872 On Sipllarla, Sfi(/maria, and Neurojiteris. 



systems explanatory of the phenomena, we must then seek for 

 this explanation in more distant parts, at points still unknown to 

 science ; or suppose, that if these terrestrial systems have not 

 been the real cause, some may have been destroyed by great 

 subsidences and depressions. It is not to be forgotten, that 

 the terrestrial systems constitute only the visible parts of the 

 dislocations of the globe ; whilst the depressed portion, often 

 the greater of the two, being frequently covered up, is un- 

 known to us, and may always continue so. In a word, the 

 separation of distinct faunas by systems and formations, is 

 only the visible result of the elevation and depression, to 

 various extents, of the crust of the globe in all its parts. 



9. I have already directed attention to the fact, that, from 

 the uniform distribution of the same animals, it follows, that, 

 until the commencement of the cretaceous formations, the 

 central heat of the earth completely destroyed the influence 

 of latitude, and of the polar cold. If at that time atmos- 

 pheric influence had no eff^ect upon the distribution of ani- 

 mals on the surface of the globe, all the faunas must neces- 

 sarily have owed their circumscribed limits to great disloca- 

 tions of the globe. It was only posterior to the cretaceous 

 deposits, that the influences of latitude could have compli- 

 cated the partition of basins, multiplied the local faunas, and 

 destroyed that uniformity of distribution, which we still find 

 in more ancient formations.* 



On Sigillaria, Stiginaria, and Neuropteris. 



In our next Number, we expect to publish a valuable paper on these 

 fossils, by Mr King", the Curator of the Newcastle Museum, who for 

 some time past has been more or less engaged in endeavouring to prove 

 that they are different parts of one and the same plant. 



The following is a summary of the principal conclusions contained in 

 the paper. t 



Owing to the bark of Sigillaria being composed of two diiferent layers 

 of tissue, it is shewn, that six different impressions may be produced ; 



* From the Annales des Scien. Natur. Mai et Juin, 1843, 



t A portion of the paper consists of an abstract of M. Adolphe Brongniart's 

 " Observations sur la structure interieure du Sigillaria elegans comparee a celle 

 des Lepidodendron et des Stigmaria ct a celle des v egetaux vivants." 



