4 ARKIV FÖR ZOOLOGI. BAND 13. N:0 20. 



Hansen (1913, Fig. 2 a) scheint es, als habe das Exemplar, 

 nach dem die Figur gemacht wurde, auch zur vorliegenden 

 Art und nicht zu M. f osthon gehört.» Last winter I therefore 

 asked Prof. Odhner to send me again the animals (some- 

 what more than a score) referred by me in 1913 to M. posthon 

 in order to re-examine them with the aid of Zimmer's paper. 

 The specimens originated from seven localities, all very far 

 from the German station; and the majority is either rather 

 mutilated or young. The result of my new inspection, is, 

 however, that my earlier determination is correct, as the 

 specimens present so much variation in the best features 

 used by Zimmer as showing specific characters, that at least 

 his M. similis cannot be maintained. But it may be useful 

 to mention several specimens. 



In the large female from lat. 65° 19' S. the shape of the 

 rostrum agrees completely with Zimmer's drawing (fig. 36) 

 and description of M. posthon, and it does not cover the 

 proximal part of the ocular or of antennular peduncles. The 

 upper spiniform process at the outer side of the antennal 

 peduncle is somewhat shorter than the lower, and the telson 

 is (measured here and in the following cases by micrometer) 

 accurately five times as long as its terminal incision; in the 

 last named feature the telson agrees more with that of M. 

 similis than with 31. posthon. — In four females with mar- 

 supium from lat. 54°24' S, the rostrum is as to size not 

 larger than in the above-mentioned specimen and does not 

 overreach the basal part of antennular or ocular peduncles, 

 but as to shape the rostrum shows individual variation both 

 in breadth and in the shape of its marginal portion, as in 

 one specimen it agrees with Zimmer's figure of 31. posthon, 

 while in another specimen it is as to the upturning of the 

 marginal part nearer to 31. similis than to 31. posthon. The 

 lower spiniform process at the outer margin of the antennal 

 peduncle varies conspicuously, being from moderately long 

 to somewhat short, while the upper denticle is short or nearly 

 rudimentary, consequently as in 31. similis Zimm. In one 

 of these females the telson is only a little less than 6 times 

 as long as the distal incision, thus decidedly as in 31. similis, 

 and in another female the telson is even 9 times longer than 

 the very short, triangulär incision, thus reminding of the pro- 

 portion in 31. Hanseni Zimm., but differing from this in 



