146 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND 



Section of Chambersburg Limestone Two Miles Southwest of Marion, Pa. 



Martinsburg shale. 

 Chambersburg limestone. 



Greencastle bed. F 

 Only residual shale and thin limestone seen. At the top are 

 black carbonaceous limestone and a thin sandstone, capped 

 by a thin, coarsely crystalline limestone bed containing 

 Lingula, representing undoubtedly the Corynoides bed 

 commonly found near the base of the succeeding Martins- 

 burg shale 150 



Christiania bed. 



Interbedded thin calcareous shale and shaly limestone with a 



few fossils which indicate the Christiania fauna 100 



Nidulites bed. 



Dark, nodular, thin-bedded limestone; fossils rare 50 



Dark, fine-grained, platy limestone; contains Nidulites and 



associated fossils 94 



Compact, dark-gray, thick-bedded limestone; upper part very 



f ossilif erous, containing numerous cystids and Nidulites . . 108 

 Echinospherites bed. 



Dark, argillaceous, cobbly limestone, shaly in lower part; very 

 fossiliferous, containing a layer filled with the ball cystid 



Echinospherites 65 



Limestone like overlying bed but even darker in color and 

 interbedded with subcrystalline limestone layers; fossils 



scarce 40 



Tetradium cellulosum bed. 



Grayish to dark, dense thin-bedded limestone, containing Tet- 

 radium cellulosum and Leperditia 150 



Stones River limestone contact not exposed. 



Four miles south of this section the Cumberland Valley Bailroad crosses 

 the Chambersburg limestone at Greencastle, Pennsylvania, and exposes 

 the Nidulites, Christiania, and Greencastle beds. This section is of par- 

 .ticular interest in showing the extreme development of the Greencastle 

 bed in the railroad cut starting at the bridge just north of the town where 

 about 200 feet mainly of dark blue massive limestone with rather numer- 

 ous fossils intervenes between the typical Christiania bed and the usual 

 strata of the basal Martinsburg shale. The details of this section, as 

 recently determined by Ulrich, are as follows 



