considerably advanced, the long filamentous processes projecting from the tips give a
novel character to the organs.
Anteriorly the buccal segment lies in a hollow between the two pillars of the dorsal
fan, a more or less separate fan-shaped lamella, tinted of a deep reddish brown, occurring
on each side. From this the marginal collar passes ventrally to expand into the prominent
and generally reflexed lamella on each side of the median fissure, where it is distinctly
thickened. A band on each side of the median oral process joins it to the fold a little
higher. The first shield on the ventral surface behind the collar is continuous from side
to side, and is the largest of the series of glandular scutes, though it is opposite the
first bristle-bundle the latter would seem to pertain to the segment behind it.
The mouth leads into a simple alimentary canal, which, when seen from the dorsum,
forms a m'oniliform tract from end to end—wider anteriorly and narrower posteriorly.
The septum in each segment retains it firmly in position. The contents can be seen
through the transparent walls of the canal, and in one consisted of pale granules
anteriorly and posteriorly of muddy sand. At each side of the gut anteriorly is a long
granular sac (segmental organ).
The body shows little or no narrowing anteriorly, remains of similar diameter for a
considerable distance, then in preservation may increase in brea-dth behind the anterior
third, and thereafter gradually tapers to the tail, ending in the anus, which is often
bilobed. In lateral view the margin of the vent slopes from above downward and
backward, the ventral edge thus projecting considerably. Seen from above the aperture
is bifid inferiorly, and a triangular area is differentiated on the dorsum in front of the
aperture. Both dorsal and ventral surfaces are plano-convex, thus in transverse section
being more or less elliptical, the dorsal, however, being generally more smopthjy
rounded, with a pale streak in the middle line from the dorsal vessel. The ventral
surface has a continuous series of scutes from one end to the other, and with the
-exception of the first all are divided by the median groove—giving a right and a left
scute to every segment. The number of segments varies from 200—270 or more.
The first region of the body (the so-called thoracic region) is distinguished by the
-direction of the bristle-tufts, which slope upward and backward, and by the presence of
ventral rows of hooks. The setigerous processes vary from seven pairs to eleven, one
side occasionally having nine or ten and the other eleven. The first setigerous process
arises immediately behind the dorso-lateral lamella, and is smaller than those following;
moreover, it has no row of hooks dorsally. The bristles (Plate CXXVII, fig. 6 d) are
arranged in a rather dense group and show a longer and a shorter series- The longer
forms (Plate CXXVII, fig. 6) have cylindrical striated shafts slightly narrowed toward
the origin of the wings which are narrow, the bristle thereafter ending in a translucent
and somewhat strong though flexible tip. No serrations on the edges of the wings have
been seen in these though striae go to the edge. The bulk of the group of bristles is
made up of those with shorter shafts and broader wings (Plate CXXVII, fig. 6 a), the
whole tip being rather broad until near its extremity, where it is abruptly tapered
to a fine point. In the cluster of bristles in the tuft various stages occur in the
developing bristles, some resembling a long, narrow knife-blade, others a deep-bellied
shorter blade.
In lateral view a forward curve of the shaft at the origin of the wings is seen, the
tip then gently curving backward to a nearly straight tip. The succeeding tufts are
of similar shape—that is, somewhat flattened—but they are longer and stronger, and the
edges have distinct serrations (Plate CXXVII, fig. 6 b)< The anterior setigerous
processes form. a somewhat flattened cone, the base ventrally being prolonged into a
prominent ridge bearing the hooks, which lie between two raised margins, constituting
a narrow flap posteriorly in each segment. Moreover, a distinct papilla occurs on the
anterior Thee dsgeeti goefr othues tpipr.ocesses of the second region form stiff narrow cones, which
project nearly straight outward, the bristles only being visible at the tip. A soft and
rather swollen process bearing the hooks lies above their dorsal edges. The bristles
form a kind of pillar, narrow at the base and enlarging at the tip to about double the
diameter at the base of the wings, which give to the distal end a characteristic lanceolate
enlargement, from which the tapering tips slope slightly inward. These differ from the
auterior groups in being all of one length, and appear to be ranged round a central
papilla. The tips are comparatively short, with somewhat broad wings, which are
obliquely striated and serrated along the wide or lower edge. The setigerous processes
and bristle-tufts remain of the foregoing structure till near the posterior end, where
longer and finer bristles project from the small, modified processes. The bristles are
fewer, and of two kinds, viz., a long, slender series (Plate CXXVII» fig- 6 fy, without
visible wings, which have long, gently tapered and slightly curved tips ; and secondly,
of a shorter séries (Plate CXXVII» fig- 6 '0» with rather longer tips than those in front
and with striated wings. The anterior hooks (Plate CXXVII, fig. 6/) are typical aviculariun forms with a
marked forward curvature of the crown and a single acute main fang, the free edge
of which is minutely serrated throughout the greater part of its extent, leaving little
more than a third smooth, and the tip is often slightly turned up. The anterior outline
has a wide gulf under the fang and a boldly rounded prow» whilst the posterior outline is
convex, and the base is considerably prolonged in this direction and abruptly finished.
Çurved striæ occur at the throat, longitudinal striæ in thé body, and horizontal striæ
in the base of the hook. The hooks form a single row. Accompanying each hook in
this region is a paddle-shaped or flag-like bristle (Plate CXXVII, fig. 6 e), the wings
and tip of which are membranous and translucent. The hooks in the middle and
posterior regions likewise form a single row, and have almost the same structure as those
above mentioned, except that the prolongation of the base posteriorly is less, and no
paddle-shaped bristles occur. The posterior hooks, moreover, are considerably less
(Plate CXXVII, fig. 60).
In a small specimen inch long only three rows of ventral hooks are present, so
that the number increases with age. Six brown pigment-specks occur behind the
branchiae. The tube of this example i$ leathery and brownish, with minute mud-particles
on its surface and clear granules here and there. Another young form was in a tube
projecting from a mass of Alcyonid/iym parasiticum growing on Sertularia rugosa and
Ascidians tossed on shore at St. Andrews.
A young example procured at the West Sands, after an October storm, measured