﻿.12 NKW YORK STATE MUSEUM 



somewhat in its faunal aspect from the beds in the neighborhood 

 of Utica, but retains about the same thickness and lithological 

 character. 



The Frankfort shale which, from 300 feet at Frankfort swells 

 to 1500 or 1800 feet in the lower Mohawk valley, has very unex- 

 pectedly furnished faunules at many horizons, although it had 

 hitherto been considered as practically barren. Altogether about 

 seventy species have been obtained, among them an entirely new 

 eurypterid faunule, the first Lower Siluric eurypterid fauna known, 

 except for the two fragments each of Echinognathus and Megalo- 

 graptus. This eurypterid fauna was found to range through the 

 entire thickness of the Frankfort shale with the exception of several 

 hundred feet at the top exposed at the foot of the Indian Ladder 

 in the Helderbergs, which carry a different fauna. The latter, 

 which will be distinguished as Indian Ladder beds, are also charac- 

 terized by the rapid alternation of shales and thin sandstone with 

 argillaceous limestone beds. 



The distribution of the eurypterid fauna in the Frankfort shale 

 is peculiar in that this fauna rapidly disappears westward while the 

 greater proportion of the other fossils continues, but the eurypte- 

 rids continue westward into the Schoharie reentrant of the Helcler- 

 berg escarpment. Since the eurypterids are associated with 

 immense masses of seaweeds (S p h e n o t hal lu s lati folium 

 Hall, et al., which have been obtained in very complete specimens, 

 and lend themselves to close study) which also fail in the finer shales 

 to the west, it is inferred that the Eurypterid-Sphenothallus associa- 

 tion was restricted to a sinking and rapidly filling "vorland " of the 

 rising Appalachian land to the east, or to the littoral region, while 

 the other Frankfort fauna was spreading farther offshore. The 

 graptolite, brachiopod, trilobite and mollusk elements of the Frank- 

 fort fauna prove that the latter is to be regarded as a direct con- 

 tinuation of the Utica beds as has been generally done. The Lor- 

 raine beds have not been found in the Mohawk valley. 



During the investigation of the Frankfort shale in the Cobleskill 

 region, evidence was also obtained showing that the Brayman shale, 

 which formerly was referred to the Clinton and later correlated 

 with the Salina, is most probably of Lower Siluric age. 



Adirondacks. Field work has been carried on by Professor 

 Miller in the North Creek quadrangle where the territory, though 

 fairly rugged, is well supplied with roads and outcrops are gen- 

 erally numerous so that very detailed observation has been possible. 



