106 ALDISA ZETLANDICA.
The animal is from 10 mm. to 16 mm. long, rather flat and elongate. The colour is
described as greenish grey, but the branchiae, rhinophores, and tentacles are bright
yellow. The integuments are spiculous. The foot has a fine furrow on the anterior
margin and sometimes projects behind the mantle. The oral tentacles are short and
reduced to small round tubercles. The pockets of the rhinophores and branchi® are
surrounded by small papillae. The branchiae are six to eight in number and tripinnate;
their pocket is round. The dorsal surface is somewhat sparsely covered with conical
pointed tubercles of various sizes. It will be observed that in Hancock’s drawing
(PI. I, fig. 3), which is apparently taken from a dead animal, the tubercles are
represented as obtuse, but, as he observes in the note quoted above, they were probably
pointed in life. In the smaller drawing (PI. I, fig. 4) they are conical.
There is no labial armature. The radula consists of about fifty rows of teeth with
a formula of 100.0.100 or more. The teeth are of a very unusual shape, fairly well
indicated in PI. 46 of Alder and Hancock’s Monograph, fig. 2. They are tall, thin,
closely packed, somewhat spatulate at the tips, and finely denticulated in about the upper
two thirds of their length. The larger teeth have a small hook at the tip. The innermost
and outermost are small.
There is a distinct division between the cerebral and pleural ganglia, and the buccal
commissure is short. The stomach lies outside the liver. The penis is armed with spines.
This animal is characterized externally by the sparse, conical papillae on the dorsal
surface, and internally by the shape of the teeth, which is unique among known Dorids
though it sometimes recalls the dentition of Sphaerodoi'is. The affinities of Aldisa are very
doubtful. It is perhaps allied to the genera Artachsea and JEchinodoris, both from the
Indo-Pacific. The latter has long papillae on the back, an armature of spines on the male
genitalia, and denticulate teeth, but differing in shape from those of Aldisa.
APORODORIS MILLEGRANA A. & H.
See Monograph, p. 42, and Appendix (2), p. 1.
Yon Jhering, Zur Kenntn. der Nudibranchien der brazilianischen Kiiste, in Malacolog. Jahrb.,
xiii, 1880, pp. 238—239.
Bergh on Thordisa dubia in 50, pp. 178—190.
By the kindness of Mr. Edgar Smith I have been allowed to see the original specimens
of this form (apparently the same as were examined by Alder and Hancock) now
preserved in the British Museum. They are labelled “ Torquay, Mus. Leach, Mrs.
Griffiths,” and considering their age are well preserved externally.
The larger of the two specimens is 28 mm. long, 18 mm. broad, and 8 mm. high.
The mantle-margin, which is rather thick and solid, is 5 mm. in breadth. The dimensions
of the other specimen are rather smaller. The colour (including the branchi® and rhinophores)
is a nearly uniform dull yellow. On the upper surface are two or three purplish
spots, clearer in one specimen than in the other and appearing as if below the surface.
On the under side of one specimen only are a few brownish spots. The dorsal surface is
closely covered with small spiculous tubercles with whitish tips. This white appearance
is due to spicules which project. These spicules, with which the dorsal integuments as
well as the tubercles are crammed, are long and often granulated. The pockets of the
rhinophores and bran chi® have only slightly raised margins, which are not more tubercu-
late than the rest of the back. The branchi® are tripinnate.
One specimen was dissected, but the internal organs were found to be soft and
considerably decayed.
There is no labial armature. The radula has a formula of 30 X 5 + 60.0.60 + 5
in the broadest rows. The teeth, except the last five, are hamate. The first six or so are
low and small. Then they gradually increase in size, and the last fifteen or so of the hamate
teeth are very large. All of these teeth bear from two to six minute denticles on the outer
side, the number . of denticles increasing as the teeth are further from the rhachis.
The denticles are hard to see and are only visible when a side view of the tooth can be
obtained. This is no doubt the reason why Alder and Hancock do not mention them.
They are probably present on all the teeth, but I was only occasionally able to see them
in the middle of the half rows. The last five teeth in each row are small, flat, transparent
plates with denticulate edges. The denticles are sometimes mere jags, but are sometimes
prolonged into long hair-like filaments.
The oesophagus enters the hinder part of the stomach, which is not enclosed in the
liver. The intestine issues from the left anterior part of the stomach and after crossing
the oesophagus turns backwards. In the much decayed genitalia a large spermatotheca
was found and also what seemed to be a prostate, but no armature of any kind.
I think this form is identical with the Thordisa dubia of Bergh (Z. c.) from Rio
Janeiro. The range of distribution is wide, but Doris verrucosa also has been recorded
from the British coast, S. Carolina, Rio Janeiro, and S. Africa. Still, as there is no
other record of the occurrence of this species in British waters, it is possible that it may
have been a casual visitor, brought on the bottom of a ship.
As a specific name millegrana (1856) has clearly priority over dubia (1894). It is
more difficult to say to what genus the animal should be assigned, and the decision
depends on which features in the existing genera are considered the most important.
Bergh refers it to Thordisa with a query, but the typical Thordisa has a back covered
with soft villous papill®. Yon Jhering created for Alder and Hancock’s D. millegrana
and for specimens from the Mediterranean which he identified with it, the genus
Aporodoris, and this genus may be provisionally allowed to stand, for a division is wanted
to include those forms which have minute spiculous tubercles on the dorsal surface.
Whether the pectinate shape of the external teeth is an essential part of the generic
diagnosis may be doubted. But if this character is rejected, a thorough revision of the
genera of the Dorididse might not improbably result in Aporodoris being included in some
older genus.1
1 E. g. Atagema. The dorsal ridge of this genus is not an important character.