416 The Upper Devon iax Deposits of ]\rARYLAND 



acterized by a very profuse development of Camarotoechia congregata var. 

 parkheadensis, Tropidoleptus carinatus, and Spirifer iDeWi7jris) mcsacos- 

 talis. The Cyclonemina muUistriata zone contains a great profusion of 

 fossils of many genera, including many gastropods. The range of the 

 species observed in these zones is shown in the chart of columnar sections. 

 (See pocket in cover.) 



SrBUivisioxs. — The Parkhead sandstone member is divisible into two 

 parts, a lower containing conglomeratic sandstones and an upper con- 

 sisting more largely of shale. 



Conglonicratic Sandstone Beds. — This division constitutes the larger 

 part of the Parkhead member. It usually contains conglomeratic sand- 

 stones at three horizons in the eastern part of the area — at its base, near 

 its middle and at its top respectively. The sandstones are not argillace- 

 ous, as are many in the Woodmont member. They are often bluish 

 black when fresh, becoming butf colored upon weathering and, in places, 

 are tinged yellow and red by iron. They usually break into large irregu- 

 lar pieces. 



The lower sandstone is, as a rule, highly fossiliferous, abounding in 

 Camarotcechia congrefinta var. parl-lieadensis and containing also a pro- 

 fusion of Tropidoleptus carinatus at many places. The upper conglom- 

 eratic sandstone is unusually massive near Parkhead, where it is finely 

 exposed in the cut of the Western Maryland Pailroad, west of the station. 

 The Parkhead member usually forms a pronounced ridge, the crest of 

 which is commonly occupied by the middle conglomerate. 



The beds of sandstone lose their conglomeratic character and become 

 reduced in volnme toward the west. West of Wills Mountain tliey are 

 largely replaced by shales so that this member can scarcely be dis- 

 tinguished from the underlying Woodmont in that region. 



The sandstone division is about 400 feet thick in the eastern sections. 

 Its limits are less clearly defined west of Washington County. 



The upper part of the Parkhead member consists largely of shale with 

 some interbedded sandstone. It contains few fossils to indicate its re- 

 lations. It lies, however, below the horizon at which the first appearance of 

 the Spirifer disjunctus fauna has been observed. The shale beds have been 



