76 
Noel M. Burkhead, et al. 
/. natalis (Lesueur), yellow bullhead; /. nebulosus, brown bullhead; /. 
platycephalus (Girard), flat bullhead; I. punctatus (Rafinesque), channel 
catfish; Pylodictis olivaris (Rafinesque), flathead catfish. Of this assem- 
blage, /. melas and Pylodictis are considered to be introduced, and /. 
brunneus probably so, to the Roanoke drainage; the same is true for the 
status of I. furcatus and /. brunneus in Virginia. 
This report discusses the distribution of each species in Virginia and 
extralimitally where pertinent. Diagnostic characters with the greatest 
utility and ease in identifying these species within the study area are dis- 
cussed and employed in a key. Osteological and other differences among 
Ictalurus species are found in Paloumpis (1964), Yerger and Relyea 
(1968), Smith and Lundberg (1972), and Lundberg (1975). 
Concepts of genera, subgenera, and species groups follow Lundberg 
(1975). However, regarding our discussion of species identification, for 
practical purposes we artificially group /. catus with the “forktail cat- 
fishes,” /. furcatus and /. punctatus of the subgenus Ictalurus. Ictalurus 
catus actually is placed, in the subgenus Amiurus, in the catus group with 
the species we collectively refer to as “flathead bullheads,” i.e., I. brun- 
neus, /. platycephalus and /. serracanthus Yerger and Relyea. The other 
three species, our “typical bullheads,” /. melas, /. natalis and /. nebulosus, 
are referred by Lundberg to the natalis group of the subgenus Amiurus. 
METHODS AND MATERIALS 
Methods of counting and mensuration follow those outlined by 
Hubbs and Lagler (1958) and Yerger and Relyea (1968), with one dif- 
ference from the latter study. Removal of the gill arch for gill raker 
counts was necessary only in the smallest specimens; otherwise a slit at 
the dorsal and ventral junctions of the operculum, and adduction of the 
latter, were sufficient to expose gill rakers. All rakers on the right arch in- 
cluding rudiments on lower limb, were counted; fused rakers were coun- 
ted as one. To count anal rays it was necessary to expose them by slitting 
the anal fin base and peeling the skin back. All anterior rudimentary rays 
were counted; the last two rays with a basal conjuncture were counted as 
one. 
Measurements were made using Helios dial calipers for all propor- 
tionally expressed characters (as % SL) and for standard length (SL) of 
smaller specimens; they were recorded to the nearest 0.1 mm. The SLs of 
large specimens were obtained with a beam compass and a steel rule, and 
recorded to the nearest 0.5 mm. Counting was aided by the use of a 
variable magnification stereo dissecting microscope. The counts from 
one I. melas, 33.6 mm SL, were omitted from tabulation due to extreme 
low counts (rakers incompletely developed). 
Complete locality data on specimens examined are on file at 
Roanoke College. Flathead bullhead localities are depicted in Figure 1 
and are listed in sequence from downstream to upstream. Typical 
bullhead localities are presented by basin or drainage and therein 
