86 



horizon, although not usually well preserved. The more 

 common fossils are: — 



Escharopora ramosa (Ulrich). 

 Homotrypella instabilis Ulrich. 

 Monticulipora sp. 

 Rhinidictya fidelis (Ulrich). 

 Rhinidictya mutabilis ( Ulrich) . 

 Rhinidictya nicholsoni Ulrich. 

 Rhinidictya trentonensis (Ulrich). 

 Dalmanella cf. subsequata group 

 Rhynchotrema ainsliei N. H. Winchell. 

 Actinoceras bigsbyi (Stokes). 

 Bathyurus sp. 



Black River Limestones. — Overlying the Leray 

 division of the Lowville are darker limestones correspond- 

 ing approximately to the Watertown limestones of New- 

 York and the Decorah shales of Minnesota. These are 

 the beds to which formerly the term "Black River" was 

 restricted, and these are the beds which present the best 

 facilities for collecting. The lower part of the section, 

 80 feet (24 m ) thick, with Columnaria halli, Nicholson, 

 and a species of Stromato cerium, is exposed for a mile south 

 of Swift Current. The upper part of the section occupies 

 the remainder of the distance across Cloche island. The 

 dip of these strata changes constantly, owing to their 

 deposition among the ranges of Huronian quartzites and 

 schists. The angle is so low and variable that it is im- 

 possible to determine, even approximately, the thickness 

 of the various formations. 



Species occurring only in the lower beds of the Black 

 River : — 



Stromatocerium rugosum Hall. 



Columnaria halli Nicholson. 

 Species occurring in the upper half of the Black 

 River; the forms marked * occur only at the top: — 

 *Calapcecia canadensis Billings. 

 *Columnaria alveolata Goldfuss. 

 *Petraia aperta Billings. 

 *Protarea vetusta Hall, Billings. 



Receptaculites occidentalis Salter. 



Solenopora compacta Billings. 



