Polychaeta © 17 8B 
Scolecolepides arctius, n. sp. 
Type specimen.—Cat. No. 36, Victoria Memorial Museum, Ottawa. 
Paratypes, Victoria Memorial Museum, No, 37; Mus. Comp. Zool., No.’s 
2194 and 2195. Four specimens. 
The type is about 23 mm. long, with a width of 1-7 mm. It consists of 
about seventy-five setigerous segments. The body is flattened dorso-ventrally 
and is pointed at both ends. 
The prostomium is long, pointed behind and broad, and truncate in front. 
Posteriorly it reaches to the second setigerous somite. Four indistinct eye- 
spots are present in the same position asin benhami but with those of the anterior 
pair nearer to each other than the posteriors instead of the reverse. The appen- 
dages are attached at the anterolateral angles somewhat beneath, asin benhami; 
they are cylindrical and are proportionately much shorter than in the latter 
species. No tentacular cirri are present. (Pl. III, fig. 5). 
The parapodia are of the usual biramous type. Each notopodium and 
neuropodium has a prominent, flattened, postsetal lobe of which the notopodial 
is longer than the neuropodial. The postsetal lobe in the anterior region is 
vertically subelliptic with one edge attached (Pl. ITI, fig. 6); but in the posterior 
region it becomes proportionately narrower vertically and at the same time 
higher (Pl. III, fig. 7). The postsetal lobes decrease notably in size in the 
caudal region. 
Branchiz are present on somites beginning with the first setigerous. They 
are free from the notodial lobes excepting at their bases. Cylindrical and 
filiform. They are moderately long in the anterior region though in no casé’ 
“equalling the width of the somite and behind the narrow pointed region scarcely 
surpassing the middorsal line. The branchiz remain of nearly uniform length 
and thickness until about somite XX when they begin to decrease in length 
and thickness and practically cease on somite XXIX, though represented in 
the form of nodules as rudiments at the bases of the postsetal processes. Pos- 
terior region wholly free from branchiz. 
The sete in both notopodia and neuropodia are in two series, an anterior 
and a posterior one, in addition to those of the inferior ventral group and superior 
dorsal group. In both branches of all paradodia occur fine capillary, apparently 
non-limbate setze in an anterior series, and broader, limbate setz in a posterior 
series. In going caudad a limited number, mostly three or four, hooded crochets 
replace setz of the posterior seties, first in the neuropodia and then in the noto-' 
podia, the sete of the anterior series remaining unchanged. The sete of the 
inferior ventral group are bilimbate, distally pointed, the tips curving caudad 
and usual. The superior dorsal setee are much more elongate than the more ' 
ventral ones. In a typical neuropodium of the middle and posterior regions, 
at least, there is also a corresponding dorsal neuropodial group of more elongate 
capillary sete, though these were not detected in all cases. (See Pl. III, fig. 7). 
The crochets are of the usual general form, distally narrowed and bidentate, 
and hooded. The hooded region colorless, more or less transparent; the shaft, 
in part strongly fibrillate. (See Pl. IV, fig. 1). 
Anus surrounded with numerous short papille. 7 
Locatity.—Alaska: Collinson point. Station 270. September 20, 1913. 
Mr. Johansen’s field-note accompanying these specimens states that they were 
“ Pelagic under 5 inches of ice over 1 foot of water in lagoon at Collinson pomn. °° 
Alaska: Lagoon at Collinson point. Station 277. September 18, 1913. 
“ Pelagic under 5 inches of ice over 4 feet of water.” Two anterior fragments. — 
This species, so far as appears from Ehlers’ account of S. benhamu', is 
congeneric with the latter, the only other known Scolecolepides. The type ot 
S. benhami was taken by Prof. Benham at Moeraki, South New Zealand. The 
1Abh. K. Ges. Wiss. Gottingen, Math.-phys Kl.,n.s. 1907 5,no.4 np. 14. 
71927—2 , 
