CATFISH GENUS NOTURUS RAFINESQUE 133 



confined to the relatively small eastern tributaries to the Mississippi 

 River in Mississippi, Tennessee, and probably Kentucky. 



Two rather uniform subspecies are recongized. They are most 

 readily distinguished by color pattern and number of preoperculo- 

 mandibular pores. An apparent change in a number of other char- 

 acters from north to south points to a cline, but because of a prom- 

 inent shift, in northern Mississippi and southwestern Tennessee, 

 in pore counts and color pattern, with relative uniformity of popula- 

 tions elsewhere, subspecies are recognized. 



The synonymy and discussion pertaining to the subspecies will 

 be found with the descriptions of the two forms. The geographic 

 variation of Noturus hildebrandi is discussed separately to facilitate 

 comparison. 



Geographic Variation. — No specimens are known from the Big 

 Black River system, Mississippi, and, aside from the Coldwater 

 River specimens, only five relatively small poor specimens are available 

 from the Yazoo system. Otherwise samples are generally adequate to 

 indicate variational trends. 



No significant variation in the number of caudal rays, branched 

 and simple caudal rays, dorsal rays, or internasal pores has been-noted 

 in any population. 



Pelvic rays: The pelvic rays appear to be almost constantly eight in 

 all populations. Very few counts of nine rays on one or both sides of a 

 specimen were obtained; they appear randomly throughout the range. 



The variation in vertebrae, preoperculomandibular pores, and anal 

 rays is shown in tables 10 to 12. The preoperculomandibular pores in 

 table 11 are the sum of the counts obtained from the two sides ol each 

 specimen. 



In the following summaries the data presented include number of 

 specimens, range (in parentheses), and mean for (a) Homochitto River 

 system, (b) Bayou Pierre, (c) Yalobusha system, (d) Yocona system, 

 (e) Tallahatchie systerr, (f) Coldwater River, (g) Loosahatchie River, 

 (h) Hatchie system, (i) South Forked Deer system, and (j) Obion 

 system. 



Preoperculomandibular pores: (a) 129 (10-12) 10.87; (b) 50 (10-12) 

 10.84; (c) 2 (11) 11.00; (d) 2 (11) 11.00; (e) 6 (10-11) 10.67; (f) 18 

 (9-11) 9.67; (g) 4 (9-10) 9.50; (h) 48 (9-11) 10.06; (i) 4 (10) 10.00 

 (j) 58 (9-11) 9.84. 



Upper-half caudal rays: (a) 65 (22-27) 24.11; (b) 25 (21-24) 23.04 

 (c) 1 (24) 24.00; (d) 1 (24) 24.00; (e) 3 (23-25) 24.00; (f) 9 (21-26) 

 23.56; (g) 2 (22-23) 22.50; (h) 25 (22-26) 24.00; (i) 2 (24-26) 25.00 

 (j) 29 (21-26) 23.76. 



Lower-half caudal rays: (a) 65 (20-24) 22.03; (b) 25 (21-24) 22.40 

 (c) 1 (23) 23.00; (d) 1 (22) 22.00; (e) 3 (22-23) 22.33; (f) 9 (19-23) 



