EEPORT ON THE PYCNOGONIDA. 11 



hair. However, these rules admit of a great many exceptions. Thus the most common 

 shallow-water species of the English, French, and Dutch coasts is Nymjylion gracile, 

 Leach, an exceedingly slender animal with very long legs, and moreover almost smooth. 

 Colossendeis prohoscidea, Sab., sp., is a blind species occurring only at a considerable 

 depth ; yet it has a highly concentrated body with short legs. Two species of Phoxi- 

 chilidium, for which I have proposed the names Phoxichilidium pilosum and Phoxichili- 

 dium moUissimum, are true inhabitants of the depths of the ocean ; yet they are not 

 smooth at all, but covered by a very hairy integument. The case of Phoxichilidium pata- 

 gonicum and its variety elegans, which I describe hereafter, must probably be considered 

 as a trifling instance of the efl"ect of depth on the slenderness of the body. 



The scientific and trustworthy material at our disposal is by no means sufficient 

 to enable us to discuss thoroughly the question of the geographical distribution of 

 Pycnogonids. Judging from what is known of the European and North American 

 coasts, it is most probable that on all coasts, and everywhere in shallow water in the 

 neighbourhood of the shore, forms of Pycnogonids will be found occurring ; and as I 

 think it improbable that any true shore-inhabitant will be found which shows a very 

 wide range, it is also highly probable that the number of littoral forms at present known 

 is very small in comparison with the number really existing. 



The distribution of those Pycnogonids which are not to be considered as shore- 

 inhabitants, but which have never been dredged yet at depths exceeding 500 fathoms, 

 is best known in the northern part of the Atlantic and the seas corresponding with it 

 (North Sea, Greenland Sea, Barents Sea). The species of the genus Nymphon, which 

 occur in the neighbourhood of the coast of New England, are found to the north and 

 east as far as Greenland, Spitzbergen, and Novaja Semlja ; but these Arctic Seas are, 

 moreover, inhabited by some forms of the same genus occurring there only. As this 

 point has been more fully discussed by me in another paper, it will suffice merely to 

 mention it here. 



Among the Pycnogonids of the Challenger Expedition, Colossendeis megalomjx, 

 Hoek, is the only species, which, though found at a depth of from 55 to 120 fathoms, has 

 a wide range ; about the 58th south parallel it was dredged off Kerguelen Island, and 

 also between Patagonia and the Falkland Isles. 



With respect to the true deep-sea species the material is by no means sufficient for 

 the study of their geographical range. Of the thirty-six species of Pycnogonids brought 

 home by the Challenger, nineteen are true deep-sea species. Of these only three belong 

 to the northern hemisphere, viz., Colossendeis miniita, Hoek, south of Habfax ; Phoxichi- 

 lidium oscitans, Hoek, west of the Azores ; and Phoxichilidium moUissimum, Hoek, off 

 Ycddo ; they were only dredged once and were new to science. Of the remaining sixteen, 

 which belong to the southern hemisphere, one was dredged at lat. 65° 42' S. 

 {Nymphon meridioncde, Hoek) and one almost under the equator {Nyvphon per- 



