684 



PROCEEDINGS OF THE BALTIMORE MEETING 



Grove section. This fauna therefore lies above a strongly developed Chemung 

 fauna containing numerous Spirifer disjunctus Sowerby, Dalmanella tioga 

 (Hall), Pterinea chemungensis Conrad, etcetera. 



CORKELATION OF THE VABIOUS SECTIONS 



An examination of the various sections (see accompanying chart) shows that 

 there are certain persistent horizons which may be traced throughout the 

 region. The black shales of the Genesee form the base of the Jennings in the 

 western sections, thinning out and disappearing eastward. Above the latter, 

 or at the base of the Jennings in their absence, occur shales and interbedded 

 flaggy sandstones resembling the Sherburne of New York and carrying the 

 Naples fauna, as in that state. 



These are overlain by shales containing the Ithaca fauna in the eastern sec- 

 tions. This fauna disappears west of Green ridge. 



These strata are succeeded by the lower Tropidoleptus carinatus (Spirifer 

 mesacostalis) zone, 8 characterized by a profusion of Tropidoleptus carinatus 

 (Conrad), Spirifer mesacostalis Hall, and associated species of Hamilton type. 

 This zone is conglomeratic in the east, but is represented by sandstones west- 

 ward, where the conglomerates disappear. 



The Spirifer disjunctus fauna overlies the preceding, being found about 1,800 

 to 2,000 feet above the base of the Jennings in the eastern sections and at 

 about 1,300 feet above the base of the formation west of Wills mountain. The 

 Tropidoleptus fauna recurs at an altitude of about 2,000 to 2,700 feet above the 

 base of the Jennings in the middle part of the area, associated with conglom- 

 erates and sandstones which become less massive westward. This fauna can 

 be traced at about the same altitude from the sections east of Pawpaw, West 

 Virginia, to the vicinity of Round, West Virginia. A similar fauna occurs about 

 200 feet above the base of the Spirifer disjunctus fauna and about 1,500 feet 

 above the base of the Jennings, west of Wills mountain. It is, however, not 

 possible at present to correlate the latter confidently with the upper Tropido- 

 leptus zone of the earlier sections. 



The upper part of the section contains massive conglomeratic sandstones. 

 The Jennings is overlain by red strata of Catskill type. 



J. J. Stevenson, in his vice-presidential address before the American Associa- 

 tion for the Advancement of Science, 9 calls attention to the existence of two 

 well defined conglomerate horizons in the Upper Devonian of Pennsylvania and 

 adjoining states which he correlates over wide areas. He terms the lower of 

 these the Allegrippus and the upper the Lackawaxen conglomerate, names in- 

 troduced by I. C. White. He believes that they are persistent over large areas 

 and that they can be recognized in regions immediately adjoining Maryland. 



A careful examination of the section shows that in Maryland the problem is 

 much more complex. There are not two, but many conglomerates in the sec- 

 tion. These conglomerates are very variable in their local development. The 

 conglomerates of the east may be replaced by sandstones in the west, while 

 other conglomerates develop at higher horizons. It thus seems to the author 



8 See discussion of this fauna, Journal of Geology, vol. xvi, 1908, p. 308. 



9 Proceedings of the American Association for the Advancement of Science, vol. xl, 

 1891 (1892), p. 219. 



