694 SCHUCHERT AND TWENHOFEL— ORDOVICIC-SILURIC SECTION 



the nature of the contact nothing is known, nor is anything known con- 

 cerning the lower formation upon which it rests. For these reasons it is 

 proposed to call it the Macastey black shale, so as not to confound it with 

 the Utica black shale with which it has been correlated. 



The shale has the physical character of the typical Utica — that is, a 

 black, highly carbonaceous material here rich in fossils, but of few spe- 

 cies, some of which are replaced by iron sulphide. The common fossils 

 are Climacograptus hicornis, C. n. sp. near typicalis, Leptobolus insignis, 

 Endoceras proteiforme^ and Triarthrus spinosus. 



Correlation. — At first sight this little biota and the character of the 

 black shale gives one the impression that it is of the time of the Utica for- 

 mation of New York. While some of the species obtained are also found 

 in the typical Utica, others have not been found in JSTew York. The ab- 

 sence of Triarthrus hecki, the common trilobite of this horizon, is sus- 

 picious, and raises the question whether the Macastey black shale may not 

 be of later time. At Ottawa^ Canada, the "Utica" has Asaphus canaden- 

 sis associated with Triarthrus spinosus, and these underlie shales of the 

 "Hudson Eiver," which have, among other fossils, Catazyga headi. On 

 Anticosti a local variety of the latter, C. anticostiensis, is associated with 

 an undoubted Eichmondian fauna, and as the genus Catazyga is unknown 

 in older strata, the writers are led to believe that the Macastey black shale 

 may also be of Eichmondian time. The "Hudson Eiver" shales are very 

 widely distributed in the Saint Lawrence Valley, and at several widely 

 separated places have yielded either Catazyga or Beatricea (Ottawa, 

 Three Elvers, Lake Saint John), genera that unmistakably point to Eich- 

 mondian time. The writers are therefore led to believe that the Macastey 

 black shale is rather of early Eichmondian than of late Mohawkian or 

 Utica time. 



GINCINNATIG SYSTEM. BICHMONDIAN SERIES 



General discussion of the series. — The visible strata of Anticosti, not 

 less than 2,372 feet in thickness, are apparently of one uninterrupted 

 sequence, beginning early in Eichmondian time and persisting into what 

 appears to be the equivalent of the Eochester stage of the Siluric. It will 

 be shown that the faunas of the lower 1,139 feet are those known else- 

 where in part as the Eichmondian, while the upper 1,233 feet have the 

 early Siluric aspect, and form a series of deposits to which Billings ap- 

 plied the term "Anticosti group," here changed to Anticostian series 

 (= Niagaran) in conformity with modern usage. 



According to Eichardson, the combined thickness of the strata of Anti- 

 costi is 2,321 feet, and the authors' restudy of his careful work determines 



