Maryland Geological Survey 45 



same stages ' iu Fulton and Bedford counties, which adjoin Washington 

 and Allegany counties on the north. Under his account of the Devonian 

 system he states that, " The Hamilton group as a whole shows •Rdthin this 

 district the threefold division recognized and named in Xew York as 

 Genesee shale, Hamilton shale, and Marcellus shale; but owing to the 

 varying thickness of these subdivisions and to the fact that the soft shales 

 yield readily to the weather, one finds much difficulty in identifying them. 

 Especial annoyance is caused by the Genesee shales, which are rarely 

 exposed." ' And in describing the divisions he reported that " The 

 HumiUon shales are rather laminated sandstones, which vary much in 

 hardness. The softer argillaceous shales are not persistent and the harder 

 beds ordinarily make a well-defined ridge, which is almost as high as that 



of the lower Chemung beds 



" These shales are often exposed in Bedford County, where the group 

 shows comparatively little variation. The argillaceous shales seldom con- 

 tain fossils, but the sandy shales or laminated sandstones are usually 

 fossiliferous. Tropidoleptus carinatus, Spirifera mucronata, Leiorhyn- 

 clius sp., and Streptorliynclius cJiemungensis, var. prevail throughout 

 while species of Belleroplion and Pleurotomaria are abundant in the 

 highest beds. A fine Spiropliyton occurs at several horizons. The pres- 

 ence of the Marcellus is shown at all localities where the sub-group is 

 present, but an exposure affording details for measurement is rare." ' 

 Two exposures of the Genesee shale were described in both Fulton and 

 Bedford counties ; but elsewhere in those counties the exposures were 

 stated to be very indefinite and the rock was described as consisting for 

 the most part of " dark shale, but it contains not a little of brown shale 

 with olive-colored flags." * On the Geological Map of Bedford County by 

 Professor Stevenson a band of the Hamilton shale which includes the 



' Professor Stevenson did not recognize tlie Onondaga age of tl:e lower 

 shales and included them in his Marcellus. In this respect, therefore, his 

 statements are not in agreement with those of this volume. 



= 2d Geol. Surv. Penn., T-, 1882, p. 81. 



^Ihid., pp. 82, 83. 



* Ibid., p. 82. 



