196 REPORT OF THE AMERICAN COMMITTEE. 
finds tlie litliology to warrant, and by auotlier so far as lie finds 
the paleontology to warrant. 
There are, hence, two laws by which wc mnst be governed in 
framing a scheme of nomenclature which shall allow the freest 
rein both to the stratigraphic geologist and to the paleontologist. 
One relates to the work of the stratigrapher, who takes account 
of the great physical changes to which the earth's surface has 
been subjected, and the other refers to the work of the paleon- 
tologist who strives to delineate the organic changes which the 
surface of the earth has witnessed. These changes have been 
supposed to be coeval and coextensive; but our investigations 
show they have not been so entirely. But we sometimes have 
the same fauna, or nearly the same, living under different cir- 
cumstances and, perhaps, also at different dates in different parts 
of the world. 
So long as the geology of the United States, for instance, was 
known accurately in only one part (New York State) the faunal 
characters which the formations were found to exhibit were seen 
to be coincident with the stratigraphic to so great an extent that 
there was no reason to dissociate them under separate schemes ; 
but since the whole area of the United States is being brought 
under careful examination, it is found that the close connection 
which these two classes of characters have in New York State is 
broken up and they begin to diverge gradually in various places 
and in different ways. The same experience is found, to a greater 
or less extent, as any local terms are extended from any of the 
states into those contiguous. This plainly shows that unless there 
be allowed great freedom to vary from the scheme adopted for 
stratigraphic designations, any nomenclature which the Committee 
or the International Congress may adopt, will be but a short-lived 
experiment. 
It will obviate all this confusion if the suggestion of Prof. 
H. S. Williams be adopted, and one set of names be chosen for 
the lithological characters and another for the faunal. 
The stratigraphic terms should be wholly geographic and 
should be allowed to change as often as local geologists deem it is 
necessary. The faunal terms should be very broad in their scope 
at the outset, and subdivisions should be introduced as fast as the 
special sub-faunas are discovered and defined. 
In makina: recommendations of the followino- table of nomen- 
