THE CRAYFISH 



145 



food. The Isopoda ' include certain marine and fresh-water 

 groups, and thc! sow-bugs or wood-hce (Fig. 144), note- 

 worthy as the largest group of land 

 Crustacea. The Amphipoda - are 

 exclusively aquatic creatures, found 

 under decaying vegetation on 

 beaches of lakes or the sea (Fig. 145), 

 and crawling amidst marine hy- 

 droids. Being laterally compressed, 

 the Amphipods tend to lie on one 

 side when at rest. 



The economic importance of the Z^^*^ 

 decapods may be inferred from the //*; 

 fact that the receipts for the Atlantic 

 lobsters taken and sold by United 

 States fishermen was estimated for 

 the year 1901 at .«f ,400,000. 



Formerly the American lobster 



was more numerous 



and attained greater 

 \ r" size than now, but 



excessive fishing has 



so depleted the sup- 

 ply that the lobster 



is in danger of extermination. 



so-called NorM'egian lobster it 



Fig. 143. — SquiUa cnipv^a, the 

 mantis yhrinip. Dorsal aspect. 

 From Rathbun. 



Fig. 144.- -Onls- 

 cus, the sow- 

 biif^. DoTsal 

 Aacw. Nat. size. 

 Photo. I.y 

 W. H. C. P. 



In Europe the 

 much used as 

 food, while on our Calif ornian coast the so-called 

 spiny lobster or sea-crayfish takes the place 

 of our true Atlantic lobster and, like the latter, 

 is said to he in danger of extermination on 



1 isos, equal ; pons, foot. 



2 amphi, both ; pous, foot. 



