98 DR. J. W. EVAN'S ON THE [Feb. 1 894, 



9. Cretaceous (?) 

 Sandstone of the Taholeiros. 1 



According to Mr. Herbert H. Smith, (8) p. 63, this formation rests 

 on the Chapada Sandstone and is perfectly horizontal. It has yielded 

 vertebrate remains, among which Mr. Derby recognized a fragment 

 of a turtle's carapace and a vertebra of another reptile. Mr. Derby 

 says " it is possible, though not very probable," that these beds may 

 prove to be identical with the sandstone with augite-porphyrite 

 already referred to as possibly Triassic. He prefers, nevertheless, 

 to class them with the Cretaceous beds in Eastern Brazil, (8) p. 68. 

 It may be remarked that on the Purus, one of the southern tribu- 

 taries of the Amazonas, and on its tributary the Aquiry, Upper 

 Cretaceous beds with remains of turtle and Mosasaurus have been 

 found ; see (9) p. 494. 2 



VII. — 10. Quaternary. 

 High-level Surface-deposits. 



In the neighbourhood of Cuyaba and elsewhere, the Cuyaba Slates 

 are frequently covered with a thick ferruginous deposit, consisting 

 largely of pebbles of vein-quartz. The ferric oxide cement is 

 abundant, and scoriaceous aggregates of the same material also occur. 

 More or less laminated deposits of iron oxide are found on the 

 Chapada, sometimes in such quantity as to render the soil unfit for 

 vegetation. Ferric oxide is also widely distributed between the 

 hills at llizama and the river Paraguay, but I did not notice it 

 to any large extent on the Matto Shales. It is found in the neigh- 

 bourhood of the basaltic rocks at Tapirapuam. 3 Where these 

 ferruginous deposits ocexvr, there also goitre and cretinism prevail. 

 The rivers are usually highly charged with iron, the rock washed 

 by them being often coated with a black deposit of iron oxide. 



At Barra dos Bugres, high-level gravels occur in the hills some 

 20 metres (65 feet) above the Paraguay. The pebbles are exactly 

 similar to those found in the present river-bed. 



1 Taholeiros are flat-topped hills. 



2 ' Genera] Conto de Magalhaes speaks of the occurrence of fossil woods on 

 the same tableland,' (<S) p. 63. I found on the Chapada a fragment of ferru- 

 ginous material full of elongate ca-vities ; it certainly has the appearance of 

 wood, but was probably formed inorganically by the deposition of iron oxide. 

 Angiosperm wood occurs fossil near Coimbra, op. cit. p. 64. 



3 These ferruginous deposits are known in Brazil as canga. Mr. Derby 

 suggested in a letter to me that they were identical with the laterite of India. 

 This is, to a large extent, true ; but both terms are loosely employed. 



