106 
IOWA ACADEMY OF SCIENCE Vor. XXIX, 1922 
really neither. A time signification of Periodic proportions was 
not possible because it would have to be applied in world-wide 
sense. For the present, at least, and perhaps for all time, the 
term cannot be expected to hold time valuation. With a provincial 
serial rank it leaves no room for real series; and there are many. 
An intermediary “group” is not only unnecessary, but burdensome, 
and serves no useful purpose. In our Continental interior, for 
example, there are no less than five rock series which, already 
well established, must eventually be accepted as valid. All are to 
be resolved out of the Coal Measures, or so-called Pennsylvanian 
section. 
In the larger sense the time-value of the Pennsylvanian is much 
too long; in the lesser sense it is much too short. According to 
most approved canons of modern nomenclature the title seems to 
have no taxonomic claims. In view of all of these circumstances 
the old name still has useful mission; the later term none. It is 
today one of the chief drawbacks to taxonomic progress in this 
country, for the principle is far-reaching. Until the term is 
dropped from our system of nomenclature the diastrophic aspects 
of Coal Measures stratigraphy are likely to be continually mis- 
interpreted and true advancement made impossible. 
