Brown bullhead in the context of Yellow bullhead

Ameiurus is a genus of catfishes in the family Ictaluridae. It contains the three common types of bullhead catfish found in waters of the United States, the black bullhead (Ameiurus melas), the brown bullhead (Ameiurus nebulosus), and the yellow bullhead (Ameiurus natalis), as well as other species, such as the white catfish (Ameiurus catus or Ictalurus catus), which are not typically called "bullheads".

The species known as bullheads can be distinguished from channel catfish and blue catfish by their squared tailfins, rather than forked.

The black bullhead or black bullhead catfish (Ameiurus melas) is a species of bullhead catfish. Like other bullhead catfish, it has the ability to thrive in waters that are low in oxygen, brackish, turbid, and/or very warm. It also has barbels located near its mouth, a broad head, spiny fins, and no scales. It can be identified from other bullheads as the barbels are black, and it has a tan crescent around the tail. Its caudal fin is truncated (squared off at the corners). Like virtually all catfish, it is nocturnal, preferring to feed at night, although young feed during the day. It generally does not get as large as the channel or blue catfish, with average adult weights are in the 1-to-2-pound (0.45 to 0.91 kg) range, and almost never as large as 4 pounds (1.8 kg). It has a typical length of 6–14 inches (15–36 cm), with the largest specimen being 24 inches (61 cm), making it the largest of the bullheads. It is typically black or dark brown on the dorsal side of its body and yellow or white on the ventral side.

Like most of the bullheads (and even flathead catfish), it has a squared tail fin, which is strikingly different from the forked tail of channel and blue catfish. It is a bottom-rover fish, meaning it is well-adapted for bottom living. It is typically dorsoventrally flattened, and has a slightly humped back. Its color depends on the area where it is taken, but it generally is darker than brown or yellow bullheads (A. nebulosus and A. natalis, respectively). It can be distinguished from a flathead catfish (Pylodictis olivaris) by the fact that the black bullhead's lower lip does not protrude past the upper lip. Distinguishing it from the brown bullhead is a bit more difficult, depending on the area where it is caught, but a distinguishing detail between the two includes weak serration on the pectoral spine of the black bullhead, while the brown's corresponding spine is more strongly barbed. The anal fin of the black bullhead also has a gray base, and its caudal fin often has a pale bar at its base. The brown bullhead is also typically mottled brown and gray-green dorsally, instead of the darker black. Both the black and brown bullheads can easily be distinguished from the yellow bullhead by the color of the barbels on their chin: the yellow bullhead has white barbels under its mouth.