428 The Upper Devonian Deposits of Maryland 



A similar recurrence of fauna characterized by the Tropidoleptus cari- 

 natus overlies the Liorhynchus glohuliforme zone in New York, where, 

 according to Williams/ it contains Tropidoleptus carinatus, Spirifer 

 marcyi, Spirifer (DeWiijris) mesacostalis, Productella lachrj/mosa, Rhipi- 

 domella vanuxemi, Cypricardella hellistriata, Pleurotomaria capillaria, 

 and other species found in the Parkhead fauna of Maryland. The re- 

 currence of similar faunas in the same relative position in New York 

 and Maryland is a most interesting fact and furnishes striking evidence 

 of the essential similarity of the conditions in New York and Maryland in 

 Upper Devonian time. 



The Parkhead fauna, like that of the Enfield member of the Portage 

 of New York, occurs in sediments that become increasingly arenaceous 

 eastward, where they are similar to the Chemung sediments. The fauna 

 vanishes westward in both areas. The similarity in composition, lith- 

 ology, stratigraphic sequence, and geographic distribution leaves little 

 doubt that the Parkhead fauna is the same as the recurrent Tropidolep- 

 tus carinatus fauna of the Enfield member of Williams. In the Enfield 

 member, however, the Naples fauna recurs above the Tropidoleptus 

 carinatus fauna, a feature not observed in the Parkhead of Maryland, so 

 that the upper limits of the two members may not be the same. For the 

 present, therefore, the term Parkhead is applied to this member instead 

 of Enfield, although the beds containing the recurrent Tropidoleptus 

 carinatus fauna are probably of the same age in both areas. 



Chemung Member. — Different values have been attached to the term 

 Chemung by different observers, rendering necessary a definition of its 

 significance as here employed. The marine Upper Devonian strata lying 

 above the Genesee, exhibit different facies in eastern and western New 

 York. In the western part of that state the lower strata consist of inter- 

 bedded shale and flaggy sandstones and contain very few brachiopods. 

 They are overlain by more arenaceous sediments rich in brachiopods. 

 Farther east sandstones develop at successively lower and lower horizons 



' Folio No. 169, U. S. Geol. Survey, 1909, p. G. 



