Ulrich—Paleozoic Systems in Wisconsin. 
79 
Although this classification was regarded from the beginning 
as a merely preliminary effort to bring order out of the confusion 
that had previously prevailed in the published accounts of the 
Cambrian sequence in the Upper Mississippi Valley it has in the 
main proved a serviceable and reliable guide in the work during 
the past nine years. With unimportant modifications, except in 
the matter of much added detail that had accumulated in the mean¬ 
time, the same classification was used in 1919 by Twenhofel and 
Thwaites.^ Also in 1920 and 1922^*^ by the writer, who on these 
occasions introduced a new formation—the Mazomanie sandstone 
—that had previously been regarded as the eastern representative 
of the Franconia but is now known to be a distinct formation that 
wedges in from the east in Wisconsin between the top of the Fran¬ 
conia and the base of the St. Lawrence limestone. 
Knowledge of the lower Paleozoic section in Wisconsin and 
neighboring states having reached the stage where I feel war¬ 
ranted in presenting my final opinions concerning the formations 
and their classification, it seems desirable and important to subject 
the names of the formations to critical scrutiny as well as the strata 
themselves. The only nomenclatural change of importance that has 
been suggested by these inquiries is the proposed substitution of 
the new name Trempealeau formation for the beds that I had pre¬ 
viously called St. Lawrence. The need for this change was first in¬ 
dicated when I sought an appropriate geographic name for the 
member to which Twenhofel and Thwaites had applied the desig¬ 
nation ‘‘Calcareous beds” and found that the concerned member 
is actually the bed to which Winchell had originally applied the 
name St. Lawrence limestone. Under the circumstance I felt un¬ 
willing to propose a new name for this member; and this unwilling¬ 
ness persisted even when it became obvious that my refusal neces¬ 
sitated the proposal of a new name for the formation of which 
the St. Lawrence limestone is a member. On the other hand, how¬ 
ever, the proposal of a new name for the broader unit clears up 
most of the confusion that at present attends the term St. Law¬ 
rence. That this confusion is very real is most clearly indicated 
in tabular form. 
® Twenhofel, W. H., and Thwaites, F. T., The Paleozoic section of the Tpmah and 
Sparta quadrangles. Jour. Geol,, vol. 27, p. 616, 1919. 
Ulrich, E. O., Major causes of land and sea oscillations. Washington Acad. Sci. 
Jour., vol. 10, pp. 74-76, 1920, and reprint of same in Ann. Rept. Smith. Instit., pp. 
333-335, 1922. 
