My former volume, published by the Ray Society, treated only of the
Lepadidæ, one family of the Cirripedia: I was induced to print it
from having the materials ready, though this partial publication has
been in some respects inconvenient. The Palæontographical Society has
done me the honour to publish, with ample illustrations, the fossil
species of this same family of Lepadidæ. This present volume completes
my work on the sub-class Cirripedia.[2] I had originally intended to
have published a small volume on my anatomical observations; but the
full abstract given in my former volume, which will be illustrated to a
certain extent in the plates appended to this volume, together with the
observations here given under the Balanidæ, appear to me sufficient,
and I am unwilling to spend more time on the subject. In the volume on
the Lepadidæ, I gave the specific or diagnostic characters in English
and Latin: I have here left out the latter, inasmuch as I have appended
at the end of this volume a Latin Synopsis of all the species, recent
and fossil, of the whole class. To each species is added a reference
to the pages and plates of my three volumes, so that the Synopsis
will serve as a systematic index to the three: an alphabetical index
to the present volume is also given. In the Lepadidæ, I gave an
additional specific character, derived from the softer parts of the
animal's body: in the Balanidæ, these parts are more alike in the
different species, and I have found it impossible to give a diagnostic
character thus derived. In those cases in which a Family contains but
one genus, or a Genus but one species, I have assigned my reasons for
the institution of such groups, but have given, as heretofore, only a
single description in full: it would have been easy to have separated,
by analogy, this description into one for the species, another for
the genus or for the family; but as I believe such separation and
subordination of the characters would have been largely conjectural,
I have thought it best to act as I have done, and give, thus saving
useless repetitions, only a single description, and leave it for my
successors, when more genera or species are known, to separate, with
such certainty as is ever possible, the generic from the specific
characters.
[2] The number of the British fossil species of the Balanidæ and
Verrucidæ in a recognisable state is so small, that I do not
know whether it will be considered worth while to publish in the
Palæontographical series more detailed illustrations than are given
in this volume.
In nomenclature, I have endeavoured rigorously to follow the rules
of the British Association, and have never, at least intentionally,
broken through the great law of priority. In accordance with the rules,
I have rejected, that is, as compulsory, all names given before the
introduction of the binomial system in 1758. I have given much fewer
synonyms than is usual in conchological works; for it is impossible to
recognise with any approach to certainty, several even of the common
European forms, in the short descriptions given by most authors; this
holds good in many cases in which figures, in appearance excellent,
have been added. I assert this the more confidently, from having had
the advantage of having gone over some of the Linnean synonyms with Mr.
S. Hanley. I may further venture to express my conviction, that giving
references to works, in which there is not any original matter, or in
which the plates are not of a high order of excellence, is absolutely
injurious to the progress of natural history.