G ICR. E. J. MIEES ON THE IDOIEIDJE. 



Is'o less apparent is the relationship of the IdoteidcB to the 

 ArctundcB ; the two families, as Harger has pointed out, resemble 

 one another in the structure of the cephalic appendages, partially 

 consolidated postabdominal segments, and operculiform uropoda. 

 This affinity is most strikingly exemplified in cova^divmg Arcturus 

 with the genus Idotea. The Arcturidcs are distinguished princi- 

 pally by their robust and elongated antennae, and by having the 

 four anterior pairs of thoracic legs directed forward and fringed 

 with long and flexible hairs. "Whether they will be finally asso- 

 ciated with the Idotceidce, or whether it will prove to be practi- 

 cally more convenient to retain Dana's threefold division of the 

 Edriophthalmia into Isopoda, Anisopoda, and Amphipoda (when the 

 ArcUiridce must be regarded as Anisop>oda Idotcsica), remains to 

 be determined by whomsoever shall undertake the classification of 

 the whole of the genera of the Edriophthalmia*. 



The following are diagnostic characters of the subfamilies and 

 genera as limited in the present revision : — 



Subfam. I. G-LTPTONOTINiE. 



Sides of the head emarginate or cleft, and laterally produced heyond 

 the eyes, which thus are situated upon its dorsal surface. The three 

 anterior pairs of legs loith tlie penultimate joint or jjropus dilated, 

 and forming, loith the refiexible dactylus, a p)rehensile hand. 



Body ovate, with some or all of the epimera distinct in a 

 dorsal view, and considerably developed. Postabdomen composed 

 of four or five distinct segments. Antennal flagellum distinct. 



GrLTPTONOTUS. 



Subfam. II. IDOTEIN^. 



Sides of the head not laterally produ,ced, entire. Eyes lateral. 

 Legs all ambulatory ; the three anterior pairs with the penul- 

 timate joint not dilated. 



Body oblong-ovate, with the epimera distinct and more or less 

 evident in a dorsal view. Postabdomen composed of one to five 

 distinct segments. Antennae with a multiarticulated flagellum. 



Idotea. 



* Prof. Clans, in the French translation by Prof. Moquin-Tandon of his 

 ' G-rimdziige der Zoologie,' p. 465 (1871), includes both Chcstilia and Arcturus 

 in his Idoteides. 



