Mr. L. J. Cole on Ten-hyged Pycnogonids. 413 



of an extra segment bearing a pair of legs would be more 

 than sufficient for the establishment of a separate family in a 

 group where family distinctions are based upon such minor 

 characters as the extent of devclopnient or suppression <•£ 

 certain appenda>;es, with no question of the loss of a segment ; 

 but Peiitanipiiphoa aj)parently resembles N^i/in/j/wn so closely 

 in all its minor details, even to the presence of a claw, denti- 

 culate on one border, terminating the oviger, that it is incom- 

 prehensible that these characters could have been developed 

 independently. I'^xcept for the extra legs Peutauymphon is 

 in all respects a true Ni/mp/iou, and this, did we not know of 

 another ten logged form, would lead us to suppose that it 

 represented the piimitive stem of the Pycnogoniila. Must 

 we, then, conclude that the group has had two points of 

 origin ? 



Hodgson (1904, p. 4G2) states that he understands 

 Mr. \\. S. Bruce, of the Scottish Antarctic Exjiedition, has 

 taken several specimens of a ten-!egged Pyenogonid from 

 the VVedilell Sea which may prove to be identie.d with 

 Pentanymphon antarct'icnm. But since the Weddell Sea is on 

 tlie opposite side of the Antarctic continent to McMurdo 

 Bay, and not far from the South Shetland Islands, it would 

 not be surprising if Mr. Bruce's specimens turned out to be 

 identical with Derolopoda australis*. Should they prove to 

 be Decolopoda rediscovered, a careful study of th( m may add 

 much of importance to our knowledge of the Pycnogonida. 

 It is noteworthy that the two species of ten-legged Pycno- 

 gouids so far described botli come from tlie Antarctic, though 

 from opposite sides of the Polar area t- 



The bearing of this extra appendieulate segment on the 

 ancestry of the Pycnogonida and their relationship to the 

 other Arthropods I shall nut discuss at this tiuie, except to 

 call attention to the fact that it adds further difficulties to 



* [Mr. C. V. Hods'son has Idudly sent us the following note on this 

 point : — Mr. W. S. Brace's collection of Pycnogonida from the South 

 Orkneys includes a single specimen of Pentanymphon antarcticiim and 

 several specimens of Eights's Decolopoda audralis. This latter has been 

 fully described in a paper communicated to the Royal Physical Society 

 of Edinburgh on Jan. 23, 190/5. With regard to the genital apertures, 

 thev exist in both sexes of Decnlopoda australis on the second coxa of all 

 the lee:s. In PentanytnphoH antarcticum they are very difficult to observe, 

 and at present I can only vouch for the female. They occur on all the 

 segments also. — Eds.] 



t South Shetland Islands, about lat. 63° S., long. 60° W. ; McMunlo 

 Bay, approximately lat. 78° S., long. 168° E. (From map showing 

 ■work of National Antarctic Expedition, ' GeograpbicalJournal,' vol. xxiv. 

 no. 2, August 1904.) 



