. S ynonyms.
1875. Hermadion assimile, McIntosh. Invert, and Fish., St. And., p. 117.
1876. ,, ,, idem. Trans. Zool. Soc., ix, 387 and 400, pi. lxx, f. 4—6.
1886. ,, ,, Harvey-Gabson. Yerm. Liverp., 151 and 348.
1891. ,, „ Hornell. Op. cit., 237.
Habitat.—First found at St. Andrews, by my sister; afterwards on the west coast of
Ireland, in 80 fathoms, eighteen miles west of Skellig, by Dr. Gwyn Jeffreys; south
of England and off the Spanish coast in the ‘ Porcupine ’ Expedition. Commensalistic
on Echinus esculentns (Harvey-Gibson).
Head has a similar outline to that in the former species, and in the preparations is
about as long as broad. The anterior lobes are smoothly rounded, and the eyes have the
same position and proportions, the larger anterior pair showing lenses. Both are
visible from the dorsum, and have a long portion of the head in front. The median
tentacle arises between the rounded anterior lobes,' is long; smooth, slightly dilated
below the filiform tip, and minutely dotted under a low power, though this seems to
disappear in the mounted preparations. The lateral tentacles are short (in spirit) and
slightly enlarged below the filiform tip. The palpi are quite smooth. The tentacular
cirri are also smooth, slightly enlarged below the extremity, and are shorter than those
of 8. communis.
Body somewhat narrow, about § inch or upwards in length, very slightly tapered in
front, and very gradually diminished posteriorly. I t is distinguished by a brownish-
black median band, which commences behind the head and continues to the tail. It is
widest towards the posterior part of the proboscidian region, though even there occupying
less than a third of the arch of the dorsum. In the preparations a darker band
occurs at the segment-junction, and a pale belt just in front. The ventral surface is
pale. The segmental eminences are prominent, but special papillaa could not be
made but.
Attached to the ventral surface1 were several long Pedicellarise, probably from an
Echinus, and some were also fixed to the feet.
Proboscis.—The proboscis seemed to agree with the preceding in structure, but in
the preparation the papillse were somewhat clavate instead of acute.
Scales (Plate XXXIII, fig. 6), fifteen pairs, even more delicate and transparent
than in the previous form, and similar in shape. The cuticle of the inferior surface is
minutely dotted throughout as in 8. comnmnis. The outer and posterior borders have
short clavate cilia, less numerous than in the latter, and they also occur on the neighbouring
surface. The finely branched nerves arise from a similar ganglion at the
posterior border of the scar.1
FeetlSLn looking at the feet of the two species from the dorsum a decided difference
is observed in the terminal region of the ventral division, which in 8. assimilis (Plate
XXX, fig. 15) is somewhat blunt and rounded, whereas it is acute in 8. communis. In
profile this divergence is more pronounced, since the fleshy part of the dorsal lobe is
larger in 8. assimilis, and the spine has a broader covering, and instead of the acute cone
1 The thickenings observed in these scales do not appear to indicate papillae in all cases.
in the ventral division of the other species, it is here a broad terminal flap or lobe with a
bluntly rounded margin in front of the tuft of bristles.
The bristles are as translucent as in the former species, but are scarcely so long in
proportion. The dorsal are smaller than in 8. communis, and slightly curved, the
spinous rows being less prominent, and covering a much shorter region of the bristle
(Plate XL, figs. 20 and 21). About seven or eight are visible. The tip is bluntly
rounded, with a minute terminal claw and a small secondary process—with a notch
between.
The .ventral division has a fan-shaped series of slender bristles, which, as in the
former case, expand at the end of the shaft, where a small collar of spines occurs, the
finely spinous region, with a slight bend to the dorsal edge, tapering to the tip, which
turns bluntly round to the spiked side and ends in a small hook; then follows an edge
directed obliquely backward between this and the secondary process, which is lateral
(Plate XL, fig. 22). So fine are the spines on the terminal region that they are scarcely
visible, but the oblique lines in lateral view are distinct. The whole bristle thus characteristically
differs from that of 8. communis.
Habits.—This is evidently a commensalistic form on an Echinus, for Pedicellariaa
frequently adhere to the skin and processes.
What relationship the Hermadion echini of Professor Giard1 has to this species
remains to be seen. I t is evidently a closely allied form, but the minute characters of the
bristles are not given with that distinctness which is necessary for critical diagnosis.
I t is interesting in this respect, that 8. assimilis was found by Harvey-Gibson near Port
Erin, Isle of Man, coiled round the peristome of Echinus esculentus, protected by the
peristomial spines. This author gives some interesting structural details. Hornell also
(1891) found one on the spines of Echinus esculentus near Liverpool Bar.
Genus XVIII.—Malmgrenia, McIntosh, 1876.
Head somewhat pyriform, with the narrow end in front, devoid of peaks, the median
and lateral tentacles springing from the front as in Lepidonotus. Eyes large, nearly
forming a square. Palpi, tentacles, and cirri smooth. Body of moderate length and
breadth. Segmental eminences fairly developed, but without papillse. Scales, fifteen
pairs, smooth with the exception of a small group of papillae at the anterior curve.
Dorsal bristles translucent, short, and with faint spinous rows. Ventral bristles trans-
lu'cent, with rather short distal regions and five rows of spines; the tip hooked, and a
secondary process beneath.
1.. Malmgrenia oastanea, McIntosh, 1876.
Specific Characters.—He ad somewhat pyriform with th e narrow end in fro n t,
without p eak s, th e late ra l and th e median tentacles springing from th e fro n t as in
Lepidonotus. Eyes large, n early forming a sq u a re ; a n te rio r p a ir in fro n t of lateral
1 f Bullet, sc. Nord/ i, 1886, p. 8.