90 U.S. NATIONAL MUSEUM BULLETIN 282 



lower surface of head usually immaculate, but sometimes lightly 

 pigmented in very large specimens; all fins lightly pigmented, especi- 

 ally near their bases, but pelvic fins relatively clear; margins of pec- 

 toral, anal, dorsal, and caudal fins frequently with a dark band or 

 with concentrations of pigment that is usually darker than the basal 

 areas of the fins, their extreme edges clear; adipose fin dusky near 

 base, clear distally. 



Variation. — Certain features of the variation in this species have 

 been discussed by Hubbs and Raney (1944). They indicate that im- 

 portant average differences rin the lengths of the dorsal and pectoral 

 spines exist between populations and describe color variations. The 

 data given by Hubbs and Raney (1944, pp. 8, 9, 10, 17) for several 

 proportional measurements of Roanoke and Kanawha specimens are 

 virtually overlapped by the data from other areas. A^. insignu is, 

 therefore, not unlike other species in the great variation in the length 

 of the spines. As discussed under Noturus gyrinus, it appears that 

 some nongenetic factors are operative in determining the develop- 

 ment of hard parts, and that the relative lengths of the dorsal and 

 pectoral spines are dependent upon these factors. 



The black-bordered fins of Kanawha and Roanoke River specimens 

 are distinctive, but there is a gradient of this character southward 

 into North Carolina and scattered samples from New York, Penn- 

 sylvania, and Virginia have similar appearing specimens. The eco- 

 logical distribution of black fin borders is apparently like that in 

 Noturus exilis, which in cool, clear streams develops black-bordered 

 fins, but in warm turbid streams lacks any trace of the dark borders. 

 One small specimen of ijisignis from Georgia has clear white fin 

 borders. 



No important variations in meristic characters are apparent. The 

 data (number of tabulations, range in parentheses, and mean) are 

 summarized from the following areas: (a) Cape Fear River to Oconee 

 River; (b) Neuse and Tar Rivers; (c) Roanoke, Chowan, and Kanawha 

 Rivers; (d) James River to Potomac River; (e) the area north of the 

 Potomac River to the Susquehanna River; (f) Holston River; (g) 

 Watauga River; and (h) total. 



Soft pectoral rays: (a) 46 (8-10) 9.07; (b) 40 (7-10) 8.90; (c) 62 

 (8-10) 9.02; (d) 12 (9) 9.00; (e) 95 (8-9) 8.83; (f) omitted; (g) 20 

 (9-10) 9.15; (h) 275 (7-10) 8.95. 



Pelvic rays: (a) 46 (9-10) 9.04; (b) 40 (9-10) 9.30; (c) 62 (9-10) 

 9.06; (d) 12 (9-10) 9.17; (e) 96 (8-10) 9.02; (f) omitted; (g) 20 (9-10) 

 9.05; (h) 276 (8-10) 9.08. 



Anal rays: (a) 23 (15-20) 18.00; (b) 22 (17-21) 18.45; (c) 31 (16-20) 

 18.48; (d) 6 (17-19) 18.00; (e) 49 (15-19) 17.29; (f) omitted; (g) 10 

 (17-21) 18.80; (h) 141 (15-21) 17.99. 



