10 Mesozoic and Coenozoic Geology and Pakeontology. 



In the same year, Prof. W, B. Rogers* described, from the Trias of 

 Eastern Virginia, Equisetum arundiniforme^ C alamites planicostatus^ 

 Toiniopteris magnifolia, Zamites obtiisifolius, and Z. tenuistriatus. 



In 1847, Sir Cliarles Lyellf described tlie Triassic coal field, on the 

 James liver, near Richmond, Virginia, as follows: The tract of country 

 occupied by the crystalline or hypogene rocks, which runs parallel to 

 the Alleghany mountains, and on their eastern side is in this part of 

 Virginia about 70 miles broad; in the midst of this space the coal-field 

 occurs in a depression of the granitic and other hypogene rocks, on 

 which the coal rests, and by which it is surrounded, along its outcrop. 

 The length of the coal-field, from north to south, is about 26 miles, and 

 its breadth varies from 4 to 12 miles. The James river flows through 

 the middle of it, about 15 miles from its northern extremity, while the 

 Appomattox traverses it near its southern borders; on its eastern side 

 it is distant about 13 miles from the city of Richmond; it occupies an 

 elliptical area, the beds lying in a trough, the lowest of them usually 

 highly inclined, where the}' crop out along the margin of the basin, 

 while the strata higher in the series, which appear in the central part 

 of the basin, are very nearly' horizontal. Tlie general strike is about 

 N.N.E. and S.S.W., while that of the uearesu ridges of the Appala- 

 chian chain is about N.E. and S.W. 



A great portion of these coal measures consists of quartzose sand- 

 stone, and coarse grit, some of the beds, in the lower part of the series 

 resembling granite or syenite, being entirely composed of the detritus 

 of the neighboring granitic and syenitic rocks. Dark carbonaceous 

 shales and clays, occasionally charged with iron ores, abound in the 

 proximity of the coal seams, and numerous impressions of plants, 

 chiefly ferns and zamites, are met with in shales, together with flattened 

 and prostrate stems of Calamites and Equisetum. These last, how- 

 ever, the Calamites and Equisetum, are very commonly met with in a 

 vertical position, more or less compressed perpendicularly'. That the 

 greater number of Calamites standing erect in the beds above and 

 between the seams or beds of coal, which I saw at points many miles 

 distant from each other, have grown in the places where they are now 

 buried in sand and mud, I entertain no doubt. This fact would imply 

 the gradual accumulation of the coal measures during a slow and re- 

 peated subsidence of the whole region. 



The coal seams have hitherto been all found at or near the bottom of 

 the series, and the plants in beds below or between them, or immediate- 



'•■• Trans. Ass. Am. Geo. and Nat. t Quar. Jour. Geo. Sci., vol.'iii. 



