A NEW SPECIES OF IDOTEA. 199 



Colour (in alcohol) yellow, dorsally densely punctated with fine irregular 

 blackish-brown coloured markings. 



Hah. Sea of Marmora and Black Sea. 



Type. In the Zoological Museum of the University of Copenhagen. 



Remarks. To the naked eye /. Stephenseni is at once distinguishable from 

 its ally, /. metallica, Bosc, by the prominent, somewhat triangular-shaped 

 coxal plates of the mesosome and the form of the terminal segment of the 

 metasome. Further, it is much more elongated than /. metallica, the sides 

 of the body being nearly parallel. 



I have carefully compared this species with specimens of I. metallica from 

 Japan, North America, the Mediterranean and Adriatic Seas, and our own 

 coasts, but all the 'Thor' specimens, excepting those from Stations 208 and 

 311, are very distinct from any of them. 



In colour there is a marked contrast to the dull bluish green of /. metallica, 

 for here the ground-colour is yellow, and, with the exception of the coxal 

 plates, the whole of the dorsal surface is densely punctated with fine, 

 irregular-shaped, blackish-brown coloured markings ; these are also present 

 on the antennulse and antennae, and the seven pairs of appendages of the 

 mesosome. 



I find very little, if any, difference in the general shape of the body in the 

 two sexes, excepting that the females are rather smaller — a feature, in a 

 somewhat lesser degree, common to /. metallica also. 



The cephalon is wide with the anterior margin curving deeply inwards, 

 whilst laterally it is produced in front of the eyes, the two processes termi- 

 nating in sharp points. Stephensen's figure does not show these in sufficient 

 detail. 



The antennulfe are short with the 1st joint expanded. The point of arti- 

 culafion with the cephalon is on the ventral side of this joint, and not at 

 the base as in /. metallica and most other members of the genus. 



The antennse are elongated — in specimens 29"5 mm. long, they measure 

 12 mm. in length. The setse on the joints of the peduncle are very charac- 

 teristic, and quite distinct from anything I can find in /. metallica. The 1st 

 joint is small, the 2nd and 3rd almost subequal, the 4th longer, and the 5th 

 the longest of all. The first four joints of the flagellum are ill-defined and 

 short, the remainder being elongated ; all have short setse at the distal end 

 of each joint. 



The first maxillse are stouter that in /. metallica, terminating in twelve 

 spines on the outer lobe, and three long setose ones and a setule on the 

 inner lobe. 



The maxillipedes are much longer than in /. metallica, and the 4th joint of 

 the palp is produced anteriorly, whilst the outer margin has a series of five 

 or six indentations. The groove on the 3rd joint is fairly conspicuous, as 



