323 



presence of a large number of nematocysts in the gut of the crustaceans. 

 Different species of Hyperia are associated with different species of jel- 

 lyfish. For example, the cold-water H. galba is generally found on the 

 scyphomedusae Cyanea arctica (= C. capillata), but in some regions 

 on Aurelia aurita, Rhizostoma octopus, Pelagia or Chrysaora, while its 

 young have additionally been found on hydromedusae Melicertum and 

 on ctenophores Beroe. Hyperia medusarum lives on the same species 

 264 of medusae. In the North Atlantic H. spinigera lives exclusively on the 

 deepwater jellyfish Periphylla periphylla from the order Coronata, but 

 the Antarctic H. macrocephala lives on the jellyfish Desmonema gau- 

 dichaudi (Thurston, 1977). 



1. Hyperia galba (Montagu, 1815) (Figs. 129, 130) 



Montagu, 1815: 4 (Cancer gammarus); Guerin, 1825: 771; Boval- 

 lius, 1889: 180; Stephensen, 1923: 17; 1924: 81; Chevreux and Page, 

 1925: 401; Dunbar, 1963: 3; Schellenberg, 1942: 241; Bowman, 1973: 

 \Q. —spinigera {x\on Bovallius, 1889): Norman, 1900: 129. 



Length of sexually mature specimens 10-24 mm. 



The head^is shorter than somites I and II of the pereon together. The 

 lower posterior angle of epimeron III terminates in minute denticles; its 

 posterior margin is quite convex. The outer lobes of the maxillipeds bear 

 several short setae along the inner margin; the inner lobes are 3/4 the 

 length of the outer lobes. The 5th and 6th segments of pereopods I-II 

 are surfacially covered with numerous setae. The 5th segment of pere- 

 opods III-IV bears a few short setae; the posterior margin of the 6th 

 segment is unarmed, denticulate. The 2nd segment of pereopods V-VII 

 is quite narrow, in pereopods V without setae, but in pereopods VI and 

 VII with a fascicle of setae in its distal angle. 



Distribution: An Arctic-boreal, far-neritic species; it lives in the seas 

 of the Polar basin and North Atlantic, including the Baltic Sea, pene- 

 trating south up to Chesapeak Bay along the western coast and up to 

 the coasts of England, Spain, and the Azore Islands along the eastern 

 coast. In the Pacific Ocean it penetrates up to the coasts of Hokkaido 

 along the western coast and up to Alaska and Kodiak along the eastern 

 coast. References to finds of H. galba in the tropical and notal regions 

 are obviously erroneous. 



2. Hyperia medusarum (O.F. Miiller, 1776) (Fig. 131) 



Muller, 1776: 196 {Cancer); Bovallius, 1889: 147; Stephensen, 



1923: 15; Bowman, 1973: 6.—latreillei Milne-Edwards, 1830: 388; 



266 Bovallius, 1889: 164. — gaudichaudi Milne-Edwards, 1840: 77; Bate, 



1862: 289 (Lestrigonus); Stebbing, 1888: 1394; Bovallius, 1889: 



175; Dick, 1970: 55; Bowman, 1973: 13.— hystrix Bovallius, 



