REVIEWS 
Stratigraphy and Paleontology oj the Ordovician Rocks of Indiana. 
By E. R. Cumincs. Thirty-second Annual Report of the De- 
partment of Geology and National Resources of Indiana, 1907, 
pp. 607-1188. 
Professor Cumings has determined as accurately as possible the exact 
range and horizons of the different fossil species found by him in the 
Ordovician strata of southern Indiana and finds that the strata fall naturally 
into eight zones differentiated faunally as well as lithologically. Nickles 
in his earlier work used the bryozoa in determining the several divisions 
he proposed for these strata but Cumings, believing that the brachiopods 
are more generally suited especially for field determination, has used the 
latter as indicators. An important result of the present work is the discovery 
that in the Richmond beds the Saluda beds lie below, rather than above the 
Whitewater beds as believed by Foerste and others. The general absence 
of the later beds to the south is believed to indicate an extensive uncon- 
formity between the Richmond and the overlying Clinton. The major 
part of the paper is taken up with redescriptions of the fossils mainly 
drawn from the original descriptions. 
The careful stratigraphic work is a credit to Professor Cumings and an 
advance in the right direction. 
J Gps 
The Geology of the Gold Fields oj British Guiana. By J. B. Harrt- 
son, Director of the Department of Science and Agriculture and 
Government Geologist. With Historical, Geographical, and 
other chapters by FRANK FOWLER and C. WILGRESS ANDERSON. 
Since 1884, when gold mining on an important scale was first under- 
taken, British Guiana has produced about $35,000,000 gold, most of which 
has been recovered from placer and residual deposits. The gold-bearing 
area is said to cover more than 1,000 square miles. The country is heavily 
forested and the rocks are exposed mainly along the streams and in ravines 
where torrential rains have cut through the deep residuum. 
The oldest rocks are crystalline schists, probably of pre-Cambrian age, 
which vary in character from granitic gneiss to very basic schist. This 
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