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NEW YORK STATE MUSEUM 



4 That in the later stage represented by the profuse fauna of 

 the Grande Greve limestones the northern passage broadened while 

 the Dalhousie passage became extinct; and that passage remained 

 open till much later in the Devonic than Helderbergian time. 

 This fact is evinced by the somewhat lessened though by no means 

 obliterated presence of Helderberg species, by the full develop- 

 ment of characteristic Oriskany species in the purest limestone 

 medium and the existence of certain types of still later (Onon- 

 daga) age in minor phases of development. The opinion has been 

 expressed that during this period of the Grande Greve limestones 

 the Gaspe Basin was a place of rapid fructification and departure 

 of the fauna toward the southwest. 



5 In northern Maine that part of the Devonic represented by the 

 arenaceous sediments of Aroostook county must have pertained 

 to a distinct geographic passageway and have been more or less 

 obstructed southward during the period of the Oriskany. It is 

 quite possible that the same channel was open in its southwest 

 extent during Helderbergian time as indicated by the fauna of 

 the Square Lake limestone, though the differences therein from 

 the New York Helderbergian would still indicate that the way was 

 then not entirely clear open and carried basins of special develop- 

 ment. 



6 The development of the early Devonic fauna in Piscataquis 

 and Somerset counties, Me., though this series of rocks is ap- 

 parently not widely separated in continuity or direction from the 

 Aroostook county faunas, is unlike the latter, is more decided in 

 its representation of New York Oriskany types, and yet has many 

 special features in common with those of Aroostook county. At 

 all events this area indicates no entire severance from the former 

 and also declares for a wide open passage southward. 



7 As far southward as northern Maine the calcareous character 

 of the Oriskany fades is already lost in spite of its predominance 

 further north and east, yet in this regard it can not be said to 

 conform more fully with the New York development for that, in 

 spite of common repute, has been abundantly shown to be more 

 calcareous than arenaceous, save as the limestones of the New 

 York Oriskany carry large percentages of silica and weather 

 freely to a silicious residuum. 



8 The more southerly of these passages show in their fauna 

 traits which the northerly do not, namely, a striking array of 

 affiliations with the Coblentzian fauna of the Transatlantic. It 

 would be difficult to assign any other reason for this than that 



