PREFACE. 



This is the 3rd in succession of the long series of Volumes which will 

 be needed to elucidate the rich carcinological fauna of Norway. It treats of a 

 group of Crustacea, which until recently has continued to be very imperfectly 

 known, and of which, therefore, as yet, scarcely any text-book exists. Indeed, I 

 have myself been fortunate enough to contribute my quota to a closer know- 

 ledge of these interesting Crustacea, having been enabled to institute rather 

 extensive studies both of indigenous and foreign forms. 



In the preparation of this Volume, I have had at hand abundance of 

 material, which has been collected almost entirely by myself at various times 

 during my numerous voyages along our coasts. Indeed, I think that there are 

 now very few additions to be made to the Cumacean fauna of Norway, which 

 at present comprises in all no less than 48 species, belonging to 17 different 

 genera, a number not as yet nearly attained by that of any other country. Of 

 these species more than half the number (28) have been first established by the 

 present author from Norwegian specimens, and have long been regarded as 

 exclusively peculiar to the Norwegian fauna. Of late years, however, some of 

 them have also been found in other places, in some cases far from Norway- 

 for instance in the Mediterranean and I think that on a closer investigation all 

 of them will prove to have a much wider distribution than was at first expected. 

 The present Volume will therefore, I hope, be useful not only for the determi- 

 nation of Norwegian species, but also for the future investigation of the Cuma- 

 cean fauna of other countries. 



The plan upon which the present Volume has been carried out, is 

 essentially the same as that followed in the 2 preceding Volumes, with one excep- 

 tion, namely, that besides the strictly systematic part, a more detailed account 

 of the internal anatomy and development has also been given at the close of the 

 Volume, an addition which may not be out of place, considering the comparatively 

 recent date of our knowledge regarding this peculiar group of Crustacea. 



