his interpretation was warranted. He noticed the peculiar curved spatulate bristles in
the anterior hook-rows.
The Sabella stichophthalmus of Grube1 (1863) does not seem to differ materially
from a variety of this species, though the author’s figure of the first bristles must
have led to misinterpretations. He represents them as long, blunt hooks, and it was
left to Marion and Bobretsky2 (1875) to give a more satisfactory representation and
description, and thus to connect it with the present form.
Langerhans (1884) found a large variety bearing from seven to ten eyes on its
filaments amongst old coral at Madeira.
Reproduction.—De St. Joseph (1894) states that the eggs are greyish. He thought
the Potamilla tortuosa of Webster, which makes its galleries in shells, very similar to
P. reniformis, and he found small examples of the latter species with the cephalic region
in process of reproduction. This author3 (1906) mentions that it occurs in Oculina, and
he thinks it approaches the condition of a commensal like Aspidosiphon (a Gephyrean)
which frequents Madrepores.
Arnold Watson’s observations on regeneration were conducted on a form which he
thought distinct from P. reniformis, P. Torelli and Potamis, as.no eye-specks occurred
on the branchial filaments, though just below the base of these on each side there are eye-
spots as in P. reniformis and other Sabellids. He counted twenty-two filaments in one
and twenty-four in another. The diameter of the detached plumes was 18—19 mm.
He called it the blushing Sabella, as its blood was red. The tube is peculiarly rugged
—constricted at the entrance to the burrow in the rock. An examination of this form,
kindly sént by Mr. Watson, shows that it appears to be a variety of Potamilla reniformis.
A variety (AB) occurred under stones between tide-marks both in Guernsey and
Herm with only five pairs of anterior bristles, and shows certain- differences from both
PotamiUd reniformis and P. Torelli. The cephalic plate of var. AB has a narrower
collar than in P. reniformis—a feature well marked in the small, pointed ventral lobes.
The edge is smooth at and near the mid-dorsal groove, then at each side is a lateral
flap which trends to the lamellae on the ventral surface. These lamellae are smaller than
in Sabella penicillus, and besides the small lamellae which project ventrally their margin
is incurved at the middle line.
The bódy is comparatively small, about f inch in length, and the number of segments
is between sixty and seventy. It is rounded dorsally with the exception óf the region
of the dorsal groove anteriorly, slightly flattened ventrally, where a median furrow runs
from the middle of the sixth scute backward to the tail. The anterior region is composed
of five bristled segments and apparently the same number of uncinigerous rows.
Posteriorly it tapers to. a somewhat pointed tail. The branchiae seem to be comparatively
short, like those of Potamilla reniformis, and the pinnae of moderate length or rather
short, whilst the terminal filament is long, large, and is often in screw-coils, thus differing
essentially from those of P. reniformis, P. Torelli and P. neglecta, and resembling
1 ‘Archiv f. Naturges/ p. 62, pi. vi, fig. 3.
8 ‘Ann. Sc. Nat./ 6é sér., t. ii, p. 92, pi. xi, fig. 23.
8 ‘Ann. Sc. nat./ 9e sér., t. iii, p. 241.
apparently those of Spirobranchus. Moreover, there are no ocelli on the filaments, and
none on the first segment or on the tail.
The first region of the body has only five pairs of setigerous processes. Each
bears a tuft of comparatively short bristles, the tips of which, unfortunately, had for the
most part disappeared, probably from their brittle nature as well as from rough usage.
Those which are perfect have shafts which slightly dilate from the base to rather beyond
the middle, then diminish at the neck and swell out at the origin of the wings, taperino*
thereafter to a somewhat long attenuate extremity. At the upper edge of the fascicle
are the longer and more slender forms, the shafts of the others being thicker. Spatulate
forms also occur as in the type. The anterior hooks (Plate CXXVIII, fig. 1 b) form
a single row, and present a sharp main fang, the rest of the anterior face of the
crown above it (about half the extent) being finely serrated in lateral view, as usual in
such hooks. When the crown is examined from the front this region is densely spinous.
The posterior outline is more or less straight below the forward bend at the crown,
whilst the anterior is also straight immediately below the main fang, curved forward over
the rounded prow. The projection of the base posteriorly is narrow, but somewhat
shorter than in Potamilla reniformis. Each is accompanied by a short, broad, cuspidate
or penniform bristle. The hooks behind the anterior region in the fragmentary example
do not materially differ, though the neck is longer, the base somewhat shorter and their
size less (Plate CXXVIII, fig. 1 c).
The small number of the anterior segments, so unusual in the group, though this
number has been found in P. Torelli, raises the question as to its relationship to the
latter, from which it differs in the terminal processes of the branchiae and in the narrower
web in the anterior bristles, but further investigations may clear up the divergences.
Like many Sabellids it is acid to litmus paper. In the example from St. Peter Port,
Guernsey, the tube is composed of a translucent, horny secretion somewhat like that of
Potamilla reniformis. Some examples have nearly ripe ova (July and August).
Amongst the forms which show similar hooks anteriorly are the various species of
Eudistylia, Bush, Schusobranchia, Bush, Parasabella, Bush, Pseudopotamilla, Leidy, and it is
possible that further examination may lead to the diminution both of genera and species.
P otamilla T orelli, Malmgren, 186 5. Plate CXIV, fig. 3— body; Plate CXX, figs. 7 and
7 a—branchiae; Plate CXXVIII, figs. 3— 3 d—bristles and hooks.
Specific Character's.—Cephalic plate and collar as in P. reniformis, the collar having
a narrow slit dorsally, then extends to the ventral lamellse, "which are usually reflected in
protrusion and separated from each other by a deep V-shaped notch. Branchial filaments
of moderate length and pale, eight to sixteen in number, and each ends in a short, thick,
distal process. Pinnae of average length, the distal ten or twelve gradually diminishing,
to end in a papilla-like rudiment at the base of the terminal process. Oral fold passes
from each side of the ventral lamella upward, and its end fuses with the middle of each
branchial fan. A considerable portion of the dorsal edge of the base of the branchiae
bordered by a mobile flap, the ventral edge adjoining the mouth. The branchiae are