I have also examined five specimens seen alive at Plymouth in April, 1905. They
vary somewhat in external appearance, and may be described separately.
A. One specimen, rather variable in shape, butyflattish. When it is fully extended
and in motion its length is 60 mm. and its breadth 32 mm. I t is active in its movements.
The main colour of the back is mottled purplish brown of various shades, the deepest of
which is almost black. The general colour is lighter towards the margin, though here
the darker shades are more conspicuous by contrast. There are a few irregular sandy-
grey markings here and there,, especially in front of the rhinophores, and twelve sandy-
yellow star-like figures arranged symmetrically in four lines between the rhinophores and
the branchial pocket. The back is covered with flat tubercles, very slightly prominent,
and more or less of the same size (not more than 1 mm. in breadth), except those forming
the centre of the stars, which are about twice as large as the others. The tubercles
forming the stars appear to be set in a stellate figure, but the pattern is llue to pigment,
rather than to the arrangement of the tubercles. The edge of the rhinophore pockets is
set with small tubercles. The rhinophores are elongate, with about fifteen perfoliations.
They are olive coloured, and the stalk is long compared to the laminated part. The
branchial pocket is slightly raised and tuberculate. The branchiae are six, tripinnate,
sandy yellow, with purplish flecks. The anal papilla is purplish, but the edge is crenu-
late and distinctly margined with sandy yellow. The foot is grooved in front and the
upper lamina notched. The tentacles are cylindrical and elongate, which makes the whole
head look unlike that of B. tubercuiata. The under side is white, but in this and in all
the specimens there are a few purplish spots on the under side of the mantle, which is
rather ample and overhangs the foot all round.
B. In a second specimen of about the same size the characters are exactly the same,
but there are only four stellate figures on each side, and they are less regular both in
their formation and their arrangement. The pockets of the rhinophores and the branchiae
are very distinctly crenulate and tuberculate.
0. Three similar, but rather smaller specimens are paler in colour, and the stellate
figures are only imperfectly developed. The branchiae are as many as seven or eight.
The internal characters of all the specimens are much the same. The blood-gland is
large and double, purple or greyish. The Central nervous system is not quite as in D.
tubercuiata. Seen from the upper side, the ganglia appear united in a horseshoe-shaped
mass in which no divisions are clearly distinguished. Seen from below, the division
between the cerebro-pleural and pedal ganglia is plain, but the cerebro-pleural ganglia
are not distinctly divided into two portions. The common commissure is thick and very
short.
The integuments, especially the tuberculate dorsal surface, are very spiculous, and
contain a dense mass of colourless rods, often slightly bent, but not swollen in the middle,
jointed, or branched.
No labial armature could be found, but on the labial cuticle in some specimens were
granular markings resembling grey dust, but not forming rods or compact plates. The
radula consists of about thirty rows, and the number of teeth on each side of the rhachis
does not appear to exceed forty-five as a maximum ; but the whole radula is fragile and
difficult to extend. The teeth are transparent and colourless, longer and thinner than in
D. tubercuiata, and with narrower bases. Near the rhachis the teeth are low and with
comparatively broad bases; but they increase in length and slenderness towards the
outside of the row until the last two or three, which are shorter, but often deformed.
Teeth with abnormal lumps and projections occur in all parts of the radula.
The oesophagus is narrow at first, but widens and enters the liver. The stomach
lies within the liver. The gall-bladder is small and pear-shaped. The intestine issues
from the liver about the middle of its dorsal surface, runs forward and then turns backward.
The liver is of a dull orange colour; the hermaphrodite gland, spread over it, is
of a dull opaque white.
The spermatotheca is large, greenish or bluish grey, and spherical. The spermato-
cyst is small, white or orange-white, less distinctly spherical, and sometimes pear-shaped.
There is no prostate. The vas deferens is very slender, long, and convoluted; the penis
small, conical, and unarmed. The duct seems to issue at the side of the tip.
Though this species is commonly confused with D. tubercuiata, it seems to differ in
the following points:
(1) The typical coloration is different, though it is very often imperfectly developed.
But there are nearly always purple spots on the lower side of the mantle, which seem not
to occur in B. tubercuiata.
(2) The general form is flatter.
(3) The shape of the tentacles and anterior part of the foot is markedly different.
(4) The tubercles are less prominent and of more equal size.
(5) The branchise are stouter and less voluminous.
(6) The shape of the teeth is different.
(7) The stomach is enclosed within the liver.
For purposes of comparison I have examined a specimen of Archidoris stellifera, most
kindly sent me from Marseilles by Professor Vayssiere. It is 31 mm. long, 16 mm. broad,
and 10 mm. high, flattish and rather smooth, with low, even tubercles. The colour of the
dorsal surface is dark olive-brown of various shades; the larger tubercles are yellowish,
but the stellate appearance is hardly visible. The under side is pinkish, with reddish
brown dots on the lower surface of the mantle. The oral tentacles are longish, conical,
and somewhat flattened. The anterior margin of the foot is grooved and perhaps notched,
but this is difficult to decide. The edge of the rhinophore pockets is set with small
inconspicuous tubercles. The branchise are eight ; the edge of the pocket is tuberculate,
much like the rest of the back, but has no special tubercles of its own. The formula of
the radula is about 18 X 30.0.30, and the shape of the teeth as described above for the
Plymouth specimens.
Neither in this specimen, nor in those from Plymouth, could I find any trace of the
armature described by Professor Vayssiere (l. c.) as “ anneau chitineux mandibulaire,
complet, assez large, offrant dans la partie interne de petits et tres courts batonnets
prismatiques.” Nothing was visible but a thick unarmed cuticle.
I refer this form to Doris section Archidoris, but if the external teeth are longer and
thinner than the internal ones, and if, as Vayssiere has found, a labial armature is sometimes
present, it is clear that the division between Archidoris and Geitodoris is not so sharp
as might be supposed. I t would be interesting to have statistics as to the uniform presence