AND RIO GRANDE DO NORTE, BRAZIL. 17 



2. The crystalline division is mainly gneiss and schists and in- 

 cludes the ancient (Archean to Paleozoic) crystalline rocks with 

 bosses and dikes of various eruptives. It covers the greater part of 

 the states of Parahyba and Rio Grande Do Norte. 



3. The rocks classified by Mr. Roderic Crandall as the Ceara 

 series are here included with the schists, since they are usually in 

 that form. These particular schists are not all crystalline schists and 

 may include layers or lenses of quartzite and of limestone. 



4. The granites form the axes of some of the principal 

 mountains. 



5. It is impossible in a short expedition to determine the distribu- 

 tion of the crystalline rocks. They have been metamorphosed and 

 intruded to a remarkable extent, and they seem to have crystallized 

 in a very irregular manner. 



6. The typical vegetation on the crystalline area is a scattered 

 growth of low trees and brush of small root development, called 

 caatinga. Caatinga forests, however, are not confined to areas of 

 crystalline rocks. 



7. The topography is characterized by great undulating plains, 

 abrupt mountains, rocky, steep-sided hills, and peaked serrotes. 



8. The crystalline rocks have been subjected to great crushing 

 forces. The schists usually stand at a high angle and the rocks are 

 everywhere cut through by quartz veins which vary in width from 

 a few centimeters to half a meter. Occasionally there are pegmatite 

 veins. 



9. The rocks are usually soft and decomposed to a depth of from 

 3 to 10 meters. 



10. The sedimentary series forms the comparatively modern 

 (Mesozoic to Recent) rocks. 



11. It is confined for the most part to a comparatively narrow 

 strip along the coast. 



12. This series reaches the entire coastal length of the states of 

 Parahyba and Rio Grande do Norte and varies in width from about 

 120 kilometers in the vicinity of Mossoro, to 30 kilometers at Natal 

 and about 30 kilometers at Parahyba. 



13. The sediments thin out on the interior side until their margin 



