AMWIOSIRIUE AUN, (CYLCH AUIL TO IBIVOISIC TRS. Dye 
sheets of southeastern Minnesota, described many years ago by 
Professor N. H. Winchell.t The fauna and flora of this horizon 
have not yet been adequately worked out, but their general indi- 
cations are not unlike those of the Helvetian stage of Europe, as 
defined by Dr. Geikie. A tentative correlation of the two may 
therefore be made. 
The lowan formation (=Polandian?).—This embraces an 
extensive sheet of till lying upon the preceding interglacial 
deposits and having its best known expression in eastern Iowa, 
where it has been most carefully worked out by McGee. It is 
known to have considerable extension in adjoining states, but its 
full distribution is not yet ascertained. It is intimately asso- 
ciated with the most important of the loess deposits. In some 
places it appears to graduate at its edge into loess which spreads 
far away from its border. In other places, it seems to pass up 
by graduation into a loess mantle. To avoid misunderstanding 
it should be remarked that minor deposits of loess are associated 
with other sheets of drift, and loess is not necessarily character- 
istic of any horizon. The close association of the greatest loess 
deposits with the lowan formation is, however, significant of the 
conditions under which it was formed. 
The Iowan formation stands in a relation to the American 
series similar to that of the Polandian to the European series. 
It has, furthermore, similar characteristics in constitution and 
surface expression. I believe I am correct in saying that the 
chief loess deposits of south Germany and Russia are associated 
with the Polandian formation in much the same way that the 
chief loess of the Mississippi basin is associated with the Iowan 
deposits. In a tentative correlation, therefore, the Iowan and 
the Polandian formations may plausibly be regarded as equivalents. 
The Toronto formation (= Neudeckian ?).— Through the recent 
investigations of Coleman? and others, and the earlier studies of 
tN. H. WINCHELL: Proc. A. A. A. S., Vol. XXIV., 1875, Pt. II., pp. 43-56; Geol. 
Minn., Final Rep., Vol. I., 1884, pp. 313, 363, 390. 
2A. P. COLEMAN: Interglacial Fossils from the Don Valley, Toronto. Amer. 
Geologist., Vol. XIII., February, 1894, pp. 85-95. 
