CHAPTER V. 

 BRANCH ARTHROPODA. 



CLASS CRUSTACEA (Continued}. 



Lobsters. With a few unimportant exceptions, the 

 structure of the lobster is essentially the same as that 

 of the crayfish. The lobster may be said to be a big salt- 

 water crayfish, or the crayfish a small fresh-water lobster. 

 Lobsters are an important food product of the North At- 

 lantic, both to the old world and the new. From twenty 

 to thirty millions are caught annually along the coasts of 

 New England and Canada. They are captured by sinking 

 large wooden traps, which are called " lobster pots." These 

 are baited with refuse fish. A buoy is attached to each 

 trap to mark its place, and to serve as a means of taking up 

 the trap. The lobsters thus caught average less than four 

 pounds in weight, but specimens have been found that 

 weighed as high as thirty-nine pounds. 



Shrimps and Prawns. Two other marine crustaceans 

 that are largely used as food are the shrimps and prawns. 

 These are essentially like the crayfish, but differing from 

 it more than the lobster. They are caught in large numbers, 

 and eaten fresh or canned, as is the lobster. Prawns have 

 a permanent hump on the dorsal surface of the abdomen ; 

 and the dorsal surface rises as a sharp ridge, perhaps to 

 diminish resistance, and thus increase its speed when swim- 

 ming. Most of our so-called shrimps, out of which the 

 famous salad is made, are really prawns, and not shrimps. 



77 



