16 NOMENCLATURE.
Nudibranch Tethys, which is put into practice by several important authors, ohiefly
A TwmlcgT, The ordinary European use of Aplysia (for a Teotibranch) and Tethys (for a
Nudibranch) creates no confusion or inconvenience. The only objection to it is that it rests
on the authority of the twelfth edition of Linnaeus’s ‘ Systema Naturae,’ whereas the tenth
edition has been accepted as the standard authority for nomenclature. But is it worth
while to upset for a mere question of bibliography Well-known names of common animals
used in hundreds of zoological works ?
Those changes of nomenclature which depend on a change in the extent assigned to
genera or species are inevitable, for they represent a change in zoological ideas. They
are nevertheless very confusing. Alder and Hancock’s use of generic names in the first
six parts of the Monograph (corrected to some extent in the seventh part) is too wide.
Eor instance, Doris tuberculata and Doris bilamellata, now brought under different
fg.TYi,Hp«J cannot be included in one genus. But the multiplication of genera by later'
authorities, such as Bergh and Trinchese, seems to go too far in the opposite direction. If
forms distinguished by only minute differences (such as Guthona, Guthonella and Gratend)
are given a generic rank nominally equivalent to that of JEolidia, Facelina and Goryphella,
the balance of classification is upset, and the fact that certain types present numerous
varieties divided by small distinctions is obscured. Incongruous results also arise from
the failure to apply the same principles of sub-division impartially. Thus, some Dqnds
(Diaidula and GargameUa) are put into separate genera merely pn account of the presence
or absence of an armature oh the genitalia. Yet it is admitted that this-armature may be
present or absent in the same species, Acanthodoris pilosa. Gadlina is made live type of a
sub-family because it has a central tooth in the radula, but Ohromodoris scahriuseuld,
which has a central tooth and other anomalous features, is not removed from the genus
Ghromodoris. Some genera have an unnaturally narrow definition; others (e. g. Thordisa)
acquire an inconveniently wide one, as various forms for which there is jio better place
are assigned to them. The classification of the Nudibranchiata wifi, I feel sure, be
improved when many of the existing genera are amalgamated, but the thorough-going
application of such a principle will be profitable only when the list of animals to bo classified
is much fuller than at present, for we still know little about the Nudibranchiata of
the tropical Atlantic, the west coast of South America, and the southern temperate seas.
In the present work, however, I have proposed some changes which seem justified by
available data. I do not think that it is either correct or convenient to abolish the generic
name Doris, first used by Limnseus and adopted by many eminent naturalists, including
Alder and Hancock! If Stamodoris verrucosa, is equivalent to Doris vetrucdsa L;, then,
according to the rules of nomenclature, this latter name must be used, and a large genus
(comprising Archidoris Bergh, Homoiodoris Bergh, Stav/rodoris Bergh, and others) is
both convenient and scientifically sound. The question is treated in more detail below.
Similarly, the distinctions drawn between Guthona, Guthonella and Gratena seem to me
to be of less than generic value, and if the three are united in one genus it must by the
law of priority be called Guthona. Again, ESolidiella, Spwrilla and Berghia differ only
in the surface of the rhinophores. These organs show a complete series of gradations
from a smooth to a perfoliate or tuberculate surface,' and there is no point in the series
which can be fixed as a generic division, for the rhinophores of JdolMiella are not always
NOMENCLATURE. n
smooth (as the definition of the genus implies), but in some species exhibit furrows or
rudimentary perfoliations. All three genera should therefore be included in the earliest,
viz. JEolidiella. In the Ascoglossa the distinctions between Eermæa, Hermæina and Placida,'
and between Stiliger and Ercolania are at most of sub-generic value. Sub-genera are
useful in thé classification of the Nudibranchiata, for in many cases the special student
finds it convenient to divide a numerous group into sections, while for general zoology it
is more important to remember that it is an aggregate of similar forms.
The following points of nomenclature may also be noticed :
In ] tendre aotvs the specific rmr.e frondnsus of Aseanius must unfortunately be substituted
for the accepted but later arborescens of Müller.
. Hancockia Gosse, 1877, is a valid name, and there is no reason why it shopld yield to
Govia Trinchese, 1886.
V. , Cv.manotus Odhner is here accepted as the proper genus for Goryphella, bedumonti.
Of Goryphella pellutMa, 0: gracilis and C. smaragdina, the last two are colour varieties,
and in the opinion of some authorities all three are varieties of 0. rufibranchialis.
Calma is a valid genus, but its characters have, been somewhat misunderstood. It
should include Galma A. & H. and Foreséiu Trinchese, but exclude Calma atpflëii Vérany.
The names Antiopa and Janus are both preoccupied, and the genus should bear the
name Antiopella (1902) proposed by Hoyle., But A, hyalina is referred by Bergh to Jamolms
(1884). The original definition of this genii fias been considerably relaxed by Bergh,
and it may be questioned if it should not be further extended so as to include. Antiopella.
The two genera are distinguished only by the jaws.
Gah-ina'tricolor probably includes as varieties E, farrnni A. & H., E.- ametliystina
A. & H., and E. adélaidæ Thomps.. Amphorina cwrufea includes A. meligs (Herdm.).
Stiliger bellulus has priority over St. mariée as the name for the British species of this
gefiufi,'
The genera Acteonia A. & 11. and Gnnia A. & H. were, subsequently amalgamated
by Alder, but had better be kept separate provisionally as the development of Acteonia is
not known. The development of Getria is unusual ; that of the allied Limapmtia, follows
the normal course.
The evidence of the type specimens indicates that D. testudinai'ia and 1). planata are
separate forms and referable to the genera Doris and Geitodons respectively. But the
second form lies under suspicion of being immature, and it is conceivable that the buccal
parts may vary in different individuals and in different stages of growth.
The perplexing Doiis millegrana A. & H., which appears from an examination of the
type specimens to be the animal described by Bergh as Thordisa ? dubia, is here referred
provisionally to von Jhering’si genus Aporodoris. Whether that genus will really prove
valid when various allied forms are better known is another matter.
1 There is some doubt as to the characters of Hermxopsis.