8 PP. UEPORT OF PROGRESS. FONTAINE & WHITE. 



exception,) and no Sigillariae, not to mentionmore recent 

 forms, have as yet been found, and this deficiency adds much 

 to the antique aspect of the flora. 



From Pennsylvania Mr. Asliburner gives, on the authority 

 of Prof. Leo Lesquereux, the following species in his "Meas- 

 ured Section of the Paleozoic Formations:" 



Sphenopteris flaccida. 



Ulodendron majus. L. & H. 



Stigmatocanna Wolkmanniana. 



Knorria acicularis. Goepp. 



Stigmaria minuta, Goepp. 



Lepidodendron. Spec 1 



The Umbral, or Lower Carboniferous Limestone. 



The only fossils found in this limestone are invertebrate, 

 and they show that it corresponds in age with the Lower 

 Carboniferous or Mountain Limestone. In West Virginia 

 it is a well defined and thick mass ; but in Pennsylvania the 

 limestone thins out almost entirely, while the red shales 

 and sandstones, which in W. Virginia, mainly overlie it, be- 

 come greatly developed. The same condition of things ap- 

 pears to exist to the southeast, in Montgomery Co. Va. 

 This passage of the limestone into the shales and sand- 

 stones of the Umbral causes a difficulty in the grouping of 

 the Umbral and the Limestone, and has led some geolo- 

 gists to place both in one group. On the other hand, to 

 the west and southwest the shales and sandstones disap- 

 pear, and leave the limestone with increased thickness. As 

 showing the variations in thickness of this rock we give 

 the following measurements : 



IS^ear the White Sulphur Springs in Pocahontas Co. 

 Prof. Wm. B. Rogers determined its thickness to be 822 

 feet. Towards the north it thins rapidly, for near West- 

 ernport Prof. Rogers found it only 80 feet thick. On 

 Cheat River, in Monongalia Co. it is about 100 feet thick, 

 and 25 miles farther north, in Fayette Co. Pa. it is ac- 

 cording to Stevenson only 40 feet thick. In Huntingdon 

 Co. Pa. Mr. Ashburner finds it to be 49 feet thick.* 



[*See foot note to page 5 above ; and Report of Progress Second Geol. Sur. 

 Penna. F, 1878, page 195.— J. P. L.] 



