meeting behind, the rest gradually becoming shorter, so as to leave a wedge-shaped, smooth
portion at the back of the tentacle. There are fourteen or sixteen laminae; the apex is small
and not much produced. The margins of the tentacular cavities are plain, without tubercles.
Branchial plumes small, simply pinnate, rather variable in number, reaching from twenty to
twenty-nine in large individuals, but fewer in smaller specimens. They are placed round
the vent, in a transverse elliptical groove, nearly straight in front and open behind, the ends
being much curved inwards: the included space is strongly thberculated. Head with a
broad veil, having the margins a good deal waved and extended laterally. Foot rather
broad, rounded in front, less broadly rounded and extending a little beyond the cloak
behind, when the animal is crawling. It is of a yellowish white colour, the liver appearing
through the centre of a purplish hue, but not very large.
The spicula of the .cloak are smallish and rather stout, blunt at the points, and more or
less bent in the centre, with usually a small inclined spur or branch at the bending.
They are arranged in a stellate form round the tubercles. The spicula of the tubercles are
very small.
The spawn forms a compressed coil of one, or, occasionally two volutions, cemented to
the surface of stones and rocks by one of its margins; spreading at the top, and often a
little curved outwards, so as to give it a vase-like outline. That of a large individual
measured a quarter of an inch in height, and half an inch in diameter at the to p ; usually,
however, it is not above half that size. The eggs are small and very numerous, showing a
slight indication of a linear arrangement in their early stage of development, which
afterwards disappears. We have taken the spawn in February, June, August, and November;
but the principal breeding season is apparently in February, when large quantities of the
spawn may be seen crowded together, forming patches of no inconsiderable size. In
August, too, it has occurred to us in abundance. This species has, therefore, probably two
breeding seasons, one in early spring, the other at the end of summer.
This is one of the most common Dorides on all our rocky coasts. It is occasionally met
with in considerable numbers between tide-marks, especially in the spring; but a few
individuals may be found in such localities all the year through. It varies exceedingly in
size, in which respect two varieties are distinguishable, one nearly twice the size of the
other, not, however, without occasional intermediate specimens. This disparity of size has
led to the supposition that there might be two species, and they have been described as such,
but after a careful examination of both kinds, we have been unable to fix upon any character
to distinguish them, unless the increased number and greater development of the branchial
plumes might be taken as specific; but we find this character, contrary to what is usual
among the Nudibranchs, so very variable in this species, that we have not thought it safe to
rely upon it, especially as the very peculiar arrangement of the plumes is the same in both,
as well as the colour and markings of the cloak.
The Boris afmis of Thompson, a specimen of which, presented by our lamented friend,
is now before us,-was described from spirits, and the elongated character of .the lateral
tubercles, which was chiefly relied upon, appears to be owing to the state of preservation of
the specimen. The same character is given as distinctive in the Boris ElfarUana .of
Blainville and Leach, which- we take to be likewise a variety of B. bUamellata, judging from
specimens in the British Museum, as well as from a living example sent us from the Frith of
Forth, the original locality mentioned by Dr. Leach, where he states it to be very abundant.
M. de Blainville says that he founded his genus * Onchidoris on a specimen in the British
Museum. It is rather remarkable that the specimen preserved in the Museum collection
with the name of ‘Onchidoris, Blainv.’ attached to it, should be an individual of T). bilamellata,
in which no such characters as, he establishes his genus upon are to be found. Besides, he
figures in the ‘ Manuel de Malacologie’ an animal with the plumes retracted within a single
cavity, according to his description. There is evidently a mistake somewhere with respect to
this genus, and until a mollusk can be found with the characters assigned to the genus
Onchidoris, it is desirable that it should remain in abeyance.
Dr. Johnston was the first, we believe, to recognise in the species now under
consideration the Boris bilamellata of Linnaeus, and it may be necessary to say a few words
with respect to the propriety of adopting this view. We do not of course profess to unite
our species with the Umax bilamellatus of the ‘Fauna Suecica,’ which appears to have been
an intestinal worm, but to that form of Boris bilamellata, in the 12th edition of the e Systema
Natures? to which the more detailed description belongs, stated, on the authority of
J. G. Koenig, to be “ frequent on stones” in Iceland. The description, ‘ anus transversus, supra
postice corpus, ciliatus plumis simplicibus,’ very well characterises our species, and Muller’s
figure of Boris fusca in the e Zoologia Danica,’ which he makes synonymous with B.
bilamellata, Linn., undoubtedly represents it, though the description, as Professor Loven has
pointed out to us, belongs to a different species. The drawing was furnished by M. Koenig,
from whom Linnaeus received his specimens, and may therefore be taken as a correct
representation of the Linnean Boris bilamellata.
This species appears to be widely distributed through the seas of northern Europe,
having been found in Greenland (Moller), Iceland (Koenig), and France (Bouchard).
M. Loven does not mention it in the Scandinavian Fauna, though we think it probable that
it will be found on the Norwegian coast.
Fig. 1, 2, 3.
4.
5, 6.
7.
8.
9.
10.
Doris bilamellata, different views.
A portion of the cloak, much enlarged, showing the tubercles.
Back and front views of tentacles.
Enlarged view of branchial plume.
Spawn.
A portion of the same more highly magnified, exhibiting the ova.
Spicula.