rEEFACE. 



The Collection of skeletons, skulls, and other portions of Cetacea in 

 the British Museum, at present the most complete in existence, was 

 brought together mainly in consequence of the zeal with which the 

 late Dr. Gray, Keeper of the Zoological Department, pursued the 

 study of this interesting, but formerly much neglected, group of 

 animals. 



It was upon this collection that Dr. Gray's numerous works on the 

 Cetacea, including those published by the Trustees of the Museum 

 in the form of Catalogues *, were based — works which are indis- 

 pensable to all zoologists wishing to become acquainted with the 

 Order of Mammals to which they refer. 



As, however, recent advances in knowledge have made great 

 modifications in the views which were held by Dr. Gray as to the 

 classification and nomenclature of the species, it seemed very de- 

 sirable that the Collection should be thoroughly re-examined, and 

 arranged and named in accordance with the ideas derived from the 

 fuUer and more critical state of knowledge of the present time, while 

 retaining references to all the published descriptions and figures 

 of the specimens, and to the various names under which many of 

 them have appeared at successive periods of their history. 



It will be observed that the principle adopted in determining the 

 number of species admitted into this List is the reverse of that of 

 Dr. Gray, and may possibly have erred in the opposite direction. As 

 species have not generally been recognized as such unless presenting 

 constant distinguishing characters capable of definition, it is pro- 

 bable that, in the imperfect state of knowledge of many forms, some 

 may have been grouped together which a fuller acquaintance with 



* Catalogue of Cetacea, 1850. Catalogue of Seals and Whales, 1866. Sup- 

 plement to Catalogue of Seals and Whales, 1871. 



