BLIND CAVE-ANIMALS 327 



colourless ; but its sense of hearing is extraordinarily 

 developed. In the typical form this fish has a small pair 

 of pelvic fin's, but in some examples (which have been 

 referred to a distinct genus under the name of Typhlichthys) 

 these are wanting. The maximum length is five inches. 

 Prof. Cope writes that if these fish " be not alarmed, 

 they come to the surface to feed, and swim in full sight 

 like white aquatic ghosts. They are then easily taken by 

 hand or net, if perfect silence is observed, for they are 

 unconscious of the presence of an enemy except through 

 the medium of hearing. This sense is, however, evidently 

 very acute, for at any noise they turn suddenly downward, 

 and hide beneath stones, etc., at the bottom. They must 

 take much of their food near the surface, as the life of the 

 depths is apparently very sparse." 



The only other genus in the family is known as Cholo- 

 gaster, and differs from the last in the retention of small 

 external eyes, and likewise in the skin being coloured. 

 Pelvic fins are absent, and the front of the head is provided 

 with two horn-like appendages. These small fish were first 

 known from three examples taken in the ditches of the South 

 Carolina rice-fields ; but another specimen was caught in a 

 well in Lebanon County, Tennessee, in the year 1854. They 

 appear to have taken to a partially subterranean life com- 

 paratively recently, and therefore retain their eyes and dark 

 coloration. 



Although these cave-fish are clearly allies of the cyprino- 

 donts, there is no evidence to show that they are directly 

 descended from any member of that family. A clear descent 

 is, however, indicated by a very remarkable family of fishes 

 known as the Ophidiidae, which are near relatives of the 

 cod tribe. With the single exception of the cave-fish of 

 the caves of Cuba (Lucifuga dentata]^ all the members of 



