Griffiths, Annual Report of the Missouri Botanical Garden 22: 25, 1911
Opuntia bentonii plants resemble small O. lindheimeri plants at first glance, but there are sustained differences. O. bentonii mature cladodes are about 7 inches by 11 inches and obovate or subcircular. There may be 1-3(5) spines in some areoles, yellow and translucent. Spines may be up to 1-inch long. Veins are visible between areoles. O. bentonii was found on Galveston Island, TX, Bolivar Peninsula, TX, and Sea Rim State Park near Port Arthur, TX. Perhaps it grows on the Gulf Coast in many areas; we have not found it away from salt water. The plants are generally 2-ft tall. See the original citation.
O. bentonii plants are distinct from Opuntia lindheimeri in several ways. Whereas O. lindheimeri can become quite large (tall and broad), O. bentonii is typically 2-ft tall or less. O. bentonii remains small in cultivation. The stigmas of O. bentonii are yellow or yellow-green in contrast to the green stigmas of O. lindheimeri, and the seeds of O. bentonii are larger than those of O. lindheimeri (about 40% larger diameter).
O. bentonii often grows with O. anahuacensis, but the two plants, while both low and with yellow spines, are quite different. O. anahuacensis has fewer spines and tends to grow horizontally. It can form large horizontal thickets, whereas O. bentonii does not. O. bentonii has obovate or subcircular pads in contrast to the elliptical or oval pads of O. anahuacensis. The areoles of O. bentonii are often raised slightly, giving pads a dimpled look. Moreover the spines of O. anahuacensis are aciculate unlike the angled spines of O. bentonii.
O. bentonii has some features in common with O. tunoidea of the South Carolina coast. If the two taxa are the same, the correct name for both is O. tunoidea. More study is needed.