Having so lately, in my volumes on the Recent and Fossil LepadidÆ, expressed as strongly as I could, and with the utmost sincerity, the obligations under which I lie to very many naturalists, I will not here repeat my thanks, and will only say that the assistance formerly rendered me from so many quarters has been most kindly continued without intermission. The references under the Habitats, in which I may remark the names of Mr. Cuming and of Mr. Stutchbury, and of the British Museum, so often recur, show my deep obligations to these gentlemen and to Dr. Gray, and indeed to most of the British and several Foreign[1] collectors of recent and fossil shells. At the period when the Introduction to this volume was printed, I stated that I did not know whether the PalÆontographical Society would publish the few British fossil BalanidÆ; the Council has now honoured me by determining on this publication, so that these species will hereafter be more fully illustrated than they could be in the present volume. I cannot conclude this short preface, without again tendering my most grateful thanks to the Council of the Ray Society for the publication of my two volumes, and for the very kind manner in which they have acceded to all my requests.

DOWN, KENT; July, 1854.

MONOGRAPH

ON

THE CIRRIPEDIA.