384 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



than Lake Canandaigua, about 100 miles distant. Hall (Report, 

 p. 212) found that it thins gradually out, west from the village of 

 Tully, in Onondaga County. In his district, this rock is first ob- 

 served on the west shores of Lake Cayuga, for many miles, being 

 continuous , from the last-named body of water to Lake Seneca, and 

 to the outlet of Crooked Lake. 



Transition. — Tully Limestone rests distinctly on the Hamilton 

 group. Besides other instances, this occurs near De Ruyter's Mills, 

 and at the beautiful section on Lake Cayuga given by Hall (Report, 

 p. 211). The transition is abrupt in the west, but more gradual in 

 the east, the two strata assimilating in mineral and fossil character. 



Position. — It dips gently to the S.W., with broad undulations, 

 which are very visible on Lake Cayuga, and, more northerly, at 

 Kidder's Ferry, rising and falling with the immediately underlying 

 blue hard shales. 



Thickness. — Vanuxem finds it to be 14-20 feet in Central New 

 York ; westward of this it becomes less than 10 feet, and, as already 

 said, it dies out near Tully Village. 



Fossils. — This rock contains very few fossils, and therefore 

 marks with distinctness the end of the fossiliferous shales of the 

 Hamilton group. A few forms, however, from below make their way 

 into it. 



With the end of Moscow Shales (Hamilton), the great mass of 

 the fauna of that group perished ; and for a long period the ocean- 

 bed appears to have been without life, save a few creatures in Tully 

 Limestone and Genesee Slate. Living existences only return near 

 the summit of Genesee Slate, and go on increasing, until, in the 

 upper part of the Chemung group, the ocean is crowded with life. 



The fossils of the Tully Limestone are — 



Strophomena linearis. Atrypa prisca. 



Orthis resupinata. reticularis. 



Rhynchonella cuboides ? Orthis resupinata. 



Atrypa affinis. Avicula reticulata. 



didyma? signata? 



lentiformis, var. Calymene marginalia. 



Tully Limestone originates 4 Brachiopoda, 1 or 2 Aviculce, and a 

 Trilobite. It neither receives nor transmits, except in Brachiopoda ; 

 all of them very recurrent. Of these it receives 6 and transmits 2. 



It is not easy to account for this absence of life in Tully Limestone. 

 Further light may be expected from James Hall. 



Fossils occurrent in Europe. — It is remarkable that four out of the 

 thirteen fossils of the Tully Limestone (so far as yet known) are 

 European, namely — 



Orthis resupinata, Phill. (O. Tulliensis) : Carbonif.-Lim., 



England and Ireland. 

 Rhynchonella cuboides? Phill. : Dev. England. 

 Atrypa didyma?, Sharpe: England. 

 Avicula reticulata, Conrad : Europe. 



