232 



NEW YORK STATE MUSEUM 



somewhat later, producing the Stafford limestone of western 

 New York. '' This invasion, too, was unsuccessful, reaching no 

 farther eastward than the eastern part of Ontario county ".^ 

 The third invasion into New York of the Hamilton fauna, which 

 had come into existence by slow modification of the Onondaga 

 species, in the northwestern portion of the interior sea, proved 



Fig. 188 Paleogeogrraphic map of Hamilton time. (After Schucbert) 



at last successful and permanent and was accompanied by the 

 sedimentation which has given us the typical Hamilton beds. 

 By this time the interior Palaeozoic sea had increased in size 

 as shown on Schuchert's map [fig. 188] and a now channel across 

 what is now eastern Wisconsin and central Illinois was opened, 

 which connected the eastern or Mississippian sea with the 

 Dakota sea to the west of the present Mississippi river. From 



1 Clarke, loc. cit. 



