PYCNOGONIDA. 



45 



Distribution. The species is circumpolar, and besides it follows as well the American as 

 the European shores far southward, thus being one of the most widely spread and most common 

 Pycnogonida on deep water. 



16. Nymphon tenellum G. O. Sars. 



Nymphon tenellum Sars, Pycnog. bor. arct, 1888, p. 353. 



Idem, Pycnogonidea, 1891, p. 109. PI. XII. Fig. i, i a-h. 



Occurrence. The Ingolf-stations are: 7, 28, and 44, showing it to be found in the northern- 

 most part of the Atlantic and in the south of the Davis Strait in depths from 420 to 600 fath. 



Distribution. The species had hitherto only been found by Sars in the sea off the Fin- 

 mark, and consequently this author took it to be a genuine arctic form; the three stations given here, 

 carry the species much farther south and west, always on very deep water. 



17. Nymphon robustum Bell. 



PI. III. Fig. 2324. 



Nymphon robustum Bell, Account Crust, 1855, p. 409. PI. XXXV. Fig. 4. 

 Chsetonymphon robustum Sars, Pycnogonidea, 1891, p. 115. PI. XII. Fig. 3, 3 a-d. 

 Nymphon hians Heller, Crust Pycnog. Tunic., 1875, p. 41. Tab. V. Fig. 35. 



The species varies very much, especially as to size; thus a grown male has measured 23""", 

 and an unripe female i9,5 mm , while on the other hand grown males of n mm are not rarely met These 

 differences for a long time induced me to suppose two or more species to be hidden under the old N. 

 robustum, and so I began to study the several small and large specimens in their mutual contrast, 

 and thought in the armature of the fourth and fifth joints of the ovigerous legs of the male to have 

 found a sure criterion. I had, however, soon to give up the thought of the systematic importance of 

 this armature; but nevertheless I have partly rendered it here in pi. Ill, fig. 23 and 24, as it seemed 

 to me to give a good idea of the powerful development and the different shapes and positions as- 

 sumed by the bristles of the legs for the attaching of the eggs and young; it is, however, also to 

 be remembered that N. robustum is likely to be the Pycnogonid, on the male of which the young 

 are most firmly attached, and cling for the longest time. 



Occurrence. The Ingolf-stations are: 3, 4, 15, 41, 101, 103, 105, 115, 116, 126, 138, 139, 140, 141, 

 143. According to this series of stations it has most frequently been taken in the west and south 

 parts of the Norwegian Sea, and some way into the Atlantic; single specimens have been taken in 

 the Greenland Sea and the Denmark Strait. The depths were mostly between 300 and 800 fath., only 

 once below 100 fath. viz. 86 fath. 



In the Zoological Museum it is found from the Greenland Sea: 70 26' I/at. N. (Deichmann); 

 72 26' Lat N. 19 35' Long. W. , 105 fath. (idem) ; 72 53' Lat N. 20 3 36' Long. W. , 96 fath. large stones 

 (idem); Scoresby Sound 325 fath. (idem); from the Davis Strait, 66 1 6' Lat. N. 25 20' Long. W. , 327 



