CATFISH GENUS NOTURUS RAFENESQUE 81 



10.23; Washita River, Oklahoma 4 (10-11) 10.25. The modal number 

 for each population in the Red River system, Oklahoma, is strongly 

 ten; the mode for nearly all the other samples outside the Red River 

 system is eleven. 



In northwestern Louisiana, specimens from Saline and Kisatchie 

 Bayous have strong modes of ten; other populations in the Red River 

 system, Louisiana, may have modes of ten or eleven but I have been 

 unable to establish trends. 



The Red River populations are confusing because of the shift in 

 pore count inside the range of the species. I do not know if this charac- 

 ter is a geographic variation of noctumus confined to the Red River 

 drainage, or if two very similar species are involved. As noted previ- 

 ously, some populations with the low pore count have relatively short 

 spines and light color; others do not. Since there appear to be no other 

 distinguishing characters I have been unable to identify populations or 

 specimens consistently without counting pores, and in the lower 

 portions of the drainage the pores may grade from ten to eleven. No 

 samples have been observed containing two distinct morphological 

 types. 



Distribution. — Noturus noctumus (map 4) is found in the lower 

 and central Mississippi drainage and in other tributaries to the Gulf 

 of Mexico in Alabama, Mississippi, Louisiana, and Texas. Base-level 

 streams and brackish water are probably avoided ; otherwise noclurnus 

 occurs throughout the lower Mississippi River system from and below 

 the following: the bend of the Tennessee River in Mississippi, tribu- 

 taries to the Ohio River in Indiana and Kentucky, tributaries to the 

 upper Mississippi River in Missouri, the Illinois River in Illinois, the 

 Osage River in Kansas and western Missouri, the Arkansas River 

 system in Kansas and Oklahoma, and the Red River system in Texas 

 and Oklahoma. It ranges eastward in most Gulf of Mexico tributaries 

 to the Mobile River system, Alabama. Westward from the Mississippi 

 drainage, noctumus is found in many larger tributaries to the Gulf of 

 Mexico, to the San Jacinto River in Texas. 



N. noctumus is notably absent from the Ozark upland (upper White 

 River system) and probably is sparsely distributed in the small eastern 

 tributaries to the Mississippi River from Kentucky to Louisiana. The 

 fauna of the latter region, however, has not been collected as ex- 

 tensively as that of the Ozarks; the predominance of shifting sand 

 streams probably limits the favored habitat here. The reason for the 

 absence in the Ozark streams is unknown. In contrast, noctumus 

 ranges throughout much of the Ouachita upland. 



The hybrid Noturus gyrinus X Notiirus miurus, and the following 

 species of Noturus have been incorrectly recorded as noctumus: 

 gyrinus, exilis, flames, and cUbater. 



