous animals. 

 They inhabit the pelagic layer of cold and tropical seas right from the 

 surface down to the lowest horizons of the abyssopelagic, though as 

 yet they have not been recorded at depths greater than, 7,000 m. In 

 some particularly temperate cold-water regions, hyperiideans form mas- 

 sive congregations and occupy a primary place in the planktonic biomass, 

 constituting the bulk of the food of planktophagous fish and whales. 



