ORIGIN OF CAVE LIFE. 23 



ed, the caves of the western and middle States are in lower Car- 

 boniferous limestone rocks, though the Port Kenned}^ 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 Palaeozoic." "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 are 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 

 the Alleghany 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 be 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 . 



