BULLETIN FLORIDA STATE MUSEUM


 A specimen of N. cornutus in the United States National Museum
(USNM 86211) bears the locality "vicinity of Medicine Hat, Alberta".
The presence of several eastern species such as Semotilus corporalis
and Pimephales notatus in the same collection suggests the locality
data may have been transposed.
 A single specimen supposedly collected in the Black River, Clark
National Forest, Missouri (UMMZ 117557) also is regarded as suspect.
There are no other records of this species from the Black River basin,
and the next closest populations are in the Missouri River system ap-
proximately 150 miles to the north. N. chrysocephalus, which was
taken in the same collection, is common throughout the Black drain-
age and, from the known relative distribution of these two forms it
is rather unlikely that they should occur sympatrically so far south.
This record may have resulted either from an introduction or, more
likely, from an accidental transfer of specimens in the laboratory.
 Two records of N. cornutus from the Arkansas River drainage in
Kansas (UMMZ 122075, Winfield, Cowley County; KU, Rock Creek,
near lola, Allen County) are also thought to be due to transposed
data. Other collections from Kansas have been found with faulty
labeling, and until these records are substantiated it seems best to
treat them as erroneous.
 The populations in the headwaters of the Platte and Kansas rivers,
those from the middle part of the White River, Indiana, and in the
lower Kanawha River system, West Virginia, are the most interesting
and significant ones in the range. Apparently N. cornutus once was
much more widely distributed than at present, and its disappearance
from large areas of the Great Plains can be attributed to the drying
this area has undergone since the Wisconsin glacier retreated north-
ward.
 The absence of N. cornutus from a large part of the Ohio River
system is due partly to natural conditions and partly to man's
influence. Trautman (1957:357) has shown that cornutus is now
missing from areas where man's activities have caused the streams
to warm and silt and the flowing springs to disappear. Commonly
it has been replaced by N. chrysocephalus, which reflects the two
species' close ecological relationship and the tolerance of chryso-
cephalus for warmer, more turbid conditions. Early collections
from the Ohio River system show that chrysocephalus has long been
the dominant form and evidently started to replace cornutus before
man started altering the landscape. Apparently a warming of the
streams occurred, and though cornutus probably could have survived
had no other factor been involved, chrysocephalus was favored by


Vol. 8