GILBERT: FISHES OF THE SUBGENUS LUXILUS


River system, Alabama (UMMZ 175746) which showed the highest
counts for any individuals of this form exhibited a number of abnor-
malities such as deformed fins and "bulldog" snout. These anomalies
were also found in other species from the same locality, suggesting
that some factor such as the chemical composition of the water was
responsible, probably during early embryological development.
 Occasionally the ordinary dark pigment on the anterior dorso-
lateral scale pockets is either faint or virtually absent. In such cases
chrysocephalus approaches cornutus in appearance and looks like a
hybrid between these two species. The resemblance is merely super-
ficial, for such individuals are found in areas where it seems unlikely
that cornutus has ever occurred. As these are typical chrysocephalus
in all other respects, the suppression of pigment along the upper side
of the body apparently is of no special significance.
 Individuals occasionally lack pigment on the chin and gular re-
gion. This is particularly common in the Tennessee River system,
where the pigment is wholly or partially absent in approximately half
the individuals.
 DISTRIBUTION. Found throughout a large part of east-central
United States from the upper Coosa River system in Alabama and
Georgia and the lower Mississippi River drainage in Alabama, north-
eastern Mississippi, Tennessee, northern Arkansas, and northeastern
Oklahoma, northward to the lower Great Lakes region from south-
eastern Wisconsin to western New York.
 Common in the upper Coosa River system of Georgia and Ala-
bama, but becomes increasingly less common in the lower parts of
that drainage. It is abruptly replaced by N. c. isolepis a short dis-
tance north of the confluence of the Coosa and Tallapoosa rivers, with
no apparent evidence of intergradation. It also occurs in the eastern-
most tributaries of the Cahaba and Black Warrior rivers and is re-
placed by isolepis in the lower parts of these drainages also. Collec-
tions are at present not extensive enough to permit an accurate pic-
ture of the relationships of the two forms, although intergradation is
proved by a series of 16 specimens (UMMZ 168613) from the head-
waters of the Black Warrior system.
 Found in the headwaters of the Illinois and Neosho rivers (trib-
utaries of the Arkansas) in northeastern Oklahoma, northwestern Ar-
kansas, and southwestern Missouri. It has not yet been recorded from
Kansas, but should occur in the extreme southeast corner of that state.
To the east chrysocephalus is common throughout most of the White
and Black river systems of northern Arkansas and southern Missouri,
but occurs sparingly in the St. Francis River system and other small


1964