REPORT OF THE STATE PALEONTOLOGIST 1899 GT1 



stratigraphic evidence pertaining to the proper age of these 

 rocks, careful investigations have been made through the 

 central and western counties. The problem is by no means 

 a simple one, as fossil remains are for the most part meager and 

 the succession of the beds has been generally regarded as gradual 

 and uninterrupted. Our recent investigations have shown that 

 the deposition of these hydraulic limestones was continued 

 without interruption upward through what has commonly 

 been regarded as the lower term of Helderbergian time, i. e. 

 the Tentaculite limestone. The fauna of the Tentaculite lime- 

 stone makes its first appearance not far above the gypsum beds, 

 and in its most perfect development it is clearly an uppermost 

 Siluric fauna, having only very remote relations with the 

 fauna of the remaining divisions of the Helderbergian group in 

 eastern New York. The inference that the upper limit of the 

 Siluric system is properly to be placed at the top of the Tentacu- 

 lite limestone is corroborated by stratigraphic structure which 

 shows in places distinct unconformity between the Tentaculite 

 limestone and the overlying strata. I regard the result of these 

 investigations as of much importance in indicating the proper 

 line of division between the Siluric and Devonic systems in 

 the state of New York and as corroborating the views ex- 

 pressed by the writer at various times during the last 10 years. 

 One outcome of these investigations is to establish the profuse 

 fauna of the Helderbergian of eastern New York as an earliest 

 Devonic rather than a latest Siluric fauna. 



Oriskany fauna of Becraft mountain, Columbia co. This 

 fauna is one of the more recent discoveries among our paleozoic 

 rocks and presents a number of problems of special interest. The 

 fauna itself is a noteworthy combination of species, many of its 

 elements being heretofore unknown. Its character and composi- 

 tion show that it constitutes the deep water or calcareous facies 

 of the fauna of Oriskany time, the common Oriskany species be- 

 ing in great part shoreward migrants which became involved in 

 more sandy sediment. The relation of this subject to the 

 problem just stated is intimate, as the character of the fauna 



