96 DR. J. W. EVANS ON THE [Feb. 1 894, 



not, however, necessary to have recourse to marine action for an 

 explanation of the present configuration of the country. 



The sandstones are of recent appearance and comparatively little 

 consolidated, so that it is easy to understand why they were origin- 

 ally considered as being of Tertiary age. Red and white sbales 

 are found interstratified with them. 



The Chapada Sandstones may extend as far west as Beira on the 

 Rio Guapore, at which locality similar sandstones were observed 

 by A. d'Orbigny dipping south-east at an angle of 12° to 15°, (i) 

 p. 203, a dip that is unknown elsewhere in these beds. 



I am informed by Mr. C. H. "Ward that the isolated hill known as 

 Morro Grande, near Sao Antonio, on the Rio Cuyaba, a short 

 distance below Cuyaba, is an outlier of the Chapada Sandstones. 



Mr. Herbert H. Smith, who, as I have stated, spent two years 

 in making zoological collections on the Chapada, found some 

 fossiliferous sandstone in the bed of the Corrego dos Morrinhos, 

 4 miles north-east of Sant' Anna da Chapada : 1 this occurs 

 near the summit of the Chapada Sandstones. According to 

 Mr. Derby's description, (<9) pp. 73-88, the fossils are in an imper- 

 fect condition, and only a few are specifically determinable. The 

 following genera were identified : — Lingula, Distinct, Strophodonta, 

 Tropidoleptus, Vitulina, Rhynchonella, Spirifer, Notothyris (*?), 

 Centronella (?), Bellerophon, Tentaculites, and Slyliola. Mr. Derby 

 adds, " The specific characters, as far as they can be made out, show 

 close relationship, if not perfect identity, with the fossils of Erere 

 on the Amazonas, and with those of the Hamilton or Middle 

 Devonian Group of New York." 



That authors paper contains an interesting discussion as to the 

 relations between the rocks of Matto Grosso and those of the rest 

 of Brazil. It also deals with the hilly region in Eastern Bolivia 

 called the Chiquitos. This, Mr. Derby considers, belongs rather to 

 the Brazilian highlands than to the Andes, (8) pp. 71-73, a view 

 which I can confirm. In reading A. d'Orbigny's account of the 

 Chiquitos (1) pp. 183-199, 1 recognized the chief types of rock that 

 I had seen in Matto Grosso. They seem from his map and descrip- 

 tion to consist of a group of hills running east-south-east and west- 

 north-west, due to an anticlinal axis lying in that direction, but 

 rising towards the west-north-west, where gneiss comes to the 

 surface in the centre, flanked by the Cuyaba Slates which form the 

 centre of the anticlinal in the east-south-east. Outside these, but 

 with a distinctly smaller dip, are found the Corumba Limestone 

 (sometimes similar to that which occurs at Coimbra) and the Rizama 

 Sandstone. 2 Above are the Chapada Sandstones, patches of which 

 lie unconformably and almost horizontally on the denuded anti- 

 clinal of older rocks. The Cuyaba Slates he calls Silurian, the lime- 

 stone and Rizama Sandstone Devonian, and the Chapada Sandstones 



1 In the short time at my disposal in the Chapada I was unable to see this 

 fossiliferous bed. 



2 Sandstone also occurs at the base of the limestone. 



