DEVONIAN. 285 



No line of division can be traced between the two, however, and therefore all the 

 beds are included in one formation. 

 Girty ^'* states : 



In general the Devonian fauna of the Ouray belongs to upper Devonian time. It is but 

 distantly related to the Devonian faunas of New York, and its relation to those of the Mississippi 

 Valley, or even to other known western Devonian faunas, is ndt close. It shows many points 

 of approximation to the Athabascan fauna described by Whiteaves and is somewhat strikingly 

 similar to the Devonian of Russia. 



J-K 17-18. SOUTHEASTERN PENNSYLVANIA, MARYLAND, AND VIRGINIA. 



Until recently the Onondaga has been supposed to be absent from the Allegheny 

 region south of northeastern Pennsylvania. In regard to the occurrence of the 

 Onondaga Kindle " says : 



This fauna, in a slightly modified form, extends southward from New York through the 

 Allegheny region as far as the northern boundary of Tennessee. The Onondaga fauna occurs 

 throughout this region in the lower part of what has been called the MarceUus shale in the 

 Pennsylvania reports, the Romney shale in Maryland and northern Virginia, and the base of 

 the Chattanooga shale in southwestern Virginia. The beds holding this fauna in the Allegheny 

 region represent an argillaceous facies of the Onondaga. They are chiefly drab or olive-green 

 shales with more or less argillaceous limestone interbedded. This set of beds is separated from 

 the Hamilton above by fissile black shales differing in no important features from the MarceUus 

 shale of New York. 



Swartz ^°^ has identified the Portage and Chemung in western Maryland. He 

 describes local sections, gives extended lists of faunas, and concludes: 



It is very difficult to determine [the Portage-Chemung boundary] when the brachiopod 

 facies of the Portage immediately underlies l^he Chemung. Of the New York section Clarke 

 remarks: "It is extraordinarily difficult to fix on a division plane between the Ithaca and the 

 overlying Chemung faunas." If this be true in New York, it must be still more true when an 

 attempt is made to correlate that section with those of other States, and the restilts attained 

 must be open to revision as fuller investigations give increased data. Nevertheless, it seems 

 reasonably probable from the preceding studies that the horizon in question is to be placed 

 between the strata bearing the Spirifer disjuncHs and Spirifer mesacostalis faunas, giving the 

 following succession: 



Chemung, Spirifer disjunctus fauna. 



{Spirifer mesacostalis fauna. 

 Spirifer pennatus var. posterns fauna. 

 Naples fauna. 

 Genesee, Black shales with Buchiola fauna. 



Lithologically the horizon is not well defined, the conditions varying at different localities. 

 In general the Portage is characterized by smooth fissile shales and interbedded sandstones and 

 the Chemung by a larger percentage of sandstones, while its shales are softer and break with 

 a hackly fracture. The transition from Portage to Chemung is, however, not sharply defined 

 by any lithological features. 



Certain facts seem to harmonize with those of New York. 



1. The general succession of forms seems to be that of New York; At the base occurs 

 the Genesee, thinning eastward, followed by the Naples fauna of the Portage. Above the 

 latter is found Spirifer pennatus var. posterns, succeeded by Spirifer mesacostalis, and finally by 

 Spirifer disjunctus. 



o Comment on manuscript. 



