Pliny the Elder (Natural History, 8.77) described the catoblepas as a mid-sized creature, sluggish, with a heavy head and a face always turned to the ground.
Claudius Aelianus (On the Nature of Animals, 7.6) provided a fuller description: the creature was a mid-sized herbivore, about the size of a domestic bull, with a heavy mane, narrow, bloodshot eyes, a scaly back and shaggy eyebrows.