26 The Middle Devoxiax Deposits of Maryland 



limestone ; the Mesodevonian, the Marcellus shale and Hamilton forma- 

 tion, and the Neodevonian the Tally limestone, Genesee shale, Portage 

 and Chemung formations together with the Catskill formation which in 

 eastern New York and northeastern Pennsylvania replaces the greater 

 part of the Chemung and Portage formations. 



Recently Dr. J. i\I. Clarke and Prof. Charles Schuchert have trans- 

 ferred the Lower Helderberg to the Devonian and rearranged the list 

 of formations for the Lower Devonian and Middle Devonian. In their 

 classification the Lower Devonian consists of the Lower Helderberg 

 limestones or Helderberg and the Oriskany sandstone ; while the Esopus 

 and Schoharie grits and Onondaga limestone were referred to the 3Iiddle 

 Devonian.^ 



General Distribution 



Eocks of Middle Devonian age have a considerable distribution, aside 

 from that of the eastern United States and Canada, for they have 

 been identified and described in Nevada; the dolomite of Manitoba con- 

 tains the European species String oceplialus hurtini; Spirifer mucronatus 

 has been found upon the banks of the Albany River south of Hudson Bay ; 

 the fauna of the Hamilton shales occurs in the Mackenzie Valley from 

 the Clear Water River to the Arctic Ocean, while it is also reported from 

 the Porcupine River, a western tributary of the Yukon in Alaska and 

 perhaps also on Kouiou Island in the southern part of that territory. In 

 the Brazilian province of Para, in the Erere district, are beds which Katzer 

 refers to the base of the Middle Devonian. Dr. John M. Clarke has stated 

 regarding the fauna of the Erere sandstone that it " is remarkably free 

 from species or representatives of subgeneric groups prevailing elsewhere 

 in early Devonian faunas and equally devoid of types which elsewhere pass 

 upward into the later faunas ; in other words, it is with all its resemblance 

 to the Hamilton, a more typical and better defined Middle Devonian fauna 

 than that." ' 



* Science, N. S., Vol. X, 1899, p. 876. 



'Archives do Museu Nacional do Rio de Janeiro, Vol. 10, 1899. Author's 

 English edition, 1900, p. 90. 



