IDOTEID®. 375 
Family—IDOTEID. 
Turis 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 antennz, 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. 
