CEUSTACEA. 



III.-AMPHIPODA. 



BY A. 0. WALKER, F.L.S. 

 (13 Plates.) 



THE collection of Arnphipoda consists of fifty-three species, of which eighteen are new 

 to science, belonging to forty-three genera, of which four are new. This may not appear a 

 very large number considering the length of time the ' Discovery ' was in the Antarctic 

 Seas, yet as (with the exception of the pelagic Hyperiids taken on the voyage) all but some 

 nine species were collected from holes in the ice at the Winter Quarters, and, therefore, from 

 a very limited area, it appears to me to reflect great credit on the energy and persever- 

 ance of Mr. Hodgson under unusual climatic conditions. The long sojourn of the 

 ' Discovery ' in one spot enables us to observe the seasons at which different species 

 visit shallow water, generally for the purpose of depositing their ova or young. In the 

 case of the most abundant species, Orchomenopsis rossi, A. 0. W., of which Mr. 

 Hodgson says that " It was quite the usual thing to take ten to thirty thousand at a 

 haul," I only observed one male with fully developed lower antennae and no females with 

 ova, though some measured as much as 25mm. The young had probably been born 

 at a considerable depth, and had a-t once made their way to comparatively shallow 

 water, the parents remaining in deep water. Again, the almost equally abundant 

 Eusirus propinquus (G. 0. Sars) only exceeded 25mm. in four specimens, three females 

 with ova or young measuring 48mm., and one male measuring 50mm. This species 

 resembles in this respect Gammardlus \Amathilla\ homari (Fabr. ), which I have 

 observed to visit the north coast of Wales in the early spring, when alone the large 

 adult females, and more rarely males, measuring nearly lin. in length, can be taken 

 between tide-marks ; in the summer months every tidal pool swarms with young 

 specimens. 



As in the Arctic Amphipoda, the Lysianassidse greatly preponderate in the number 

 of genera, species, and individuals. The typical Gammaridse, as restricted by Mr. 

 Stebbing in establishing the families Melphidippidae and Lilljeborgidaj, are unrepre- 

 sented. In Professor G. 0. Sars' Amphipoda of Norway there are nine genera with 

 twenty-one species ; and in Professor Herdman's Ceylon collection seven genera with 

 fifteen species. 



Among the Gammaridae several species are remarkable for their wide distribution : 

 Ampelisca macrocephala (Lilljeborg) is an abundant Arctic species, though found also in 



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