Cape V erde. W est I ndies. B razil.
Tntoniay 1. Marionia, 1.
Doris, 1. Doris verrucosa*
Discodorisy 2. 2. 2..
GeitodoriSy 1. o
PeltodonSy 1. 1.
Platydorisy 1.
1.
Rostanga, 1.
Gadlinay 1.
AphelodoriSy 1.
Phlegmodoi'is (?), 1.
Thordisa (?), 2.*
Chrom-odoriSy 1. 5.
Doridopsis, 1.
2.
Doriopsillay 1.
PlocamopheruSy 1.
Phyllidiopsisy 1.
Nembrothay 1.
Bornella, 1.
1.
DotOy 2. Heromorphtty 1.
TethySy 1.
Spurilla, 1.
Amphorinay 1.
JEolidiellay 1. Spurilla, 1.
Phidianay 1.
Facelinay 1.
Favorinus, 2.
1.
PhyllobranchuSy 1.
Tridachia, 2.
Elysia, 2.
1.
Pleurophyllidiay 1.*
The forms marked with an asterisk were taken about 28° S., and hence outside
tropics strictly speaking.
In drawing any conclusion from the above lists it must be remembered that they
are fragmentary, and that the littoral zone in the regions where the collections were made
is probably not so favourable for Nudibranchs as in the Indo-Pacific. This is certainly
true of long stretches on the "West Coast of Africa. I t is therefore probable that an
adequate knowledge of the Atlantic Nudibranchs can be obtained only by dredging.
Still, after making all allowance for possible lacunas, it is interesting to notice that many
of the commonest and most striking Indo-Pacific forms (such as Hexabmnchus, Kentro-
doris, Asteronotus, Ceratosoma, Trevelyana, Phyllidia, and Placobranchus) are not recorded
from the tropical Atlantic, and also are not replaced to any considerable extent by other
large or brilliantly coloured forms. The specimens hitherto obtained are mostly modest in
dimensions and colour, and do not indicate that there is any great difference between the
tropical and temperate faunas. But the occurrence of Nemjbrotha and Bornella (typical
Indo-Pacific forms) in the West Indies suggests the need of further exploration.
A collection of Nudibranchs from S. Africa, comprising about thirty-five species, has
been described by Bergh. This region is in about the same latitude as southern Brazil,
and Doris verrucosa occurs in both. But the Cape is clearly a meeting-place for the two
oceans, and it is hard to say which forms in the collection should be regarded as Pacific and
which as Atlantic, particularly as the specimens come from both the east and west coast.
But whatever may be the real character of the tropical Atlantic fauna, it is
interesting to see that the waters of the south Atlantic beyond the tropics contain forms
very similar to those found in the north, if not identical with them. Dons tuberculata
and Gadlina repanda are recorded from the east coast of Patagonia (42° S.), and the
former also from the Antarctic south of Cape Horn (64°—65° lat. S. and 64° long. W.).
On the coast of the Falkland Islands have been found :
Tritonia, 1.
Diaulula, 1.
DoriSy 1, nearly allied to D. verrucosa.
AcanthodonSy 1.
Gratena, 1.
Galvina, 1 „ „ G. fiava.
Goryphellay 1 ,, „ G. lineata.
AEJolidia, 1 „ „ A . papiilosa.
I t is possible that some of the above may be specifically identical with north Atlantic
forms, and in any case all the genera are found there except Diauhday which is not very
different from Thordisa recorded from the temperate Atlantic. But further south in the
Antarctic we find new types such as Notseolidia and Tritoniopsisy for which no counterparts
have been found in Arctic regions.
Thus our information (though imperfect for many regions) indicates that the fauna
of the Atlantic is more homogeneous than that of the Pacific. The tropical Nudibranchs
are not sharply distinguished from the temperate: the temperate zones north and south
of the equator seem to have the same genera and to some extent the same species. Thus
D. verrucosa and D. tuberculata are recorded from both. There are definitely northern
forms, such as (a) Dendronotus, (6) large ASolids such as Ghlamylla and some species of
Goryphellay (c) the Pseudorididae, viz. Acanthodoris9 Lamellidoris and Adalariay (d) various
Polycerids. These make the great majority of the known fauna within the Arctic Circle;
most of them are abundant as far south as the British Isles, but they nearly all1 disappear
before the Mediterranean. But, so far as can be judged from our scanty records, they reappear
in the southern hemispherey for an Acanthodoris and JEolidia serotina (closely allied
to A. papillosay if not a variety of it) have been found in the Falkland Islands, In
the northern hemisphere the genera Ghromodoris and Doridopsis mark the transition to
warmer waters, beginning about Lat. 40° N. The fauna of the Cape makes it probable
that much the same phenomenon occurs in the southern hemisphere. The genera which
are common to both cooler and warmer waters are more brightly coloured in the latter.
1 The small and doubtful Lamellidoris grseffei is the only representative in the Mediterranean of
the large group Pseudodoridid®.