90 The Middle Devonian Deposits of Maryland 



The correlation of these sediments will now be considered, discussing 

 first their faunal and stratigrapliic relations and then their age. The 

 fauna of the Onondaga member is rich both in species and individuals 

 in the Maryland area, contrasting strikingly in this respect with that of 

 the overlying Marcellus. The accompanying table shows the species that 

 have been observed in the Onondaga member in Maryland and adjoining 

 parts of West A'irginia, and indicates their range in the New York 

 section. 



Four elements may be discriminated in this fauna, according to their 

 habitat in the New York section, i. e., species found in black shale, in 

 arenaceous shale, in the Marcellus limestones and in the Onondaga lime- 

 stone. 



Four species, Liopteria loevis, Orbiculoidea lodiensis, Styliolina fissu- 

 rella, and Bactrites aciculus, which are among the most common species 

 of the fauna, are also common in the black shale of the Marcellus of 

 New York. The three last species are frequent in the Genesee in which 

 similar shale recurs. Since such carbonaceous muds are known to 

 occur in different formations it is possible that these species are not so 

 diagnostic of a particular horizon as of a definite kind of sediment. 

 Kindle, who holds this view, urges that they have little value for purposes 

 of precise correlation. However, such weight as they possess is clearly in 

 favor of the i-elation of the beds under consideration to the Marcellus shale 

 of New York. 



A second element of the fauna consists of 12 species that are found in 

 the arenaceous shale of the Hamilton, as well as in the Marcellus, none 

 of which are known in New York in beds older than the Marcellus. They 

 constitute 46 per cent of the species significant for purposes of correlation 

 and strongly suggest the close faunal relation of these beds to the Mar- 

 cellus. 



Eeference has already been made to the impure limestone occurring in 

 the Marcellus of New York in which Agoniatites expansus and Bactrites 

 adculaius are found, the former species occurring in such numbers that 

 this bed has been called the Goniatite limestone. A very similar lime- 



