6B Canadian Arctic Expedition, 1913-18 
Arctonoe, n. gen. 
Body of moderate length, tapering caudad. Number of segments moderate. 
Prostomium bearing three tentacles which are inserted marginally. Cera- 
tophores distinct, the styles short and thick, each more or less enlarged proximad 
of the slender terminal filament. Palpi long, with a slender terminal filament. 
Two pairs of eyes, these typically on posterior half of prostomium. , 
Parapodia biramous, but with the notopodia much reduced. Notocirri 
with cirrophores large, the styles moderate, with terminal filaments. Neurocirri 
excepting the first, very small. 
Both notopodial and neuropodial sete 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 Halesydna, with 
typically near thirty-five pairs present. 
Genotype.—A. lia, n. sp. 
This genus is nearest to Halosydna, of which H. patagonica Kinberg (= H. 
brevisetosa Kinberg) may be regarded as the type. It is separated from this 
genus primarily because of the difference in the notopodial sete, 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 setw, 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. 
