Hancook made several drawings of this species,,pjwhioh two (PI. VII, figs. 6 and 8)
are here reproduced. The others, including the dorsal view of the whole animal, are
extremely rough. They are all labelled “Doris testudinaria, Hem.” Among the notes
(which are not very legible) are the following: “ Tubercles small, somewhat irregular,
pale with minute pale lines radiating from them. Colour of mantle an obscure chestnut
with indistinct pale yellowish blotches at the sides.” _ -
Figs. 5 and 7 were drawn from living specimens taken at Plymouth in the summer
of 1908. .
Both the nomenclature and the specific limits of this form present many difficulties,
and it is with great diffidence that I submit it should be called Dons testudinaria,
that it is identical with the Archidoris stellifera of Vayssiere and von Jherang, and that it
is probably distinct from the Dons planata of Alder and Hancock. Two points, however,
seem certain: first, that the specimens from Plymouth here described are the Doi'is
testudinaria of Alder and Hancock; second, that they are distinct from Archidoris tuber-
culata, with which they are often confounded in practice.
In 1862 Alder and Hancock described (l. c.) a new British Dorid, which they
identified with the D. testudinaria of Risso. From some unpublished notes preserved
in the Hancock Museum at Newcastle-on-Tyne, it is probable that they based this identification,
not on Risso’s description, but on specimens sent from the Mediterranean and
labelled D. testudinaria, which they considered identical with their specimen from Herm
Island.1 Risso’s description is vague, inadequate, and, as pointed out first by Philippi
(Enum. Moll. Sicil., vol. ii, p. 78), probably inaccurate. Bergh and others have thought
that it refers to Platydoris <vrgo. But since Alder and Hancock have given the name to a
fully described animal, which is possibly identical with Risso’s animal, it would seem that
their interpretation of the name must be regarded as authoritative. After Alder and
Hancock had assigned the name D. testudinaria to an identifiable form, von Jhering gave
the name Archidoris stellifera to Mediterranean specimens, which seem to me to belong to _
the same species. His description appears to have been only in MS., and publication
dates from the memoirs of Vayssikre, who uses the same name. As will be seen from
the notes here given, stellate forms are found on the British coast, and are specifically the
same as the less ornate variety described by Alder and Hancock. I t is remarkable, however,
that Vayssifere states that the mouth of his specimens is armed with a chitinous ring.
I could not discover this structure in a specimen which he kindly sent to me.
Alder and Hancock (l. e.) expressed the opinion that D. testudinaria and D. planata
are distinct though similar species. Subsequently Alder in Jeffreys’ ‘ Conchology,’
came round to the opposite view, and stated that an examination of further specimens
of different sizes from the Clyde proved that D. planata is the young of D. testudinaria.
It is extremely difficult to form any decided opinion on this question. The external
characters are likely to vary considerably at different periods of the animal’s growth,
and it would appear that in D. testudinaria (stellifera) a labial armature may or may
not be developed. Vayssi&re reports its presence, and Alder and Hancock (Z. c.)
1 I t is even possible that A. & H. may have obtained the specimens from Risso, or from someone
who knew the animal which he called D. testudinaria. They were writing about Nudibranchs
in 1841, but probably began collecting earlier.
say of D. testudinaria and D. planata, “ the character of the tongue is similar in
each.” On the other hand, in a number of specimens from Plymouth which I have
examined, I have found a decided labial armature in the small flat individuals and
none at all in the large plump ones. It is present in the specimen of D. planata
from Alder and Hancock’s collection at Newcastle. On the whole I am inclined to
think that there are two separate forms which are very much alike in their younger
stages.
(1) D. planata. This is a remarkably flat form, which appears not to exceed an
inch in length in British waters. The dorsal surface is finely granulated, there is a
distinct labial armature, and the radula is decidedly of the type of Geitodoris Bergh,
that is to say, there are two kinds of teeth, the inner teeth being of the ordinary hamate
shape, and the outer very thin and crowded together in sheaves. It is possible that
some specimens (about 50 mm. long) which I have received from the Cape Verde Islands
may be adults of this species. They resemble the Plymouth specimens, except that they
are much larger and were red in life. The richer colour may perhaps be due to the
climate.
(2) D. testudinaria. This is a plump form of considerable size (60 mm.). The back
is covered with flat tubercles, which are sometimes arranged in a stellate pattern. In
the specimens from Plymouth, which I have myself examined, there is no labial armature,
but Vayssiere .states that it is present in the Mediterranean form, which is otherwise
undistin guishable. The radula is not unlike that of the last species, but the differentiation
of the teeth is less marked. The outer are thinner than the inner ones, but the
change is less abrupt, and the thinner teeth are not gathered together in such distinct
sheaves or packets.
The names Platydoris testudinaria and Platydoris planata would seem to be in any
case incorrect, for none of the animals have the characters of Platydoris (which include a
peculiar hard consistency and an armature of hooked scales on the reproductive organs).
I t is possible, but not demonstrable, that the Dons testudinaria of Risso was a Platydoris;
but, if so, it is neither the D. testudinaria nor the D. planata of Alder and Hancock.
Alder and Hancock’s type specimen labelled “ Doris testudinaria Herm ” has been
kindly lent to me by the Council of the Hancock Museum, Newcastle.
I t is 3.0 mm. long, 23 mm. broad, and 15 mm. high. The mantle-margin is broken
in many places, but it apparently covered the sides and the foot entirely in its original
condition. The general colour of the animal is greyish yellow. Some of the dorsal
tubercles are lighter than the surrounding surface. There are some reddish spots on the
under side of the mantle.
The texture is soft, and the specimen is a little decayed. The back is covered with
low flat warts of various sizes. No stellate arrangement is visible. The branchial and
rhinophorial pockets are surrounded by tubercles which do not amount to valves. The
branchiae are retracted within the pocket, and their number could not be ascertained.
The anterior part of the animal is much retracted, but the long linear tentacles are
clearly visible.
The buccal parts have been extracted.
No further examination was made in order not to injure the unique specimen.