466 NEW YORK STATE MUSEUM 



The Trenton substage is composed of two members, a lower, 

 massive, crystalline and an upper, thin bedded, fine grained member. 

 The lower member is usually about 8 feet in thickness and the 

 upper probably not far from 30. In section 46F where the Utica 

 is present the thickness of this upper member is 27 feet. T r i n u - 

 cleus concentricus and Monticulipora (Praso- 

 pora) lycoperdon are the characteristic fossils of this mem- 

 ber and the former is scarcely found below it. It is interesting to 

 note that at Tren-ton Falls and Rathbone brook these two fossils 

 are found similarly associated in the lower layers of the Trenton. 

 This would lead us to conclude that the massive member at the 

 base of the Trenton in its eastern extension is related to the Black 

 river Hmestone^ and does not correspond to the massive member 

 at Trenton Falls which occurs at the summit of the stage. The 

 greatest thickness of the Trenton stage measured in this region 

 is 46 feet, at Morphy's, 46F. 



The accompanying chart illustrates the distribution of the species 

 listed from the Calciferous and Trenton stages. In the vertical 

 columns the relative abundance of the species for any locality, as 

 indicated at the heads of the columns, is given by a letter opposite 

 the name of the species. The meaning of the letters is the same as 

 explained in another place. The starred localities are those from 

 which no extensive collection was made. 



The lithologic characters of the Utica and Hudson river shales 

 were described in some detail in the discussion of the Minaville 

 section, for the purpose of showing that in this region at least the 

 two formations may be separated by a fairly definite line. The 

 transition is not marked till within 165 feet of the Hudson sand- 

 stones and after the sandstones are reached they tend soon to pre- 

 dominate as seen in the Rotterdam section. The Utica stage has 

 a thickness in this region of between 950 and 1260 feet composed 

 entirely of black calcareous shales and thin layers of limestone. 

 The hill back of Rotterdam, reaching an elevation of 1200 feet 

 above the Mohawk, is entirely composed of argillaceous shale and 

 sandstones without any appreciable amount of calcareous material. 



A maximum section for this region is as follows: 



6 Argillaceous crumbling shales and sandstones. 

 Hudson river. i20o'=28o2' 



5 Black slaty calcareous shales and thin lime- 

 stones. Utica. i2CX)'=i6o2' 



