GILBERT: FISHES OF THE SUBGENUS LUXILUS


New and Roanoke show some red on the fins or body. Large adult
males taken in the Tar River 20 August 1946 by Reeve M. and Joseph
R. Bailey (UMMZ 147583) also showed some red on the caudal fin.
Red pigment when present occurs only on the tips of the fins, not
including the pectorals. I have never seen specimens of albeolus so
colored, so I cannot assess possible differences from cornutus in distri-
bution of red on the fins. Apparently the only part of the body on
which red pigment appears is the snout.
 Some individuals, particularly those from the Neuse, Tar, and
Cape Fear systems, have a few vertical crescent-shaped bars along
the side similar to those in cornutus, cerasinus, and chrysocephalus.
Such specimens are extremely difficult to distinguish in preservative
from sparsely pigmented individuals of cornutus.
 Analysis of vertebral variation in albeolus (table 8) shows that
specimens from the Roanoke and New river systems usually have 40
vertebrae, individuals from the Neuse generally 39. Specimens from
the Tar drainage have either 39 or 40 vertebrae with equal frequency.
The Cape Fear population could not be analyzed because of lack of
material. At first glance the differences in vertebral counts appear
to be directly correlated with variation in body depth, though the
presence of either 39 or 40 vertebrae in Tar River specimens indi-
cates otherwise. Possibly these counts reflect ecological differences
between the several streams.
 RELATIONSHIPS. The forms albeolus and cornutus are so close to
the species-subspecies line in their degree of evolution that it is diffi-
cult to decide their proper taxonomic relationship. In the past al-
beolus has been treated both as a subspecies and, in recent years, as
a species, which Moore (1957: 126) has questioned.
 I myself have had doubts about the correct taxonomic status of
albeolus. My first inclination (1961a: 2411) was to regard it as a sub-
species of N. cornutus, primarily because not all preserved specimens
of the two forms can be distinguished. This situation is by no means
unique, and may be noted in other North American Cyprinidae, for
example in species of the genus Hybopsis (subgenus Nocomis). Mem-
bers of this group are very similar in over-all appearance, and several
forms are positively distinguishable only by means of the number and
arrangement of the nuptial tubercles on the heads of breeding males.
Thus though only a small percentage of individuals of these species
can be- told apart, the constant differences in the character of the
tubercles leaves little doubt that their relationships are at the spe-
cific level. Many other pertinent examples exist in. fishes, as well
as in other groups of animals.


1964