GEOLOGY OF THE LOWER AMAZON REGION 737 



Conclusion. — The present knowledge of the Amazon Devonic 

 stratigraphy and faunas indicates that the Maecurii formation is near 

 the top of the Lower Devonic, and is comparable with the North 

 American Oriskanian, not only in its facies, but also in its having six 

 of the guide fossils of the class Brachiopoda of the latter formation. 

 These facts indicate, further, that the two areas (Brazil and the 

 Oriskanian of the southern United States) were at this time in com- 

 munication. The northward extension of the Amazon Maecurii 

 fauna is known sparingly about Frog Mountain, Alabama, for here 

 occurs Spirifer arenosus, *5. murchisoni, and Amphigenia. This 

 fauna is better represented in the region of Armuchee, near Rome, 

 Georgia, as here are found ^Rhipidomella musculosa, Stropheodonta 

 magnifica^ Anoplotheca dichotoma, ^Spirifer tribulis, Amhocoelia 

 umbonata, and Meristella rostellata n. sp. The best of the southern 

 localities are in the Camden formation of Tennessee and southwestern 

 Illinois. The more important forms found at the last-named locali- 

 ties are Lingulopholis terminalis, Chonostrophia reversa, ^Anoplia 

 nucleata, Metaplasia pyxidata, *Spirifer tribulis, ^Anoplotheca flabel- 

 lites^ Eatonia peculiaris, ^Amphigenia curta, and Megalanteris condoni. 



The southern Oriskanian sea appears not to have connected 

 openly, but rather sparingly northward, either across western or 

 eastern Tennessee, with another basin of the same age whose deposits 

 are found in the Appalachian (Cumberland sea) — Gaspe region. 

 The northern basin is characterized by Edriocrinus, Hipparionyx 

 proximus, Spirifer arenosus, and Rensselaeria, none of which are in 

 the southern facies of the Oriskanian — the Camden- Armuchee-Frog- 

 Mountain-Maecurii faunas. On the other hand, this southern Oris- 

 kanian has Spirifer of the S. macro pleura type, Amphigenia, Tropido- 

 leptus (one species has been found in Maryland), Vitulina, Productella, 

 many pelecypods strongly reminding one of the American Middle 

 Devonic faunas, and Styliolina, that either do not occur in the north- 

 ern Oriskanian or make their appearance with the pronounced south- 

 ern invasion of Onondaga time. In other words, the Oriskanian of 

 the United States is not only an outgrowth of the Helderbergian fauna, 

 but also has received many migrants from the southwest Brazilian- 

 Pacific region and from the North Atlantic (Gaspe) along a path not 



*Either the same or a very closely related species also occurs in Brazil. 



