BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 13, pp. 149-186 June 13, 1902 



HAMILTON GROUP OF THEDFORD, ONTARIO 



BY HERVEY W. SHIMER AND AMADEUS W. GRABAU 



{Presented before the Society December 31, 1901) 

 CONTENTS 



Page 



Introduction , . 149 



Descriptions of the sections 1 50 



In general 150 



Section A— Thedford 150 



Section B 152 



Section C — Brickyard 153 



Section D — Eock glen 154 



Section E — Bartletts mills 157 



Discussion and correlation 159 



Discussion 159 



Correlation with Hamilton beds of Eighteen-mile creek, New York 163 



Notes on some of the Hamilton species from Thedford and vicinity 167 



Ceratopora intermedia (Nicholson) and C. nobilis (Nicholson) 167 



Heliophyllum lialli E. and H 167 



Leiorhynchus multicostus Hall, L. laura Billings, and L. huronensis Nichol- 

 son 168 



Spirifer mucronatus var. arkonensis var. nov 170 



Spirifer mucronatus var. thedfordensis var. nov 171 



Platyceras arhonense sp. nov 176 



Platyceras subspinosum Hall , 177 



Platyceras thetis Hall 179 



Platyceras bucculentum Hall 179 



Platyceras quinquesinuatum Ulrich 179 



Table showing distribution of species in the Thedford region 179 



Literature of the subject 186 



Introduction 



The following notes on the stratigraphic and faunal succession in the 

 Hamilton group of the Thedford region were made during a short visit 

 to that locality in the summer of 1901. They are intended merely as a 

 contribution to the geology of that well known and often visited region, 



XXIII— Bull. Gkol. Soc. Am., Vol. 13. 1901 (149) 



