NORTH AMERICAN GEOLOGY. 205 



is wanting and tlio change in rock and fauna abrupt. The Mar- 

 cellus, Hamilton, and Genesee form a group about 750 feet in thick- 

 ness, which in its u[)per part hoUls fossiliferous limestone beds. The 

 Catskill is a transition scries in every respect. The subdivisions of 

 the Subcarbouiferous are well characterized the lower division bear- 

 ing small quantities of coal, and is supposed to have furnished the salt 

 of theHolston valley deposits.* 



49. In describing the coal district in Sullivan County, Pennsylvania, 

 Ashburnert makes some observations on its general stratigraphy, and 

 conside s White justified in assigning the whole of Wyoming County 

 east of the Susiiuehanua to the Catsk 11 formation, but finds the sup- 

 posed equivalency of some of the conglomerates n the Xorth Mountain 

 region open to question. 



50. Tlie same author describes the occurrence of a thin bed of fossil- 

 iferous lim stone in the anthracite coal measures in Wyoming vallej^', 

 Pennsylvania. The fossils are reported upon by Heilprin, and are all 

 of a most pronouuLcd Carboniferous type.| 



51. Li'ui and Linton report on an examination of borings from gas 

 wells in Washington County, Pennsylvania, in which they find evidence 

 of the occurrence of the mountain or silicious limestone, witli character- 

 istics similar to those in the outcrops described b}^ Stevenson in the 

 gaps of Laurel Hill and Chestnut Kidge. Its thickness is about 80 feet. 

 It lie ! about 1,100 feet below the Pittsburgh coal, is 170 feet below the 

 Piedmont sandstone, and is overlain by 30 feet of blick shales. § 



52. Ashburner reports on the examination of the coal beds in the Po- 

 coMO formation (iSTo. X), at Ti[)ton Kuu, Blair County, Pennsylvania. 

 The horizon of the beds is considered unquestionable. The coal is bi- 

 tuminous, and one bed is as much as 3 feet in thickness. || The same 

 author^] rei)orts on the progress of the elaborate survey which is now 

 being made of the anthracite coal region, and while little matter of gen- 

 eral geologic interest is presented, the report contains much special in- 

 form :tion upon details of struc'ure, stratigraphy, ;jnd progress of the 

 survey in several fields. 



53. Lesley discusses the horizon of the Wellersville coal bed and fire- 

 clays. The former belo ig to the barren series, with the exception of a 

 very small patch of outlying Pittsburgh, and are thought to represent 

 the Piatt and Price Coleman and Philson beds of Berlin.** 



54. In a paper on the geology of the Pittsburgh coal region, the same 

 author describes the coal beds and associated members, and discusses 



* Am. Jour. Sci., in, vol. 81, pp. 193-202. 



t Second Geological Survey of Peunsylvauia, Anaual Report for 1885, pp. 486-490, 

 tibid., pp. 437-458; Wyomiag Hist, aud Geol. Society, Proc, vol. 2, pp. 254-264. 

 $ Ibid., pp. 222-226. 



•II Secoud Geological Survey of Pennsylvania, Annual Report of Progress for 1885, 

 pp. 250-258. 

 H Tbid., pp. 269-490. 

 ** Ibid., pp. 227-229. 



