I22 CRUSTACEA MALACOSTRACA. III. 



The antennal squama is feebly developed (PI. XI, fig. 7 a, sq. ; figs. 8 b and 9 b) or indistinct, 

 it being a low protuberance on the outer side of third joint, and sometimes not marked off. 



Sars paid no attention to the existence of epimeral plates or processes at the four anterior 

 thoracic segments. For instance, his figure of the female /. hmgicomis, seen from above, shows the 

 antero-lateral corners of the four segments a little produced and triangular, but according to my exa- 

 mination of specimens from Skager Rak the structure is in reality rather different, agreeing more with 

 Tattersall's figure of his Plunketti Tatt. (Isopoda, PI. VII). The first segment is at each side produced 

 into a somewhat small, conical protuberance directed outwards, and with a single spine or two to four 

 spines on the end; below and a little in front of this protuberance is seen a process, which originates 

 from the basal joint of the leg, is directed obliquely outwards and more or less forwards, and termi- 

 nates in a spine or in two to four spines. The epimera of second segment are broad, bilobed, the 

 posterior lobe rounded, the anterior conical, directed obliquely forwards and terminating in a spine; 

 the antero-lateral corner of the segment itself is produced into a kind of lobe which, seen from above, 

 is narrow, directed forwards and outwards and, at least generally, without any spine. Third and fourth 

 segments have their antero-lateral corners produced and shaped as in second segment, but not marked 

 off by any suture as figured by Tattersall, while the epimera are rounded, without any spine. As I. 

 longicornis G. O. S. is not known from the "Ingolf" area, it may perhaps be inserted here, that by the 

 remarks on the anterior segments the two best characters between / longicornis G. O. S. and I. Plun- 

 ketti Tatt. have disappeared; the third character (Tattersall, op. cit. p. 29), derived from the apparently 

 strong difference in the shape of first joint of the antennula, must be cancelled, as the figure of Sars 

 (see above) is quite wrong as to this feature; the fourth character, derived from the shape of the fe- 

 male operculum, also disappears, as the upper (the basal) half of Sars' figure of the operculum is incor- 

 rect. Consequently / Plunketti Tatt. must be cancelled as a synonym for /. longicornis G. O. S. 



Of llyarachna as defined by Sars in the Account I have four species from our area, and three 

 of them are new; a fifth species not seen by me, but described by Ohlin from East Greenland (and 

 Spitzbergen), is mentioned later on. But it is with considerable hesitation that I follow Sars in adopt- 

 ing his genus Echinozone, which is so closely allied to llyarachna and based on two characters of so 

 slight value (see later on) that it ought perhaps to have been withdrawn. My report here on llyarachna 

 and Echinozone is unsatisfactory as to several points, because most of the specimens are mutilated, and 

 of some species the material is very scanty. The single species, of which a rich material is to hand, 

 showed furthermore much variation according to age, locality and, apparently, also variation of purely 

 individual nature. Perhaps the first pair of male pleopods may afford reliable specific characters, 

 when a good material of several species is studied. 



78. llyarachna hirticeps G. O. Sars. 

 (PI. XI, fig. 7 a). 

 1870. llyarachna hirticeps G. O. Sars, Forh. Vid. Selsk. Christiania for 1869, p. 167. 

 ! 1897. G. O. Sars, Account, II, p. 137; PI. 60. 



! 1897. denticulata G. O. Sars, op. cit. p. 138; PI. 61, fig. 1. 



