30 ' NEW YORK STATE MUSEUM 



About Middleville the formation ranges from 15 to 21 feet in 

 thickness, the 6 to 8 feet of passage beds being excluded. To the 

 westward it is still thicker, as shown by Prosser about Jifewport, 

 South from Middleville it quickly dwindles to an average thick- 

 ness of about 10 feet, and this it keeps all along the Mohawk to 

 the east limits of the map, ranging from 8 to 12 feet thick. About 

 Ingham Mills, Prosser has measured one thickness of a little more 

 than, and another of a little less than, 10 feet. 



The upper boundary of the formation is commonly sliarply de- 

 fined, the overlying Black river or Trenton being of quite different 

 character and passage beds being lacking. Occasionally a layer 

 with the lithologic character of the Lowville recurs a few feet 

 above the summit of the main formation, as has been shown by 

 Prosser at Ingham Mills, but this is exceptional. 



About Diamond hill and thence northward, the Lowville shows 

 nowhere in outcrop, and in places the Beekmantown and Trenton 

 occur sufficiently close together to show that, if the Lowville 

 occurs here at all, it must be under 5 feet thick. In the Mohawk 

 valley to the eastward, beyond the map limits, it disappears en- 

 tirely for an interval. 



Black river limestone. Normally this formation consists of 

 thick bedded, black, brittle limestone which underlies the Trenton 

 directly. In the Little Falls district it is mostly absent, the 

 Trenton directly following the Lowville. So far as the writer is 

 aware, Prosser was the first to show its presence in the district, 

 he reporting the 5 foot thickness which is shown at Ingham Mills.^ 

 But just north of the mills, at the second bridge, the old quarrj 

 face shows 10 feet of Black river limestone, with the Lowville 

 below and Trenton above, in a vertical 25 foot section [see pl.5]> 

 It consists of 4 to 8 inch layers of black, brittle, blocky limestone 

 separated by shale partings of approximately equal thickness. 

 The limestone bands are like the Black river in lithologic char- 

 acter and in stratigraphic position, and contain fossils rather 

 numerously, &o that it will be easy for the paleontologist to de- 

 termine wliether or not it is the normal Black river fauna, as it 

 seems to the writer to be. 



'N. Y. State Mus. Bui; 34, p.469. 



