ARCTURIDA. 059 
Family—ARCTURID ZA. 
Tus family, corresponding with the tribe Idoteides 
Arpenteuses of M. Milne Edwards, is composed of the 
single genus Arcturus, of Latreille, remarkable amongst 
the Isopoda for its slender, cylindrical form, the length 
of its lower pair of antenna, and the delicate ciliated 
structure of the four anterior pairs of legs; whilst the 
hind ones are short and very robust. In the British 
species, the fourth segment of the body is greatly elon- 
gated, and as the animals affix themselves by means of 
their hind pairs of legs, elevating the front part of the 
body, and twisting it about in various directions, they 
exhibit considerable resemblance to the Caprelle, as also 
to the loopers, or Geometrical Caterpillars of the Geo- 
metre, whilst the elongated antenne give them also a 
strong resemblance to the Amphipodans, constituting the 
genus Corophium (vol.1 p. 493) ; in fact it is by the assist- 
ance of the great antennz that these creatures chiefly 
_ progress, their fore legs being too delicate to serve as 
instruments of locomotion. 
The species of the group found in the Arctic seas 
are of very large size, sometimes reaching three inches 
in the length of their bodies. This is the case with the 
type of the genus Jdotea Baffini, Sabine, first described 
in the appendix to Captain Parry’s fourth voyage. This 
species has the fourth joint of the body not much longer 
than the adjoining segments, and if it should be con- 
sidered necessary to separate the British species, as form- 
