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. Trinu- 
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 Trenton 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 limestone, 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 thé 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. 1200’—=2802’ 
5 Black slaty calcareous shales and thin lime- 
stones. Utica. 1200’—=1602/ 
s 
