178 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



If the previous statement of the geological relations at Petit Coeur 

 be, as I think, accurate, /. e. if the plants and belemnites really lie 

 in the same deposit, as was also concluded by the geologists of the 

 French Society, who met at Chambery, the anomaly is great, and 

 involves us in considerable natural-history difficulties. But are these 

 difficulties insurmountable, and ought geologists to shrink from en- 

 deavouring to reconcile them because they interfere with the general 

 distribution of fossil plants ? Excluding for the present all theory, 

 let me say that I cannot admit the presence of certain species of fossil 

 ])lants to be as decisive of the age of a deposit as that of the remains 

 of any well-known animal. Thus, the Calamites arenarius cited by 

 Brongniart as pertaining to the old coal, is found both in the Permian 

 system and in the Bunter sandstein and Keuper, or throughout the 

 Trias, a system in which no one palaeozoic animal has been detected. 

 Again, the JEquisetum columnare^ which so abounds in the Brora 

 (oolite) coal, and is most abundant on the Yorkshire coast beneath 

 the Kelloway rock, is one of the most common of the trias plants of 

 Germany. And yet as a whole, both the fauna and flora of the middle 

 oolite and trias are utterly dissimilar. Look, on the other hand, to 

 the weight attached to the presence of belemnites. In no instance 

 has a belemnite been detected in any part of the world below the 

 lias. The trias, of which there is not a trace in Savoy, but now so 

 well known in the Eastern and Tyrolese Alps, affords no sign of a 

 belemnite any more than the same group in other regions ; still less 

 has any one ever heard of a belemnite in an old carboniferous deposit 

 in any part of the world. 



In giving the previous description of the section at Petit CcEur, I 

 have done so in opposition, I repeat, to the strong wish I entertained 

 to be able to offer any explanation which might obviate the dilemma 

 in which such a recognition places us. I tried, for example, to 

 account for the phsenomenon by an inverted dip, and endeavoured 

 to reconcile the overlying position of the coal plants by a reversal, 

 similar to that which clearly operated on the north face of Mont 

 Blanc : but there the belemnitic strata plunge under crystalhne 

 rocks, whilst at Petit Coeur they overlie and are intercalated in them. 

 I could not speculate on the crystalline rocks of the Isere being ori- 

 ginally of younger age than the belemnite beds, like the well-known 

 examples on the northern face of Mont Blanc in the vale of Chamo- 

 nix, and having been metamorphosed by the influence of the ellipsoid 

 of granite before adverted to ; because if so, and that these fossili- 

 ferous beds were inverted, other older strata besides the mere bed 

 with coal plants would be found above them, which is not the case ; 

 the same liassic or Jurassic group being manifestly developed m con- 

 siderable force on the line of dip. 



Those geologists who have explored the environs of Mont Blanc 

 have long been acquainted with the fact first indicated by Sir Henry 

 de la Beche, that coal plants also appear in the well-known con- 

 Piedmont, which include other known species of Sowerby, V. Buch, Schlotheim, 

 Agassiz, &c., as given by M. Sismonda, with a descriptive plate of the species 

 from the Encombres (Bull, de la Soc. Geol. Fr. vol. v. New Series, p. 410). 



