674 REVIEWS 
by Foerste,’a new species of crinoid by Springer, and two new species of 
corals by Chadwick. 
The important physiographic feature of the area is the Niagara 
escarpment which is formed by the outcropping edge of the Niagara 
dolomite. 
The Silurian formations classified on the basis of lithology fall into 
the following three groups in ascending order: (1) Alternating sand- 
stones, shales, and limestones represented by the Medina-Cataract, 
Clinton, and Rochester formations and indicating changing conditions 
of land in respect to the sea. (2) Massive dolomites represented 
by the Lockport and Guelph formations and suggestive of widespread 
seas of moderate depth. (3) Saline sediments containing lenses of salt, 
gypsum, and impure clastic dolomites represented by the Cayugan 
group which were formed in shallow, practically isolated interior water 
basins. ' 
The disconformity between the top of the Ordovician represented 
by the Richmond and Queenston shale, and the base of the Silurian 
represented by the Whirlpool sandstone is distinct. The Bass Island 
group of the west and the Akron dolomite of the east are put at the 
top of the Silurian and the disconformity between these formations and 
the basal Devonian is also well marked at a number of localities. Breaks 
in sedimentation occur at the base of the Lockport and Salina. 
Chapter vi contains notes on the salt, gypsum, petroleum, natural 
gas, and other materials of economic importance found in the area. 
The report is well illustrated and is a careful, detailed, and concise 
statement of the Silurian geology of southwestern Ontario. 
JES We 
The Geography of Maryland. By WrtitAM BULLOCK CLARKE. 
The Surface and Underground Water Resources of Maryland, 
Including Delaware and the District of Columbia. By Wm. 
BuLLock CiarkE, E.B. MatTuews, and E. W. Berry. Mary- 
land Geological Survey, Vol. X, 1918. Pp. 553, figs. 96. © 
Part Lis a brief discussion of the geology and physiography, including 
the Coastal Plain, Piedmont Plateau, and the Appalachian physiographic 
provinces, climate, flora and fauna, and the natural resources of the 
state. Among the chief resources may be mentioned coal, clays, building 
and decorative stones, limestone products, agriculture, and timber. A 
number of suggestions for physiographic and geologic excursions within 
the state are included. 
