328 MOSTLY MAMMALS 



the family are marine forms, some inhabiting shallow water, 

 while others are found only at great depths. Now the 

 Cuban blind fish, in which the eyes are totally wanting 

 or rudimentary, is a very close ally of a marine form 

 named Brotula, in which the eyes are fully developed, and 

 has evidently been specially modified from the former for 

 a subterranean existence. The barbels, which are present 

 in the marine fish, are replaced in the cave form by minute 

 tubercles. This, however, is not the only point connected 

 with this curious family, as there are two species, belonging 

 to as many genera {Typhlonus and Aphyonus), found at great 

 depths in the southern oceans, which are also completely 

 blind, and apparently have no phosphorescent organs. And 

 it would appear from these examples that the fish of this 

 family have some special disposition towards a life of 

 darkness. 



The only other fish that can be said to belong to the 

 cave-fauna is a member of the great fresh-water family of 

 cat-fishes {Siliiridae)^ and has been named by Prof. Cope 

 Gronias nigrilabris. This fish, which attains a length of 

 about ten inches, is closely allied to an ordinary fresh- 

 water American form, and occurs in the Conestoga River 

 in Lancaster County, Pennsylvania, where it is stated to 

 be occasionally taken by the fishermen, and is beheved 

 to issue from a subterranean stream said to traverse the 

 limestone of that district, and to discharge into the Conestoga 

 River. Although blind, the fish has a rudimentary eye, and 

 is therefore in process of modification for a completely sub- 

 terranean life. 



To refer in detail to the invertebrate inhabitants of caves 

 would far exceed my allotted limits, and only a few words 

 can be said on this part of the subject. Among the most 

 interesting are the blind cray-fish, in the ordinary form of 



