BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 26. AFD. IV. X:0 12. 19 



Also. in respect to tbe dorsal impressions. I cannot like 

 Saks regard tliem as eonstant charaeteristies, becanse I have 

 found theni snbjected to great variations. In tbe most spe- 

 ciiuens tbey are distinctly developed. altbo^^g•b in a greater 

 or smaller degree, bnt tbey disappear sometimes, nntil it be- 

 conies quite impossible to distinguisb tbem. For instance, 

 from stat. 84, nearly all specimens are M'itbont tbese dorsal 

 impressions. Anotber cbaracter, at least as often occnrring 

 as tbe impressions, bat whicb does not seem to exist in Särs' 

 specimens. as be bas no record of it, is a more or less pointed 

 tnbercle a little before tbe posterior margin of tbe bead. 

 Heller refers to tbis in bis nota speciftca of Faranthura arc- 

 fica, and Haroer believes tbat it must be regarded as a spe- 

 elfie cbaracter for tbis arctic form from bis P. brackiata. 

 Låter on, Särs bas compared specimens from Nortb America 

 and Europé, but be cannot iind any difference; and. as to tbe 

 tubercle, Weber tbinks tbat it is a cbaracter belonging to 

 tbe male sex, as be did not find tbem in adult feraales nor 

 in young ones of eitber sex. In nearly all my specimens, 

 even in very young ones and also fullgrown females, I ob- 

 served at least sligbt traces of tbe tubercle, so tbat I bave 

 no opinion as to tbe correetness of Weber's view. 



As to tbe form of tbe body it is very variable on ac- 

 count of difference in age and sex. To sbow tbat, I give 

 bere tbe following measurements of a fullgrown male and 

 female. 



Lengtb of male 43 mm. 



Breadtb » ^ (above tbe coxal joint of tbe sixtb 



pair of pereipods) 3 » 



Lengtb of female 31 » 



Breadtb » * 3,2 » 



Tbe smaller size of C. norvcgica ^ ougbt to be considered, 

 in my opinion, as of no importance. It is a well known fact 

 tbat true arctic species, wben occasionally occurring in more 

 soutbern seas as in tbe deep Norwegian fjords, never attains 

 their full size. Tbey are always smaller and dwarflike; 

 generally tbey differ also in points of sligbter importance. 

 Once before - I bave pointed ont tbis circumstance especially 



^ Acc. to Särs, the length is 12 mm. 

 2 1. C. pp. XIV, 33. 



