THE BLIND FISHES OF NORTH AMERICA. 477 



method of locating and securing food which has enabled the Am- 

 blyopsidae to establish themselves in caves. 



The Chologaster in general make-up is like Amblyopsis, but is 

 somewhat longer-jointed. It sits with its pectorals extended. 

 When it moves horizontally for some distance the pectorals are 

 usually pressed to the sides, the propelling being done largely by 

 the tail very much after the manner of a salamander, which it 

 resembles. In swimming toward the surface it uses its pectoral 

 fins chiefly, and the fish usually sinks to the bottom as soon as its 

 efforts to raise itself are stopped. 



Individuals kept in aquaria -with one end darkened either col- 

 lected in the darkened area floating about, or under leaves or 

 sticks in any part of the aquarium. They are frequently found 

 under a floating board, where they float with the tops of their 

 heads in contact with the board, their bodies slanting downward. 

 They seek the dark, regardless of the direction of the rays of light. 

 These characteristics they have, in great part, in common with the 

 blind members of the family. The adult Amblyopsis frequently 

 floats with its head to the top of the water, the tail sloping down- 

 ward, and in swimming along ledges of rock the top of the head 

 is applied to the ledge. I have captured many specimens simply 

 by scraping my net along the surface of a ledge. 



Typhlichthys, living in total darkness, has retained the habit 

 of staying under floating boards, sticks, and stones. Miss Hoppin 

 noticed that Troglichthys swims with its back to the sides of the 

 aquarium, and I have repeatedly noted the same in the young of 

 Amblyopsis up to fifty millimetres, and the still younger Ambly- 

 opsis frequently hides under rocks. 



Amblyopsis. — The general impression given by Amblyopsis is 

 that of a skinned catfish swimming on its back. The expressions, 

 "They are catfish"; "They look as though they were skinned"; 

 " They are swimming on their backs," are heard from those who 

 see these fishes for the first time. 



The largest individual secured by me measured 135 millime- 

 tres in total length. Individuals as large as this are rare. The 

 usual length of an adult is about 90 millimetres. One individual 

 was mentioned to me at Mammoth Cave having a length of 200 

 millimetres! 



Amblyopsis is found in pools in the cave streams it inhabits. 

 I have secured as many as twelve from a pool perhaps ten by fifty 

 feet in size. Very rarely they are to be found in the riffles connect- 

 ing the pools. I have seen them lying at the bottom, or swimming, 

 or rather gliding, through the water like " white aquatic ghosts." 

 In the aquarium they lie at the bottom or at various depths in the 



