REVIEWS IQI 
grains of an undetermined mineral, probably orthorhombic pyroxene. 
The olivine had become closely compacted and the grains jagged in 
outline, with numerous inclusions of dark grains, probably iron oxide. 
Analyses of the fresh and altered rock showed that the recrystallization 
involved oxidation and dehydration. 
E. STEIDIMANN 
Geology of the Thousand Islands Region. By H. P. CUSHING, 
H. L. Farrcsitp, R. RuUEDEMANN, and C. H. Smytu, JR. 
New York State Museum Bulletin 145. Albany, 1910. 
Pp. 194; Figs. 14; Pls. 63; Maps s. 
The Thousand Islands region embraces the Alexandria Bay, Cape 
Vincent, Clayton, Grindstone, and Theresa quadrangles of northern 
New York. It is a district of pre-Cambrian, Cambrian, and Lower 
Silurian rocks and Pleistocene deposits, which are described and faunas 
and structures of which are discussed. 
From facts gathered outside of this district the formerly called 
“‘nassage beds” lying between the Potsdam and the overlying Beekman- 
town have been separated into two formations, the Theresa of the Upper 
Cambrian and the Tribes Hill of Beekmantown age. Although the 
unconformity that causes the separation has not as yet been detected 
in this region, the paleontological evidence indicates that the separation 
should be made. Of special interest is the new Pamelia formation, 
here first differentiated, which represents an arm of the Upper Stones 
River sea when that sea had encroached farthest to the northeast. No 
deposits of the Stones River sea have previously been known to occur 
in New York. The Pamelia basin was entirely separated from that of 
the Chazy, but is considered to be contemporaneous with the interval 
between the Middle and Upper Chazy. The term “Black River” as 
applied to Lower Silurian formations, has been redefined to include, be- 
sides the ‘‘Seven foot tier” of Hall, now renamed the Watertown lime- 
stone, the Lowville formation of which the upper part (the ‘“cherty 
beds”’) is called the Leray limestone member. 
The Pleistocene deposits consist of three kinds; those formed by 
glaciers, those formed in the glacial Lake Iroquois, and the deposits in 
Gilbert Gulf, an arm of the Atlantic after Lake Iroquois had been drained 
to sea-level. 
The pre-glacial course of Black River has a new interpretation 
which states it to have been the headwaters of the St. Lawrence drain- 
age instead of the Ontario valley. 
