— 44 — 



structure of the copulatory organs, especially the shape of 

 the proximal process (i6 : PL xxu, Fig. 29) affords the 

 most excellent character. The species varies much in 

 length and in the shape of the long rostrum, and conspi- 

 cuously in length and relative depth of the sixth abdominal 

 segment. Some few among the adult males captured by 

 the Swedish Antarctic Expedition are small with sixth 

 abdominal segment slender and not much shorter than the 

 sum of fourth and fifth, thus in this feature differing but 

 little from small specimens of the two antarctic species, 

 but they are instantly separated by the peculiar copulatory 



organs (Fig. i5); some other males from the same area are 

 good-sized with sixth abdominal segment deeper and 

 proportionately a little shorter. — Length of adult speci- 

 mens 8.5 -16. 5 mm. 



The geographical distribution is interesting. The 

 species is known from the temperate North Atlantic, the 

 temperate South Atlantic and southwards in the antarctic 

 area to about lat. 53 1/2 0 S. (Swedish Antarctic Exp.), 

 furthermore from lat. 39 0 56' S., long 40 0 E. (Copenhagen 

 Museum), South Pacific (Sars), temperate North Pacific 

 (Sars, Holmes), and northwards at least to Bering Island 

 (U. S. Nat. Museum) — but it has never been taken in the 

 tropical area and, so far as I can see, perhaps not in the 

 subtropical belts of any ocean. 



Fig. i 5. Thysano'ëssa 

 gr eg aria G. O. S. 

 Inner lobe of left 

 copulatory organ, 

 from behind. 



