290 ZOOLOGY. 
the sharp hook-like legs around the margin of the body. The 
head has no eyes nor appendages. The male (Fig. 257, C, D) 
is but slightly modified, is very minute, and is lodged partly 
out of sight under the ventral plates of the female, whose 
body is about five millimetres (a fifth of an inch) in length, 
Fig. 258.—Arcturus Bafint, with its young clinging to its antenne.—After Wyville 
Thompson. 
Various species of Porcellio (sow-bugs) live under stones 
on land; and allied to Asellus, the water sow-bug, is the 
marine Limnoria lignorum White, which is very injurious 
to the piles of bridges, wharves, and any submerged wood. 
The highest Isopods are Idotwa, of which I. irroratus Say 
(Fig. 250) is our most abundant species, being common in 
eel-grass, etc.. between and just below tide-marks ; and Are- 
turus (Fig. 258, A. Baffini Sabine), from the Arctic seas. 
