342 Methods of Stratigraphy. — Winchell. 
left valve ; 9, a left valve, showing (like fig. 9) a faint oblique sulcus 
on the posterior lobe. 
10-13. Bollia ungula (Claypole MS.) Internal casts. Magn. 15 
diam. 
14. Klcidenia simplex, Bp. nov. Internal cast of right valve, x 15 
diam. 
15. Primitia pennsylvanica, sp. nov. a, internal castof a left valve ; 
b, edge vievi'; x 15 diam. 
Fig. 14: is from the mottled Devonian limestone shale at King's Mill, 
Perrv countv, Pa. 
Figs. 1, 2," 10, 11, 12, 13 and 15 are from the bufi" shale of the Marcel- 
lus limestone of Perry county, Pa. 
Figs. 3, 4, 5, 6, 7, 8 and 9 are from the dark-gray Lower Helderberg 
limestone of Perry county, Pa. 
METHODS OF STRATIGRAPHY IN STUDYING THE 
HURONIAN. 
Written for the Madison meeting of the Western Society of Naturalists, Oct. 24, 1889. 
N. H. Winchell. 
CONTENTS. 
. What is the Huronian? • 
Its description by Mnrray, Logan -nd Hunt. 
" " " Bigsby and T. Sterry Hunt. 
" " " the officers of the present Canadian geological survey. 
Principles of stratigraphy employed by Murray, Logan and Hunt. 
'' " " " " Bigsby and Hunt. 
" " " " " the present Canadian survey. 
The new departure necessary. Why? 
The methods of the new departure. 
The elements of the new departure. 
The application of the new method. Bonney, Irving, Lawson, the Minnesota 
survey. 
The results"of the new mpthod. 
Recoustruction of the Huronian. 
Treatment of correlated terranes. 
Recent work in the Archaean rocks in the Northwest has 
shown that the Huronian system has been variously under- 
stood by geologists working in the different states and in the 
Dominion of Canada. This difference of understanding con- 
cerning an important series of strata of the earth's crust, 
resulting in differences of nomenclature, prompts me to offer 
to the Society some remarks on the methods pursued by the 
different investigators, and a comparison of them and their 
results with the methods and results arrived at by more recent 
research. 
What is the Huronian? It will be in accordance with the 
equities of scientific nomenclature to accept the definition of 
the Huronian as given by the originators of the name as they 
finally left it. It was first named by Sir Wm. Logan and Dr. 
T. Sterry Hunt jointly, in a small pamphlet published in 
