THE SHOP.FS 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 



