106 Wisconsin Academy of Sciences, Arts, and Letters, 
northeast side against the beaches and low coastal plains of land 
areas then prevailing over and beyond the area of Michigan. The 
Lower Ozarkian seas, on the other hand, shallowed to beaches on 
the west side where seas with abundant life had prevailed in the 
preceding period. These suggestions are raised to the status of 
practically demonstrated facts when the distribution and origin of 
their respective faunas is carefully taken into account. Unpub¬ 
lished studies of Cambrian faunas have reached the point where 
we can say definitely that direct marine connections existed re¬ 
peatedly and perhaps continuously between the Cambrian seas of 
the Upper Mississippi Valley and those of Wyoming and Montana 
and Oklahoma and central Texas. Indeed, there is no reason to 
doubt that the most characteristic genera and species of the Cam¬ 
brian faunas found in the Upper Mississippi region migrated here 
from the west and southwest. But the case with respect to the 
Lower Ozarkian faunas of Wisconsin is totally different. These 
are like and must have been in communication with the Potsdam 
and Hoyt faunas of New York and, by extension of colonies south¬ 
wardly, with Missouri. Moreover, the Lower Ozarkian faunas in 
the Mississippi Valley and New York are almost totally different 
from those of similar age in the Cordilleran province. The latter 
evidently invaded from the Arctic side of the continent. 
The facts here presented in brief outline in support of the re¬ 
puted high taxonomic importance of the break between the Cam¬ 
brian and Ozarkian systems might by themselves be accepted as 
sufficient proof of the author’s contention regarding the actual dis¬ 
tinctness of the two systems. But it is unnecessary to be satisfied 
with the data supplied by Wisconsin localities alone. Other and 
many of them mucn more convincing data have been procured from 
other parts of North America. In fact, the Ozarkian is very in¬ 
completely represented in Wisconsin. A fuller sequence of its de¬ 
posits is found in the Ozark Uplift of Missouri and Arkansas. But 
very much thicker deposits of this period have been observed and 
carefully studied in the Appalachian Valley region. There, par¬ 
ticularly in central Pennsylvania and central Alabama, Upper 
Cambrian deposits consisting largely of limestone and aggregating 
thousands of feet in thickness are succeeded unconformably by 
Lower Ozarkian dolomites and relatively pure limestones that 
measure as much as 2,000 feet or more in a single completely ex¬ 
posed section. On these, then, rest thousands of feet of Middle and 
Upper Ozarkian limestones and dolomites giving a total volume of 
