56 ME. E. J. MIEES OK THE TDOTEIDiE. 



rate size. Antennules scarcely reaching to the base of the ante- 

 penultimate joint of the peduncle of the antennae, with their basal 

 joints considerably dilated. Antennae with, the joints of the 

 peduncle short, the last two subequal, and each but little longer 

 ttan the antepenultimate j oint ; flagellum 16-2 1-j ointed and longer 

 than the peduncle. The epimera are narrow, and in the second, 

 third, and fourth thoracic segments scarcely occupy more than 

 half the length of the lateral margins ; in the fifth segment they 

 reach nearly, and in the sixth and seventh segments quite, to the 

 postero-lateral angles, and in these segments are of a more or 

 less ti-iangulate shape. The legs are very slender. The terminal 

 plates of the opercular valves are three-sided, with their outer 

 margins curving to the distal extremity, which is subacute or 

 blunt. Length of the largest male about If inch (48 millim.), 

 breadth nearly y^^ inch (10 millim.) ; but most of the specimens 

 are much smaller. 



In the British-Museum collection are specimens : — from York 

 Peninsula, Australia, a female, preserved dry (Gr. P. Angas); 

 Tasmania, a male, dry (Ronald Grunn) ; and a small example, 

 also in a dry state, from Plinders Island, Bass's Straits (Surgeon 

 Eayner, H.M.S. ' Herald ') ; also a good series of males and females 

 from Plinders Island, preserved in spirit (Dr. Milligan). 



The examination of the type of M.-Edwards's Idotea Peronii 

 (a male, from King's Island, M. Peron), in the collection of the 

 Paris Museum, seems to show that M. Guerin's Idotea distincta 

 cannot be specifically distinct. In M.-Edwards's type there are 

 in reality tivo lateral sutures (not a single one as stated) on the sides 

 of the terminal segment near its base. The only distinctive cha- 

 racter is the more rounded apex of the terminal segment in 

 I. Peronii, which, in this instance, is probably due to the contrac- 

 tion of the specimen (which was formerly in a dry state), audit is 

 not, moreover, a character of much importance. M. Gruerin's 

 types were from the Cape of Grood Hope. In the Paris collec- 

 tion are a considerable series from Melbourne. 



The description was taken from sjDecimeus in the British 

 Museum, with which M. Milne-Edwards' s type, now somewhat 

 shrivelled and with imperfect antennae, has been compared. In 

 Australian specimens the apex of the terminal segment is often 

 just of the form described by Gruerin-Meneville in I. distincta. 



In a small example from Elinders Island in the British Museum 

 the head is less distinctly emarginated, the terminal segment is 



