INTRODUCTION 
This index comprises the indexes contained in Bulletins Nos. 130, 
135, 146, 149, 156, 162, and 172, tog-ether with the index to the litera- 
ture for the year 1900. It is planned to accompany Bulletin No. 188, 
in which will be found the bibliographic entries to which all the 
authors' names and the numbers in this publication refer. 
The subject headings, their subdivision and arrangement, are shown 
in the following "Classified key to index." They comprise geo- 
graphic, geologic, mineralogic, paleontologic, and petrologic sub- 
divisions. Under "Economic geology" is given a list of the useful 
minerals and ores described in publications examined; under "Miner- 
alogy," a list of minerals described in such publications; under "Pale- 
ontology," a list of genera and species of fossils therein described; 
and under "Petrology," a list of rocks described; reference being 
made in each case, by author's name and number of entry in the 
Bibliography, to the paper in which the fossil, mineral, or rock is 
described. 
9 
