PYCNOGONIDA. 



By T. V. Hodgson, RL.S. 



(10 Plates.) 



The collection of Pycnogonids brought from the Antarctic by the 'Discovery' is a 

 large one, including as it does no less than twenty-eight species, three of which have 

 been assigned to as many new genera. Only one species can be regarded as of morpho- 

 logical importance, Pentanymphon nntarcticum, which is now known to be abundant 

 and to have a circumpolar distribution. It differs from the genus Nymphon only in 

 the possession of an additional pair of legs. At first this was thought to be quite a 

 novel feature in the morphology of the Pycnogonida, but the Scotch expedition brought 

 another and much finer species from the South Orkneys. This proved to be identical 

 with Decolopoda australis, described by Eights some seventy years ago, and taken at 

 the South Shetlands. Eights' work was lost for a long time, and though it has been 

 noticed recently by modern zoologists, the reception afforded it was extremely curious, 

 involving as it did the point-blank refusal to accept the possibility of the existence of 

 a Pycnogonid with more than the orthodox four pairs of legs. Mr. L. J. Cole (7), who 

 apparently looked with more sympathy on the work of a fellow-countryman, was the 

 first to appreciate this discovery properly. The genus Leionymplwn was defined by 

 Professor Mobius for a large but immature specimen taken by the ' Valdivia ' in the 

 vicinity of Bouvet Island. It has been found necessary to re-cast this genus ; as now 

 defined it contains no less than eight species, including two which had been assigned 

 to the genus Amviothea, and another which Professor Mobius thought should be placed 

 in the genus Colossendeis. No less than five species were taken by the ' Discovery,' 

 and four of them are new. No true member of the genus A mmothea was seen, but two 

 new species assigned to new genera, Austrodecus and Austroraptus, belong, as does the 

 genus Leionymplwn, to the family Ammotheidse as defined by Professor G. 0. Sars. 



Austrodecus is perhaps a close relation of Tanystylum, Miers, and is a curious little 

 form with a slender and elongated proboscis, like the snout of a weevil beetle, no chelifori, 

 six jointed palps, and small ovigers. Austroraptus is remarkable for its spurred body 

 and the length of its legs. 



Rhynchothorax australis is another curious form ; the only other species of the 

 genus is found in the Mediterranean, but, notwithstanding certain diff"erences, there 

 does not seem to be any justification for giving the ' Discovery ' species other than 

 specific rank. 



M 2 



