386 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 
Accompanying this paper will be found a bibliography of the 
more important literature, and in the footnotes some additional refer- 
ences are given. Nearly all of the literature of the subject has been 
consulted in the preparation of this review, but it has not been deemed 
advisable to publish a more complete bibliography, since some of the 
articles with elaborate titles have in reality little value and, being 
quite inaccessible to the general student, can hardly hope to hold a 
place with the more important contributions, which embody the 
essential truths with fewer errors. 
Puysicau AND CiimatTic REGIons. 
THE THREE REGIONS OF PERU. 
The dominant physical feature of Peru is the lofty range of the 
Andes which lies near the Pacific Ocean and forms a barrier between 
the narrow strip of desert coast and the extensive wooded plains of 
the Amazon. Accordingly, the country is commonly recognized as 
presenting three naturally defined regions which differ in their phys- 
ical features and climate; namely, the coast, the sierra, and the forest, 
or “ montafia,” as it 1s called in Peru. The use of these terms orig- 
inated with the inhabitants, and they have to a considerable extent 
found their way into scientific literature. The name “ montafia” is 
apt to be misleading, especially to a foreigner, since it suggests moun- 
tains. “ Selva,” meaning forest, would seem to be more appropriate. 
If terms are selected which may be broadly used in considering the 
South American continent one may appropriately speak of the Pacific 
coastal region, the Andes Mountain region, and the Amazon plains 
region. ‘These terms have physiographic signification and should — 
come into use in scientific writings. The extension of these regions 
may be learned from the accompanying map (pl. 1). 
PACIFIC COASTAL REGION. 
Definition. 
The distinction between the coast and the sierra as commonly made 
is one of climate and is indicated by differences in agriculture. In the 
coast the agricultural products are those of the tropical and sub- 
tropical climates, while those of the sierra are such as are found in 
the temperate zones. The transition from one region to the other is 
abrupt because of the steep declivity of the Pacific slope of the 
Andes. 
With the exception of the part of Peru adjacent to the Gulf of 
Guayaquil, the division between the coast and the sierra corresponds 
with the approximate western limit of general annual rainfall on 
