430 



The UrPER Devoxiax Deposits of Maryland 



lowing table. Clarke's section is from the Watkins-Elmira quadrangles 

 in wliich tlie seciuence of tlie beds below the Chemung differs from that 

 in central New York. 



Divisions 



Hall 



Vanuxem 



Williams 



Clarke = 



19071 



1909 



Ueds containing the 

 Spiriferdisjunctus 

 fauna 



Chemung 



Chemung 



Chemung 



Chemung 



* o 



13 



Chemung 



Beds containing- the 

 Naples and Tropi- 

 doleptus carinatiis 

 fauna 



c 



3 



Enfield 



1 



Enfield 



Prattsburg 



Beds containing the 

 Ithaca fauna 



Ithaca 



Ithaca 



Ithaca 

 Sherburne 



Senecan 



Beds containing the 

 Naples fauna 



Portage 



Portage 



Sherburne 



Genesee 



Genesee 



Genesee 



Genesee 



Genesee 



Genesee 



It will thus be seen that the term Chemung has had a very lax usage. 

 The low'er limit of the formation has not only been placed at different 

 horizons by the different authors, but has also probably been drawn 

 obliquely across strata of the same age by all but Clarke. 



The upper limits of the Chemung is equally lacking in precision. It 

 is known that it descends obliquely across strata of the same age towards 

 the east, owing to the earlier development of Catskill conditions there. 

 It is hence probable that, however defined, the Chemung will embrace 

 different units east and w^st so that it is questionable whether the term 

 meets the needs of scientific nomenclature.' 



As employed in the present discussion, the base of the Chemung is 

 drawn in Maryland at the base of the Spirifer disjunctus fauna and its 

 upper limit at the upper limit of the observed marine fauna of the Upper 

 Devonian, since these afford the most precise limits for correlation. 



' Journal of Geology, vol. xiv, 1906, p. 579. 



= Bull. N. Y. State Museum, No. 87, 1905, p. 20. 



= See remarks by J. M. Clarke in Bull. N. Y. State Museum, No. 87, 1905, p. 20. 



