ADVERTISEMENT.
It is - intended in the present work to give, as far as possible, a complete history of
the British species of Mollusca included in the order Nudibranchiata of Cuvier, together
with careful and detailed drawings of each. The latter are the more necessarv on account
of the perishable nature of these animals and the impossibility of preserving them with their
proper forms and colours in museums.
From the difficulties attending their study on this account, many authors, in treating of
the Mollusca, have entirely omitted the 'Nudibranchiata, and have confined themselves to a
description of the testaceous Mollusca alone, thus leaving a gap in the chain of affinities inconsistent
with a proper knowledge of this sub-kingdom of nature as a whole.
The authors of the present work confidently hope that they will be able, as far as the
British species are concerned, to supply this deficiency, and to give such full delineations and
descriptions of most of the species as may prevent any difficulty in their recognition by future
observers. By the kind assistance of their friends, added to their own researches, they have
been enabled to accumulate a large store of materials, but there are still several species
described by other naturalists which they have not met with. As the Society to whom
they are indebted for the publication of this Monograph have determined to bring it out in
Parts, extending over a period of four or five years, the authors hope yet to obtain many of
these species before its completion.
For the purpose, therefore, of affording an opportunity of adding drawings and descriptions
of these from the living animals, it has been thought advisable to publish the species
promiscuously, adopting such a plan as will allow of their being arranged systematically on
the completion of the volume.