Lisboa — Permian Geology of Northern Brazil. 429 



3. Lowlands of the Parnahyba. — In the region of the Par- 

 nahyba river in the states of Maranhao and Piauhy, silicified 

 dicotyledonous woods occur very abundantly and usually asso- 

 ciated with conifers or with Psaronius. Along the channel 

 of the Parnahyba specimens were found in the high banks of 

 the lowlands which border the river. 



Whenever it was possible to determine the conditions of the 

 peculiar association it was found that these silichications occur 

 in a recent conglomerate, in which I could identify, with cer- 

 tainty, detritus or pebbles of rocks from the different strata of 

 the region, ranging from the Permian up. These woods show 

 by their rounded surfaces, positive signs of transportation. I 

 found with them on the surface of ground trunks of dicotyle- 

 dons which I believe to be Permian, but without any traces of 

 rounding through erosion, or indicating, at most, very little 

 transportation. 



This is explained by the occurrence of Cretaceous chapadas 

 very near the river and probably covering the Permian sedi- 

 ments. The slight erosion due to transportation for a short 

 distance is sufficient explanation of the occurrence of these 

 silicifications on the bank of the river and above the Permian. 

 The dicotyledonous trunks showing evidence of an almost 

 imperceptible amount of transportation which are found at 

 Pedras, twenty-four kilometers south of Floriano, lie in a 

 residuary sandy soil derived from the Permian sandstone. 



Under the circumstances above described fossil dicotyledon- 

 ous woods occur in the following localities : 



{a) Surubi on the Parnahyba river, between the " grota do 

 Mendes'' and Floriano, close to a sheet of compact diabase. 



(b) Pedras, twenty-four kilometers south of Floriano, on 

 the Maranhao bank of the Parnahyba. 



(<?) In the vicinity of Floriano on the Maranhao bank of 

 the Parnahyba. 



(d) Alagoas, five leagues from Amarante (?) (Specimens 

 donated and the location doubtful.) 



(e) Neighborhood of Amarante in Piauhy. 



(f) Logoa near Floriano on the Maranhao bank of the 

 Parnahyba river. 



Gymnosperm phanerogams. 



(a) Conifers. Trunks of conifers in the " grota do Mendes," 

 associated with Psaronius. These were collected by me from 

 a gray sandstone directly overlying marly calcareous disinte- 

 grating shales along the bank of the Parnahyba. There is no 

 doubt that these fossils were collected in their original resting 

 place. 



