Maryland Geological Suhvey 431 



It is, hoAvever, questionable whether it would not be better to define 

 the Chemung simply as the arenaceous phase of the marine Upper De- 

 vonian including the Chemung and Parkhead members as here defined. 

 In that case it would have very difFerent limits in different areas and be 

 without definite time value, resembling in this respect the term Catskill. 

 This usage has not been followed, however, in the present case. 



The most diagnostic species of the Chemung of New York are Spinfer 

 disjunctus and species of the genera Dalmanella and Douvillina. the 

 Chemung fauna having been called the Spirifer disjunctus fauna by 

 Williams.' These are also important members of the Chemung of 

 Slai^land and are associated with many other species restricted to the 

 Chemung in Xew York and in Maryland. The number of species and va- 

 rieties identified in the Chemung of Maryland is 101, of which 3 i are new. 

 Of the 77 species formerly described, GO, or 78 per cent, occur also in the 

 Chemung of New York. A list of the species occurring in these beds is 

 given in the table showing the distribution of species, in which their 

 vertical range and occurrence in other areas are indicated. 



The lithological character of the Chemung sediments is the same in 

 both areas and the development of arenaceous sediments below the range 

 of the Chemung faunas is the eastern sections in Maryland is in harmony 

 wdth the same condition in New York. Moreover, the beds occupy a simi- 

 lar relation to the underlying Portage and overlying Catskill. These 

 facts clearly establish the Chemung age of this member. 



A conspicuous feature of the Mainland fauna is the abundant occur- 

 rence of species of Dalmanella and Douvillina west of Wills Mountain, 

 and the almost entire absence of the former genus and the rarity of the 

 latter genus east of that mountain. Williams notes ' a similar n'stiiction 

 of the species of Dalmanella. to western and central New York. 



The lower shale and sandstone beds correspond in their stratigrapliic 

 position to the Cayuta member of the Chemung of New York. They 

 contain certain species which are reported by Williams" from that member 



' Bull. U. S. Geol. Survey, No. 210. lOO.'',, p. 83. 



= Proceedings of the U. S. National Museum, vol. xxxiv, pp. 35-64. 



= Folio of the U. S. Geol. Survey, No. 169, 1909. p. 6. 



