THE SHORES OF BRITAIN. 95 
are placed on the side which is kept uppermost, 
where both are available. The inferior side of a 
Flat-fish is always white. The Turbot is the most 
highly esteemed of this family, and perhaps of all 
our fishes, the flesh being of very delicate flavour. 
The Sole is also a valuable fish. Both of these spe- 
cies are taken chiefly by trawl-nets, but the former 
is also caught with the hook. 
The Crustaceous and Testaceous classes afford 
employment to a considerable number of our po- 
pulation, and demand our brief attention. Of the 
former, the chief species selected for food in this 
country are, the Crab, the Lobster, the Prawn, and 
the Shrimp. Both our salt and fresh waters, how- 
ever, contain multitudes of other species, some of 
which are exceedingly curious in structure and form. 
The Crustacea, like insects, have no internal skeleton ; 
but instead of it, are encased in a jointed framework, 
resembling the plate armour of our forefathers, of 
a texture between shell and bone. The muscles 
which move the body are attached to the interior 
of this crust, as our muscles are attached to the 
bones. The body consists mainly of two parts; 
the fore-division contains the head and chest, co- 
vered with a large single plate, and the hinder, the 
belly covered with several smaller plates, joined by 
a tough skin, and lapping over each other. As this 
shelly covering is possessed by the animal from its 
very birth, it is natural to inquire how it can pos- 
sibly increase in size, seeing it is enclosed in an 
unyielding prison. In the Tortoises, which are 
somewhat similarly encased, the difficulty is met 
