SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. VIII. 
THe ISOPODA — Part I. 
CHELIFERA, FLABELLIFERA, VALVIFERA. 
HARRIET RICHARDSON. 
Tue Isopoda represent an order of Crustacea widely dis- 
tributed and varying greatly in their mode of life and in their 
habitat. They abound not only in the sea, where they are 
taken in shallow water and from the greatest depths, but large 
numbers of them are also found in ponds and streams and other 
bodies of fresh water. The terrestrial Isopoda form a large 
and important group, and are commonly known as “ pill-bugs." 
Many of the Isopoda live a free existence, while others are 
parasitic. These latter are found in the mouths and gills of 
fishes, in the branchial cavities of Decapoda, on Copepoda, 
and on other Isopoda. 
In the following key the marine forms have not been limited 
bathymetrically. Where it has been possible, the depth from 
which the specimens were taken has been given. The fresh- 
water and terrestrial forms are included. 
The lettering for the distribution of species has been adopted 
in accordance with what has been used in former papers of this 
series of synopses on marine invertebrates: A for Alaska south ; 
P for Puget Sound to San Francisco; D for Monterey to San 
Diego; JW, Atlantic coast south to Cape Cod; M, Cape Cod to 
North Carolina ; S, South Carolina to Florida ; G, Gulf of Mexico. 
The literature on the Isopoda has been limited in the 
following list to those papers which treat especially of 
North American forms. The most important of these are: 
1817. Sav, THOMAs. An Account of the Crustacea of the United States. 
Journ. Acad. Nat. Sci. Philadelphia. Vol. i, pt. i, pp. 393-401, 
423-433, 482-485. 
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