_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.
Type--M. C. Z. 2, 157.
Taken among Phyllospadix, September 17, 1917.