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 (Szlur¢dae), 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 believed 
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 
