UPPER PRODUCTIVE COAL MEASURE. PP. 21 



Many fine fruiting specimens of Alethopteris aquilina 

 occur. There are numerous specimens of Pecopteris Can- 

 dolleana, wliicli dilfer somewhat from tlie forms found in 

 the Waynesburg Coal at West Union, and Avhich will be 

 described further on. The plant at the horizon now in 

 question has thinner leaflets, on which the nerves are very 

 distinctly shown, while the West Union plant has very 

 obscure nerves, and a very thick leaf-substance, as well as 

 longer and more deciduous pinna3. The remarkable plant, 

 Lescuropteris Moorii, hitherto found only at a higher hori- 

 zon, in the Upper Productive Measures, is found in detached 

 pinnae here. 



The Upper Productive Coal Measures. 



This is the only one of the sub-divisions of the Carbon- 

 iferous Formation which has not a great sandstone every- 

 where at its base. But even in this case, we often find a 

 tendency in the rocks of the Lower Barren Measures to pass 

 into sandstone, within a short distance below the Pittsburg 

 Coal bed. 



The Upper Productive Coal Measures begin with the great 

 Pittsburg Coal Bed, and end with the Waynesburg Coal. 

 In the northern part of the State, the average thickness is 

 about 350 feet. The series thus begins and ends with an 

 important coal bed. The Pittsburg Coal, which forms the 

 base, is the most widely extended and important coal bed 

 in the Appalachian Coal Fields. It covers an area of more 

 than 20, 000 square miles in W. Virginia. Its greatest thick- 

 ness is towards the east, where it is often from 10 to 14 

 feet tliick, as is shown in Mineral Co. W. Va. and in the 

 Cumberland Coal basin of Maryland. The least thickness 

 is found in the southern part of the State, where, towards 

 the southern line of its outcrop, it thins down to 3 or 3^ 

 feet of coal. 



But little is known of the character of the Upper Produc- 

 tive Coal Measures in the southern part of the State, but it 

 seems evident that they are less developed there than in 

 the northern portion, both in thickness, and in the number 

 of the coal beds which they contain. In the south, we find 



