Geology and Mineralogy. 69 
Heretofore the commingling of brackish-water and fresh-water 
fossils has been explained on the supposition that the beds in 
which they were found were estuary deposits. Dr. White says 
that there is evidence “that the fresh-water fauna proper of the 
Laramie system not only inhabited the streams which emptied 
into its sea, but that in great and shifting areas of the sea itself, 
the waters were sufficiently fresh to allow the existence in them 
of such Mollusca as Unio, Goniobasis, Viviparus, Campeloma, 
etc., and saline enough in other parts for the existence of Ostrea, 
Anomia, Corbula, etc.” The volume is handsomely illustrated 
and has a full table of contents and index. 
flexure. 
Chance describes and figures sections of the slate- 
