98 The Lower Devonian Deposits of Maryland 



berg was also termed the Iveyser member, although the Keyser-Coeymans 

 boundary was defined later. Ulrich subsequently studied the Helderberg 

 of Maryland more fully and discussed its correlation in the Pawpaw- 

 Hancock Folio of the U. S, Geological Survey/ He recognized four divi- 

 sions of the Helderberg formation, the Becraft, New Scotland, Coeymans, 

 and Keyser members. The Keyser member was divided into three faunal 

 zones, each characterized by a definite association of species as follows ; 

 a lower zone containing species related to the Decker Perry fauna of New 

 Jersey, a second zone extending to the top of the Gypidula bed, a third 

 zone embracing the beds above the Gypidula bed. Minor faunal horizons 

 were discriminated in each zone. 



The Tonoloway was correlated, in a general way, with the Cobleskill 

 and Manlius of New York, while the lower zone of the Keyser was cor- 

 related with the Decker Ferry of New Jersey, which was considered 

 younger instead of older than the Manlius of New York. The Coeymans, 

 New Scotland, and Becraft were correlated with the fomiations of the 

 same name in New York. 



The writer also made an independent investigation of the problem at 

 the same time and his results are embodied in the following discussion. 



FAUNAL AND LITHOLOGICAL SUBDIVISIONS 



It has been shown in the preceding discussion that four divisions may be 

 recognized in the Helderberg formation, the Keyser, Coeymans, New 

 Scotland and Becraft members, which differ both in their lithology and 

 faunas. These members may be further subdivided into a number of 

 more or less persistent faunal zones and subzones. 



Keyser Member 

 Two rather well-defined lithological units may be recognized in the 

 Keyser member. The lower of these is a nodular limestone varying from 

 100 to 130 feet in thickness, while the tipper division is rarely nodular and 

 contains many shaly beds. This member may also be divided into two 

 faunal zones, although the limits of the lithological divisions do not 

 coincide precisely with those of the faunal zones. 



' Pawpaw-Hancock Folio, U. S. Geol. Survey, 1912, Field Edition, pp. 55-56. 



