Geology and Paleontology. 1105 
correction, First, on pp. 814-815, occurs the statement: “It is 
probable that Cacidotea stygia is seldom, if ever, broughtin contact 
with Asellus communis, which abounds in the pools and streams 
throughout the cave region.” For this I cansee no reason. As I 
have lived for sometime in the cave region, I may say that Cæcidotæa 
is not confined to “caves and wells fed by underground streams,” 
but occurs in Bloomington in springs and in the ordinary streams, 
mingling with its near relative Asellus. Again, except for the 
single element of darkness, I cannot see how the cave* fauna, 
occurring in the numerous caves around this town, and extending 
south to Wyandotte and Mammoth, “is almost completely isolated 
from that of the upper world.” ‘Too many of the streams in this 
carboniferous belt drop out of sight, and can be traced directly 
into caves about here to afford much isolation to aquatic animals. 
Not having seen the complete article from which his paper “On 
Certain Factors of Evolution” is an extract, I do not know on what 
Dr. Packard bases his conclusion (p. 815) that the cave faunz are 
to be regarded as products of Quaternary times. Of course the 
peel facies of that fauna is recent, but it is, on the other hand, 
yond question that the caves themselves have been in process of 
formation since their rocks were elevated above the carboniferous sea. 
I know of no argument which forbids the idea of their being peopled 
in Permian times. The fact that we have no cave fossils giving 
evidence of a Mesozoic fauna is easily explained by the fact that 
there was no locality for such fossils to form. Caves are constantly 
being enlarged by a solution of their walls, and with the wearing 
away of the rock all cave-animal remains would of necessity be 
destroyed. 
find a single morainic boulder. It is rather a region of topographic 
old he “ Knobs” which skirt the Ohio, from Louisville to 
. 
the floods caused by the melting ice of the Continental glaciers, but 
the river-courses of tc si 
which must be invoked to explain the presence of the caves. To 
explain the existence of the caverns we must predicate streams whose 
