POLYC'HjETA- HENHAM. 93 



The uncini are uniserial, small, closely-set, and numerous, there being at least sixty 

 in one of the posterior lobes. When seen from the side the uncinus presents two teet'.i 

 above the great fang, one large and one small, as Mclntosh (1915, p. 29) states for 

 T. cincinnatus, there is but a " single tooth," " though occasionally a minute third 

 tooth is visible." I find that when viewed from above the fang is crowned by a row 

 of three teeth usually of approximately equal size, and a single minute tooth placed 

 eccentrically outside this series ; sometimes two of these minute teeth occur. 



The gland shields number 10-13, they are not at all distinctly defined, being 

 rough and traversed by furrows. In T. cincinnatus Mclntosh gives 30 shields. I 

 looked carefully into this, and found not more than 13 in any specimen. 



The tube, as usual, is membranous, covered with sand-grains of very varied sizes ; 

 in some cases they are so coarse as to deserve the name " pebbles," so that the outer 

 surface is extremely rough and uneven ; in others, the grains are finer and more uniform 

 in size and the surface much smoother. Mixed with the sand-grains are fragments of 

 brown or green algae, and occasionally portions of Echinid tests. 



Localities. 



Boat Harbour, 25-30 fathoms. 



Commonwealth Bay, Station C, 15-20 fathoms (very abundant ; bottom rock, 

 with small amount of brown algae). 



Distribution. York Bay, .Bucket Island, Magellan Strait (Kinberg) ; Cape Adare, 

 S. Victoria Land (Willey). 



Remarks. According to De St. Joseph, " Thelepus " may have one, two, or three 

 pairs of gills. Mclntosh says of " Neottis " that it differs from Thelepus in 

 having three gills, whereas Malmgren's diagnosis defines TJielepus as having 

 two pairs only. Willey, and I agree with him, points out the confusion that 

 ensues from the wider use of the word ; but modern writers continue to use it 

 in this extended sense. It is evident that this large common antarctic form is 

 common off Adelie Land, and differs from T. setosus. 



Fauvel has identified T. spectabilis with T. setosus Quatrefages, and in a 

 later paper (1917, p. 269), accepting Willey's suggestion that Kinberg's species 

 is conspecific with the Northern T. cincinnatus, goes even further, and, relyiiig 

 on the possibility that in the same species the gills may vary from two to three 

 pairs, puts forward the view that the latter may be identical with T. setosus : 

 " Mais ceci n'est encore qu'une simple hypothese." 



The fact that in dozens of this Southern form, whether it be T. cincinnatus 

 or not, there is no sign of any such variation shows that this " hypothese " is 

 still unproven, and that for the present the two species, T. setosus and 

 T. antarcticus (or T. cincinnatus), are distinct. 



