240 POTAMILLA TORELLI.
tinted with brownish and grey pigment. Body small, about 1 inch in length (Plymouth),
grooved anteriorly on the dorsum, flattened ventrally, and with the median groove behind
the five to eight anterior segments. The posterior region has from thirty to fifty or
more segments, and ends in an anus often with a lateral projection on each side. Colour
brownish with large spots of white.
The anterior bristles are in two groups, viz. an upper series with longer shafts and
tapered winged tips, and an inferior group of spatulate forms with a filiform process at
the tip. The bristles of the posterior region have comparatively broad wings and finely
tapered tips, those near the tail being extremely attenuated. Anterior hooks with a
moderately long base, a sharp main fang with a series of minute teeth above it. They are
accompanied by the short (pennon-like) bristles with the spatulate tips (hook-like). The
posterior hooks are smaller and have a shorter base. Scissiparous (Caullery and Mesnil).
Synonyms.
1851. Sdbella neglecta, Sars. Nyt Mag., vi, p. 132,
1863. „ fragilis, Grube. Archiv f. Naturges., Bd. xxix, p. 61, Taf. vi, fig. 6.
1865. PotamiUa Torelli, Mai mgr en. Nord. HaFs.-Annul., p. 402.
1867. „ „ idem. Annul. Poly eh., p. 222, Tab. xiv, fig. 76.
1880. Sdbella (PotamiUa) Torelli, Langerhans. Zeitschr. f. wiss. Zool., xxxiv, p. 112, pi. v, fig.. 26. '
1881. „ ,, breviberbis, idem. Nova Acta Leop. Carol. Akad. Naturf., xlii, p. 118, fig. 27.
1883. ,, fragilis, Levinseu. Vidensk. Meddel., p. 187.
1884. PotamiUa incerta, Langerhans. Zeitschr. f. wiss. Zool., xl, p. 267, pi. xvi, fig. 29.
1885. ,, Torelli, McIntosh. AnrieL “ Challenger" p. 484, pi. liii, fig. 2, and pi. xxix, figs.
16—19.
,,. ,, „ Marenzeller. Denks. k. Akad. wiss. Wien, xlix, p* 210, Taf. iii, fig. 1.
,, ' „ Carus. Fauna Medit., i, p. 272.
1892. Sdbella neglecta, Marenzeller. Zool. Jahrb., Bd. vi, p. 429.
1893. Potamilla Torelli, Lo Bianco. Atti R. Accad. Sc. Nap., 2nd ser., vol. v, No. 11, p. 71.
1894. •. : „ De St. Joseph. Ann. Sc. nat., 7e sér., t. xvii, p. 296, pi, xi, figs. 299—302.
1901. „ ,, Whiteaves. Mar. Invert. E. Canada, p. 72.
1904. „ „ Journ. M. B. A., vol. vii, p. 231.
1906. „ 'jiffilp 'Treadwell. U.S, Comm. F. & F„ p. 1178.
1908. „ „ Ehlers. Deutsch. Tiefsee Exped., p. 156.
1909. : ■ ’ „ Fauvel, Bull. Inst. Oceanogr., cxlii, p. 42.
1910. v ; „ . „ Elwes. Journ. M. B. A., vol. ix, p. 65.
1911. „ ,, Mesnil and Caullery. Bull; Sc, Fr. et Belg., 7e sér., t. xlv, p. 89, pis. v andvi.
1913. „ ; -,, Ehlers. Deut. Sudppl. Exped., p. 575.
1914. „f- „ Southern. Proc. Roy. Irish Acad., vol. xxxi, No. 47, p. 139.
,, ,, „ Fauvel. Campag. Scient. Monaco, xlvi, p. 314.
1915. „ „ Allen. Journ. M. B. A., vol. x, p. 642.
,, 1 ;,,xf Southern. Irish Sc. Invest., No. 3, p, 49.
1916. „ „ McIntosh. Ann. Nat... Hist., ser. 8, vol. xvi, p. 11.
,, ,, ,, (young of P. torelli), idem. Ibid., ser. 8, vol. xvi, p.,15.
1917. ,, „ Rioja. Annél. Poliq. Cantâb., p. 65.
Habitat.—Plymouth and as P. incerta (Allen); Torquay, in limestone rocks (Elwes);
West Coast of Ireland (Southern).
The distribution is wide:—Cape Agulhas and Antarctic Seas (Ehlers); Iceland
(Malmgren); Canary and Madeira, young as P. incerta (Langerhans); Southern Japan
(Marenzeller); amidst Cynthia glomerata and the tubes of Pomatoceros triqueter; and
smaller forms also dredged on oyster shells at Dinard (De St. Joseph); Canada
(dredged by Whiteaves); shores of France and Monaco (Fauvel); Hawaiian Islands
(Treadwell).
The general aspect of the cephalic plate when the branchiae are removed agrees with
that of its allies, and in the preserved examples some have a prominent T-shaped
projection formed by the developing bases of the branchiae—a condition not observed in
other forms. The collar has a narrow slit' dorsally, then it extends on each side laterally
and ventrally with an even edge to the ventral somewhat triangular lamellae, which are
reflected in protrusion, and which are separated from each other by a deep V-shaped
notch. No eyes are visible in the spirit-preparations from Britain or from Canada. In
the young forms the pinnss develop as papillae and the terminal filament appears to be
slightly webbed—that is, has a thin border at each side. Moreover in some young examples
the terminal process is moniliform—it may be from diminished vitality.
The branchial filaments are of moderate length and are opaque white in life, pale in
the preparations. The structure of each filament is typical, and it ends in a short, thick
process distally. The pinnss are of average length, and it is only at the tip of the organ
that shorter forms occur, the last ten or twelve gradually diminishing to end in a short
papilla-like rudiment at the base of the distal process. The number of the filaments
appears to be from twelve to fourteen in each fan.1
When the oral region is in a state of expansion a fold passes on each side from the
ventral lamellse upward and its end fuses with the middle of each branchial fan, and
indeed, appears to be the only representative of the tentacle of other forms. Malmgren
states that it is very short, broad and sub-circular. This fold is quite separate from the
ventral edge of the basal tissue of the branchiae On the other hand, a considerable
portion of each dorsal edge of the base of the branchise is bordered by a free and mobile
flap—the ventral edge adjoining the mouth.
The body (Plate CXIV, fig. 3) is of small size in the examples from Plymouth, viz.
about an inch in length and of the thickness of stout thread, whereas in the Canadian
forms it is between 2 and 3 inches long and as thick as a crow-quill. De St. Joseph
also found large examples at Rocher-VidA It is grooved dorsally in the anterior region,
rounded posteriorly, whereas the ventral surface is more or less flattened and marked by
the median groove from the anterior region backward. The first region has a variable
number of segments, viz. from five to eight (Langerhans—seven to nine). The posterior
region has from thirty to fifty. Toward the tail it is flattened and tapered to end in the
anus, which often presents a lateral projection. De St. Joseph describes the body as
brownish with large spots of white. The first segment has two oval eye-spots (Langerhans).
Fauvel3 describes anal eyes, which are absent in the preserved examples from Plymouth.3
The first bristle-bundle consists of simple bristles with moderately tapered tips and distinct
1 Langerhans (1884) notes that the branchias (as in other Sabellids) are regenerated.
2 ‘ Campag Sc./ p. 315.
8 Both are seen in small specimens kindly sent by Major Elwes from Babbacombe.