128 THE CAMBRIAN AND ORDOVICIAN DEPOSITS or MARYLAND 



species occurring in the Middle Chazy of the Champlain Valley. The 

 Maryland Stones River fauna and its occurrence elsewhere is listed below. 



FAUNA OF THE STONES RIVER LIMESTONE IN MARYLAND 



The lower and upper division of the Stones River in Maryland, par- 

 ticularly the latter, frequently exhibit layers crowded with gastropods 

 and pelecypods. These show at the surface as natural sections and 

 weather away as fast as the rock. Without a knowledge of the fauna of 

 the similar dove limestone of the Stones River elsewhere, it is impossible 

 to identify such natural sections with certainty. 



The areas of the Stones River limestone east of the Martinsburg shale 

 belt have yielded few fossils because the rocks weather into a deep soil 

 and outcrops are consequently infrequent. The boundaries of these areas 

 have in most cases been determined by the occurrence of the basal Stones 

 River cauliflower chert zone. In northern Maryland, the broad folded 

 area of this formation just northeast of Maugansville and another a mile 

 northwest of the same place show the best development of the Middle 

 Stones River limestone with the characteristic chert hills left by its 

 weathering. In this chert all of the fossils in the above list have been 

 noted. West of the shale belt the band of outcrop starting at Pinesburg 

 Station and going east of north through Wilson to the state line affords 

 numerous outcrops of the dove limestone of the lower and upper divisions. 

 Some of the layers in the Upper Stones River at Pinesburg Station arc 



