2 jS 
The Ohio Naturalist. 
[Vol. XI, No. 4, 
A more recent, although less detailed section of the Maecuru 
valley is given by Friedrich Katzer 22 as follows: 
Carboniferous. 
Unconformity. 
Devonian. 
6. Black shale. 
5. Red micaceous sandstone. The upper fossil-bearing horizon. 
4. Darker sandstone. 
3. Homstone. 
2. Spirifer sandstone. The principal fossil-bearing horizon. 
1. Thin-bedded sandstone interbedded with shale. 
Silurian. 
Mr. Schuehert makes the hornstone of the above section the 
dividing line between the lower and upper Devonian 23 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 Katzer. 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 Maecuru 
group, as indicated by the few fossils collected. The same hori- 
zon is reported from Parana 24 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 
gypsum-bearing red sandstones of the Cretaceous. The Devonian 
is overlain by Carboniferous only in the northern part of Bolivia. 25 
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. 26 
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 grayvvackes 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. Grundzuge der Geologie 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 fur Mineralogie, Geologie, und 
Palaeontologie, Vol. 25 (Beilage Band), 1908, pp. 574, 575. 
26. Steinmann, Gustav, Am. Nat., Vol. 25, p. 856. 
