IOWA CAMBRIC SUCCESSION 
321 
title, without geographic designation. Waukon Sandstone takes 
its name from the county seat of Allamakee County. In this 
vicinity the formation is well exposed. 
Irving’s names Madison Sandstone and Mendota Limestone 
are sometimes regarded as synomymous with “Jordan” (Waukon) 
Sandstone and St. Lawrence Limestone; but personal examina¬ 
tions of the type localities north and south of the city of Madison, 
do not seem to support this assumption. This view is also further 
and independently verified by F. W. Sardeson, many years ago, 
by means of extensive collections of fossils. These sections were 
visited in the summer of 1893, during the sessions of the Ameri¬ 
can Association for the Advancement of Science which were being 
held in the Wisconsin capital. In company with Professors Van 
Hise, Winchell, Calvin, Lonsdale and a number of others who 
were especially interested in this particular topic, I had oppor¬ 
tunity to inspect closely the stratigraphic relations of these forma¬ 
tions. At the time, I remember, it was concluded that the Madi¬ 
son division appeared to be composed of two distinct formations, 
of which one only might prove to be the so-called Jordan (Wau¬ 
kon) of the Iowa sections. The Mendota Dolomite was thought 
to be probably merely a local development. Sardeson believes it 
to be traceable to St. Lawrence, Minnesota. Recently Ulrich 
carries out the first suggestion further, by considering the place 
of the Mendota Dolomite to be between the Madison Sandstone 
and the so-called Jordan, or Waukon, Sandstone. Sardeson’s cor¬ 
relation that the Mendota and so-called St. Lawrence (Allama¬ 
kee) dolomites near Madison City are parts of the same terrane 
is accordingly certainly wrong. 
The Waukon Sandstone appears to be unrepresented along the 
Minnesota River. Elsewhere it is often masqued under the vague 
title of St. Croix sandstone. 
Were it not for the unfortunate circumstance that the title 
St. Lawrence Limestone was originally applied only to some of 
the upper layers of the main body of the Lower Magnesian lime¬ 
stone of Owen, and the further fact that in subsequent correla¬ 
tions wrong determinations were so often and so widely made, the 
38 Am. Jour. Sci., (3), Vol. IX, p. 441, 1875. 
39 Bull. Geol. Soc. America, Vol. XXVII, p. 460, 1916. 
40 Bull. Geol. Soc. America, Vol. VI, p. 172, 1895. 
