18 B Canadian Arctic Expedition, 1913-18 



present species is a less slender form than the genotype and consists of a much 

 smaller number of somites, seventy-five as against two hundred and six. 

 The branchiae in benhami become much longer, at their maximum equalling 

 the width of the segments; they continue to the eighty-sixth segment, instead 

 of terminating near the twenty-ninth or earlier. In arctius the fine, elongate 

 capillary setae of the superior group of notopodia, and in part, at least, of neuro- 

 podia, seem to form a characteristic feature. 



A mis pin, n. gen. 



Prostomium without cornua, rounded anteriorly and prolonged caudad; 

 without nuchal cirrus. In genotype one pair of eyes. Branchiae in genotype 

 two pairs, on third and fourth somites, wholly free from the parapodial lamellae. 

 Parapodia all free from each other, none of the neuropodia being connected 

 by a membrane; no interparapodial pouches. Anterior parapodia bearing only 

 capillary setae. Hooded crochets appearing in neuropodia caudad but notopodia 

 remaining with only capillary setae. Crochets with beak bifid and lacking 

 apical tooth. 



Genotype. A. boreus, n. sp. 



Close to Spionides but wholly lacking the characteristic lateral pouches 

 of the latter and the nuchal cirrus. The crochets seem to be of distinctive 

 form. 



Anaspio boreus, n. sp. 



Type specimen. Cat. No. 38, Victoria Memorial Museum, Ottawa. 

 One specimen. 



The type is incomplete caudally, at present embracing the head and thirty- 

 six setigerous somites. It is only 12 mm. long. Body depressed, moderately 

 convex above, more flattened beneath, covered in part anteriorly by the foliaceous 

 developments of the parapodia. 



The prostomium is elongate, narrowly subtriangular with base cephalad. 

 Anterior end weakly convex. Posteriorly it is prolonged to or nearly to the 

 third setigerous segment in a thick palpoidal process fused with the dorsum 

 throughout. Just in front of the beginning of this posterior region is one pair 

 of eyes; these are small and wide apart. Vague pigment specks may represent 

 a second pair of eyes farther forward and farther apart. (PL IV, fig. 2). 



The peristomium forms the lower lip and the usual lateral cephalic lobes, 

 the latter broadly rounded posteriorly and narrowing cephalad. Tentacular 

 cirri lost. (PL IV, fig. 2). 



The parapodia are prominent and conspicuous, particularly anteriorly. 

 They are broadly attached, with two lobes almost continuous. Presetal lobes 

 low, but the postsetal lamellae large and foliaceous. The postsetal lamella of 

 notopodia I of moderate size, rising above in a triangular tip. The corresponding 

 lamellae of the second, third, and fourth parapodia are much longer, being longer 

 all along the setigerous line with the dorsomesal ends much more prolonged; 

 those of the third parapodia largest, overlapping above the dorsum. The 

 notopodial lamellae of the fifth and sixth parapodia are abrunptly smaller and 

 more widely separated, though still large and pointed above. The fol- 

 lowing ones rapidly lose their dorsal prolongations, becoming lower and evenly 

 rounded, their dorsomesal edges in the first few extended mesad and conspicu- 

 ously connected across dorsum in a low ridge or integumental fold, this fold 

 becoming less marked posteriorly. Posteriorly the postsetal lamellae both of 

 notopodia and of neuropodia become low and inconspicuous. The postsetal 

 lamellae of the anterior neuropodia vertically much shorter than those of the 

 notopodia, but high, decreasing in size in correspondence with the reduction of 

 the dorsal lamellae. 



There are only two pairs of branchiae, these occurring on the third and 

 fourth setigerous segments. They are thick, subconical processes free from 



