786 



CRUSTACEA. 



of last segment a little sinuous in outline. Caudal appendages 

 extending somewhat beyond line of extremity of abdomen ; inner 

 lamella straight truncate; outer acuminate, narrower than the same 

 lamella in the typica. 



Plate 52, fig. 14 a, head, much enlarged ; b, dorsal view of extre- 

 mity of abdomen ; c, under view of same ; d, basal portion of second 

 antennae. 



New South Wales. 



Length, ten lines. The resemblance to the typica is at first sight 

 very close; yet the differences are important, and authorize the sepa- 

 ration of the species. The surface is smooth and naked. 



Teibe II. ANISOPODA. 



The relations of the group Anisopoda to the other Choristopods 

 have been briefly pointed out. The exact extent of this subtribe is, 

 however, not yet ascertained. We may briefly mention the genera 

 hitherto ranked with the Isopoda that appear to be Anisopodan, and 

 remark upon the characters which lead us to conclude that this is 

 their true relation. 



1. Arctwrus and Leachia* — The thoracic members in these genera 

 are Amphipodan in arrangement, and, as in the Caprellids, the three 

 posterior pairs are used as feet for clinging, while the four anterior 

 pairs are extended forward as arms for collecting their food. The 

 abdominal members are as in Idotaea. 



* These are the Idoteides Arpenteuses of Edwards, Crust., iii. 122. 



