No. 4.— Expedition to the Baltic Provinces of Russia and Scandinavia, 
1914. 
Part 2.— THE SILURIAN AND HiaH OrpovicrAN STRATA OF ESTHONTA, 
RuSSIA, AND THEIR FAUNAS. 
By W. H. TweEnHoFELt. 
TABLE OF CONTENTS. 
. Part 2. 
PAGE. 
Introduction : : ; i ; : ; : . . 289 
The Russian Section . : : ; ; ; . ;’ ae 
The Ordovician System : : : . ; ; ‘ . 293 
The Silurian System . : : ; - 814 
PaRT 3. 
Introduction , c . : , : jf : é . 341 
Conclusions . : 3 ‘ ; . : ; P “ .. om 
Explanation of Plates 
INTROD UCTION. 
THE present paper is based on work done under the auspices of the 
Shaler Memorial fund. In company with Prof. Perey E. Raymond, 
an expedition was undertaken in the summer of 1914 for the purpose 
of examining the Cambrian, Ordovician, and Silurian strata exposed 
around the Baltic in Russia, Sweden, and Norway, with the object 
in view of attempting a correlation with strata of the same systems 
of eastern North America. The writer was primarily concerned with 
the highest Ordovician and Silurian, while the Cambrian and the 
remainder of the Ordovician were studied by Professor Raymond, 
although mutual assistance was rendered. The outbreak of the war 
to some extent necessitated a curtailment of the study, but in my case 
this amounted to the loss of only a few days’ work in northern Got- 
land and a considerable shortening of the time allotted to Norway. 
The failure to see certain sections of northern Gotland will be ulti- 
mately overcome by detailed collections which have been made (1915) 
