Maryland Geological Survey 415 



In the absence of the Genesee, tlie Woodinont is readily discriminated 

 from the underlying Eomney by the marked difference in the shape of 

 the fragments produced by weathering, the Eomney yielding pieces of very 

 irregular shape, while the Woodmont yields smooth thin plates whose two 

 larger surfaces are nearly parallel. The abundance of brachiopods in 

 the Eomney and their almost entire absence from the lower beds of the 

 Woodmont member is another decisive diiference. 



Parl-head Sandstone 21emher 



Character axd Thickness. — The Parkhead sandstone member re- 

 ceives its name from Parkhead, Washington County, Maryland, a station 

 on the Western Maryland Eailroad, 7 miles east of Hancock, where its 

 strata are well exposed. It consists of shale interbedded with massive, 

 frequently conglomeratic sandstones. Certain beds of the latter are 

 highly fossiliferous at many places. The shale is more arenaceous than 

 that of the Woodmont member and tends to break more irregularly. 

 When freshly exposed the strata vary in color from gray to olive-green, 

 while some beds are nearly black. Upon weathering they usually become 

 yellowish or buff in color. The thickness varies from 400 feet in the 

 eastern exposures to 800 feet west of Green Eidge. 



Fauna. — The fauna of the Parkhead member has strongly pronounced 

 affinities with the Hamilton fauna. Among the more diagnostic species 

 found in it are Tropidoleptus carinatus, CamarotcecMa congregata var. 

 parkheadensis and Spirifer (Delthyris) mesacostalis, while S. marcyi var. 

 superstes and RhipidomeUa vamixemi, etc., are also abundant in the more 

 westerly sections. 



Three faunal zones may be distinguished in this division. These are, 

 in ascending order: The lAorliynchus mcsacosiale zone, the Camaroice- 

 clda congregata zone and the Cyclonemina muUistriata zone. 



The Liorhynchvs mesacostah zone is chiefly developed in the western 

 sections. It is found at the base of the member in somewhat shaly beds 

 that lie below the more massive sandstones. Among the more diagnostic 

 species are Liorliynchus mesacostale, Leptodesma naviforme, and several 

 species of the genus Lingvla. The Camarotcechia congregata zone is char- 



