284 C. SCHUCHERT MEDINA AND CATAKACT FORMATIONS 



XPlectorthis mediuaeusis Grabau (uom. luul.).'- Niajjara River Gorge. 

 Is probably one of the two following species of Hehertella. 



h*Hel)ertella fausta (Foerste). This Brassfield form also occurs in the 

 Manitoulin member, 



h*Eelertella cf. daytonensis (Foerste). This Brassfield form may also 

 occur in the Manitoulin member. 



h-\-Platystrophia hiforata (Schlotheim). Common in Manitoulin member. 



h+Plectamdoiiites transversaUs (Wahlenberg). At times common in 

 Manitoulin member, as at Hamilton. 



h-\-LeptcBna rhomhoidalis (Wilckens). Of wide distribution throughout 

 the two upper members of the Cataract. 



h+Schuchertella suhplana (Conrad). This Siluric form also occurs rather 

 rarely in the Manitoulin member. 



*Atrypa, n. sp. This large and fine multistriate form of the A. margindUs 

 group occurs in the Manitoulin member at many localities, especially 

 at Dimdas. 



H — \-Atrypa rugosa Hall ? A form similar to this species occurs at many 

 localities in the Manitoulin member. 



*Ccelospira planoconvexa (Hall). Originals from Flamborough Head as 

 Atrypa planoconvexa. Restricted to Manitoulin member and the best 

 guide to the Cataract. 



Whitfleldella, 2 sp. A small form that is common in the Manitoulin mem- 

 ber. Another larger form is less often seen and has been identified 

 as W. naviformis, a Clinton species of New York. 



m* Whit field ella cf. ohlata (Hall). This may be the Upper Medina W. 

 ohlata. It occurs rarely in the Manitoulin and Cabots Head members 

 at Cataract and Stony Creek. 



XHyattidina congesta (Conrad). Hall (1852) identifies this form as 

 Atrypa congesta, from Flamborough Head. As no one has since seen 

 this fossil in the Cataract, it seems probable that an error was made 

 here. In the lower Manitoulin at Hamilton occurs a Whitfieldella 

 that may have been identified as that form. As Hy at ella is preoccu- 

 pied, Schuchert in 1913 changed it to Hyattidina. 



jn-\-Camarot€cchla neglecta (Hall). This widely distributed form is com- 

 mon throughout the two upper members of the Cataract. 



*Camarotcechia janea (Billings). In Manitoulin member, Manitowaning. 



-j-Uncinulus stricl-landi (Sowerby)." Niagara River Gorge. In all prob- 

 ability not the higher Siluric U. stricl'landi. 

 Pelecypoda : 



jn*Modiolopsis (?) orthonota (Conrad). This Medina form also occurs at 

 the top of the Whirlpool member and in the Manitoulin. 



m*Ftermea (?) primigenia (Conrad). This Medina species is also in the 

 upper part of the Cabots Head member. 

 Gastropoda : • 



-\-Cyclonema cancellatum (Hall). This Clinton form also occurs in the 

 Manitoulin member of the Cataract. 



"Loc. cit. 



" Grabau : Loc. cit. 



