AGE OF THE GASPE SANDSTONE 693 



Summary of Evidence 



To sum up the evidence, the facts briefly stated are as follows : 



In the York River beds at the base of the Gaspe sandstones there is found a 

 number (at least a dozen) of fossils which if found alone would be inter- 

 preted as positive evidence of an Oriskanian fauna ; associated with these is 

 another lot of fossils, at least as many, which if found alone would be as 

 positive evidence of a Hamiltonian fauna. The sediments were deposited at 

 some particular epoch of the geological time scale. What does this composite 

 fauna signify as to the epoch to which the York River beds belong? 



Doctor Clarke in the volume referred to gives the decision in favor of the 

 Hamiltonian epoch, apparently on the ground of the greater number of species 

 identical or closely related to Hamiltonian forms. If we accept his view it 

 follows that the associated Oriskanian forms continued to live on after the 

 epoch of the Oriskanian fauna into Hamiltonian time. 



By the interpretation here offered it is assumed that the Hamiltonian types 

 of the fauna are possible ancestors of Hamilton species living in the Oris- 

 kanian epoch, which by some movements of the currents of the ocean were 

 brought together in the Acadian province before the revolution which upset 

 the biologic equilibrium of the Oriskanian fauna had completed its work. 



The further conclusion is that it was the same events which caused the 

 cessation of the distinctive Oriskanian fauna, which brought into this area the 

 ancestors of the Hamilton species, and that the geologic time of the events 

 was approximately equivalent to the Schoharie epoch of New York state. 



The following specific facts seem to corroborate this interpretation: 



1. Lower Devonian faunas of the Rhine and Hartz regions of Europe con- 

 tain a similar combination of species ; Rensselaerias, Eatonia-like Rhynchonel- 

 lids, large coarse-ribbed Spirifers, associated with Tropidoleptus, Grammysia 

 hamiltonensis, Cyrtini heteroclita, etcetera, to mention but a few striking 

 cases. 



2. Tropidoleptus, a prominent representative of the fauna, is already traced 

 downward as far as the typical Oriskany in the Maryland Oriskany. 



3. The Nictaux fauna of Nova Scotia and the Moose River sandstone fauna 

 of central and northern Maine, in both of which there is also found Spirifer 

 arenosus, show similar admixture of species having close affinity with the 

 Hamiltonian fauna. 



4. The upper mass of the breccias of Saint Helens, which contains the Cote 

 Saint Paul species, also has undoubted example of Spirifer arenosus. 



5. The Nictaux, Moose River, and Upper Saint Helens beds contain domi- 

 nant Oriskany species as the dominant constituents of their faunas, which 

 taken alone would, I believe, lead any paleontologist acquainted with the 

 faunas to assign them to the Oriskany epoch. 



6. The Oriskanian fauna, although intimately associated biologically with 

 the Helderbergian, is in North America biologically quite distinct from the 

 Hamiltonian fauna which is an evolutional expansion of the Onondagaian, 

 and in its dominant elements ceased with the opening of the Onondagaian 

 epoch. 



7. The evidence seems convincing that the origin of the Onondaga-Hamil- 

 tonian fauna is from a source south of the "Indiana basin" (of Ulrich and 



