140 U.S. NATIONAL MUSEUM BULLETIN 282 



and the distribution of pigment in the dorsal fin of hildebrandi and 

 lautus are similar, except that the saddle-like blotch below the adipose 

 fin does not enter that fin in lautus; the adipose fin is yellowish and 

 immaculate or sometimes with small brown chromatophores scattered 

 throughout; bar at rear end of caudal peduncle similar in shape to 

 that of hildebrandi but ending near bases of the upper and lower 

 procurrent caudal rays — these rays mostly immaculate distally; 

 caudal fin yellowish \vith one or two narrow, short, brown bars 

 distally and a wider brown bar near base; much of the upper and 

 lower portions of the fin often immaculate; anal fin immaculate or 

 with a few chromatophores distally on posterior long rays; pelvic 

 fins, lower barbels, abdomen, and lower surface of head immacidate; 

 pectoral spine brown with some pigment on adjacent soft rays; head 

 dark reddish brown above with a bar across its rear end to the lower 

 margin of the opercle; a similar band extending forward from beneath 

 the eye to the nares; a small round yellowish spot usually present 

 behind the eye; cheek yellowish; upper barbels heavily pigmented. 



HoLOTYPE. — The holotype (pi. 10, fig. 2) is a female, 40.3 mm. in 

 standard length. It has 15 anal rays, 16+7+8 + 15=46 caudal rays, 

 and 6 soft dorsal rays. The left pectoral fin has eight soft rays and 

 the right has nine including a tiny basal splint. On each side there 

 are eight pelvic rays, ten preoperculomandibular pores, two internasal 

 pores, and seven recurved serrae on the posterior edge of the pectoral 

 spine. The anterior edge of the pectoral spine is roughened; the 

 serrae are greatly reduced in size and indistinct. The head length is 

 projected into the standard length 3.8 times, and the distance from 

 the rear end of the adipose fin to the tip of the caudal fin into the 

 distance from the dorsal origin to the rear end of the adipose fin 2.0 

 times. Further measurements are given in table 28. 



Distribution. — Noturus hildebrandi lautus is known only from 

 western Tennessee but it may range into southwestern Kentucky 

 and into northern Mississippi in the Hatchie River system. It inter- 

 grades with Noturus hildebrandi hildebrandi in southwestern Tennessee 

 and northern Mississippi. 



Etymology. — The name lautus (Latin) meaning washed or clean 

 and neat refers to the trim, neat, and pleasing color pattern of this 

 subspecies. 



Ecology. — In the Obion River, Tennessee, lautus was taken in 

 water 12 to 18 inches deep, over a bottom of shifting sand with some 

 gravel up to one inch in diameter. In the Hatchie system it lives in 

 highly turbid, but perhaps seasonally clear, moderately deep streams 

 with slow to moderate current. Where collected in this system little 

 riffle habitat was available; the bottom consisted of shifting sand 

 and debris with occasional gravel or of mud, sand, and silt with 



