84 HEMERAL DIVISIONS OF CLASSIFICATION 
Nomenclature of the Hemeral Divisions of Terranal 
Classification 
When in the interests of practical chartography it was decided 
to establish lithologic units for portrayal and to assign to such ac¬ 
cepted units geographic names it was thought that the main map¬ 
ping troubles of the geologist were over. Unlooked for compli¬ 
cations soon set in. Rock sequences which lithologically appeared 
to form compact and homogeneous sections sometimes revealed 
within themselves faunas of the most diverse aspects. A lith¬ 
ologic unit, with officially stamped title, frequently was discov¬ 
ered to carry two, three, or half a dozen assemblages of fossils . 
each of different geologic age. 
Since geologists generally seemed loath to give up the biotic 
criterion, which had been so firmly grounded in their natures, even 
after full realization of its practical shortcomings, and the indis¬ 
putable fact that it really indicated not a basis for rock classifica¬ 
tion but was merely a scheme of organic sequence, confusion soon 
arose from attempted use of a double standard. In the wild 
desire to multiply titles, such as would have done credit to paleon¬ 
tologists a generation ago, the fundamental principle in establish¬ 
ing practicable mapping units was not only soon lost sight of, but 
entered upon a new field of easily avoidable difficulties. 
In terranal classification the first grand division in \vhich rock 
units assume genetic import is the provincial series. In this con¬ 
nection its geologic age is of little consequence. Being made up 
of lithologic units, designated as formations or terranes, mapping 
becomes severely restricted to portraying them faithfully and 
with genetic expression. No grouping of them other than as pro¬ 
vincial series advances our knowledge of their taxonomy. An 
intermediate “Group” is as unessential as the proverbial fifth 
wheel of a wagon. Use of such intermediary rather carries with 
it the tacit admission of an entire want of knowledge concerning 
the taxonomic relations of the included lithologic units and forstalls 
the very object for which the mapping is initiated. Yet the prac¬ 
tice of instituting useless divisions in the columnar scheme gives 
large outlet to the passion for disfiguring terranal classification 
with new and strange names however unnecessary and burdensome 
they may be. 
