NAPLES FAUNA IN WESTERN NEW YORK, PART 2 365 



DISTINCTIVE FEATURES OF THE SUBPROVINCIAL FAUNAS 

 The last of the tables given brings out with force the fact that, while 

 there is but a small proportion of species common to the extreme east and 

 west sections of the Genesee province in New York, there is a striking 

 preponderance of species whose genera are common to both regions. This 

 commonalty of genera however is a no more impressive feature of these 

 subprovinces than it is of the development of the Intumescens fauna 

 throughout the world. 



We have previously noted that these subprovinces are regarded not as 

 contemporaneous divisions throughout, but as sequential in this degree : 

 that the fauna of the Naples or eastern subprovince covered the westward 

 area at the opening of Portage time and is represented in moderate degree 

 in the contracted deposits of Cashaqua shales of that area. So far as its 

 eastward and westward representatives are concerned, there is no important 

 variation, but the fauna attained its profusion of development toward the 

 east. The distinctive fauna of the Chautauqua subprovince comes in with 

 the Angola gray shales, while in the east at this time the Naples fauna 

 continued and at a still later date, during the perdurance of the Chautauqua 

 fauna at the west, was replaced by the invading brachiopod fauna. Hence 

 the Chautauqua is sequential to the Naples fauna in western sections and 

 contemporaneous with the late stages of that fauna in the Genesee valley 

 and eastward. 



The discrepancies in these faunas east and west, we have in a measure 

 already noticed in our previous discussion of the cephalopods. Here we 

 observe the prevalence of the Manticoceras intumescens type in 

 both, but under very distinct expressions, the M. pattersoni of the east 

 being a more highly progressed species than the common M. rhynchos- 

 toma of the west. The smaller expressions of this genus which are 

 frequent in the east have a highly local significance and are absent in the 

 Chautauqua region. With Gephyroceras much the same is the condition. 

 We recognize no form of this genus in the Chautauqua subprovince except 



