VUl INIEODUCIION. 



Prof. A. von Kocnen has devoted much time and labour in correlating the 

 Erockenhurst fauna with that of the Oligoconcs of Northern Germany 

 and Belgium. Prof. J. W. Judd was, however, the first English geologist 

 to recognize the importance of this Continental work and the necessity 

 for the application of the term Oligocene in England to the rocks hitherto 

 grouped as Upper Eocene. Our standard text-books of Geology have now 

 adopted it, but most important of all is its recognition by the Survey in 

 their ' Isle of Wight ' memoir, edited by Messrs. Reid and Strahan. It will 

 be observed that the " Correlation Table of the Tertiary Beds of Europe," 

 drawn up by m)' friend Mr. Geo. F. Harris, and which forms an Appendix 

 to this work, indicates the Headon Beds as the topmost portion of the 

 Eocene deposits, which is, of course, contrary to Survey classification, but 

 in accordance with Continental views maintained chiefly by M. Dollfus. 



No attempt has been here made to subdivide the Oligocenes further 

 than indicating the name of the various beds composing them ; but in the 

 case of the Eocenes they have been termed the Upp(;r, Middle, and Lower, 

 each of which has again been split up into subordinate beds. 



Much valuable information as to localities and horizons has been gathered 

 from the works of Prof. Prestwich, Mr. Whitaker, Mr. J. S. Gardner, and 

 others ; and constant reference to such authorities has been absolutely 

 necessary, as it will be remembered by those acquainted with the Edwards 

 Collection that no definite geological information was ever placed with the 

 specimens or indicated in Mr. Edwards's published descriptions, although 

 each specimen was carefully localized, this author having included them 

 under the general term of Eocene. 



Some remarks are now necessary on the Conchological nomenclature 

 adopted in this work, a subject which has been somewhat neglected in 

 this country, and chiefly because certain authors resent any reform 

 which is likely to abolish some familiar and well-known names. But we 

 must keep pace with the work of Continental and American authorities, 

 who are doing their utmost to eradicate all those generic names which 

 have been previously applied to other groups in the Animal Kingdom. 

 Tlieir action in this matter is out of respect to the " Law of Priority," 

 which, if not adopted internationally, is certain to result in endless 

 confusion to our Science. Bearing in mind the importance of this subject, 

 this law has been strictly adhered to in drawing up the nomenclature 

 for this work, with the result that many well-known names have been 

 abolished, either on account of pre-occupation or because an earlier one has 

 been discovered of precisely the same value as the later name which maj- 

 have been previously employed for it. The law of priority has been fixed 

 from the 12th edition of Linnaius's ' Sj-stema Natura;,' the Molluscan part 

 of which was published in 1707 ; Solandor's species, however, contained in 



