The horned dinosaur Centrosaurus ("well-horned lizard") resembled a large rhinoceros. Like the rhinoceros, it had a heavy head, strong shoulders, pillar-like legs, broadhoofed toes, a small tail, and a long, pointed nasal horn. In Centrosaurus, the massive head also had two small brown horns above the eyes. The original specimen was an isolated crest. 

More complete skulls with a large single nose-horn were only identified later, and the two hook-shaped spurs of bone that face each other at the very top of the frill are the source of the name, not the prominent nasal horn as commonly stated. Lambe originally misidentified a piece of another hook-like bony process that projects downward over the parietal opening on each side of the frill as part of a nasal horn. 

(The name Centrosaurus Lambe is not preoccupied. Centrosaurus Fitzinger 1843 was first published as a junior synonym of Phrynosoma in Fitzinger's Systema Reptilium--then wrongly listed as a junior synonym of Heloderma by Romer in 1956, in invalid usage. Under ICZN 1985 Art. 11 (e), Fitzinger's genus name does not appear to meet the requirements of an available name for purposes of scientific nomenclature--it was not used before 1961 as a valid genus name nor cited as a senior homonym of another taxon.)