158 
HISTORY OF BRITISH CRUSTACEA. 
Division EDRIOPHTHALMA, Leach. 
In the Crustacea of this division the eyes are sessile, that 
is, are not elevated on foot-stalks, while the body is more 
or less distinctly divided into three parts; the different 
parts of which the thorax and abdomen consist are almost 
always very distinct from each other, and movable. There 
is no great dorsal shield corresponding to the carapace of 
the Podophtfialma , neither do they breathe, like the latter, 
by means of gills, but by the aid of a portion of their limbs, 
the structure of which is wholly or partially modified for 
this special purpose. 
The animals of this division are small in size and mostly 
found in the sea or on its shores, where they abound ; and 
by the removal of decaying animal and vegetable matter, 
they effect great good, while they afford ample stores of 
food to many fishes and sea-birds. 
♦ 
Order AMPHIPODA. 
The abdomen, in the species of this order, is always well 
developed, and furnished with five to six pairs of limbs. 
The head is formed of a single segment, and has generally 
only two sessile eyes and two pairs of antennae, though in a 
