_Myxicola monacis_ sp. nov.
In size and general appearance resembling _M. pacifica_ Johnson, with
the type of which it has been compared. From that form the present
one may readily be distinguished in having the ventral median process
from the first segment drawn out into a slender entire tip instead of
being broad and presenting distally two angles or lobes; the process
is furrowed longitudinally and the edges are somewhat turned down.
Branchiæ twenty-two pairs. Readily distinguished by the form of the
abdominal uncini. These have the general form of those of _pacifica_
but as a whole are longer with the body proportionately more slender
and its abvertigial end more rounded; the beak is longer and less
divergent, distally curving a little back toward the body; the sides
of the sinus parallel. The body in the type is somewhat fusiform,
being narrowed both ways from the middle but more strongly so caudad.
In a paratype the body is scarcely narrowed cephalad. Body somewhat
depressed dorsoventrally, less terete than in pacifica. Total number of
segments near seventy.
Length of type, exclusive of branchiæ, 40 mm.; greatest width, 6.2 mm.
Type--M. C. Z. 2, 170.
Taken from holdfasts of seaweeds.
_Potamilla clara_ sp. nov.
The body in general light brown; but ventrally there is a median
longitudinal fulvous stripe over the ventral plates. The branchiæ are
crossed by a series of dark bands or annuli which fade out proximally,
about three distad of the middle of length being deep and distinct.
There are nineteen pairs of branchial radioles; barbs numerous, densely
arranged to near tip, the naked distal region of axis very short, pale
excepting where partially or completely involved by the transverse dark
bands. Ventral lobes of collar moderate, rounded, edges a little rolled
down; dorsal ends separated; no lateral incisions, being but two-lobed;
not produced forward below, lobes rounded and separated. Thoracic
segments eight. Ventral plates all rectangular, those of the abdomen
divided by the midventral sulcus. Total number of segments, sixty.
Length without branchiæ, 21 mm.; length with branchiæ, 28 mm.; greatest
width, 3 mm.
Type--M. C. Z. 2, 171.
Taken on beach at low tide.
_Potamilla omissa_ sp. nov.
The general color is dusky or pale brownish with the anterior ventral
plates lighter and the branchiæ rather weakly transversely banded with
dark. Radioles of branchiæ in a simple series; seventeen pairs. Collar
well developed, produced forward below in two pointed lobes overlapping
at the middle. Eight setigerous thoracic somites. Most dorsal thoracic
setæ in each fascicle long and finely pointed with wings narrow; the
ventral setæ much more numerous, shorter, spatulate, with fine tip.
The uncini have the posterior process very short, rounded at the end,
much shorter and more slender than the neck, which is rather strongly
curved; vertex high and narrowly rounded; beak not strongly depressed.
Type incomplete, only seven of the abdominal segments being present.
Length of first sixteen segments, 15 mm.; including branchiæ, 21 mm.;
width, 2.5 mm.
Type--M. C. Z. 2, 172.
_Potamilla colorata_ sp. nov.
The type is notably marked with black pigment; the collar membrane
crossed with a close series of longitudinal dark stripes, one in
line with each radiole and narrowing caudad; the branchiæ crossed
transversely with dark bands. Thoracic somites, more notably the
anterior ones, with a dusky to black band in front of each uncinigerous
torus and a dark spot on the dorsum mesad of the setigerous papilla.
The collar with a dark area ventrad and also dorsad of the fascicle.
Ground color greyish of light brown cast, lacking the yellow dominating
in omissa. Sixteen (or seventeen) pairs of radioles in the branchiæ.
Ventral lobes of collar pointed, widely overlapping in the median
line, dorsal ends free, projecting toward each other in dorsal groove.
Setigerous thoracic somites eight in number. Inferior setæ numerous,
spatulate, usually in two series. Total number of segments present
about fifty-one, a few of the most caudal being lost.
Length, 25 mm.; with branchiæ, 30 mm.
Type--M. C. Z. 2, 173.
_Pseudopotamilla paurops_ sp. nov.
A rather slender species with branchiæ of moderate length. Excepting
the eyes with no pigmented markings. Radioles fifteen pairs. Eyes
few, not present on all radioles; where present usually but a single
one on each radiole, in one case two; the eyes deep purple, variable
in side from moderate to small; situated at varying distance between
base and middle of length of radioles. Free dorsal edge of branchial
membrane with two short obtuse lobes overlapping in the middle line.
