375 



Family IDOTEIDA 



THIS family, which contains the largest known Isopoda, 

 some of which are above four inches in length, is distin- 

 guished by the long, narrow form of the animals, by the 

 subequal segments of the pereion, by the fusion of three 

 or more of the segments of the pleon into one large 

 caudal shield, by the absence of uropoda or external 

 caudal appendages, by the conversion of the fifth pair of 

 pleopoda into a continuous operculum for the protection 

 of the branchial organs, by the nearly uniform size and 

 structure of the seven pairs of legs, and by the shortness 

 of the superior pair of antennas, which never exceed the 

 length of the cephalon. Some interesting exotic genera 

 of this family have been described by Mr. Dana, in his 

 great work on the American Exploring Expedition. 



