6 B Canadian Arctic Expedition, 1913-18 



Arctonoe, n. gen. 



Body of moderate length, tapering caudad. Number of segments moderate. 



Prostomium l.caiinjj; three tentacles which are inserted marginally. Cera- 

 tophores distinct, the styles short and thick, each more or less enlarged proximad 

 nf tin- >lrinlrr t rrmiu:il 'filament. Palpi long, with a slender terminal filament. 

 Tw<> pain of eyes, these typically on posterior half of prostomium. 



Parapodia biramous, but with the notopodia much reduced. Notocirri 

 with rirrophores large, the styles moderate, with terminal filaments. Neurocirri 

 excepting the first, very small. 



I '.mil notopodial and neuropodial setae present, both simple. Notopodials 

 shorter, setose or scaled, distally notched or bidentate. Neuropodials of first 

 postperistomial segment slender, distally bidentate, scaled. The neuropodials 

 of succeeding segments, excepting sometimes one group of those on second 

 parapodia, coarser, with curved hastate heads and simple tips which are not 

 prolonged., more weakly scaled or serrulate. 



Elytra present on somites II, IV, V, VII, IX, etc., as in Halcsydna, with 

 typically near thirty-five pairs present. 



Genotype. A. lia, n. sp. 



This genus is nearest to Halosydna, of which H. patagonica Kinberg (= H. 

 hrcrisetosa Kinberg) may be regarded as the type. It is separated from this 

 genus primarily because of the difference in the notopodial setae, which are 

 distally incised or bidentate, and in the neuropodials of the first parapodia, 

 which are distally bidentate, instead of both neuropodials and notopodials of 

 these parapodia being prolonged into fine, hair-like, entire tips. Arctonoe 

 includes also a second Pacific form, S.fragilis (Baird), which is closely related 

 to the genotype. 



Arctonoe lia, n. sp. 



Type specimen. Catalogue No. 26, Victoria Memorial Museum, Ottawa. 

 Paratypes, Victoria Memorial Museum, No.'s 27, 28; Museum Comparative 

 Zoology, No.'s 2190 and 2191. Five specimens. 



General colour of the body pale yellow. The elytra in general practically 

 colourless, or slightly whitish, and translucent to transparent, or nearly so. 



The body is of moderate length. It is widest over about the second fourth 

 of its length in front of which it narrows a little and back of which it narrows 

 continuously and decidedly. The type is 25 mm. long, with a maximum width, 

 to ends of setae, of 4-5 mm. The number of segments appears to be typically 

 between 55 and 60, though none of the types is entirely complete at the caudal 

 end, the maximum number actually present being 56. 



The prostomium continues into the ceratophores of the lateral tentacles 

 anteriorly, though rising back of the base of each of these in a rounded elevation, 

 the ceratophores often rather abruptly set off; with a median notch anteriorly 

 in which the median tentacle is inserted. All tentacles short and proportionately 

 thick, with terminal filaments as shown in PI. I, fig. 1. The palpi are much 

 longer than the tentacles, subcylindrical, distally abruptly narrowed into a 

 terminal filament. Two pairs of eyes are present on the posterior half of the 

 prostomium of which those of the anterior pair are slightly the larger and are 

 much more widely separated. The posterior eyes are more strictly dorsal in 

 position and are near the caudal border. 



The tentacular cirri, i.e., the cirri of the peristomial parapodia, are attached 

 at the level of the base of the ceratophores of the lateral tentacles. They exceed 

 the tentacles, which they resemble in form, in length, and the ventral on each 

 side is shorter than the dorsal. 



The metastomial segments are moderately convex above and a little less 

 so ventrally, with a distinct neural furrow. Intersegmental furrows distinct. 

 Most segments divided above by a more or less distinct transverse sulcus. 



