152 PROF. J. W. JTJDD OlS THE OLIGOCENE 



sented in the Paris basin by the " Sables Moyennes " or " Sables de 

 Beauchamp," and in Belgium by the " Systeme Laekenien " of 

 Dumont. Most geologists, too, regard this well-marked fossiliferous 

 zone as constituting the highest member of the Eocene or Nummu- 

 litic formation. This being admitted, we have an admirable and 

 safely established base-line from which to start in our comparison 

 of the English and foreign representatives of the succeeding geolo- 

 gical periods. 



Lying upon the Barton Clay we find a great series of estuarine 

 strata, which in places attains a thickness ;of nearly 400 feet ; and 

 this is succeeded by the beds containing the second marine fauna. 

 At Whitecliff Bay these marine beds are 100 feet in thickness ; at 

 Colwell Bay they are reduced to 25 feet, while in the New Eorest 

 we have evidence that their thickness is considerable, though it has 

 never been exactly determined. Our knowledge of these marine 

 beds in the I^ew-Forest area is derived entirely from an examina- 

 tion of exposures in artificial openings — brickyards, wells, and rail- 

 way-cuttings. Some of the peculiar fossils of this horizon were ob- 

 tained so long ago as 1823 by Sir C. Lyell, and by him submitted 

 to Mr. Sowerby for description. Mr. F. E. Edwards made many 

 interesting collections from beds on this horizon at Brockenhurst, 

 Eoydon, Whitley Eidge, and Lyndhurst, especially during the period 

 when railway-cuttings were being opened at the first-mentioned 

 of these localities. Erom information communicated to him by Mr. 

 Edwards, supplemented by his own studies, Yon Konen, who was 

 well acquainted with the equivalent beds on the Continent, was 

 enabled to give the account of these beds which was published by 

 this Society in 1864 *. Professor P. M. Duncan about the same time 

 described the important coral-fauna of these beds, the distinctive 

 character of which he was the first to recognize. 



Now the marine fauna of these beds is a very rich and highly in- 

 teresting one. Yon Konen was able in 1864 to enumerate 5Q 

 species of MoUusca as occurring at Brockenhurst ; but we are now 

 acquainted with nearly 200 marine forms from the several localities 

 at which the beds representing this horizon occur. 



The first point which claims our attention in connexion with this 

 second marine fauna is its striking distinctness from that of the 

 Barton beds. Of the 200 forms which it contains, not more than 

 20 per cent, are found in the Barton beds. Now this second fauna 

 is found to occur at many points upon the Continent, and always in 

 strata which distinctly overlie the Bartonian deposits. In the 

 Paris basin, it is true, this second marine fauna is not represented ; 

 for there the gypsum of Montmartre and other freshwater deposits 

 occur at this horizon, to the exclusion of marine beds ; but in 

 Belgium, Northern Germany, and Switzerland we find the exact 

 equivalent of our English strata everywhere containing the same 

 well-characterized fauna. The fossils of the " Tongrien inferieur '' 

 of Dumont (the Lower Limburg of Lyell), those of the strata which 



* " On the Correlation of the Oligocene Deposits of Belgium, Northern Ger- 

 many, and the South of England," r Quart. Journ. Geol. Soc. vol. xx. p, 97. 



