94 



DE. J. "W. EVANS ON THE 



[Feb. 1894, 





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the Rizama Sandstone, because 

 the country between Rizama and 

 the Rio Paraguay is mostly 

 covered by recent deposits and 

 vegetable soil. 



None of the rocks previously 

 described in this paper afford very 

 fertile soil : the ground is gene- 

 rally lightly timbered, and the 

 vegetation suffers severely from 

 want of water during the dry 

 season, so that the country has 

 then an almost wintry aspect. 

 The transition to the Hatto Shales 

 is marked by the incoming of a 

 continuous forest (matto) of lofty 

 trees, beneath whose shade grows 

 thepoaia (as ipecacuanha is locally 

 called), the roots of which are the 

 principal export from the State. 

 Even towards the end of the dry 

 season these trees preserve their 

 leaves, and many of the streams 

 continue to flow. 1 



The Matto Shales can be well 

 studied in the neighbourhood of 

 the settlement of Santa Cruz, 

 Barra dos Bugres, 2 already re- 

 ferred to. There they undulate 

 in gentle curves, but are re- 

 peatedly disturbed by reversed 

 faults. Some of these faults are 

 well shown in the fine section on 

 the rigbt bank of the Paraguay 

 about 6 kilometres or 3J miles 

 above Barra dos Bugres (see fig. 2). 



The shales are red, with streaks 

 and patches of white. They are 

 comparatively soft, and have a 

 greasy feel. Laminae of calcite 

 occasionally occur in them. 



In travelling up the Paraguay 

 from Barra dos Bugres, exposures 



1 This forest, or an extension of it, 

 appears to furnish the explanation of 

 the name Matto Grosso (' thick forest '), 

 (5) toI. ii. p. 1. 



2 Barra dos Bugres means ' the mouth 

 of the Eio dos Bugres,' so called from 

 the Bugres Indians. 



