18 



THE CARBONIFEROUS. 



Prof. T. Rupert Jones has kindly examined and described a 

 number of Entomostraca found in connexion with the exploration of 

 the erect trees.* They occur, not in the trees themselves, but in the 

 roof shale of the coal on which the trees stand, in fine shale which repre- 

 sents the first deposit of silt over the peaty soil on which the SigiUarice 

 grew. In the same paper he has ably summed up our knowledge 

 of Entomostraca in the Carboniferous of Nova Scotia generally. Prof. 

 Jones determines the most common crustacean in the shale — and, 

 indeed, in the Joggins shales generally — as C arbonia fahulina, J. and 

 K. This is the species figured at page 206 as Cytherella inflata. 



I may add that Dr Scudder has given much attention to the 

 Myriapoda, Insects, and Arachnidans of these deposits, but must refer 

 for his results to his papers in the Memoirs of the Natural History 

 Society of Boston. One correction which has resulted from his recent 

 labours is, that the species figured at page 53 of the Supplement as 

 Libellala carbonaria, and supposed to be the larva of a dragon-fly, is 

 now found to belong to the Arachnida, and to that curious group 

 between the mites and the scorpions represented in modern times by 

 the well-known Chelifer or scorpion-crab. Its name must now be 

 changed to Anthracomartus carbonarius, and it may be restored by 

 prefixing a squarish cephalo-thorax, furnished with eight spider-like 

 legs, and probably a pair of claws in front. 



I entertain the hope that I may be able fully to revise and to 

 publish in a connected form the fossil plants which I have described 

 at various times, and the specimens of which are now in the Peter 

 Redpath Museum ; but this is a work requiring years, and unfor- 

 tunately interrupted by many engagements. 



One fact of general application which is admirably illustrated in the 

 Carboniferous of Nova Scotia is the extreme sensitiveness of the earth's 

 crust to unequal pressure. The coal-formation of the Cumberland 

 district, 5000 feet in thickness, and consisting wholly of beds which 

 must have been deposited almost exactly at the sea-level, shows that 

 for every inch of sediment or of vegetable matter there must have 

 been a corresponding depression of the crust. This accurate corre- 

 spondence of sedimentation with subsidence has long appeared to me 

 one of the most striking facts in geological dynamics. 



IV. THE ERIAN, OR DEVONIAN. 



This formation, most largely and completely represented in the 



great " Erie Division " of the Geological Survey of New York, which 



occupies an immense area in the district around the lake from which 



* London Geol. Magazine. August 1884. 



