380 



I have been informed lately that Messrs. Logan, Hunt, and 

 Hall maintain the age of the Hudson River group for the strata 

 of Quebec and Georgia on stratigraphical grounds, which to Mr. 

 Logan are very clear ; and that they are disposed to think the 

 so-called Primordial fauna extends much higher in Canada than in 

 Europe, and has reajp'peared after a first extinction. Such a de- 

 cision should not be reached without the most decisive proofs, for 

 it breaks through the laws of paleontology, and annihilates almost 

 all the results arrived at by the labors of Smith, Cuvier, Brongniart, 

 De Buch, D'Orbigny, Agassiz, Barrande, etc., for the last fifty 

 years. Nor is this the first attempt of geologists recognizing Mr. 

 James Hall as their leader against the recognized laws of pale- 

 ontology. During the last six years they have placed an Oligocene 

 flora helow the cretaceous rocks, a Triassic flora among what they 

 call Jurassic rocks, Jurassic fossils in cretaceous rocks, the moun- 

 tain limestone fauna ahove the coal-measures, cretaceous fossils in 

 Triassic rocks, etc. etc. 



There is at least one proof that Messrs. Hall, Logan, and Hunt 

 can give, to show that the Primordial fauna extends over the second 

 fauna, — it is to show, in those parts of New York where the strata 

 are without dislocation and succeed regularly, such as Utica, 

 Loraine, Pulaski, and the neighborhood of Rome, that the Pri- 

 mordial fauna is ahove the second fauna. 



There is only one point on which I differ from Prof. Emmons, — 

 it is as to the propriety of placing the Potsdam sandstone as the 

 base of the Silurian. Until now not a single fossil of the Calcifer- 

 ous sandrocks, of the Black River group, or of the Trenton group, 

 has been found in the Potsdam of the State of New York ; on the 

 contrary, it contains the Primordial fauna, such as Conocephalites, 

 Dihellocephalus, Orthis, and Lingula. Thus, the Potsdam group 

 is paleontologically entirely independent of the Lower Silurian, 

 while it possesses fossils belonging to the Taconic system. I 

 am not sufliciently acquainted with its distribution and position 

 as regards the Taconic and the Calciferous sandrocks to give 

 a decided opinion based on stratigraphical grounds, but from 

 the description of Prof. Emmons in his Taconic system, and 

 from what I have seen at Little Falls, the Calciferous sand- 

 rocks are certainly very differently distributed from the Pots- 

 dam, and a dislocation and disturbance of strata have taken 



