221 



rock forms a dyke, or a bed iiiterstratified "with the ckay-rock, I 

 could not determine. In the rain-courses of the Maecurii road the 

 diorite has given rise to a great number of well-rounded boulders 

 of decomposition, imbedded in a dark soil of decomposed trap ; 

 and, at a hasty glance, they might be taken for erratics. On the 

 nortliern side of the gap the ridge appears to be continued for some 

 distance. Looking from the top of Erere there appears to be a 

 ridge running northward from the Serra de Aroxi like that just de- 

 scribed. I made an attempt to reach it, but lost myself in the thick 

 woods. An attempt to explore the zone of highlands to the west 

 of the campos proved very unsatisfactory. I made a very long 

 excursion among these hills, but I cannot give an intelligible 

 account of their structure, because of the want of exposures and 

 the difficulty of making and recording observations in the dense 

 undergrowth, and in the beds of the exceedingly tortuous igarapes. 

 The prevailing rock appears to be similar to that exposed in the 

 ridge extending northward from Erere, but I found also a few 

 wretched exposures of a firmly laminated, dead-black shale without 

 fossils. I know nothing of the relation borne by these beds to the 

 undoubted Devonian beds of the plains. Trap dykes are very nu- 

 merous, and some are very heavy. The whole region seems to have 

 been much disturbed. At Matarupi and elsewhere in the vicinity 

 there are superficial deposits of impure haematitic iron ore. Cam- 

 pos, apparently composed of Devonian rock, extend from the ridge 

 running north from the serra of Erere to the serra of Aroxi. 



Almost directly north of Monte- Alegre is an isolated, precipitous 

 hill several hundred feet in height, which, in company with Messrs. 

 Smith and Staunton and my guide Sr. Liberato, I tried to reach from 

 the campo on the southern side. All I was able to do was to climb 

 a sort of high platform, in front of the hill, which was so covered 

 with spiny plants, yurupari pitidd and underbrush, that I was 

 obliged to turn back. I should have persisted, but that I had sev- 

 eral hours' march before nie over the stony plain to Erere that 

 evening. I could only determine that the platform above spoken of 

 Avas composed of diorite like that of the ridge just west of Erere. 



The little hamlet of Erere is situated on the Devonian plain, a 

 little more than a mile to the north of the eastern extremity of the 



