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NOTE.—At the request of the late Dr. Davidson, and with the sanction of the Council, the proof-sheets of this Memoir have been laid hefore Miss Agnes Crane, of Brighton, hy whom they have been read on the Author's behalf.
Previous to Dr. Davidson's lamented death, Miss Crane had been studying the Brachiopoda under his guidance, and was conversant with his wishes respecting the publication of this work.
2nd Ser. ZOOLOGY.] [VOL. IV. PABT 1.
THE LINNEAN SOCIETY OE LONDON
A MONOGRAPH OF RECENT Beachiopoda.-part I.
THOMAS DAVIDSON, LL.D., E.R.S., E.L.S., F.G.S.K &c.
PRINTED FOE THE LINNEAN SOCIETY
BY TAYLOR AND FRANCIS, RED LIOtTcOURT, FLEET STREET.
SOLD AT THE SOCIETY'S APARTMENTS, BURLINGTON-HOUSE, PICCADILLY, W.,
I. A Monograph of Recent Brachiopoda.—Part I.
Head 5th November, 1885.
DURING the last hundred years the recent Brachiopoda have attracted considerable attention, and a large number of valuable memoirs and papers have been published upon them. Their shells, shell-structure, anatomy, embryology, and affinities have alike been carefully investigated. Observations on the living animals of several genera have also been recorded. The sea-bottoms have been dredged for Brachiopoda in many latitudes and over a wide geographical area, and their habitats and ranges of depth accurately ascertained to a very considerable extent. Four or five incomplete monographs, in which the shells only of a large number of species have been well illustrated and briefly described, have appeared during the present century; but no satisfactory general monograph treating of the shell and animal conjointly has yet been published. This omission I have now endeavoured to supply.
In 1843, Kiister, in his new edition of Chemnitz's 'Conchy lien-Cabinet,' described some twenty-six or thirty species, of which several are now known to be synonyms. These he figured in six quarto plates.
In 1846, G. B. Sowerby, in his 'Thesaurus Conchyliorum,' described and beautifully illustrated forty-seven species, of which number several are synonyms.
In 1859-62, Lovell Reeve, in his 'Conchyliorum Iconica,' described the shells of seventyfive species, of which some were synonyms, accompanied with a series of beautiful illustrations, drawn by G. B. Sowerby.
In 1873, in the 'Proceedings of the Academy of Natural Sciences of Philadelphia,' Mr. W. H. Dall published a catalogue of all the recent species of Brachiopoda known to
SECOND SERIES.—ZOOLOGY, VOL. IV. 1
him up to that date. In this catalogue without figures, about one hundred species are enumerated, some of which are synonymous.
During the last thirty-five or more years, I have devoted much time to the study of the recent forms, in conjunction with that of the fossil species, and have lost no opportunity of making myself acquainted with all that has been done and written upon the subject, as well as in assembling all available material, so as to enable me to bring together in a single monograph the chief results of many independent researches published in a number of scattered papers and works often difficult of access. The literature of the subject is indeed voluminous, as may be realized by a glance at the 'Bibliography of the Brachiopoda,' compiled by Mr. W. H. Dalton and myself, and published in vol. vi. of my * British Fossil Brachiopoda' (Palaeont. Soc, 1886).
I have also, I believe, had advantages which few have possessed in being able to follow out the observations made with respect to the animal and its anatomy, and in having been able to draw a very large number of figures from the types of the best-preserved examples of almost all the known forms, as well as of a large series of individuals of the same species at different stages of development. The study of the adult condition of a species gives insufficient data, and it is requisite to follow out the modifications it has to go through during the different stages of its existence, and to note these differences.
The study of the embryo has also shown that the animal assumes a series of welldefined stages in its development, a fact that was but little known prior to the publication in 1861 of Prof. Lacaze-Duthiers's admirable memoir on Thecidium mediterraneum. These observations were subsequently followed by the excellent researches of Fritz Miiller, Kowalevsky, E. Morse, H. Friele, M°Crady, Dall, Van Bemmelen, A. E. Shipley, M. A. Schulgin, and one or two more. The results obtained by these authors will be referred to in the sequel. It is very desirable that these important investigations should be continued, as much still remains to be discovered, described, and illustrated.
The shell-structure of the recent Brachiopoda has been admirably worked out by a number of accurate observers, such as Dr. W. B. Carpenter, W. King, Van Bemmelen, Hancock, and many others, and has led to very important results. To Herman Friele, E. Deslongchamps, and one or two others we are indebted for much accurate and important knowledge with respect to the development of the loop, of which but little was known previous to 1852.
The anatomy of the animal has also been admirably investigated and worked out, and it is sufficient to mention the names of Cuvier, Owen, Huxley, Hancock, Vogt, Gratiolet, Lacaze-Duthiers, King, Brooks, Dall, Morse, E. Deslongchamps, Van Bemmelen, Woodward, Shipley, Schulgin*, and others, to show how important and varied have been the additions to our knowledge with respect to this very necessary branch of investigation. In drawing up the description of each species, I have considered it desirable, whenever possible, to reproduce the words and illustrations of the authors, and thus give them all credit for their careful, painstaking researches.
* To these names Dr. Davidson would doubtless have added that of H. G. Beyer, who contributed an important paper on the shell-structure and anatomy of Lingula (Glottidia) jryramidata, Stimpson, to the Studies from the Biological Laboratory of the Johns Hopkins University, Baltimore, vol. iii. no. 5, March 1SS6.—[A. C]