

Geology and Natural History. 



The other differences are all very slight, scarcely sufficient to dis- 

 tinguish the subterranean form as a species, and certainly so slight 

 that they would almost surely be overlooked if the two forms 

 were found together. 



As the crustaceans have recently been several times referred to 

 as indicating the partially marine origin of the cave fauna of the 

 Western States, a word in regard to their affinities may not be out 

 of place. The species already described from Indiana and Ken- 

 tucky are the following: Gambarus Bartonii Erichson, Mam- 

 moth Cave ; G. pellueidus Erichson, caves in Ky. and Ind. ; 

 Crangonyx vitreus Smith, Mammoth Cave ; G Packardii Smith, 

 wells, Ind. ; Gcecidotea stygia Packard, caves and wells, Ind., 

 and Mammoth Cave ; Eupfiiloscia Elrodii Packard, caves, Ind. ; 

 Gauloxenus stygius Cope, caves, Ind. The genus Gambarus is 

 strictly confined to American fresh waters, and G. Bartonii is 

 one of the commonest species in the streams of the Western 

 States. Grangonyx, as far as known, is wholly confined to fresh 

 water. Gcecidotea,. as far as we can judge from description and 

 figures, is scarcely distinguishable, except in wanting eyes, from 

 Asellus, a characteristically fresh water genus. The Euphiloscia 

 was found also outside the caves and is allied to other terrestrial 

 genera. The Gaidoxenus, a Lernaean parasite of the blind fish, 

 is so poorly described and figured, and the genera of the whole 

 group to which it belongs are so difficult and imperfectly known, 

 that it is useless to speculate on its exact affinities. In our 

 Western and Southern States, species of perch, brook trout, the 

 siscowet, lake white-fish, species of Gatostomus and Pomotis, and 

 other fresh water fishes, are infested with diffei-ent species of 

 Lernaeans, and there is no more reason for regarding Gauloxenus 

 as a " marine form" than any of these parasites. As well might 

 we call a Gambarus or a Grangonyx a marine form because the 

 great majority of the species of the orders to which they belong 

 are marine. Considering the crustaceans alone, I can see no 

 reason for supposing that the fauna of the caves of Kentucky and 

 Indiana has been derived from any other source than the recent 

 fauna of the surface of the neighboring region. 



