and on the Deposit in lohich it was found. 289 



great general resemblance to the leaves of existing trees^ but not in such a 

 state as to be satisfactorily identified/' 



In addition to these observations 1 may remark, that the greater number 

 of the leaves of forest trees have their petioles still adherent, as if they had 

 fallen off spontaneously, and in their due season. 



In conclusion it may be observed, 



1st. From the nature of its organic remains, that the deposit of (Eningen 

 is of unmixed lacustrine origin ; and, from the fine lamination and structure of 

 the beds, that they could only have been formed during a long period of time. 



2nd. This deposit of marl rock having taken j)lace in a basin of the molasse, 

 that formation must have been deeply excavated prior to the existence of the 

 lake in which the marly strata were accumulated. 



3rd. From the intermixture of species undistinguishable from those now 

 existing, with others decidedly extinct, this deposit may be considered an 

 important link in the history of the earth's structure, indicating an intimate 

 connection between the ancient state of nature and that which now prevails. 



4th. The deposit differs essentially in its organic remains from any other 

 freshwater formation at a distance from it with which we have hitherto been 

 made acquainted, either in France, or in the adjacent regions of Germany*; 

 thus satisfactorily affording proof of the independence and isolation of these 

 lake formations, amongst which, this of ffiningen, both from its contents and 

 superposition to the molasse, must be considered one of the most recent. 



5th. Yet recent as must have been the epoch of this formation, the basin in 

 which it was deposited has subsequently been re-excavated to a considerable 

 depth ; the proof of which is, that horizontal beds still present escarpments 

 several hundred feet above the Rhine, without any barrier between them and 

 that river. 



Lastly. However long the epoch of this accumulation must have pre- 

 ceded the period wlien the Rhine attained its present level, we are taught by 



* The freshwater limestone of Ulm is deposited in Jura limestone, and contains the Helix 

 moi'ognesi, the Limnea ova(a, and other shells, wliich peculiarly characterize the lacustrine 

 formations of the Limagne d'Auvergne, and a striated Planorbis, like that of the Isle of Wight. 



At Steinheim near Heidenheim the freshwater strata are also deposited on Jura limestone, and 

 contain the Linuiea vcntricosa (Brongn.) of the Paris basin, and a shell (Paludina variabilis 

 of Bronn) which M. Deshayes refers to " Ampullacere," a genus of New Holland, &c. 



At Bouxweiller near Strasbourg, the lacustrine limestone rests upon a rock of about the age of 

 tTie great oolite of England, and some of its fossils are identical with those of the freshwater for- 

 mations of the Isle of Wight. These and several other analogous formations in Swabia, &c. were 

 visited by Professor Sedgwick and myself, on our return from the Austrian Alps, in the autumn 

 of 1829. 



VOL. III. SECOND SERIES. 2 P 



