482 THE JOURNAL OF GEOLOGY. 



ing members have been recognized, the faunas of which are dis- 

 criminated in the annexed table. The characteristic feature is a 

 blue amorphous limestone containing beautifully preserved silici- 

 fied fossils which, by the decay of the limestone where washed 

 by the river, become dissolved out of the rock and accumulated 

 on the beach. Similar limestone cavern and beach specimens 

 are reported by Mr. Chandless and the late Major Joao Martins 

 da Silva Coutinho, the companion of Agassiz and first discoverer 

 of fossils on the Amazonas, at Pedra do Barco and Frutal on the 

 Maueassu, a small river between the Tapajos and Madeira. 



The localities on the northern side have been examined by 

 the writer at the Serra de Tajauri near Monte Alegre, and on two 

 small lakes, Araptou and Abui, in the flood plain of the Trom- 

 betas at the margin of the highlands; by Mr. H. H. Smith on 

 the Curua and in the district about Alemquer between that river 

 and the Maecuru, while the occurrence of beach-worn fossils 

 similar to those of the Tapajos has been reported by the Brazil- 

 ian botanist Barbosa Rodregues on the Uatuma, a small river 

 between the Trombetas and the Rio Negro. At the Serra de 

 Tajauri, at Lake Cujubim (bed No. 3 of Mr. Smith's section) in 

 the Alemquer district and Lake Abui on the Trombetas, limestone 

 with silicified fossils occurs ; at Praia Grande on the Curua, beach 

 specimens similar to those at Itaituba ; at Lake Curucaca and 

 Cujubim (Nos. 5, 8, and 9) in the Alemquer district, Pacoval on 

 the Curua and Lakes Arapicu and Abui on the Trombetas, shales 

 with fossils. Those from the Trombetas are apparently decom- 

 posed limestones and are associated with flints like those of Itai- 

 tuba, which are also represented with chance specimens from 

 one or two other Trombetas localities. 



To the Cretaceous is referred the disturbed sandstone mass 

 with fossil leaves of the Serra de Erere, and a similar mass, in 

 which, however, no fossils have been found, near Obydos, and to 

 the Tertiary, the low plateau (100 meters more or less) of hori- 

 zontal sands and clays back of Santarem on the Tapajos, the 

 denuded ridges of Monte Alegre and Obydos and the high pla- 

 teaus (300 meters more or less) on the Curua and Maecuru, which 



