a F. Hartt on Amazonian Drift. 295 



beds dip to the southeastward (approximately), with an angle 

 in some places of 15 or 20°. 

 On the northern side of the sen-a and extending close up to 



shaly sandstones, shales, and cherty heds, quite horizontal. mkI 

 not participating in the disturbance which the strata ol the 

 serra have suffered. These beds contain trilobites of the geini- 

 Dalmanites^ with species of Spirifer, Orthisina, Chonetesf, D/.^C'iui, 

 Lingula^ Leptoccelia, Tentaculites, &c. Specimens of these have 

 been submitted to Prof Hall who writes me that they indicate 

 a horizon equivalent to the Upper Helderberg. The conclusion 

 seems inevitable that the serra is pre-Devonian in age. The 

 Devonian rocks of the plain are broken through by a perfect net 

 work of dikes of trap now decomposed. The end of a curious 

 low ridge that runs off at right angles from the sen-a consists 

 of a large mass of trap. This has given rise to a great num- 

 ber of boulders of decomposition which lie on the surface or are 

 buried in decomposed rock. They have been carried down 

 the beds of torrents but they are nowhere erratics. To speak 

 broadly, I did not see either at Erere or in any part of the 

 Amazonas, anything that would suggest glacial action. So far 

 as the province of Para is concerned, the clays, sands, &c. form- 

 ing the lower lands are far from being uniformly distributed, 

 and are very puzzling to study. The arrangement of the mate- 

 rials varies in different regions, and many of the deposits are local 

 In part, the lower lands are formed from the wearing down ot 

 the great sheet of clays, &c., of which the Almeyrin 

 relics, in part they are of brackish or fresh \-^- ^^ 



1 when 



tmct epochs. Superficially examined they appear 

 versally distributed, but it is very far from being the e^^o^. ^^ ~ 

 impossible to recognize beds of clay in the Amazonian valley 

 simply from lithological characteristics. It is suflacient to say 

 that variegated clays of exactly the same appearance and struc- 

 ture, because formed of materials reworked or drawn from the 

 same source, occur in the Devonian, Carboniferous, Tertiary and 

 in half a dozen successive formations of recent tiinea 

 . I Have referred the beds of the table-topped hills to the ler- 

 tiary. Some of the clays and sandstones of the lower Amazo- 

 nas may also be later Tertiary ; but many are undoubtedly recent 

 ttiey are full of leaves of modern specie& Near bantarem i 

 found a bed of recent fresh water mussels, Owtafecw, Uyarea^, 

 l^nios, &c., whose upper limit was at least fifty, feet above the 

 level of the highest Amazonian floods. This is m exact accord 

 ;yith the facts I have given elsewhere-being on the late n e ot 

 tbe Brazilian coast, a rise which extended itself into the inte- 

 '^or. . Before this rise the land stood much lower than at present : 



