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U.S. NATIONAL MUSEUM BULLETIN 2 82 



Map 12. — Distribution of Noturus eleutherus Jordan. The verified localities are indicated 

 on the map. Many other records are considered doubtful. I suspect that this species 

 is found also in the lower sections of the rivers from which it is known and that there 

 is no significant distributional gap between Arkansas and the Ohio drainage. 



Ecological consideration. — A survey of the field records for 

 eleutherus suggests that it is chiefly a resident of large or fairly large, 

 moderate or swift-flowing streams or rivers. It has been taken princi- 

 pally in streams containing moderate or large stones, rubble, gravel, 

 and sand, and usually lives in clear water. Dr. George A. Moore has 

 informed me that in the Mountain Fork River, the species came almost 

 exclusively from a heavily vegetated, gravel riffle with gentle flow. 

 Species of Noturus that have been coUected with eleutherus are: 

 gyrinus, nocturnus, flavus, stigmosus, miurus, and flavipinnis. 



Remarks. — The name eleutherus (Greek) means not bound, or 

 free; it refers to the relatively free posterior flap of the adipose fin. 



Although both sexes are present in each species, Noturus eleutherus 

 has been regarded by some workers as the male and Noturus stigmosus 

 as the female. This has led to lumping populations containing both 

 species under the name Schilbeodes eleutherus. A comparison of the 

 two forms is given in table 13. Figure 4 compares their caudal ray 

 counts. 



