HARPACTIOUS. 151 
(fig. 11) about as long as broad, and the inner of the 
two principal tail-setz is excessively long, being quite 
equal in length to the whole body of the animal. 
Length ;';rd of an inch (1:1 mm.). 
Considerable interest attaches to this species on 
account of its wide geographical distribution. It 
is restricted almost exclusively to the uppermost 
margin of the littoral zone, haunting more especially 
shallow pools at or above high-water-mark, and often 
occurring in prodigious numbers towards the end of 
summer when the water has become warm with 
prolonged exposure to the sun. In such situations it 
occurs almost everywhere round the British Islands, 
and has been found by Continental naturalists in 
various places on the coasts of the Baltic and North 
Seas. I have also had specimens sent to. me 
from Kerguelen Island in the southern hemisphere, 
where it was found by Mr. Haton of the “ Transit of 
Venus Expedition.’ Some specimens which are 
indistinguishable from H. fulvus were dredged by Mr. 
Robertson and myself in a depth of thirty-five fathoms 
off the Yorkshire coast, and were noted by us in the 
British Association Report for 1875, as a new species 
under the name H. crassicornis. This name must, 
however, now be withdrawn, as, notwithstanding the 
unusual nature of the habitat, there seems nothing to 
separate these specimens from the species now under 
consideration. In one fresh-water locality (Kinny 
Lough, County Donegal) we have found this species ; 
but there is little reason for surprise here, the Lough 
being in close proximity to the sea, almost on the sea- 
