11 



first to the Atnphascandria, the 2nd to the f-ieterarthmndria. I think that this 

 premary division of the Calanoida proposed by Giesbrecht, and now generally 

 accepted by carcinologists, may turn out to be a less natural one, and I am 

 also now in doubt about the validity of the 3rd intermediate section, Isoker- 

 andria, added in my earlier account of the Calanoida (Vol. IV of the present 

 work). Indeed, it seems to be very difficult to decide, to which of these 3 

 sections the present genus should be referred. 1 ) Two nearly allied species of 

 this remarkable genus will be described below. 



6. Platycopia perplexa, G. O. Sars. 

 (PI. VI, PI. VII, fig. 1). 



Platycopia perplexa, G. O. Sars, Archiv f. Mathem. & Naturvidenskab, Vol. XXXI, No. 7, p. 4, 



PI. I & II. 



Specific Characters. Female. Body short and stout, with the anterior 

 division greatly vaulted above and somewhat compressed, the greatest width 

 not fully attaining the hight and about equalling half the length. Cephalic 

 segment very large, occupying nearly half the length of the whole body, and 

 evenly curved in front; inferior edges somewhat bulging in their anterior part, 

 rostral projection comparatively short and acutely pointed at the end. The 4 

 succeeding segments densely crowded and of about equal length, though 

 diminishing somewhat both in height and width; last segment deeply emarg- 

 inated behind in the middle and having the lateral lobes rounded at the end. 

 Urosome scarcely exceeding in length 1 /z of the anterior division and narrow 

 cylindrical in shape; genital segment comparatively small and only slightly 

 dilated; penultimate segment the longest and produced at the end dorsally to 

 2 juxtaposed lanceolate lappets superposing the anal segment and apparently 

 replacing the usual anal opercle; last segment much smaller than any of the 

 others. Caudal rami short, being only slightly longer than they are broad; 

 seta of outer edge small and attached somewhat in front of the middle; apical 

 setae rather unequal in length, the innermost but one being, as usual, the 



: ) At this occasion I will mention another instance, which still more seems to debilitate 

 the validity of Giesbrecht's arrangement. On a closer investigation of the Calanoida from the 

 Monaco Expedition instituted in the latter years, I have to my great astonishment found, that in 

 the male of Bathycalanus Richardi G. O. Sars, a form unquestionably nearly allied to Megaca- 

 lanus, the right anterior antenna is very distinctly hinged. According to this character the 

 genus Bathycalanus should of course, if the primary division proposed by Giesbrecht is accepted, 

 not only be wholly removed from the family Calanidce (in the restriction here adopted), but 

 transferred to quite another section of the Calanoida, the Heterarthrandria, an arrangement 

 which in reality would be absolutely unreasonable. 



