286 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 22, 



of the question ; but I venture, with great diffidence, to lay before 

 the Society the reasons which have led me to incline to the opinion 

 that the Marine Sands of Weinheim ought to be looked upon as 

 Miocene rather than Eocene. 



I say Miocene rather than Eocene, because I am not altogether 

 prepared to admit the correctness of these terms, in the sense of 

 looking upon them as two subdivisions the exact boundaries of which 

 can be accurately laid down or defined. I believe that if we could 

 obtain sections of all the European tertiary deposits, from the num- 

 mulitic limestone up to the most recent post-pliocene formation, we 

 should be able to make out, in one section or another, a constant un- 

 broken sequence, without either break or interruption. I do not 

 mean to assert that no local changes or interruptions took place during 

 this period ; on the contrary, they were probably very frequent. 

 Animal life also was undergoing a slow but gradual change, from 

 the earliest post-cretaceous to the existing forms, regulated according 

 to the more or less favourable conditions under which it was placed, 

 contemporaneously with the changes going on in the physical 

 condition of the region ; but I do not believe that these changes or 

 disturbances were universal, or that the causes which occasioned the 

 destruction of one species and the introduction of another operated at 

 the same epoch in all parts of the then European seas. In process 

 of time, as the different changes in relative height, in elevation above 

 and depression beneath the mean level of the ocean, extended, did the 

 change in animal life also extend, modifying it everywhere on the 

 same general principles, again to be locally modified by the differ- 

 ences of soil, rocks, and sea-bottoms, until it had traA^elled through 

 all the changes from the commencement to the close of the tertiary 

 epoch. 



I have said thus much to show that I do not attach any great im- 

 portance abstractedly to the question as to whether the beds we are 

 now considering should be called Upper Eocene or Lower jNIiocene ; 

 for although I think they contain a greater number of fossils iden- 

 tical with those found in other countries in formations above 

 rather than below them, the mere name of the beds is not the real 

 question before us. One thing however is certain, that they have a 

 greater resemblance with the Limburg, and particularly with the 

 Eleyn Spawen beds, than with any other known European formation. 

 They contain also some fossils similar to those below, and others 

 identical with those above. As however the question has been raised, 

 whether they should be placed in the Eocene or ISIiocene subdi- 

 vision, I will briefly state my reasons, founded on physical as well 

 as on palseontological grounds, for the conclusion at which I \\z.\e 

 arrived. 



It is well known that the author of this nomenclature founded his 

 system on the different proportions of the fossil shells foimd in each 

 formation which are identical with living species, on the assumption 

 that, in proportion as Ave ascend to a higher bed, the greater is the 

 identity between its organic contents and the existing fauna ; and 



