54 TiiE Middle Devonian Deposits of Maryland 



A portion of the Mareollus shale is exposed above these limestone beds 

 in the eastern part of this cut. In the Baltimore and Ohio IJailroad cut at 

 Twenty-first Bridge nearly the whole of the Marcellus is exposed. The 

 lower part of the beds at the south end of the cut contain in certain 

 strata a great profusion of the flattened shells of Liorli ynclius limitare 

 which seem to occupy the strata in which they occur almost to the exclu- 

 sion of other fossils. The southern half of the Baltimore and Ohio 

 Eailroad cut is nearly all in the highly inclined, soft bluish-black Mar- 

 cellus shales which appear to be nearly barren except for the Liorhynchus 

 limitare beds in the lower part. The development of minor crumpling 

 and folding in these beds makes it difficult to estimate their thickness. 

 There appears to be more than 100 feet of these nearly barren dark 

 shales between the Onondaga shale and the beds holding the Hamilton 

 fauna. In the northern half of the Baltimore and Ohio Eailroad cut 

 about 75 feet of gray argillaceous and sandy shales are exposed. These 

 contain a rich Plamilton fauna with such characteristic species as Tro- 

 pidoleptus carinatus and Spirifer mucronatus. 



The comparatively poor exposure of the Onondaga shale one-third mile 

 west of Twenty-first Bridge, near Eosedale switch, affords a richer fauna 

 in the lower beds than the cut at Twenty-first Bridge. The most abund- 

 ant species at this point are Anoplotheca acutiplicnfa and Orhieuloidca 

 media. 



Exposure at Queens Point, opposite Keyser, ^yest Virginia. — The most 

 westerly exposure of the Onondaga shale in the state occurs opposite 

 Keyser, W. Va., at the foot of the Queens Point cliffs. Only a few feet 

 of drab shales can be seen here. The fossils noted here include Pholidops 

 sp. undet., Bollia nnguJa and some goniatite and trilobite fragments. 

 West of this point the structure brings to the surface nothing older than 

 the Upper Devonian. 



Exposure on ilir WiJIidms It'oad 3V> ntilcs east of CuinhcHund. — This 

 section affords a nearly continuous exposure of the beds from the Oris- 

 kany sandstone to the Parkhead meinber of the Jennings, and affords a 

 clear conception of the essential characteristics of the different divisions 

 of the Eomney. The Hamilton beds are described by Prosser in a subse- 



