entom6straca and phyll6poda. 257 



CHAPTER X. 

 entom6straca and phyll5poda. 



The reader is familiar with the crayfish, lobster, and 

 crab as members of that great group of animals called 

 the Crustacea, because they are covered by a hard, 

 shelly coating; but, with the exception of the crayfish, 

 he may associate them all with salt water, while in 

 reality our fresh-water ponds are densely peopled 

 with minute crustacean creatures. 



The little fresh-water animals are often enclosed in 

 a bivalve shell, which some of them have the power to 

 open and to shut; or the back of the body may be sim- 

 ply hardened, but without a distinct shell. The feet, 

 or legs, are usually numerous, and very hairy or 

 bristly; in one section of those referred to in this chap- 

 ter they are flattened, and each one bears near the 

 body a flattened plate; consequently, since these parts 

 are somewhat leaf-like, these animals have, as a class, 

 been called the leaf-footed or the Phylldpoda, which is 

 putting the words into Greek. Many others, to be 

 found much more abundantly and frequently than the 

 Phyllopoda, are without these plates, although the 

 feet are as numerous and, in some, almost as flat, and 

 the shells or shelly back as well marked. These have 

 been, by naturalists, grouped together under the name 



