1^4 NEW YORK STATE MUSEUM 



fauna of one representing essentially one congeries, that of the other a 

 different congeries of species which are apparently commingled in New 

 York. 



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

 Grande Greve limestones the northern passage broadened while the Dal- 

 housie 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 development of characteristic Oriskany species in the 

 purest limestone medium and the existence of certain types of still later 

 (Onondaga) age in minor or prenuncial 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. 1 



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 indi- 

 cated 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 development. 



6 The development of the early Devonic fauna in Piscataquis and 

 Somerset counties, Me., though this series of rocks is apparently not 



1 Lest some misconception arise as to the real value of the Grande Greve fauna it may 

 be well to rehearse the fact that the predominant element is the Oriskany and that such 

 suggestions of the Onondaga fauna as are present are ontologically and chronologically 

 immature, so that the time or correlation value of the fauna can not be estimated on the 

 basis of these species. The stratigraphic division of the Grande Greve limestone begins 

 at its base with beds carrying a commanding Oriskany expression but the species of Rens- 

 selaeria, Hipparionyx, large Leptostrophia and Camarotoechia which these basal beds 

 contain are continued through the higher strata with such uniformity that a division of 

 the fauna on the basis of stratigraphy is not to be entertained. 



