166 BULLETIN FLORIDA STATE MUSEUM Vol. 8

The northern limits of distribution of the two species seem to indicate
that such differences do exist. Both species hybridize with other
species with roughly equal frequency.

 Notropis chrysocephalus: chrysocephalus X isolepis
Notropis megalops, Gilbert, 1891: 157 (not of Rafinesque; in part; collections from
 area of intergradation in Black Warrior River system, Alabama).
 The only collection I have seen that contains positively identified
intergrades (UMMZ 168613) is from Blackburn Fork (9 miles south-
west of Oneonta, Alabama), a headwater tributary of the Black War-
rior River. Further collecting will probably reveal intergrading pop-
ulations in a number of localities, most likely in other headwater trib-
utaries of the Black Warrior and Cahaba systems. Other areas where
intergrades might occur are the lower Coosa drainage where the two
subspecies appear to be allopatric, the headwaters of the Tallapoosa
River, the more westerly headwater gulf tributaries bordering the
Tennessee River drainage, and the Arkansas River system in Arkansas.
 The chief basis for identification of UMMZ 168613 as an inter-
grading population is the presence of typical individuals of both sub-
species together with intermediates. Several specimens have pro-
nounced, straight, dorso-lateral stripes running along the side of the
back, while in others these stripes are crooked and poorly defined.
The predorsal and anterior dorso-lateral scale rows in the former
(isolepis type) individuals are regular and even, while these rows are
irregular and uneven in the latter (chrysocephalus type) specimens.
 The subspecies chrysocephalus and isolepis are readily distin-
guished not only on the basis of the criteria discussed above, but also
by notable differences in both the anterior dorso-lateral and circum-
ferential scale counts (tables 9 through 11). These differences by
themselves are not sufficiently great to permit identification of small
series of intergrades, such as the above.
 The apparent scarcity of intergrading populations of chrysocepha-
lus and isolepis, together with the rather unusual distribution of these
forms in the Coosa system, suggest that these forms are close to the
specific level of separation. I maintain them as subspecies because,
in addition to the intergrading population previously cited, specimens
of isolepis living well out of the area of potential intergradation occa-
sionally have rather uneven anterior dorso-lateral stripes, causing the
individual to appear more or less intermediate. Also past collections
from near the known area of intergradation usually contain too few
specimens or the individuals are too small to permit accurate identi-