148 bulletin: museum of comparative zoology. 



Evidences of Elevation. 



While the evidences of depression stand out boldly in the topog- 

 raphy and geography of the Brazilian coast, — so much so that by an 

 inspection of the maps alone geographers who have never visited the 

 region have been able to interpret them, — yet there are here and there 

 evidences of a late elevation. 



This elevation, however, was a feeble one as compared with the 

 depression. Although the uplift was the later movement of the two, 

 the marks of it ai-e not so abundant or so bold as are those of the great 

 depression. The evidence of the elevation is here brought together. 



Reference should again be made to what was considered by Capanema 

 and Liais as evidence of an uplift of the Brazilian coast. These matters 

 have already been disposed of on pp. 118 to 125. Unfortunately, out of 

 seven classes of fiicts brought forward by these writers the only one that 

 has any claim to attention in support of the theory of elevation is one 

 given by Capanema as islands joined to the mainland, and possibly that 

 of coastal lakes. But even in these cases islands joined to the land 

 and coast lakes cannot be accepted in support of the theory of elevation 

 unless they have the characteristics of islands and lakes produced by 

 elevation. Islands are joined to the land after depressions as well as 

 by elevations, and coast lakes are formed along depressed coasts quite as 

 readily as along elevated ones. In order to know how islands have 

 been joined to the mainland, and how lakes have been formed, it is 

 necessary to know something of the local geology and geography. In 

 the absence of such knowledge the islands and lakes, excepting the 

 cases already cited, must be left out of the discussion. 



The " evidence of elevation collected by the author consists of : 

 1. -Elevated sea beaches; 2. Elevated sea-urchin burrows; 3. Death 

 and decay of the coral reefs. These will be treated in this order. 



1. Elevated beaches, State of Alagoas. — Tatuaraiuha is a small village 

 on the south side of a river of the same name that enters the Atlantic in 

 S. lat. 9° 16', State of Alagoas. South of the village a flat bit of 

 country from one to two kilometres wide lies between the Tertiary hills 

 inland and the sea-coast. Mangrove swamps cut into this flat land at 

 several places, but most of it is covered with very calcareous sand con- 

 taining vast quantities of marine molluscan shells, such as are only found 

 living on the open coast. No note was made of the elevation of this 

 plain above tide-level, but my recollection of it is that it is from one to 

 three metres. 



