STACBA MAJ.ACOSTRACA III. n 



two pleopods of second pair independent to their sternite. The fusion of the second pair of male 



;-<K!S in two genera is a very interesting morphological feature. 



As already im-miunol. tin fauna from the "IngolF area comprises 105 species, 61 of which are 

 new, and it was deemed necessary to establish 10 new genera. The sub-order is rich, and the general 

 aspect of many of the genera extremely different. The necessity of dividing it into families has long 

 been felt, and some attempts have been made. In his account, G. O. Sars divided the Norwegian forms 



!u sub-order (or tribe) into five families, while Yanhoffen in his work on the Isopoda (and Tanai- 

 dacea) from the German South-Polar Expedition has eight families. In the above-named paper (1905) 

 I critisi/ed the classification of Sars, showing that four of his families are "far from distinct from each 

 other"; based on a number of characters found in the pleopods I divided the sub-order into three 

 families, Asellidse, Stenetriidae and Parasellidae, the two first-named quite small, the third comprising 

 the great majority of forms, in reality uniting the four families of Sars. Especially is his family Desmo- 

 somatidse badly defined, because it comprises forms like /schnomtstis (Ischnosotna). Natmoniscus. 

 Mtcrostylis and Dfsmosoma, which, according to many features, are very distant from each other. And 

 such types as Sckistosoma n. gen. and J'sriidomt-sus u. gen. would be very difficult to place in his 

 system. In vain I have attempted to find leading characters in the shape of any organ. As the best 

 example may be taken the mandibles which in lanira and allied genera have the molar process robust, 

 snbcylindrical with the end cut off, and passing through a number of types as Plfurogonium, Nanno- 

 niscus. Afatrostylis, Desmosoma, Ilyarachna and Aspidonotus that process is gradually reduced, more 

 slender, gradually conical and smaller, until it is very small in Aspidonotus and disappears in .I///// 

 nopsu. But in Eurycope cornula G. O. S., which by Sars is placed in the same family as the .three 

 last-named genera, the molar process is well developed, thick, and differing from that in lanira only 

 in being more obliquely cut off; in Aftittnopsurus giganteus G. O. S., which is closely related to F.ury- 

 cope and by Sars is referred to this genus, the molar process is only a quite low, broad and rounded 

 protuberance. 



Kvery attempt to divide the very numerous genera of course including those not found in 

 our area belonging to the four families of Sars into moderately well defined families will, in my 

 opinion, be impossible. But as a kind of arrangement is very desirable I attempt here to subdivide 

 the family Parasellidae H. J. H. into a somewhat larger number of smaller, but tolerably equivalent, 

 groups. In this way it is possible to arrange genera showing somewhat close relationship into a kind 

 of unit and point out its essential features, and the name "group" is much more neutral and somewhat 

 less exacting as to sharp diagnoses than the name "subfamily" or "family". 



Of the three families into which I divided the Asellota, the Asellidac with its single species 

 Asflliif afita/ifMs L. known from Iceland and Greenland is omitted as being not marine. The Stene- 

 triidse have no representative; all the forms dealt with belong to the family Parasellidae. 



