Observations on the Unification of Geological Nomenclature. 293 
Among the Crustacea, Dolichopterus extends to the Coal Measures, 
and Pterygotus is peculiar to it. 
Of the twenty genera that commenced an existence in this group, 
eleven never passed beyond it, three are known in the succeeding 
group of the Lower Devonian, three became extinct in higher groups 
of the Devonian, and the other three passed up into the Carboniferous. 
With this group we close the Upper Silurian, because we have here 
another great stratigraphical and palzontological break, and because 
we have arrived, as near as can be determined, at the top of the for- 
mation as established by Murchison. Out of 141 genera that com- 
menced an existence in this formation, 82 became extinct within it, or 
a much larger proportion than became extinct among the genera that 
arose in the Lower Silurian. The paleontological chasm is, therefore, 
wider between the Upper Silurian and the Devonian than it is between 
the Lower and Upper Silurian. 
In conclusion, it may be proper to remark, that among the genera 
from these formations there may be a few synonyms, and while 
numerous species will be added to the 3,560 that have been described, 
it is not probable that many genera will be added to those mentioned. 
I am not prepared to draw the comparison between the groups which 
have been thus established, in North America, and those within the 
same formations in Europe and other countries, because this must be 
done after great study of the variable specific characters, and an ex- 
haustive comparison of the species. If, however, 1 have broken the 
ice, in this regard, and furnished any assistance to others by calling 
attention to the distribution of the genera, it is all that can be ex- 
pected. 
THE PREHISTORIC MONUMENTS OF ANDERSON 
TOWNSHIP, HAMILTON COUNTY, OHIO. 
By Cuartes L. Merz, M.D. 
Anderson township is situated in the southeastern portion of Ham- 
ilton county, the Ohio river forming its southern and southwestern, and 
the Little Miami its northern and western boundaries; at a point near 
the junction of the two rivers is the village of California. The general 
surface or plain of the township, is elevated about six hundred feet or 
more above the Ohio, and broken up by deep ravines, especially on its 
southern and western borders, Whilst along the course of the Ohio, the 