The dorsal notch in the collar lobe on each side is mesad of the line
of setigerous tubercles, wide open, rectangular or slightly obtuse;
lobe mesad of notch small, anteriorly rounded, the mesal edge extending
into the dorsal furrow; median ventral lobes separated by a narrow
incision, short, the ectal edge passing out in an even concave curve to
the anterior lateral margin. A characteristic feature of the species
is the presence of ten setigerous thoracic somites. Dorsal setæ of the
usual two types of which the upper are much fewer spatulate setæ in two
series with distal expansion broad and wings asymmetrical, tip short.
Total number of segments, seventy-eight.
Length without branchiæ, 31 mm.; with branchiæ, 36 mm.
Type--M. C. Z. 2, 174.
Tube tough, corneus.
_Pseudopotamilla parva_ sp. nov.
The type of this species is a small individual which, as preserved,
appears of a uniform dusky color throughout. Branchial radioles
fourteen or fifteen pairs; in a single series, the membrane not
being coiled. No eye spots. Collar with ventral lobes proportionately
long and acute, the dorsal lobes small and approximate. Notopodial
setæ of usual two types; few. Uncini with beak divergent, nearly
horizontal, the "neck" short and the edge of body below bulging much
as in _Paralaonome japonica_. Body furrowed along each side just
above notopodia excepting anteriorly. Ventral plates sharply limited,
elevated; all of abdominal plates bisected by the median longitudinal
sulcus excepting the first one, which is entire. Total number of
somites, fifty-six, of which eight are thoracic.
Length without branchiæ, 12 mm.; with branchiæ, near 15 mm.
Type--M. C. Z. 2, 175.
Taken among tufted algæ, June 25, 1911 (C. F. Baker).
_Pseudopotamilla lampra_ sp. nov.
In this form the collar membrane is crossed by a series of longitudinal
dark stripes, one in line with each radiole, as in _Potamilla
colorata_, these narrowing caudad. Branchiæ sometimes mostly dark with
light transverse bands. Anterior thoracic segments darkly pigmented
both above and below, and also along both sides of tori, and most
setigerous papillæ and tori of succeeding regions of body also
surrounded in some degree with a pigmented area. Branchial membrane
with free dorsal edges produced into two lobes on each side, the two of
each pair overlapping, the posterior lobe rounded, the anterior angular
with its caudal margin transverse and the other long and oblique.
Radioles nineteen pairs, several of these at dorsomesal end of series
much reduced. Eyes conspicuous but few, only one, or occasionally two,
on a radiole and some radioles wholly lacking them. This species has
only seven setigerous thoracic somites. Total number of segments, near
ninety-four.
Length, about 28 mm.; with branchiæ, 33 mm.
A note states that this form is pinkish in life. A paratype was taken
"in a large white sponge."
Type--M. C. Z. 2, 176.
_Pseudopotamilla macrops_ sp. nov.
While the type of this species includes only the anterior end of
the body, its characters seem sufficiently marked for subsequent
identification. As in _lampra_, the anterior segments are darkened
with purplish brown pigment, especially adjacent to the setigerous
papillæ and about the tori, the ventral plates, however, remaining
pale. Branchial membrane also pigmented caudally, and the branchiæ
transversely banded. Only two eyes on each side are present in the
type, a single one each on the second and third radiole from the dorsal
end of the series. These eyes are exceptionally large and prominent,
much larger than in any of the other species here recorded, embracing
practically the entire width of the stalk. The free dorsal edges of
the branchial membrane nearly straight, each with only a very slight
angulation near its anterior end, not being truly lobate. Nine pairs
of radioles. Minor dorsal lobes of collar prominent, produced well
forward, curving a little mesad distally, the mesal edge reflected down
the dorsal groove as usual.
Width, .75 mm. Length of branchiæ, 2.5 mm.
Type--M. C. Z. 2, 177.
_Pseudopotamilla scotia_ sp. nov.
Differing from the other species here described in having nine
setigerous thoracic somites. Anterior somites of thorax darkened
above, down the sides on both sides of the tori and also more or less
ventrally with purplish brown pigment. Processes or lobes on free edge
of branchial membrane above almost of same form as in _P. lampra_ and
similarly overlapping. Nineteen pairs of branchial radioles. No eyes.
Ventral lobes of collar prolonged, subacute, not overlapping. In the
dorsal fasciæ of the ordinary thoracic somites the dorsal setæ are
arranged mostly in more or less single, curved, longitudinal series,
the clavate ventrals being arranged in two vertical series at right
angles to the line of the dorsals. Pennoned setæ of the uncinigerous
tori very prominent. Only a few of the most anterior abdominal segments
present in type.
Greatest width, 2 mm. Length of branchiæ, 4 mm.
Type--M. C. Z. 2, 178.
Taken in a large white sponge.