Faiinal Aspects of the Origi/ial Kiiiderhook. — Keyes. 315 
80' with the first. The crests from the corners of these ter- 
minal edges fade away gradually toward the center, which is 
nearly circular in cross section. The pebble is, as it were, a 
graphic solution of the equation of motion of the water in the 
confined space beneath the rapidly moving wheel. 
The stone is (in the figure) placed in front of a mirror and 
the chisel edge in front, marked by a long pin, slopes from 
left above to right below, while the opposite direction of the 
rearward edge is shown by the opposite position of the other 
pin, and is seen in the image in the mirror, though here the 
shading could not be managed so as to bring out the regular 
adze-like edge of the stone, nor the symmetrical way in which 
the crests from the outer corners of the cutting edge pass into 
.the general ellipsoidal shape of the central portion of the stone. 
CERTAIN FAUNAL ASPECTS OF THE 
ORIGINAL KINDERHOOK. 
Ry Charles R, Keyes, Dos Moines, Iowa. 
The original Kinderhook formation, as exposed along the 
'upper Mississippi river has long been of special interest be- 
cause holding a stratigraphic position on the division line of 
the Devonian and Carboniferous. On this account, also, the 
beds composing this terrane have been put first in one system 
and then in the other, until finally the uncertainty regarding 
their geological age has increased rather than diminished. 
Until very recently* the correlations of the various sections 
with the typical Kinderhook have had to be inferred from im- 
perfect fossil data. Certain peculiarities in the local stratigra- 
phy have prevented parallelism of strata by visible continuity. 
For present requirements, with its refined methods, the avail- 
able information has been too inexact to be of very much 
value. For the most part the fossils have to be studied anew in 
■order to find out in just what layers the various forms occur. 
Only in this way can useful and exact comparisons of the fau- 
na be made. 
Already Weller has begun, along the lines indicated, a 
*Journa! Geolojiy, \'()1. VIII, pp. 315-321, igoo. 
