Arabella mimetica sp. nov.
Resembling the preceding species though smaller and more slender. Superficially differing obviously in the form of the prostomium which is much more narrowed distad and is neither depressed nor furrowed either dorsally or ventrally. Eyes smaller, obscure. Maxillae resembling those of the other species in general, but differing strongly in the second pair in which the right plate, instead of being symmetrical with the left one, is decidedly long and extends far proximad along the dental line of I and bears about fifteen teeth as against only six on the left one and eight on the corresponding plate in lagunae. Maxillae I on right side with nine teeth, on left apparently with seven. Maxillae III with teeth in arrangement as in lagunae but only four in number and different in all being blunt and shorter. IV as in the other species but teeth four instead of five. The number of segments in the type is near one hundred and sixty-five.
Length, 40 mm.; width, 1.1 mm.
Type—M. C. Z. 2, 156.
Taken among holdfasts of kelp. (C. F. Baker, June 30, 1911.) Also a small specimen taken August 2, 1917, by Prof. Hilton.
Biborin gen. nov.
Setae all simple, limbate, well developed. First two segments achaetous. Eyes none. Maxillae absent, but the mandibles normally developed, the wall of the alimentary canal opposite the latter simply thickened. Notocirri rudimentary.
Biborin ecbola sp. nov.
The type as preserved is greyish brown of a dull bluish green cast. A note with the specimen also states that it is greenish in life. The body is strongly attenuated and pointed caudad, more moderately cephalad. The prostomium larger than wide and somewhat longer than the first two segments; subconically narrowed distad, apically rounded, flattened dorsoventrally. The two achaetous segments subequal in length or the second slightly longer, not produced forward below. Mandibles short and broad, not toothed, the edges meeting at an acute angle in front; the caudal stems shorter behind point of separation than the blades in front of this point, rather slender, blunt behind. Posterior lobes of parapodia subcylindrical, a little conically narrowed distad but with apex well rounded, extending ectad or caudoectad; in middle region of body reaching to or a little beyond middle of longer setae, the setae relatively shorter in anterior region. Setae all simple and limbate with the usual double curve, the first curve or angulation obviously less marked than in A. lagunae, which form this species superficially resembles. Number of segments in type, two hundred and seventy-seven.
Length, 92 mm.; width without parapodia, 2.2 mm.