Portage 

 invasion 



656 NEW YORK STATE MUSEUM 



The Hamilton deposits of Michigan, Wisconsin and Iowa, how- 

 ever, belong to a distinct subprovince, and received their main 

 accessions from another direction. 



We believe another Atlantic invasion of the eastern Mississip- 

 pian sea occurred during early Portage time, introducing a good 

 part of the very characteristic Naples fauna, as Manticoceras, 

 Gephyroceras, Beloceras, Sandbergeroceras and Cyrtoclymenia. 

 The goniatite fauna of this formation, according to Dp Clarke's 1 

 work, consists of no less than eight genera and 25 species, and 

 yet in no other American area holding beds of similar age, occurs 

 more than one species of goniatite. (Manticoceras intu- 

 m e s c e n s , the widely dispersed European species, is also 

 found in Iowa and on Hay river, latitude 60° north.) This 

 fauna is closely related to that "of Martenberg in Westphalia." 2 

 How long this Atlantic invasion continued we do not pretend to 

 state, but it is certain that the indigenous Upper Devonic faunas 

 of New York not only received the above supposed Atlantic 

 migrants, but also some from Iowa, as in the High Point (N. Y.) 

 faunula. The Mackenzie basin Upper Devonic fauna, charac- 

 terized by Stringocephalus burtini, is of a distinct 

 subprovince; but the geographic derivation of that fauna we do 

 not yet know. We are however satisfied these Mackenzie 

 Devonic deposits had no direct connection with those of Iowa. 



Carbonic 3 



There appears to be a cqmplete series of Devonic deposits, 

 with the possible exception of the Onondaga, in the middle third 

 of the Appalachian Valley trough, but early Mississippian seems 

 to be wanting in this portion. In the southern end, the early 

 Carbonic, represented just west of the Rome barrier by the 

 Fort Payne chert, also was partially excluded; but the St Louis, 

 and possibly Chester, are represented in the trough at several 

 points. The Fort Payne chert is represented within the extreme 



iAm. geol. 1891. p. 86-105; N. Y. state geol. 15th an. rep't. 1898. 

 p. 31-81; also ib. 16th rep't, extract. 1898. p. 31-143. 



2 Clarke, p. 136. 



3 For this section Mr Ulrich alone is responsible. 



