GILBERT: FISHES OF THE SUBGENUS LUXILUS


and uniformly parallel; pigment always present on chin and gular
region, often with a streak of black running posteriorly down gular
membrane.
 A comparison of N. c. isolepis and N. c. chrysocephalus is presented
in table 3.
 DESCRIPTION. Body proportions and counts of fin rays and scale
rows are listed in tables 6 and 9 through 15. Characters mentioned in
the description of Notropis chrysocephalus and in the above diagnosis
are not repeated in the following paragraph.
 Arrangement of circumferential scales above and below lateral
line (10-2-11 or 11-2-10) 11-2-11 to 13-2-13 (15-2-13); dorso-lateral scale
pockets darkest around edges which, with the intensification of pig-
ment caused by the overlapping scales, results in three straight, well-
defined, parallel stripes running lengthwise along dorso-lateral part
of back, the stripes converging posteriorly with those from opposite
side to give the appearance of long, narrow, parallel "Vs" when viewed
from above (figure 15A); pigment always present on chin and gular
area.
 The following color description is based on an adult male (UMMZ
161262) collected on 6 June 1949 from a tributary of the Ouachita
River 0.3 mi. southeast of Vernon, Jackson Parish, Louisiana: snout,
branchiostegals, lower surface of head, and belly rosy, shading to
scarlet along sides of body; dorsal and caudal fins of breeding males
washed with yellowish, outer margin clear, bordered inside by a nar-
row band of crimson; distal half of pectoral, pelvic, and anal fins
brilliant scarlet, except for the edges which are clear; proximal half
of anal fin cream, distal half a brilliant scarlet except for the narrow
border which is colorless; proximal half of pectoral and pelvic fins
slaty gray, distal half scarlet, with the border colorless.
 VARIATION. This form shows relatively little geographic variation.
Occasionally an unevenness is evident in the arrangement of the pre-
dorsal and anterior dorso-lateral scales, but this is slight and never
approaches the usual situation in N. c. chrysocephalus. Anal ray
counts vary to some extent, the extremes in this subspecies being the
greatest encountered in any form of Luxilus. A specimen with 7
anal rays (UMMZ 128116) was found from the Red River drainage of
Arkansas, and one with 12 anal rays (UMMZ 161396) from a tributary
of the Mississippi River in northern Mississippi; other specimens in
these series have normal counts. Occasional populations contain an
unusually high percentage of individuals with an anal ray count
other than 9, a condition also encountered in certain populations of
Notropis cornutus. Counts of 31 specimens of isolepis (UMMZ 157780)


1964