it is not usually folded backward as in that species; moreover, no eyes are present in
many Of the preparations. The upper lip in front of this forms a large frilled process,
and the lower lip is also prominent. A median tongue-like process lies above and
internal to the latter. In extreme protrusion of the mouth-parts some have the lower
lip folded backward'ventrally with a smaller and a larger fold above it, whilst in others
the lower lip projects downward and outward as a cyathiform process marked, by a fold
at each side.
The body is comparatively small in comparison with P. nebulosa, is convex and
smooth dorsally, deeply grooved ventrally from the ventral shields almost to the tip
of the tail, which in perfect examples has two longer median and two lateral cirri on
the ventral surface, the rest of the vent being crenated or with short papillae. Two
segments following that bearing the lower lip have a lamella at their outer edges
ventrally, and are opposite the first and second branchiae. The anterior, indeed,
often stands out as a frill. on the front edge of the shield. In all, about sixteen
shields are present ventrally, and they bear traces of the two-ringed condition of the
segments generally. They are narrow and transversely elongated in front, broad and
transversely shortened posteriorly. The ventral groove abuts on two rounded lateral
ridges (probably marking the ventral longitudinal muscles), and bearing the elevations
or lamellae for the hooks. The segments are two-ringed. It is a smaller species than
Polymnia nebulosa, and of a firmer consistence. Colour yellowish, with brownish grains,
ventral surface dull yellow (chamois, Marenzeller).
The branchiae are three in number, the anterior being the largest, the second and
third regularly diminishing. In proportion to the size of the body they are somewhat
larger than in P. nebulosa, and they have a stiffer outline. They are dichotomously
branched, and have very short terminal divisions—a distinctive feature when contrasted
with P. nebulosa. A variety-(?) from the West Voe of Scalloway, in 6—8 fathoms, has
longer tips to the branchiae, but the hooks appear to be identical.
The setigerous processes are seventeen in number, the first occurring close to the
base of the last branchia. The bristles are long, translucent, slightly yellowish and
finely tapered (Plate CXXVa, figs. 5 and 5 a), and, as usual, in two series, a shorter
and a longer. In the latter the wings are narrow and indistinct; in the former they are
broader and easily recognised, but they do not proceed to the finely tapered extremity
of the bristle. A curvature of. the tip occurs at the winged region. Little difference
exists between the first bristles and the last except in the fewer number as contrasted
with the middle and anterior groups.
The rows of hooks commence on the second bristled segment, and they are
. comparatively short to the seventh bristle-bundle, the last ten of the region, being
longer. Moreover, whilst they form a single row in front they are arranged in a double
row from the eleventh to the twentieth segments, the main fang in each pointing to
a median line between thé rows. Behind the bristles the hooks are borne on an
uncinigerous process or lamella, and form shorter rows than in front. The lamellas have
a concave distal margin anteriorly, but posteriorly the tip is bifid, and the processes
diminish toward the tip of the tail.
The hooks (Plate CXXVa, fig. 5 6) somewhat resemble those of Polynmia, nebulosa,
in general form, but are readily distinguished by the presence of a second tooth above
the main fang and the somewhat shorter base. The posterior incurvation is below the
middle, and the process bn. the anterior outline is prominent.
Reproduction.—This species, according to Lo Bianco (1909), is ripe in spring.
Southern found it mature from February to May.
The tube is fragile, covered with grains of sand and small stones.
Malmgren thought that Terebella lutea from the Mediterranean was allied, yet
distinct. Moreover, he considered that T. debilis and T. nebulosa, G-rube, should form
a distinct genus {Polynmia), since their branchias and hooks are so characteristic.
De St. Joseph (1894) found in this species Gregarines pertaining to the genus
Polyrabdina, Mangazzini,1 also Gregarina terebellse, Kolliker, and encysted Distomes
of the same kind as in Nicolea venustula and Pol/ymnia nebulosa.
Examples of Polynmia have been found by Orton2 (1914) to attain a good size in
much less than a year, so that their development is somewhat rapid.
A variety, of small size, procured at various parts of the British coast, at first
sight resembling Malmgren’s P. arctica, shows finer divisions of the branchial filaments,
which are proportionally long. Two teeth as a rule are present in the hooks above
the main fang, a trace of a process occurs midway along the curve below the latter, and
the ventral outline (of the base) is more convex.
2. Polymnia nebulosa, Montagu, 1818. Plate CXIV, fig. 6—body; Plate CXXVa,
figs. 3 and 3 a—bristles and hook.
• Specific Characters.—Cephalic region with a large collar or upper arch, at the
junction of which with the body posteriorly is a dense series of eye-specks, whilst it
has a frilled inward curve at each lower edge. The upper arch folds inward to form
the upper lip. Tentacles pale orange and spotted with white. Below the mouth is
a transversely elongated tongue-like fold, and then the lower lip extends to the dorsal
fold on each side. Body 70—100 or more mm. in length, as thick as a man’s little
finger, and having ninety or more segments, soft in consistence, fragile, of the typical
shape, tapering posteriorly and ending in an anus with a crenate margin. Segments
two-ringed. Orange-red, sometimes inclining to brown or paler and speckled all over
with white. First segment massive ventrally; second, third and fourth with small
lamellae. Ventral shields fourteen or fifteen, the anterior narrow and broad, the posterior
wider and shorter from side to side. Seventeen pairs of bristle-bundles. Segments in
a line with the second and third branchiae have a free lamella. The tentacles have the
same hue as the body. Branchiae three, on segments 2, 3 and 4, the first the largest,
sub-dichotomously divided, the terminal processes numerous so as to give the organs
a dense arbuscular aspect, or like a corymb. Nephridia from the third to the eighth
segment. Setigerous processes with two sets of bristles, long, minutely striated forms
with curved, tapering and winged tips, and a shorter series with translucent tapering
1 * Atti Acad. Lincei/ 4® ser., t. vii, p. 229, 1891; see also Schneider, ‘ Arch. Zool. Exper.,’ t. iv,
1875, p. 598, pi. xxii, figs. 85 and 86.
8 ‘ Journ. M. B. A.,’ vol. x, p. 316.