| Item Description: | At head of title: Pennsylvania Geological survey. Fourth series. Maps inserted: plate 1. Map showing surface structure of plateau region of north-central and western Pennsylvania (in 4 sheets) [approximately 1:250,000]--plate 2. Map showing anticlinal and synclinal axes in Pennsylvania [approximately 1:500,000]--plate 3. Map showing subsurface structure of plateau region of north-central and western Pennsylvania on top of Oriskany formation (in 4 sheets) [approximately 1:250,000]. |