. THE ROMNEY FORMATION OF MARYLAND 371 



York, gives the Mesodevonic as composed of the Marcellus shale and 

 Hamilton beds/ but in the text he says: 



The American geologists generally still classify the Onondaga limestone 

 as Lower Devonian; according to European experience, one would be rather 

 inclined to classify it entirely or mostly as Midddle Devonian. The great simi- 

 larity of the characteristic Spirifer acuminatus Con. with our S. cuUrijugatus 

 argues for this classification.^ 



Regarding the classification of the Hamilton the professor says: 

 Although the Hamilton shale locally might represent the entire Middle Devon- 

 ian, yet, on the whole, it corresponds to the upper division. This is surely shown 

 by the frequent overlying beds of the TuUy limestone and Genesee shale, the first 

 of which contians the Brachiopod fauna of our Iberg limestone (Rhynchonella 

 venustula =cuboides, etc.). 3 



Finally, this writer has given the correlation of the Middle Devon- 

 ian of Europe and North America in the following table: 



Mnenian limestone. 



Onondaga limestone* 



Dr. Hermann Credner gives the Middle Devonian of New York 

 as composed in ascending order of the Upper Helderberg (Onondaga), 

 Marcellus shale, and Hamilton sandstone, shale, and limestone. 

 The Upper Helderberg he correlates with the Eifelien and stage of 

 the Calceola sandalina, and the Marcellus and Hamilton with the 

 Givetien and stage of the Stringocephalus hiirtini.^ 



Sir Archibald Geikie considers the Middle Devonian of New 

 York as composed of the Marcellus and Hamilton groups,^ while 

 the same division in Europe he gives as composed of the Eifelien 

 and Givetien, with which he correlates the Marcellus and Hamilton.'^ 



GENERAL DISTRIBUTION OF THE MESODEVONIAN. 



Rocks of the Mesodevonian age have a considerable distribution, 

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



1 Lehrbuch der geologischen Formationskunde, 2d ed. (1902), p. 150. 



2 Ibid., p. 151. 3 Ibid., p. 151. 4 Ibid., p. 155. 



5 Elemente der Geologic, 9th ed. (1902), p. 447. 



6 Text-Book 0) Geology, 4th ed., Vol. II (1903), p. 997. 

 T Ibid., "The Geological Record," opposite p. 861. 



