113 The Middle Devonian Deposits of Maryland 



so unlike the usual species of the limestone that without definite knowledge 

 of its horizon it would be difhcult to locate its stratigraphic position. 



" It is a deposition synchronous with and in continuation of the Tully 

 limestone in a region where that formation is no longer represented by 

 limestone sedimentation, M'here indeed bathymetric conditions did not 

 permit the deposition of such a sediment." ' 



In Maryland we have in the Onondaga shale member of the Romney 

 formation a fauna which, like the Tully pyrite band of western New York, 

 shows peculiarities which are unkno^^oi in the pure limestone fauna of the 

 Onondaga limestone of New York. In it we find corals almost entirely 

 wanting while fragile-shelled brachiopods quite unknown in the Onondaga 

 limestone of New York are conspicuous. The extraordinary long fragile 

 spines on the new CJionetes rngosa in this fauna and the even more 

 tenuous spines of remarkable length on Chonetes buttsi of the Pennsyl- 

 vania Onondaga speak decisively of bathymetric conditions which differed 

 materially from those under which the Onondaga limestone accumulated. 

 But we have as faunal evidence of the identity of the Maryland fauna 

 with the New York Onondaga the presence of such well-known pre- 

 ]\Iarcellus species as Anoplea michnia, Anoplotheca Camilla, Anoplotheca 

 acuiiplicata^ Dahnanella Icniicularis. Fluicops cristata, and BoUia ohesa. 



In order to comprehend the ."^tratigraphic relations of the beds holding 

 the Onondaga fauna, it will be helpful to refer briefly to the general condi- 

 tions controlling sedimentation during the Devonian in what has been 

 called the Alleghany province. The greater part of the Alleghany prov- 

 ince was occupied during the Devonian by a broad arm of the sea known 

 as the Appalachian Gulf. Along the eastern border of this sea was de- 

 posited the 5000 to 10,000 feet of Devonian sediments found in the 

 Alleghany region. 'J'lic chief source of this clastic material has been 

 shown to be a land area known as the highlands of Appalachia which lay 

 immediately southeast of the Alleghany region. This old land area 



^Bull. New York State Mus., No. Ixix, 1903, pp. 892-893. 



- Prof. C. S. Prosser informs me that he has found A. acutiplicafa in a 

 Hamilton fauna at one point on Evitts Creek, Md. No other post-Onondaga. 

 occurrence of this species is known so far as the writer is informed. 



8 



