i88 DISCOVERY REPORTS 



styliform extremity. In the abdomen the uncini are very similar to those of the thorax 

 and the bristles are also similar to the thoracic, but more slender. 



Remarks. This species is very close to the northern S. fabricii, Kroyer. 



Genus Potamilla, Malmgren 

 Branchiae symmetrical, not spiral, without dorsal appendages. The filaments often 

 carry rows of simple or compound eyes. The collar is lobed. The first chaetiger has 

 winged bristles. The dorsal bristles of the remaining thoracic chaetigers consist of 

 winged chaetae and spatulate chaetae. The thoracic tori carry avicular hooks and pick- 

 axe bristles. The abdominal uncini are also avicular and the abdominal bristles are 

 winged. 

 Potamilla antarctica (Kinberg). 



Potamilla antarctica, Gravier, 1907, p. 59, text-figs. 38-43. 

 Potamilla antarctica (Kinberg), Fauvel, 1916, p. 474, pi. viii, figs. 4-7. 

 Benham, 1921, p. 109, with synonymy. 

 Occurrence. St. 190 (numerous); 363 (numerous); 366 (3); 371 (9); 474 (4); WS 231 (i); 

 WS 583 (6); WS 782 (i); WS 785 (4); WS 787 (2); WS 804 (i); WS 805 (i); WS 811 (i); WS 837 



(2). 



Specific characters. Up to about 230 mm. in length exclusive of the gills. There 

 may be no colour or the gills may have a number of conspicuous bands of reddish brown 

 pigment confined to the barbules and to the inner faces of the filaments. The collar is 

 widely open on the dorsal surface. It slopes upwards and backwards from the front, is 

 entire laterally and forms two ventral lobes separated by a deep incision. The normal 

 number of thoracic chaetigers is eight, but this is subject to variation {vide Benham, 

 loc. cit., p. 1 11). There is no branchial palmar membrane. There is a pair of palps about 

 one-third as long as the gills. They are foliaceous at the base and have long cirriform 

 terminations. There are winged bristles only in the first chaetiger. The remaining 

 thoracic notopods have winged bristles and spatulate bristles, and there are no chaetae 

 transitional between the typical spatulate bristles and the winged bristles. The thoracic 

 tori carry uncini with a crest of denticles and a long base. There are also pickaxe bristles. 

 In the abdomen the uncini have shorter bases than in the thorax. The abdominal 

 bristles are rather more curved and widely winged than the thoracic. 



In this species the eggs are incubated inside the branchial plume. The tubes are 

 yellowish, horny and to some extent incrusted with sand grains. 



Genus Oridia, Rioja 

 The members of this genus are small. The branchiae are symmetrical, not spiral and 

 without dorsal processes or eyes. A collar is present. The first chaetiger carries bordered 

 bristles. The dorsal bristles of the remaining thoracic chaetigers have narrow wings and 

 are all of the same type. The thoracic hooks have a long downwardly directed manu- 

 brium. There are no pickaxe bristles. The abdominal hooks have a short base and no 

 posterior prolongation. The abdominal bristles are capillary and often geniculate 

 towards the base. 



