Robert O. Bell — Notes on Pliocene Beds. 555- 



Eesearch on similar lines was advocated some years ago by the 

 late Edward Forbes to the zoologists of his day. He remarks that 

 "to get at the causes of such phenomena (the distribution of species), 

 we must trace the history of the species backward in time and 

 inquire into its connection with the history of geological change." 

 It is evident that such a course of investigation as that suggested by 

 Forbes must prove to be equally beneficial to palDsontological students, 

 and its wisdom has been often manifested of late years, during which 

 experience has shown how dependent each line of study is upon the 

 other. 



The earliest indication of the Pliocene period in Britain seems to 

 be the strongly ferruginous deposit at Lenham near Maidstone, 

 occupying the so-called pot-holes of the Upper Chalk surface, and 

 spreading OA'er a considerable extent of the North Downs ; at thi& 

 place the impressions of shells in this hard rock are plentiful, and sO' 

 far as present observation goes are of Pliocene forms. The locality 

 has never been thoroughly examined, and would well repay patient 

 exploration. The latest list of the species, which, however, is not 

 exhaustive, is in a communication by Mr. Clement Eeid, F.G.S., to 

 "Nature" (No. 876, August 12th, 1886), and contains some which 

 have not yet been found in our Crags. The age of this Lenham bed 

 is now generally regarded as that of the similar Diestien deposit in 

 Belgium. 



Mr. Eeid holds that this deposit is contemporaneous with our 

 Coralline Crag. However that may be, the writer must strongly 

 demur to the association of either of these deposits with those found 

 in the well-sinkings near Utrecht, the fossils of which are so well 

 identified and delineated by Dr. J. Lorie, in the paper referred to 

 by Mr. Eeid. 



The high northern character of many of the Mollusca found in 

 these beds is unmistakeable, and is closely correspondent with that 

 of the fauna of the upper deposits of the Eed (Butley) Crag. It is 

 significant that no such Arctic forms as several of those mentioned by 

 Dr. Lorie have ever occurred either in the Lenham or Coralline beds. 



The fauna of these earlier deposits indicate a warmer temperature 

 and a nearer relation to Miocene times than that possessed by the 

 Eed Crag. The Cassidarias, Pijrulas, Volutes, and other shells, 

 Fusiis alveolatus and F. consociale, for instance, all of semi-tropical 

 character, occur in certain zones of the earlier Crag in some 

 profusion, and generally in perfect condition ; indeed, where the 

 matrix is dry, they may compare favourably with the French 

 Tertiary shells. In the later Crags the southern species thin out 

 and fast disappear as we rise higher in the series, and in the case of 

 species which are not uncommon to both, e.g. Vohtta Lamherti, the 

 condition is rarely perfect, and the fine sculpture observable in the 

 Coralline Crag shells is always absent ; even those shells which un- 

 doubtedly lived in both formations, such as Buccinopsis Dalei, have 

 materially altered in shape and size after the advent of the Eed Crag, 

 and appear in greatly increased numbers. 



The changes both in diversity of climate and of life have doubtless- 



