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one may ascend the serra on horseback. To the westward of this 

 incline, the sides of the serra are exceedingly rough and picturesque. 

 On this side there is hollowed out of the sandstone a large and curi- 

 ous grotto, called Ita-tupa-oka.* This is situated at some little 

 height above the base of the mountain, and is reached by a steep 

 ascent, encumbered by blocks of sandstone, and overgrown with 

 cacti and stiff bushes. The cavern forms 'a large, irregular, bat- 

 inhabited chamber 50-60 feet long, and with a sandy floor. Wallace 

 had already described the entrance, which is 10-15 feet high, and 

 divided into two parts by a layer of sandstone that runs horizon- 

 tally across the opening about five feet from the floor. This layer 

 is harder than the rock above 'or below, much of which is very 

 friable. 



Immediately west of the serra of Erere, and separated from it by 

 a deep notch, is a short, angular ridge, with the same trend and 

 geological structure, called Aroxi. In this mountain, which is a 

 little lower than Erere, the inclination of the sandstone is very 

 marked. On the southern side a broad belt of large cactuses ex- 

 tends from top to bottom. 



Serras of Erer6 and Aroxi from the South-west. 



To the Avestward of Aroxi, at a little distance, is another short, 

 high, conical ridge, called Aracuri, while beyond appear to be sev- 

 eral other hills, in a line with those just enumerated, and apparently 

 part of the same outcrop. 



The sandy campos decline towards the southward from the serra 

 for several miles, when they rise gradually to the rocky plateau of 

 the serra of Paitiina. This serra I did not visit, but in 1870, Mr. 

 Phineas Staunton examined it for me, reporting it to be composed 

 of horizontal beds of the same kind of sandstone as that of the 

 serra of Erere, so that the two serras probably form part of a syn- 

 clinal fold. Paitiina is flattened on top, and very broken and pre- 

 cipitous on all sides. Wallace, who visited it, says that the curious, 

 mushroom-like pillar on the southern end is composed " of friable 



* Literally, God's stone house. //«, stone ; Tupa. or Tupana, God ; and oka, house. 



