578 MESSES. GAEDNEE, E:EEP1N"G, ASTD MONCKTON Oi;r THE 



35. The Fppee Eocene, comiorising the Baeton and Uppee Bagshot 

 FoEMATioNs. By J. Staekie Gaednee, Esq., E.G.S., E.L.S., 

 Hekrt Keeping, Esq., and H. W. Monckton, Esq., E.G.S. 

 (Eead Marcli 28, 1888.) 



The introduction of the Oligocene stage into onr classification has 

 necessitated a partial revision of the grouping of our older British 

 Tertiaries. Whether this introduction of a new primary division 

 into the Tertiary system was necessary or expedient may stiU be ques- 

 tioned ; but it has been generally adopted and is, for the time being, 

 established. The division does not coincide in England with a 

 marked change in either fauna or flora, though the series seems 

 nevertheless tolerably complete and well developed; its limits, 

 however widely stretched, show that the Oligocene stage compares 

 neither with the Eocene nor the Miocene in importance. 



Opinions have differed as to where the line of division should be 

 drawn ; whether this should be as low down as the top of the 

 Barton Beds or at the base of the Headon Beds, or even higher. 

 Por our part, we think it desirable to uphold the view which places 

 the demarcation between the top of the Bagshot Sands of Alum Bay 

 and the base of the Lower Headon Series, though it is perfectly ob- 

 vious that any such line in the midst of our series must be a purely 

 artificial one. 



An almost necessary consequence of the change in the classifica- 

 tion has been the readjustment of the divisions of our truncated 

 Eocene, only the middle and lower division remaining, so that the 

 term " Middle " without an Upper Eocene would no longer be an 

 appropriate one. But the Middle Eocene, embracing as it does such 

 formations as the Nummulitic and the Calcaire grossier, has a litera- 

 ture of immense importance, which it appears to us in the highest 

 degree inexpedient to disturb or render obsolete. We therefore 

 propose to adopt the view which reconstructs an Upper Eocene from 

 the Barton and Upper Bagshot Beds, and to show that they form a 

 sufficiently natural and well-marked group*. Neither the Upper nor 

 the Middle Eocene, however, will then continue to equal the Lower 

 Eocene in importance, and we cannot but look on the necessity for 

 any revision as unfortunate. The Eocene, as it stood, was a compact, 

 useful, and by no means unwieldy group, with a literature and 

 history that should have preserved it from dismemberment. The 

 Upper Eocene was by no means so preponderating or so distinct as 

 to render its removal expedient, and the transition beds were either 

 satisfactorily located or might easily have been so. Finally the 

 flora of the Oligocene, on which some stress has been laid, is so 



* A paper by Prof. Prestwich has been published (Quart. Journ. Geo! Soc. 

 vol. xliv. p. 88) since this was written. He treats the classification we propose 

 here as the one already estabHshed, vide table p. 88. This would render further 

 insistance on its expediency unnecessarj^, did he not propose, I. c. p. 108, to sup- 

 press this classification by totally abolishing the Middle Eocene. 



