CATFISH GENUS NOTURUS RAFINESQUE 103 



Gill rakers on the first arch six to nine. There are (extremes in 

 parentheses): (17) 19 to 21 (23) upper simple caudal rays; (16) 

 17 or 18 (20) branched caudal rays, of which there are typically 7 

 in the upper half of the fin and 10 or 11 in the lower half; and (13) 

 15 to 18 (19) lower simple caudal rays. The soft dorsal rays are five 

 (in 2) or six (148). 



In five stained and cleared specimens there are eleven vertebrae 

 anterior to the anal fin origin; the pectoral radials are fused on each 

 side, except the fusion on one side is incomplete. As judged from x- 

 rays and cleared specimens the hypurals are seldom fused; no fusion 

 was observed in 34 specimens; hypurals 2-3 were fused in 7, and 6-7 

 in 2. The largest known specimen is 123 mm. in standard length. 



The general background color is light or dark brown in life as well 

 as in most preserved specimens. No bright colors are present. The 

 upper surface, barbels, fins, and side are nearly uniformly brown; 

 the lower surface may be somewhat lighter, but is sprinkled with 

 large distinct, brown chromatophores. These may become diffused 

 with age, so that some old specimens, noted especially in those from 

 western Tennessee, appear to have the medial portion of the abdomen, 

 as well as other parts of the body, unpigmented. The fins are all 

 heavily pigmented, sometimes light edged. The dorsal and anal fins 

 may have a distal dark band of pigment. 



Type.— The holotype, USNM 202143, is a male, 94.6 mm. in 

 standard length. It is light brown colored with narrow pale or whitish 

 margins to the fins. There are 6 soft dorsal rays, 21 anal rays, 20+7 + 

 10 + 15 = 52 caudal rays, 1 epural, 6 (3+3) unfused hypurals, and 36 

 vertebrae. On each side there are nine pelvic rays, eight soft pectoral 

 rays, eleven preoperculomandibular pores, two internasal pores, and 

 eight serrae posteriorly on the pectoral spines. The serrae are sharp 

 pointed, but two left serrae and one right serration have split distally 

 so that they have two sharp points instead of one. The head length 

 is stepped into the standard length 3.35 times and the distance from 

 the rear end of the adipose fin to the tip of the caudal fin is contained 

 1.8 times in the distance from the origin of the dorsal fin to the rear 

 end of the adipose fin. Measurements are given in table 27. 



Variation. — Noturus phaeus apparently has relatively little geo- 

 graphic variation in most structures studied, but the variation in 

 pectoral rays (table 8) is prominent. In specimens from Kentucky, 

 Tennessee, and northern Mississippi the modal number of soft pec- 

 toral rays is eight and the mode in Louisiana and southern Mississippi 

 is nine. This would point to a break, or shift, in characters in central 

 Mississippi rather than a change across the Mississippi River low- 

 lands. To the contrary, a break could be expected in the floodplain 

 of the Mississippi River where little suitable habitat for phaeus is 



