PREFACE TO THE MOLLUSCA
The general plan of classification adopted in this work is not that of any single authority. It has been thought better to adopt the views of recognised leading specialists in the various groups, and thus place before the reader the combined results of recent investigation. This method may, perhaps, occasion a certain number of small discrepancies, but it is believed that the ultimate effect will be to the advantage of the student.
The classification adopted for the recent Cephalopoda is that of Hoyle (‘Challenger’ Reports, Zoology, vol. xvi.), for the fossil Cephalopoda (Nautiloidea) that of Foord (Catalogue of the Fossil Cephalopoda in the British Museum, 1888–91), and (Ammonoidea) P. Fischer (Manuel de Conchyliologie, 1887). In the Gasteropoda the outlines are those adopted by Pelseneer (Mém. Soc. Malacol. Belg. xxvii. 1894), while the details are derived, in the main, from P. Fischer. The Amphineura, however, have not been regarded as a separate class. The grouping of the Nudibranchiata is that of Bergh (Semper, Reisen im Archipel der Philippinen, ii. 3). The Pelecypoda are classified according to Pelseneer’s most recent grouping.
Acknowledgment of the principal sources of information has been made in footnotes, and a short list of leading authorities has been appended to the chapters on anatomy, for the use of students desirous to pursue the subject further. In the case of geographical distribution the authorities are too numerous and scattered to admit of a list being given.
A special word of thanks is due to Mr. Edwin Wilson for his patient care in preparing the illustrations, the majority of which are taken from specimens in the University Museum of Zoology. Mr. Edgar Smith, besides affording the kind help which visitors to the British Museum always experience at his hands, has permitted me to use many specimens for the purposes of illustration.
A. H. COOKE.
King’s College, Cambridge,
20th December 1894.