17 NEW YORK STATE MUSEUM 



They are found under rocks and logs on the shore, or burrowing 

 in the sand or in timber. Other forms are pelagic or cling to float- 

 ing seaweeds, eelgrass or the hydroids on piles. Many forms are 

 parasitic. Some are found in fresh water and still others, prob- 

 ably the most familiar to the casual observer and known as sow- 

 bugs or pill-bugs, are found under stones on land or under bark. 



The principal paper on the marine Isopoda is by Harger, " Report 

 on the Marine Isopoda of New Engancl and Adjacent Waters," 

 U. S. Fish Com. Report for 1878, Washington, 1880. This contains 

 descriptions and figures of most of the species mentioned in the 

 following. 



A key to the Isopoda of North America was published by Har- 

 riet Richardson in the American Naturalist, 1900, 34:207-30, 295- 

 309. This was incorporated in the " Key to the Isopods of the 

 Atlantic Coast of North America, with Descriptions of New and 

 Little Known Species," by the same author and published in Proc. 

 of the U. S. Nat. Mus. IQOI, 23 : 493-579. A bibliography of Amer- 

 ican forms is there given. 



Say's work mentioned before [p. 125] gives descriptions of 

 several of our forms ; and Sars, in the Crustacea of Norway, figures 

 several cosmopolitan species which occur here. References to Yer- 

 rill's Invertebrates of Vineyard Sound are also given. 



i CHELIFERA 



Distinguished from all other Isopoda by the first pair of legs or 

 gnathopoda being chelate. Pleopoda when present, natatory. 

 Uropoda terminal, with a short basal part and one or two terminal 

 filaments. Respiration thoracic. 



A very anomalous group which differs in several respects from 

 the typical Isopoda and by some authors has been entirely removed 

 from the order. Divided into two families, of which one is repre- 

 sented, i Tanaidae, 2 Apseudidae. 



Family XANAIDAE, 



Body cylindric. Antennulae close together, short in female, 

 much longer in male, with minute rudiment of a flagellum and with- 

 out secondary flagellum. Antennae shorter with flagellum generally 

 biarticulate. Uropoda short. 



