112 bulletin: museum of comparative zoology. 



tinent/ while the dendritic flords and islands along the coast from 

 Tierra del Fuego to south latitude 41° show that there has also been a 

 comparatively recent depression in that region.^ A late paper by Pro- 

 fessor Gormaz of the University of Chile directs attention to the fact 

 that while there are evidences of elevation along that coast, certain 

 localities show equally satisfactory evidences of depressions, even within 

 the historic period.' 



But the localities mentioned by these writers are far from the region 

 with which we have to deal. The question with which we ax'e chiefly 

 concerned is whether there have been changes of level within historic or 

 geologically recent times along the northeast coast of Brazil, and whether 

 such changes, if they did occur, bear directly upon the existence and 

 forms of the stone and coral reefs of that region. 



We must also keep in mind the great length of the Brazilian coast-line, 

 — about sixty-four hundred kilometres from the northern end at the 

 mouth of the Oyapoc on the frontier of French Guyana (5° 10' north 

 lat.) to the frontier of Uruguay at the mouth of Rio do Chuy in south 

 latitude 33° 45'. As in other parts of the world, where so long and so 

 nearly straight a coast-line is concerned, the orographic movements over 

 this distance have not necessarily been at the same rate or even in the 

 same direction. 



The evidence of a geologically recent elevation of the southern coast 

 of Brazil is fairly satisfactory, while still further south in the Argentine 

 Republic it is remarkably impressive, and considerable elevations are 

 reported to have taken place even within the historic period. Many 

 facts concerning the southern end of the continent are given by Darwin 

 in his " Geological Observations," Chapters VIII. and IX.,* and by J. B. 

 Hatcher in his paper upon the geology of southern Patagonia.^ These 

 facts show that the change of level affected the east coast for a distance 



1 Darwin's Geological observations, Chap. IX. 



2 Professor Shaler notes, however, that the submarine cutting of ice may be 

 responsible to some extent for the form in this case. Bull. Geol. Soc. Amer., 1894, 

 VI., p. 162. 



3 Francisco Vidal Gormaz. Depressions and elevations of the southern archi- 

 pelagoes of Chile. Scottish Geog. Mag., Jan., 1902, p. 14-24. 



* Dr. Friedrich Gustav Halm published at Leipzig in 1879 a paper upon the 

 elevation and depression of coasts. ( Untersuchungen uber das Anfsteigen und Striken 

 der Kustcti) — in which he gives a brief re'sume' of the evidence of the upheaval of 

 the southern part of Brazil (pp. 93-97). This paper, however, in so far as it relates 

 to the coast under consideration, contains only the facts given by other authorities. 



5 J. B. Hatcher. On the geology of southern Patagonia. Amer. Journ. Sci., 

 Nov., 1897, CIV., p. 345-350. 



