Maryland Geological Survey 29 



faunas ranged southward into Maryland is shown by the occurrence of the 

 Naples fauna in abundance in the Genesee and lower beds of the Woodmont 

 member of the Jennings formation of the western sections and the replace- 

 ment of the Naples fauna by the Ithaca fauna in the upper teds of the 

 Woodmont member in the eastern sections, while it still continued to live 

 in the west, indicating conditions essentially similar to those that existed 

 in New York at this time. 



It results that three independent faunas coexisted in this province in 

 early Upper Devonian time, their range being determined by the physical 

 conditions under which they dwelt, while they migrated back and forth as 



WEST WESTERN MARYLAND EAST 



CATSKILL FORMATION 



CARINATUS 



ROMNEY FORMATION, HAMILTON MEMBER TROPIDOLEPTUS CARINATUS FAUNA 



Fig. 2. — Diagram showing probable relations of the Upper Devonian faunas 

 and sediments in Western Maryland and adjacent areas. 



these conditions varied. These faunas were succeeded in the Mar}'land 

 region by species of purer Hamilton type, characterized especially by the 

 presence of Tropidoleptus carinatus, one of the dominant forms of life of 

 the Hamilton. This assemblage, termed the Parkhead fauna, probably 

 arrived before the disappearance of the Naples fauna from western New 

 York. The Naples fauna of western New York and the Parkhead fauna 

 of Maryland were finally displaced by the arrival of the Chemung fauna 

 which differed greatly from the Naples fauna and had many points of 

 resemblance with species of Middle Devonian time. That species of purer 

 Hamilton type continued to live somewhere in the adjoining regions is 

 shown by the temporar}^ return of the Tropidoleptus carinatus fauna in 



