11 



ON A PYCNOGONID OF THE GENUS HALOSOMA, 



From New South Wales, 



by 



Peofessoe T. Thomson Flynn, University of Tasmania. 



[Received 30th May, 1918. Read 10th June, 1918. J 



(PI. I., figs. 1-6.) 



1. Inteoduction. 



Being engaged on a re-examination of the holotypes 

 of Australian Pycnogonida described by Haswell in 1885 

 {1) I have found it necessary to- supplement the material 

 available by collecting at the localities mentioned in 

 Plaswell's paper. During one of these excursions recently 

 to Shark Island, Port Jackson, I obtained a Pycnogonid 

 which could without any difficulty be refeiTed to the genus 

 Ilalosoma defined by Cole in 1904 (2). I have, therefore, 

 taken the opportunity of describing this new species, and 

 of discussing the position of the genus Halosoma. 



Shark Island is a simall islet a few miles from the 

 entrance to Port Jackson, aiid its little coast presents tho 

 main ecological features which have been so excellently 

 described for Port Jackson by Hedley (3j. This author 

 points out that in the sheltered parts of Port Jackson 

 between tide marks the rocks are plastered with a more 

 ■or less thick layer of rock oysters {0. cucuUata, Born.). 

 This: layer becomes exposed at ordinary low tides. Deeper 

 than this, and only usually seen at the very lowest tides, 

 is a zone occupied by mussels {Bracliyodontes hirsuiu-i). At 

 that island this region of mussels is by no means con- 

 tinuoiis, but is, nevertheless, well represented. The vari- 

 ous noioks and crannies between the mussels serve as lurk- 

 ing places for many unique and rare forms, and it is in 

 this position that the single male specimen of Halosoma 

 was found. It is easily overlooked on account of its ex- 

 tremely small size. Nevertheless there is no doubt that 

 further detailed search would lead to' the discovery of 

 fresh specimens. 



2. Genus Halosoma, Cole, 1904. 

 Halosoma, Cole. Harrim. Alask. Exp., Vol. X., Crust., 1904. 

 Pi. XIV., fig. 11; pi. XXIV., figs. 6-8; pi. XXV., figs. 1-4. 



The genus Halosoma was based by Cole in 1904 on a 

 single female specimen of H. viridintestinalis from Dillon's 



(1) 1885 Haswell, W. A. Proc. Linn. Soc, ]Si.S.W., Vol IX., 



p. 1021. 



(2) 1904 Cole, L. J. Harriman Alaska Expedition, Vol. X., 



Crustacea, p. 286. 



(3) 1915 Hedley. C. Presidential Add. Proc. Royal Soc. N.S.W., 



Vol. XLIX. 



