92 NEW YORK STATE MUSEUM 



two areas of fossiliferous rocks : the outcrops along the Presque Isle stream 

 and those at Edmunds Hill. The fossils from these places studied by Pro- 

 fessor Williams were not closely identified but only brought into com- 

 parisons, often remote, with known New York species of all ages from the 

 Upper Siluric to the Middle Devonic. As the outcrops are not extensive 

 nor widely separated, it has been impossible to credit with value these 

 comparisons between really unlike objects. The main argument of the dis- 

 cussion of the Chapman Plantation fauna assumes to find an agreement in 

 species between that and the fauna of the so called Tilestones of South 

 Wales, which Murchison, after having referred to the Devonic, eventually 

 placed at the top of his Siluric system. Palpably misconceived species of 

 each having been admitted as evidence in this contention and the equiva- 

 lence in part of the Chapman sandstone fauna with that of the Oriskany of 

 New York being conceded, it is concluded that the line of division between 

 the Siluric and Devonic formations in eastern America is to be drawn at a 

 factitious division line somewhere within the Oriskany formation. 



With the species of the fauna before me compared with some care with 

 both American and European contemporary forms I expressed dissent 

 from the conclusions of the writer referred to in a brief address before the 

 American Association for the Advancement of Science in July 1900, notes 

 on which were published in the proceedings of that meeting and in Science 

 of the same year. 



During the last four years, deeming it desirable to present the fauna 

 in detail and its portrayal an essential part of this treatise, I have availed 

 myself of the further assistance of Mr Nylancler to acquire still more com- 

 plete collections and stratigraphic data from the Chapman Plantation, and 

 the same gentleman has also placed at my disposal the entire suite of these 

 fossils from his private collection. To further test the suggestion of the 

 affinity of this fauna with that of the Tilestones of Murchison, I have been 

 so fortunate as to acquire collections both from localities in Wales and 

 those in the Ludlow section representing the upper part of the Downtonian 

 series, made in the field at my request by such accomplished observers as 



