OF DFNISON UNIVERSITY. 
5 ' 
prepare the way for the intelligent study of the difficult group of rocks 
below.' 
In fact, a larger number of species than are here described have 
been already figured from the Waverly and only a beginning is yet 
made. These plates it was hoped to' print at this time but circum- 
stances forbid. In the neighborhood of eighty-five species have 
been collected by the class from the coal measures during a few hasty 
trips to Flint Ridge. This is as many as have been described 
from the coal measures of Indiana. Meek, in the Ohio Paleontology 
describes only about twenty. 
APPENDIX L CARBONIFEROUS TRILOBITES. 
P was intended to devote space to a somewhat extended discus- 
sion of the carboniferous Trilobites of America but lack of space and 
the incompleteness of the discussion possible at present has induced 
us to give up the idea, especially in view of the hint that a special 
work is soon to appear upon this subject. The following notes are, 
however, appended to the present paper in the hope that they may 
prove useful. 
It is well known that during the carboniferous period trilobites 
rapidly approach extinction and but few remained to struggle with the 
adverse conditions of the Permican. But why the seas of the car- 
boniferous were less favorable than those of the Cambrian and Silurian 
remains a mystery. Although the trilobite of the early Palaeozoic was, 
perhaps, a synthetic type as argued by Agassiz, it would seem that the 
trilobites of the carboniferous belonged to a closed type with slight 
powers of adaption. 
A careful study of the trilobites of the carboniferous rocks of 
America ought to throw some light on the5e matters if undertaken in 
a truly comparative spijit rather than from the standpoint of the mere 
systematist. Nevertheless it is necessary to first devote the requisite 
systematic study in order to give critical value to determinations^ A 
review of the whole field is necessary, but its difficulty has been much 
lightened by the works of two European authors from which many of 
our statements are drawn. ( Valerian v. Moeller. Ueber die 
Trilobiten der steinkohlen formation des Ural, nebst einer Uebersicht 
und einegen Ergaenzungen der bisherigen Beobachtungen ueber 
Kohlen Trilobiten, 1867; H. Woodwai^d. A Monograph of the 
