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bold a one to make, especially as some forms of life are 

 found in these subterranean streams which, at present, 

 seem to indicate a marine origin, and brackish water ani- 

 mals of certain forms once enclosed in the cave, would be 

 very likely to survive under the peculiar conditions in 

 which they were placed, as we know to have been the 

 case under other, but somewhat similar, circumstances. 

 That many, or, with two or three exceptions, nearly all 

 of the thirty or forty species of vertebrates, articulates, 

 mollusks and still lower forms, including a few plants, 

 now discovered in the caves of Kentucky, are of com- 

 paratively late introduction, is probable from the fact that 

 they are so closely allied to forms living in the vicinity 

 of the caves, but that the blind fishes, the Chologaster 

 and a few of the lower forms of articulates, as the Ler- 

 mean, parasitic on the blind fish, may have been inhabi- 

 tants of the subterranean streams for a much longer period 

 is worthy of consideration on the following grounds : — 



First, the blind fish family has no immediate allies ex- 

 isting in the interior waters,* the only species of the fam- 

 ily, in addition to the three found in the Mammoth Cave, 

 being known at present only from the rice ditches of the 

 low coast of South Carolina. 



Second, the Lernsean parasite is much more common 

 on marine fishes than on strictly fluviatile species, and is 

 more decidedly a marine than a fresh water form. These 

 facts may therefore be taken as at least indicating the 

 probability of the early origin of some part of the great 

 cave system of the region of the Ohio valle}-, and while 

 there may be nothing in the present structure of the caves 

 to indicate their having been formed in part while in con- 



* In common with others I have considered the Heteropygii as belonging to tho 

 same order with the Cyprinodonte*, but I now have, from further information of 

 their structure, doubts as to their close association with that group. This subject 

 will be presented on another occasion. 



