54 Introduction 



" a typical upper Oriskany fauna, and other Oriskany species are found in 

 adjoining areas, so that correlation with the Oriskany of New York is 

 established." ' The Eomney and Portage shales, which are apparently 

 recognized as two formations, '" are faulted out at the surface " in the 

 Mercersburg quadrangle. The northwestern corner of the quadrangle is 

 covered by higher rocks which are referred to the Chemung formation. 

 Only "' Spirifer mesistrialis, Choneies scitula, Schuckertella chemungensis 

 arctostriatiis, and undetermined Bryozoa " were obtained from these rocks 

 in this quadrangle ; but nine species are listed from the Hancock quad- 

 rangle. Mr. Stose states that " These forms are not all diagnostic of the 

 typical Chemung of New York, as recently restricted by Williams to the 

 Spirifer disjunctus fauna. Spirifer disjunctus was not found in the 

 Mercersburg quadrangle and its range was therefore not determined. In 

 the Hancock quadrangle the lower part of this formation, characterized 

 by the presence of sandy strata with granular sandstone beds, does not 

 contain the typical Chemung or Spirifer disjunctus fauna but a recurrent 

 Hamilton fauna characterized by Spirifer mesistrialis. In New York the 

 sandy strata that characterize the Chemung at Chemung Narrows, the 

 type locality, descend below the base of the Spirifer disjunctus fauna 

 toward the east, and the Chemung fonnation there includes strata that 

 contain a Spirifer mesistrialis fauna. The formation in the Mercersburg 

 quadrangle is therefore mapped as Chemung." " 



Finally, it is stated that " Eed arkosic sand and shale of the Catskill 

 formation occur just beyond the northwest comer of the Mercersburg 



quadrangle No fossils except unidentified plant remains have 



been found in tliis formation, but its lithologic character and stratigraphic 

 position establish its correlation with the Catskill of New York and north- 

 eastern Pennsylvania. It is undoubtedly a land or fresh-water deposit 

 replacing the upper part of the marine Chemung." ' 



In 1910 Dr. C. K. Swartz published a paper on the recurrence of the 

 Tropidoleptus fauna in the Chemung of Maryland, in which he shows that 

 there are two recurrences of the Tropidoleptus carinatus fauna in the 



^Loc. cit, pp. 87, 88. 

 "hoc. cit., p. 89. 

 ' Loc. cit., p. 90. 



