420 Extinct Pleistocene Mammals 



less area" of the state, as usually limited, but it is not as yet known 

 how much drift pertaining to some of the older epochs of the Glacial 

 period may still exist below the veneer of loam with which the region 

 is covered. There is a cor.spicuous terrace formation extending along 

 the Mississippi valley, which also ascends the tributary valleys, 

 meeting with a series of terraces which were of the same date but 

 which were formed from material derived from the west, brought down 

 the valleys by the rivers whose sources were within the glaciated area. 

 These conspicuous terraces are of the age of the Wisconsin epoch, and 

 doubtless contain materials derived for the most part from the Wis- 

 consin ice, but also embrace the wastage of the lowan loess, which 

 forms a surface mantle over the region. Indeed the lowan loess must 

 have suffered greatly from the action of the flooded streams of the 

 Wisconsin epoch. From present knowledge it is impossible to affirm 

 whether this skull dates from the lowan loess epoch or from the ter- 

 race epoch of the Wisconsin, although it seems to have been found in 

 a Wisconsin epoch terrace. 



The interesting and important fact however is this, — that the 

 musk ox occupied the region during either the loess epoch of the 

 lowan ice age, or the closing stage of the Wisconsin ice age. In either 

 case it implies that the climate was considerably colder than the 

 present climate, — a conclusiDU which is indicated also by the existence 

 of what we know only as an arctic animal in temperate latitudes. It 

 may be inferred that the Mississippi and its tributary gorges were a 

 favorite habitat for arctic spscies. 



The extinct musk-ox species, O. cavifrons, is regarded as specific- 

 ally different from the living musk-ox, O. moschatus, although the 

 latter is also regarded as the genetic descendant of the former. Like 

 the mammoth and the reindeer the musk-ox retreated southward as 

 the country became enveloped in ice on the approach of the Glacial 

 epoch, or successive epochs, so as to destroy his feeding grounds, and 

 on its retirement, probably in company with the Eskimo, followed the 

 ice border again to the arctic region. 



The remains of the musk-ox have been found at several places 

 further south, viz., in Iowa, Missouri, Arkansas, Oklahoma, Kentucky, 

 Ohio and West Virginia. These localities are all too far south to 

 suppose that the Wisconsin ice sheet was the prime cf.use of the 

 migration that brought the musk-ox into that latitude, but they might 

 be due to the incursion southward of the earlier lowan ice-sheet. This 

 leads us to refer the Minnesota specimen to the loess of the region 

 rather than to the terrace gravel of the Wisconsin. 



4. Bison (latifronsf) About a year ago I was shown a couple of 

 large fossil teeth by Mr. Edstrom, a student at the University, who had 

 procured them from the discoverer. They were found near Mora, in 

 Kanabec county, in Minnesota, in excavating for a drainage ditch. 

 They were below several feet of tenacious clay, and were embraced 

 in it. They are stained a dark brown, almost black, as teeth thus 

 buried are frequently known to be. They were associated with sev- 

 >eral other teeth, and bones, probably belonging to the same animal, 

 ibut the rest were scattered and lost. In the determination of the 

 species to which theso teeth belong I have been aided by Prof. S. W. 



