STRATIGRAPHY OF THE POTOMAC GKOUP 483 
Ohio Railroad, where a gulch, known as ‘Deep Ditch,” on the 
southern side of the hill, has opened up one of the finest sections 
of the Potomac group. The Patuxent, Arundel, and Patapsco 
Fic. 1. View at School House Hill, Baltimore County, showing Patuxent sands 
overlain by Arundel clays. 
formations are all exposed at this locality. The section is as 
follows: 
SECTION AT SCHOOL HOUSE HILL, BALTIMORE COUNTY. 
Patapsco. Argillaceous sands more or less iron-stained, with varie- 
gated clays, and with ferruginous crusts ; ash-colored, lig- 
nitic and somewhat indurated toward the base; silicified 
coniferous and cycacean trunks. . . - - Eon ite 
Arundel. Slightly indurated, ferruginous ledge containing abundant 
impressions of monocotyledonous plants. - - aE it, 
Drab-colored clays, with beds of lignite, containing 
“brown”’ and ‘white ore,’”’ exhibiting impressions of ferns; 
dinosaurian teeth; ferruginous ledge at base. - - - 50 ft. 
