728 CHARLES SCHUCHERT 



In the valley of the Trombetas this series rests unconformably 

 upon felsite or eurite (6:145). It 



consists almost exclusively of hard argillaceous and micaceous [variously colored, 

 white, yellow, red, and purple] sandstones, generally thin bedded, but with some 



massive beds of pure sandstone One set of beds of cherty schist, about 



20 feet thick, is found at the base of the series, in contact with syenite Just 



above the cherty rocks there is a bed of fine-grained, yellowish sandstone contain- 

 ing a few fossils (6:168). 



These fossils, according to Clarke (5), are of the following species, 

 restricted to Brazil: Lingulops derbyi, Orhiculoidea hartti, Pholidops 

 trombetana, Orthis callactis amazonica, Dalmanella freitana, D. 

 smithij Chonetes cf. novascoticus^ Anabia paraia, Anodontopsis putilla, 

 A. austrina, Tellinomya pulchella, T. subrecta, Clidophorus brazil- 

 ianus, Bucaniella trilobata viromundo, Tentaculites trombetensis, 

 Conularia amazonica^ Primitia minuta, Bollia lata brasiliensis. 



In higher beds occurs Arthrophycus alleghaniensis. 



Clarke (5) regards this fauna as transitional between Ordovicic 

 and Siluric or Middle Siluric, but quite different from that of the 

 island of Anticosti. Derby (6:168) states that it indicates "a close 

 correspondence with the Medina sandstone." Katzer refers it to 

 the lower portion of the Siluric. 



The correlations of these authors are harmonious, but the question 

 is raised: What is meant by transitional between Ordovicic and Sil- 

 uric? In other words, is the Brazihan Siluric fauna comparable 

 with the Medina of the Appalachian region or with the Middle Siluric 

 of Anticosti ? Nothing definite can be said in regard to Anticosti 

 Divisions i and 2, as these faunas need to be restudied in the Hght 

 of modem knowledge. In regard to the Medina no new reading 

 could be given, were it not for considerable evidence gathered by 

 Ulrich in the Mississippi valley from Iowa south into Arkansas, 

 and as yet unpublished. Underlying unmistakable CHnton faunas 

 of the Interior type (Dayton, Ohio) he has found a zone usually 

 quite thin and intimately connected with the highest Ordovicic or 

 the uppermost Richmond member of the Cincinnatian division. In 

 this zone, near Edgewood, Mo. , Ulrich has collected a Stromatoporoid 

 of Siluric character, Zaphrentis n. sp. , Favosites near asper, Calapoecia 

 canadensis^ Tentaculites incurvus, Dalmanella of the meeki or jugosa 



