THE AGE OF ANTHRACOLITHIC ROCKS 729 
raphy and the invertebrate fossils on the age of the rocks under the 
following seven heads: 
1. The physical conditions and climatic history of the Permian 
of America and Europe were similar. They were marked by the 
deposits of dolomites, limestones, gypsum, and red sediments on both 
continents. 
2. The upper Pennsylvanian sediments were in each case marked 
by a superabundance of Fusulinas, and by other similar faunal ele- 
ments. 
3. The fauna of the lower Permian—including the Artinsk 
is characterized by the development of a peculiar molluscan element 
and its dominance over the Molluscoidea. 
4. The general comparison of the elements in common in the 
upper Pennsylvanian faunas indicates that Series III is as young as 
the uppermost Carboniferous faunas of Europe. 
5. The great reduction of Pennsylvanian species near the close 
of Series III and the base of Series IV, together with the introduction 
of species in the basal part of Series IV which become very important 
and characteristic elements in the faunas of the higher rocks, seems 
to justify the provisional location of the Pennsylvanian-Permian 
boundary at the base of Series IV. 
6. The general similarity of the faunas of Series IV and the over- 
lying rocks of the Kansas basin with the Permian of Europe seems to 
be suggestive of their homotaxy. 
7. The extent of Permian time represented in the Texas Panhandle 
region by the unconformity of the Permian Red Beds and the Triassic 
Dockum beds is unknown. 
What the final evidence of the fossil vertebrates and plants may 
be remains, to some extent, to be determined. With the rapid prog- 
ress now being made in the study of the former on both continents 
and the rapid collection of the plants now in progress in the western 
Mississippi basin, we may look in the near future to a fuller determi- 
nation of the homotaxy of American and European Permian. In 
the meantime I am inclined to take the evidence of the physical 
conditions and the invertebrate fossils at its face value and draw the 
conclusions in accordance with it. 
