Habitat.—Dredged in St. Magnus Bay, Shetland, by Dr. Gwyn Jeffreys.
Malmgren’s examples came from the Koster Islands; Vardo (Danielssen);
Bergenfjord (Wolleb®k). Sweden (Malm). Atlantic and northern waters (Hessle).
The cephalic plate passes forward from a small dorsal collar and is thrown into
various folds, the edges of which appear to be somewhat thinner than in Polycirrus, and
hence show a more elegantly frilled margin. Ventrally the plate forms a broad flap fixed
laterally but with the inner edge free. The surface is covered with numerous clavate and
grooved tentacles, but the ventral flaps have clusters of more minute filiform organs.
The mid-ventral region behind the mouth has a large and prominent tongue-shaped
process, smoothly continuous with the oral surface anteriorly, where it is fixed; it is free
and somewhat conical posteriorly. In lateral view it forms, indeed, a spout-like process
at right angles to the body, with an elevation (glandular) in the centre.
The body is enlarged anteriorly, marked by the two lateral rounded bands minutely
tuberculated and ringed, the largest tubercles or papillae being on the ventral surface of
the longitudinal bands. The segments are not distinctly defined except by the setigerous
processes in front, but Malmgren states that the posterior region (absent in the British
example) presented about twelve deep sulci. He gives the length of 30—50 mm. and the
width of the tumid anterior region as 5—6 mm., that of the posterior part 2—2'5 mm.,
and the latter, though minutely ringed, is smooth.
Six setigerous processes occur anteriorly in the groove, though no bristles are visible
under a lens. Each consists of a slightly conical process with a curved tip and
presenting a white streak in the interior due to the bristles (Plate CXXVII, fig. 3),
which consist of a single closely arranged fascicle of simple translucent bristles, which
curve distally in conformity with the outline of the process, and end within the tissues at
the tip. Except for stiffening the setigerous processes these ..bristles are thus devoid of
function. In the foregoing segments are the nephridia. It is curious that in a variety
of this species, var. macintoshi, from the Antarctic seas, Gravier found the tips of the
bristles spatulate.
Sub-family III: No representative of Malmgren’s Sub-family III, Artacamacea,
occurs in Britain unless the fragment described below pertains thereto, but the fourth
sub-family has two examples.
A fragment of the posterior end of a small annelid procured from a specimen of
Gellepora dredged off St. Peter Port, Guernsey, in 1868, presents certain features of
interest. It is apparently a tubicolar form, of firm consistence, and measuring scarcely
a quarter of an inch in length, rounded dorsally and with a distinct mid-ventral groove
from end to end. It tapers from the anterior to the posterior end, the pygidium being
smooth, with a slight swelling on each side in front of it. The segments are numerous
for so minute a form, no less than between 60 and 70 occurring on the fragment, those
in front being considerably wider than those near the tip- of the tail. The feet in the
anterior part of the fragment bear prominent lamellae armed with hooks on the free
edge and it was the structure of these (Plate CXXVa, fig. 9 a) which first drew attention
to the animal. They have four teeth above the main fang, so that the crown is high,
thus approaching those of Artacama proboscidea. A hook of the latter is shown in
Plate CXXVa, fig. 9.
Sdb-Family IV.—Trichobranceudea, Malmgren, 1866.
The cephalic lobe as in the Amphitriti. The branchiae are filiform. Rostrate hooks
(that is, with long shafts) occur in the anterior, avicular in the posterior region. The
stomachs of the three genera, viz. of Trichobranchus, Terebettid.es and Actobranchus, are
complex, dorsal folds being developed. No ventral shields are present.
Hessle (1917) makes a separate family for the genera Trichobranclms and Terebellides
instead of the sub-family of Malmgren, and they certainly show considerable divergence.
He makes them intermediate forms between the Ampharetid® and Terebellid®, and he
gives the characters as follows: Tentacle-membrane (cephalic lobe?) reduced; tentacles
not invaginated; branch!® simple or pectinate; ventral shields absent; posterior region
not shortened; pale® absent; hooks with elongated shafts anteriorly, short shafts
posteriorly, and in a single row. As shown elsewhere the presence of shafts to the hooks
is seen in other forms, such as Rhodina, but, in any case, the advantages of this change of
classification are not obvious.
Genus CLIX.—Trichobranchus, Malmgren, 1866. -
Cephalic lobe reduced and bifid, having on each side anteriorly a prominent rounded
boss and a flattened fan-like plate. No distinct cephalic collar, though the lobe is
ensheathed by the first segment. Pigment-spots (eyes) occur behind the tentacles. The
lobe gives origin to a dense series of grooved tentacles, filiform and fusiform, the two
being intermingled in front, but posteriorly the filiform are predominant. Both the
longer and the shorter are grooved. Nuchal organs two ciliated flat surfaces (Hessle).
Body terebelliform, enlarged anteriorly and tapered posteriorly. Buccal segment large
and turgid posteriorly (lateral lobe). The body terminates in an anus with two papill®.
Branchi® filiform, on segments 2, 3 and 4. The lateral lobe of the stomach provided
with deep folds. Setigerous processes on each side bearing simple bristles with wings,
and commencing on the sixth segment. Unicinigerous processes (on the tori), from
the sixth to the last setigerous lobe, and bear long hooks ; the posterior, on the pinnules,
bear minute avicular hooks with short bases and spinous crowns. All are uniserial.
Nephridia occur in the fifth segment and are large at the diaphragm, smaller behind,
the latter probably transmitting the reproductive elements (Hessle). Tube membranous,
coated with mud. •
1. Triohobranchus GtAcrALis, Malmgren, 1866. Plate OXV, figs. 5 and 5 d—dorsal and
lateral view of body; Plate CXX, figs. 2 and 2 a—body and anterior end;
Plate CXXVII, figs. 4—-4 c—bristles and hook; figs. 4 d and 4 e—anterior end.
Specific Characters.—Cephalic lobe with the characters of the genus, and numerous
ocular points occur at its posterior part. Buccal segment roll-like and transversely
grooved. Sides of the second and third segments with small lappets. Three pairs of