﻿J2 NEW YORK STATE MUSEUM 



lar to those which prevailed during the formation of the Siluric 

 waterlimes of central New York. 



The thickest measured section of the upper division, i mile 

 southwest of Depauville, Clayton sheet, gave a thickness of 82 feet. 

 The contact with the over/lying Lowville was shown, and the base 

 of the section can not have been greatly above the base of the upper 

 division. Near the river west from Clayton a similar thickness was 

 found, though the upper part of the section was considerably in- 

 terrupted. In all probability the thickness does not vary greatly 

 from this over the entire map limits, with the exception of the 

 eastern margin of the Theresa quadrangle. The thickness of the 

 two divisions together then indicates a maximum of about 150 feet 

 for the formation hereabout. 



The fauna of the formation consists chiefly of ostracods, which 

 are found at all horizons, and Ulrich remarks on the absence in 

 the formation of certain large sized species of Leperditia and 

 Isochilina which occur in the Lowville above. The marine fauna 

 of the lower division includes gastropods, cephalopods, lamelli- 

 branchs, trilobites, corals and sponges. The most abundant and 

 characteristic form is the coral Tetradium syringopo- 

 roides, which abounds in certain layers of the black limestone. 

 The most common trilobite is a species of Bathyurus which is very 

 like the common Bathyurus extans of the Lowville, but 

 which Ulrich distinguishes as a different and unnamed species, 

 which is a common Stones River form. Among the gastropods he 

 identifies Lophospira perangulata, another Lophospira, 

 and a Helicotoma. The fauna as a whole is quite similar to that 

 of the Lowville, though the differences are characteristic. 



Since the formation is a new one to the State the publication of a 

 few detailed sections is advisable. The best continuous section of 

 the lower division is found in the bed of a small creek which tumbles 

 down the steep bluff face east of Perch lake (Theresa sheet), cutting 

 the 400 foot contour where the figure 400 appears on the map. 



White, earthy limestone in thin beds, often shaly looking 



Brittle, tough, blue to blue black limestone, thick bedded 



Gray, subgranular, magnesian limestone, weathering white 



Massive bed of blue, subcrystalline^ limestone 



Massive bed of gray, magnesian limestone 



Blue, subcrystalline limestone 



Gray, magnesian limestone, two layers 



Concealed 



Finely laminated gray to blue gray, magnesian limestone, fine-line 



weathering on edges 

 Concealed 

 Black to blue black, fossiliferous limestone, upper 3 feet thin 



bedded, remainder fairly massive 



6' 





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