REVIEWS Be 
it contains a fresh water fauna consisting of gastropods and Unios, and 
in some instances species common to two or more localities. 
The Colorado formation is represented by a characteristic fauna, 
consisting for the most part of Inocerami. The Montana formation 
is recognized, but its divisions are not easily differentiated. It seems 
probable that only the lower part of the Montana is represented. 
In all, thirteen new species are figured and described. The major- 
ity of these belong to the Jurassic. 
W. N. Locan. 
The Glacial Gravels of Maine and their Associated Deposits. By 
GEORGE H. Stone. Monograph XXXIV, U. S. Geological 
Survey, 499 pp., 52 plates, 36 figures. Washington, 1899. 
The enthusiastic pursuit of kames and eskers through the forests of 
Maine without official aid, in the later seventies, by Professor Stone, 
led to his engagement for a monographic study of all the glacial 
gravels of that phenomenally rich region by the U. S. Geological 
Survey. The results appear in this monograph. It would be an 
error, however, to overlook the second half of the title, for much 
attention is given to the formations associated with the glacial gravels, 
and tributary to their formation, so that the volume falls little short of 
being a monograph on the Pleistocene deposits of Maine. 
So far as present knowledge extends, two regions surpass all others 
in the richness of their esker or osar phenomena— Maine on this con- 
tinent, and Sweden on the eastern. This singular distribution is per- 
haps due to a critical relation between the general slope of the land 
surface in these regions and the minimum gradient at which glacier 
ice flows effectively, so that a condition of approximate stagnation was 
assumed in the closing stages of glaciation and the internal drainage 
lines of the ice sheet were permitted to develop with exceptional facil- 
ity. However that may be, Maine is certain to be the classic field for 
esker studies in this country. 
The plan of the volume embraces a preliminary discussion in which 
the fundamental facts of surface geology as illustrated in Maine are set 
forth with considerable fullness (chapters 1, 11, and 111). The opera- 
tive agencies are discussed in close connection with the phenomena 
described. This is followed by a general description of the systems of 
glacial gravels (chapters 1v, and v). By systems is to be understood 
