Dr. FiTTON on the Strata below the Chalk. 329 



bottom of the sea, and the Lower green-sand, a series of beds coeval with 

 the Wealden in point of date, but differing from it in possessing the charac- 

 ters of a marine deposit, and including marine shells and other productions of 

 salt water; — with which, near the shore, the productions of the land, or even 

 the freshwater shells of the rivers, might be occasionaly intermixed. And if 

 the Portland strata constituted at that epoch, both the dry land, and the 

 bottom of the sea, and were afterwards submerged, we ought now to find the 

 Lower greensand, in some places immediately in contact with the Portland, — 

 in others with the Wealden, — and in others again with the marine equivalent 

 of this latter group. 



Two results would probably attend the state of things here supposed, which 

 are deserving of notice : 1st, That the Wealden and its marine equivalent 

 could not both be found in the same place; and consequently, (since we have 

 the former in England), that the marine beds of that date are not to be 

 expected generally in this country : 2ndly, That the marine fossils of the 

 beds cotemporaneous with the Wealden would probably be distinct, both 

 from those of the Portland group beneath, and of the Green-sands above 

 them ; a consideration which gives peculiar interest to the fossils of this in- 

 termediate group. 



The strata between the chalk and the oolitic system on the continent of 

 Europe have not yet been sufficiently examined, to furnish all the evidence 

 that may be expected upon this subject ; but indications of such an equivalent 

 to our Wealden as has been mentioned, have been already found in so many 

 detached points, that its occurrence in other places, or even the existence 

 of a continuous marine deposit of that age, is by no means improbable. 

 Mr. De la Beche* has brought together evidence which shows that such a 

 group exists in the department of the Haute Saone, in France ; at Candern, in 

 the Brisgau ; near Aarau ; in Poland ; and on the confines of Silesia. To these 

 may be added the Isle of Bornholm in the Baltic, and the vicinity of Helsing- 

 burg, in Scania, which have afforded specimens of fossil plants resembhng those 

 of our Wealden, along with marine shells ; but at Bornholm, although the 

 shells are also marine, they are generally such as may be supposed to have 

 inhabited, either the estuary of a large river, or the seas immediately ad- 

 jacent to the coast. 



In most of the cases mentioned by Mr. De la Beche, a group of strata between the chalk and the 

 oolitic system is found to contain pisiform iron ore ; but the fossils which accompany that mineral 

 are marine. A very extensive deposit of this kind in Poland and Silesia is described by Professor 

 Pusch, which includes also argillaceous iron ore; and among its fossils are the genera Ammonites, 



* Geological Manual, (1833.), p. 309. 

 2 U 2 



