466 



Mr. Horner on the Geology of the Environs of Bonn. 



stated to have occurred ; but Mr. Agassiz mentions that several species of the 

 genus Leuciscus are found in the beds of ffiningen. 



With regard to the remains of Frogs, they do not appear to have been 

 known to exist in a fossil state previous to the memoir of Professor Goldfuss 

 on those found in the papierkohle of this district ; for Cuvier says, under the 

 head Des Ossemens de Batraciens, " Je crois qu'il ny a de certain que ceux 

 " des carrieres si problematique d'OEningen * ; " and here he does not allude to 

 Ranae. Mr. Murchison, however, in his late memoir on (Eningen, when 

 speaking of the collection of fossils from that place in the museum at Carlsruhe, 

 says, " I observed specimens of Rana and Testudo." I have had no means 

 of ascertaining whether the same species of Salamander exists at (Eningen 

 with that found in our papierkohle; but Professor Goldfuss informs me that 

 the Salamander Ogygia is scarcely to be distinguished from the living species. 



The insects in the papierkohle are another distinctive character of this 

 brown-coal formation, for no such occurrence has been mentioned in any of 

 the other great lignite deposits above alluded to, and two of those found in 

 the papierkohle also occur at (Eningen, viz. Anthrax and Cerambyx. 



It is impossible to decide whether the siliceous mass of Marienforst belongs 

 to the lower or the upper part of the brown-coal formation, but the quartzose 

 sandstones are always found in the lower part. As far as casts enable one to 

 decide, and these only are met with, the species Planorbis rotundatus and 

 Lymneus longiscatus have been made out by M. Deshayes. Mr. Lyell 

 enumerates them in his Tables of shells, constructed on the authority of 

 M. Deshayes, as occurring in his Eocene and Miocene periods, and not in the 

 Pliocene. 



It thus appears that there is no evidence to prove that this brown-coal for- 

 mation belongs to the period of the plastic clay, and all the phaenomena seem to 

 assign it to a more recent period, and they prove it to be of purely lacustrine 

 origin. It seems to have been deposited in a vast inland lake of fresh water, fed 

 by some great river or rivers, which brought the sand and clay and wood, that 

 subsided gradually to the bottom ; and the perfect state of preservation of some 

 delicate leaves shows also that the lake was surrounded by trees or shrubs. 



I have been thus particular in endeavouring to fix the age of the brown-coal 

 formation, not only on account of the great extent and importance of the 

 deposit in itself, but because it affords, as I shall presently show, a criterion 

 for judging of the period when the unstratified rocks of the Siebengebirge 

 were ejected. 



* Cuvier, Ossemens Fossiles, torn. v. p. 385. 



