ORIGIN OF CAVE LIFE. 
23 
ed, the caves of the western and middle States are in lower Car- 
boniferous limestone rocks, though the Port Kennedy cave explored 
by Wheatley and Copef is in the Potsdam limestone. They could 
not have been formed under water, but when the land was drained’ 
by large rivers. This could not have occurred previous to the Tri- 
assic period. Prof. Dana in his “Manual of Geology” shows that 
the Triassic continent spread westward from the Atlantic coast “to 
Kansas, and southward to Alabama ; for through this great area 
there are no rocks more recent than the Palieozoic.” “Through the 
Mesozoic period [comprising the Triassic, Jurassic, and Creta- 
ceous periods] North America was in general dry land, and on the 
east it stood a large part of the time above its present level.” 
Though at the close of these periods there was a general extinc- 
tion of life, yet this was not probably a sudden (one of months 
and even years), but rather a secular extinction, and there may be 
plants and animals now living on dry land, which are the lineal 
descendants of mesozoic and more remotely of Carboniferous forms 
of life. So our cave animals may possibly be the survivors of Mes- 
ozoic forms of life, just as we find now living at great depths in 
the sea remnants of Cretaceous life. But from the recent explora- 
tions in the caves of Europe and this country, especially the Port 
Kennedy cave, with its remarkable assemblage of vertebrates and 
insects, we ate led to believe from the array of facts presented by 
Prof. Cope that our true subterranean fauna probably does not 
date farther back than the beginning of the Quaternary, or Post 
pliocene, period. We quote his “general observations” in his 
article on the Port Kennedy fauna. 
“The origin of the caves which so abound in the limestones of 
tbe Alleghan}^ and Mississippi valley regions, is a subject of much 
interest. Their galleries measure many thousands of miles, and 
their number is legion. The writer has examined twenty-five, in 
more or less detail, in Virginia and Tennessee, and can add his 
testimony to the belief that they have been formed by currents of 
running water. They generally extend in a direction parallel to 
the strike of the strata, and have their greatest diameter in the 
direction of the dip. Their depth is determined in some measure 
by the softness of the stratum, whose removal has given them 
existence, but in thinly stratified or soft material, the roofs or large 
t A notice of the animals found in this cave will he found in the Proceedings of the 
American Philosophical Society, April, 1871. The insects there enumerated would 
probably not come under the head of cave insects. 
