CATFISH GENUS NOTURUS RAFINESQUE 63 



The largest specimen known, an unusually large individual, was 

 retained in an aquarium at the Museum of Zoology, University of 

 Michigan, for one and one-half years, at which time it had attained 

 113 mm. in standard length. The color of its sides, dorsal surface, 

 and pectoral fins is a slate-gray; the pelvic fins and lower surface 

 are darkly pigmented but somewhat lighter than the sides. Other 

 specimens are less than 100 mm., rarely more than 90 mm., in stand- 

 ard length and lack the darkened undersurface. 



General color in life yellowish brown to gray-black. In preserved 

 material: ventral surface much lighter than side or upper surface; 

 top of head, upper barbels, back, and most of side nearly uniformly 

 grayish; an obovate, light yellow spot extends backward from the 

 base of the last two or three dorsal rays; side lightly but uniformly 

 pigmented; mental barbels and lower surface of head and belly light, 

 but all under surfaces becoming darker with age; ventral surface 

 immaculate (individuals to about 90 mm. in standard length); old 

 specimens nearly unicolored and only slightly lighter below; a band 

 of pigment crosses the chin in front of barbels and a faint one lies 

 just in front of the pelvic fins; all median fins lightly pigmented with 

 gray; dorsal, caudal, and anal fins often with black borders; the fins 

 unicolor in some populations; pelvic and pectoral fins of small indi- 

 viduals unpigmented, but becoming darker with age; tips of pectoral 

 rays unpigmented. 



Variation. — There is considerable variation in Noturus exUis, as 

 noted by Hubbs and Raney (1944, p. 21). The degree of pigmentation 

 of the fins varies from place to place. They have very dark margins 

 in the White River system and are often unicolor in many other areas. 

 Also in the White River, exUis is more elongate. 



Average meristic differences among samples from the Arkansas 

 River system. White River system, and Missouri River system can 

 be demonstrated. Subspecific separation, however, probably is not 

 warranted. In fin ray counts, specimens from Tennessee, Illinois, and 

 Iowa appear to be much like those of the Missouri basin. The data are 

 listed as follows: number of tabulations, range (in parentheses), and 

 mean in samples from (a) Arkansas River system, Arkansas, Missouri, 

 and Oklahoma, (b) White River system, Missouri and Arkansas, 

 (c) Missouri River basin, (d) Tennessee, Minnesota, Iowa, Illinois, 

 and the Meramec River, Missouri, and (e) total. Data for the speci- 

 men, USNM 56615, reputedly from Guyandotte River, West Vh-ginia, 

 are omitted here, but included in tables 17 and 19 comparing the 

 species of Noturus. 



Pelvic rays: (a) 126 (8-10) 9.02; (b) 68 (9-10) 9.06; (c) 100 (8-10) 

 9.03; (d) 100 (8-10) 9.15; (e) 394 (8-10) 9.06. 



