278 The Ohio Naturalist. [Vol. XI, No. 4, 



A more recent, although less detailed section of the Maccurti 

 valley is given by Fricdrich Katzer-- as follows: 



Carboniferous. 



Unconlormity. 

 Devonian. 



6. Black shale. 



5. Red micaceous sandstone. The upper fossil-bearing horizon. 



4. Darker sandstone. 



.3. Hornstone. 



2. Spirifer sandstone. The principal fossil-bearing horizon. 



1. Thin-bedded sandstone interbedded with shale. 

 vSilurian. 



Mr. vSchuchert makes the hornstone of the above section the 

 dividing line between the lower and tipper Devonian-''' of the 

 lower Amazon and on the basis of fossils refers that below to the 

 age of the Oriskany and that above to Hamilton. In this he 

 follows Katzcr. The Devonian of this region is frequently faulted, 

 but only slightly folded and often cut by diabase dikes. In the 

 province of Mato Grasso the horizon of the Devonian exposed is 

 not known but it is probably that of the lower part of the Maecuni 

 group, as indicated by the few fossils collected. The same hori- 

 zon is reported from Parana-'* where the deposits are principally 

 brown and black shales. 



The Devonian of Bolivia, east of Lake Titicaca, consists prin- 

 cipally of yellowish to gray sandstones and black shales. Only 

 in the strongly folded part of the Cordillera does the rock take on 

 a graywacke character. The Devonian is easily distinguished 

 from the underlying Silurian by its never failing mica content, 

 and by its normal sedimentation from the overlying salt and 

 gypstmi-bearing red sandstones of the Cretaceous. The Devonian 

 is overlain by Carboniferous only in the northern part of Bolivia.^^ 

 These rocks are all highly fossiliferous and are thought to repre- 

 sent the Oriskany sandstone, the Onondaga limestone and the 

 Hamilton beds of North America.-'' 



In Argentine the Devonian is well exposed in the region of 

 Rio del Jachal. On the east side of the river the system is 400 

 meters thick and consists of 200 meters of unfossiliferous shales, 

 above which lies 200 meters of shales and gra>"wackes with three 

 fossiliferous horizons. To the west of the Jachal two other out- 

 crops occur. Here the Devonian consists of 2,000 to 3,000 meters 



22. Grundziige der Geologic des Amazonasgiebetes. 1903 (Leipzig), p. 

 191. 



23. Jour. Geol., Vol. XIV, 1906, p. 731. 



24. Thomas, Ivor, loc. cit., p. 238. 



25. Knod, Reinhold, Neues Jahrbuch ftir Mineralogie, Geologie, und 

 Palaeontologie, Vol. 25 (Beilage Band), 1908, pp. 574, 575. 



26. Steinmann, Gustav, Am. Nat., Vol. 25, p. 856. 



