104 U.S. NATIONAL MUSEUM BULLETIN 2 82 



apparent, and is not expected across Mississippi where the distribu- 

 tion is probably continuous. 



The variation in anal rays and vertebrae is included in tables 6 and 

 8. Variation from the strong modes is small in the pore counts and 

 number of dorsal rays. The variation from nine pelvic rays is random 

 and very similar to that of most other species of Noturus. The means 

 for the same specimens as the pectoral ray counts range from 8.93 to 

 9.07, except the three specimens from Beaver Creek, Louisiana, with 

 nine or ten pelvic rays, have a mean of 9.33. 



Variations in caudal ray counts appear to be slightly irregular, but 

 probably insignificant. The following data include number of counts, 

 range (in parentheses), and mean for combined samples for each 

 river system. 



Caudal rays: Forked Deer River, Tennessee 13 (51-57) 53.92; 

 Yazoo River, Mississippi 70 (50-58) 53.70; Little River, Louisiana 3 

 (55-57) 56.33; Brushy Creek, Louisiana 22 (53-59) 55.18; Beaver 

 Creek, Louisiana 3 (51-54) 53.00. 



Upper-half caudal rays: Forked Deer River 13 (27-31) 28.00; 

 Yazoo River 70 (24-29) 26.50; Little River 3 (28-30) 29.33; Brushy 

 Creek 22 (26-29) 27.82; Beaver Creek 3 (26-27) 26.67. 



Lower-half caudal rays: Forked Deer River 13 (24-28) 25.92; 

 Yazoo River 70 (24-30) 27.20; Little River 3 (27) 27.00; Brushy 

 Creek 22 (26-30) 27.36; Beaver Creek 3 (25-27) 26.33. 



Distribution. — Noturus phaeus (map 6) is confined to the lower 

 Mississippi Valley and the headwaters of Bayou Teche, Louisiana. It 

 occurs in most eastern tributaries to the Mississippi River from south- 

 western Kentucky to Louisiana, in the lower Ouachita drainage, and 

 in the Red River system upstream to northwestern Louisiana. The 

 population now in upper Bayou Teche is the result of recent diversion 

 of streams from the Red River. 



Etymology. — The name phaeus (Greek) meaning of the hue or 

 color of twilight, dusky, brown, or grayish brown, refers to the 

 color of this species. 



Relationship. — Noturus phaeus is closely related to Noturus 

 funebris. The somewhat similar Noturus nocturnus may be confused 

 with phaeus, but the two differ in several characters, including num- 

 ber of anal rays and relative slenderness of the dorsal spine, in addition 

 to other skeletal characters. N. phaeus has prominent pectoral spine 

 serrae; A^. nocturnus never has uniformly developed serrae — when 

 present the serrae typically are few, relatively short, and of irregular 

 sizes. Aside from Noturus funebris, phaeus is probably closest related 

 to insignis and nocturnus among the species of Noturus. 



Ecology. — A'^. phaeus is most commonly collected from permanent 

 springs and small streams. It is frequently found under vegetation in 



