462 Scientific Intelligence. 



ciated forms, none of which are known to appear before Marcellns 

 time. It therefore seems to the writer unwarranted to conclude, 

 as does Professor Williams, that "the black shales range from 

 as low as the Onondaga." Admitting this identification, then, 

 not only does the form in question persist into Marcellus or later 

 time, but there are, as is well known to Professor Williams, many 

 other Onondaga species persisting into Hamilton time in other 

 faunules than those listed in this Bulletin ( Ghonetes mucronatus, 

 Pentagonia imisulcata, Parazyga hirsuta, Phipidomella vanux- 

 emi, Spirifer acuminata^ etc.). With these facts in view, it does 

 not follow that the Black Shale ranges "from as low as the 

 Onondaga." The Buchiola retrostriata fauna is a puzzle to 

 stratigraphers other than Professor Williams. It comes to 

 America as a migrant along an unknown path (there are three 

 possibilities), appearing in part first in the Marcellus, recurring 

 always with the Black shale conditions, and evidently is finally 

 made up of other later migrants and stragglers from the American 

 Hamilton faunas. 



The sections and faunal lists of " Devonian sections in Central 

 and Northern Pennsylvania " are given in great detail and have an 

 especial value in connecting the type area of New York with the 

 middle and southern Appalachians. For the first time, here is 

 found a carefully collected sequence of Upper Devonic faunules; 

 also the relation of the Catskill formation to the Chemung of 

 Pennsylvania. 



In conclusion, the writer will state that it is not shown that 

 stratigraphers can not rely upon the fossil assemblages, as pre- 

 sented in these faunules, for definite correlation of formations 

 over wide areas and especially within faunal provinces. The top 

 and bottom of the correlated formations may not be everywhere 

 exactly contemporaneous, yet for practical purposes they are 

 fairly exact. It is true that the faunules are ever changing and 

 that they are controlled to some extent by the character of the 

 sediments (in some cases very largely so, and this is particularly 

 true of the Black shale condition), but in nearly every faunule 

 this constant change preserves a something by which its time 

 position can be recognized. At times this something is the pres- 

 ence of a certain species, the dominance of a certain few species, 

 the assemblage or absence of a certain species, controlled by the 

 stratigraphic position of the faunule. It is known that many of 

 the New York Hamilton Bryozoa and Ostracoda occur at the top 

 of the Onondaga in the Falls of Ohio region, and Dr. Clarke has 

 suggested that the top of the Onondaga limestone in New York 

 probably is a tangential horizon, one end of which lies in Onon- 

 daga, the other in Marcellus time. Features further complica- 

 ting these Devonic faunas, and to which but very few paleon- 

 tologists have given attention, are the sources of the faunas, the 

 paths of migration, and the barriers or low anticlines that origi- 

 nated at different times in the American Paleozoic epicontinental 

 seas, resulting from Appalachian and Arkansas-Oklahoma move- 

 ments. 



