24 U.S. NATIONAL MUSEUM BULLETIN 282 



From 1875 through 1891, Nelson described Noturus exilis, and 

 Jordan and his co-workers described most of the remaining known 

 species. The generic names Rabida and Pimelodon were established in 

 1896. Since then only two vaUd species have been named. 



The common name madtom also originated locally. Jordan (1889, 

 p. 353; 1890, pp. 101, 122) found the name to be in use in Virginia for 

 Noturus insignis and possibly for Noturus gilberti. He said (1890, 

 p. 101) of insignis: "Well known . . . here [Luray, Virginia locali- 

 ties] as elsewhere in Virginia, by the appropriate name of Mad-Tom." 



Zoogeography 



Noturus belongs to the large fish fauna of eastern North America. 

 There, its species are found in tributaries to the Atlantic Ocean from 

 the Nueces River, Texas, to the Hudson River, New York, and have 

 spread into the Saint Lawrence and Hudson Bay drainages. Repre- 

 sentatives have been introduced into Germany (unsuccessfully), into 

 the Snake River of Idaho and Oregon, and into several New England 

 streams. The discovery of Prietella, an apparent relative of Noturus, 

 in northeastern Mexico suggests a more widespread distribution of 

 the ancestral Noturus, possibly throughout eastern North America 

 into Mexico. 



Two ecological factors seem to contribute importantly to the 

 present distribution of Noturus: water sufficiently warm for reproduc- 

 tion and a good supply of oxygen. Avoidance of cold water is indi- 

 cated by the few species living in northern regions and by the infrequent 

 occurrence of any species with cold water inhabiting trout. Of these, 

 Noturus insignis is most commonly reported from trout streams — 

 perhaps submarginal trout streams. Other evidence of a requirement 

 for warm water are late season breeding in the north and general 

 disappearance, after one or two years, from and below the area of 

 large impoundments that release cold water. 



Although one species seems to prefer lowland areas and water 

 with little or no current the remainder appear characteristic of 

 moderate to rapidly flowing streams. In the latter they are most often 

 found on or just below riffles, where there is an abundance of cover 

 for hiding and the water is well oxygenated. Although wet specimens 

 will often survive for several hours in air, deficient oxygen appears 

 to be a critical factor in controlling distribution. This is most noticeable 

 in late summer and fall when species become almost entirely restricted 

 to a riffle where there is deficient oxygen in the adjacent pools. 



The present centers of greatest number of species of Noturus, and 

 perhaps of their evolution, lie in the upland regions of the east central 

 United States, roughly in a band from Arkansas and Missouri through 



