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Proceedings of the Royal Society of Edinburgh. [Sess. 
6. Genus HYGROBATES, C. L. Koch. 
Rygrobates longipalpis, Herm. — Found at Rannoch and Morar, June 
1902 ; Ghriama, Loch na Claise Fhearna, and Suardalain, September 1902 ; 
Loch Tarff, August 1903 ; Dores Pond, February 1904 ; Hundland (Orkney), 
September 1906. 
Hygrobates reticulatus, P. Kram. — Found at Morar, June 1902; Loch 
Ness, August and September 1903. 
7. Genus HYDROCHOREUTES, C. L. Koch. 
Hydrochoreutes ungulatus , C. L. Koch. — Found by Mr Murray at 
Loch Lydoch and Dubh Lochan, June 1902. 
Hydrochoreutes Jcrameri, Pier. — Found by Mr Murray at Loch na Claise 
Fhearna, September 1902. 
8. Genus PIONACERCUS, Pier. 
Pionacercus leuckarti, Pier. — Found by Mr Scourfield near Fort 
Augustus, August 1903. 
A specimen found by Mr Scourfield at Loch Rannoch, June 1902, has 
not been identified. 
9. Genus ATAX, (Fabr.) Bruz. 
Atax crassipes, Mull. — Found at Rannoch and at a pond near Mallaig, 
June 1902 ; Loch of the Lows (Perth), 1903 ; St Mary’s Loch (taken from 
a depth of 100 feet), January 1906. 
In this species the first pair of limbs are much stouter than the other 
three pairs, are armed with movable spines, and appear to be used, not for 
locomotion, but mainly to seize the entomostracans on which the creature 
feeds. When stalking its prey, it now and then halts for a few seconds, 
the body sinks to one side, is raised up again to sink to the other side, 
and in turn to be raised again ; or it may be that the posterior end of the 
body is lowered to rest on the papillae, — all as if the long slender limbs were 
too weak to support the weight of the body during its brief rest. If, 
however, a daphnia or cyclops comes within range, the limbs which hitherto 
appeared to be rather in the way are suddenly bent round the entomos- 
tracan, which is passed under the palpi, and when it is held securely so 
that the mouth-organs may do their work, the first pair are again unbent 
and held up in front as before. Although the palpi have now the weight of 
