84 The American Geologist. August, 1903 
per Devonian is a fauna closely related in its species with the 
Upper Devonian of western Europe, Russia, Siberia, China and 
Britisli America, and down ~s far as Iowa in the interior the 
Nevada Devonian also showing close affinities with this type. 
But in western Europe, where the statistics are abundant 
and clear, and. -1 1 far as evidence bore on the case, also in Rus- 
sia. Asia and British America, the Cuboides fauna is the natural 
successor of the middle and lower Devonian of those regions. 
In his view, therefore, the Upper Devonian fauna of Appal- 
achia is descended from a fauna which migrated into the reg- 
ion at the close of the Hamilton period from the northwest, and 
which had previously occupied not only the northwest part of 
this continent, but also Siberia, Russia, China, etc. The earlier 
fauna which these immigrants in part displaced was connected 
with and descended from one which occupied South America, 
the Faulkland isles. South Africa and possibly some part of 
Europe. He thus separates the Devonian into two areas, one 
chiefly in the southern hemisphere, extending from South 
America to Africa, and the other mainly in the northern hemi- 
sphere, extending from the region of the upper Missouri, or at 
least from the Mackenzie river, across Asia to Europe. He fur- 
ther inclines to the belief that in the earlier part of the Devonian 
period the Appalachian area was tenanted by the fauna of the 
former, which in the latter part of the same period was in great 
part displaced by that of the latter. 
Professor Williams proceeds to strengthen his position by 
showing that, at the end of the Hamilton period, elevation took 
place in the southern part of Xorth America, whereby a land 
barrier was brought into existence that cut off the Appalachian 
region from the former connection with the South American 
area, thus isolating its fauna from its ancestral stem and near 
relatives, and exposing it to competition with the Eurasian 
fauna threatening it from the northwest and. which, in the 
struggle which ensued, succeeded in largely supplanting it in its 
old home during Upper Devonian days. 
Conclusions so momentous, should they be altogether con- 
firmed and established by the further study of their author or 
of other geologists, will constitute one of the most important 
steps in the study of the American Devonian that have been thus 
far taken. 
