Asaphus is a genus containing at least 35 species of Ordovician trilobites found primarily in Europe. All were benthic predators or detritivores. The typical individual was about 2–7.5 cm in length. The cephalon was smooth, and the glabellum tends not to be distinct from the cephalon. The segments of the pygidium are fused together, though some hint of segmentation may be apparent.
Sometime during the Ordovician period, an inland sea formed in what is now Eastern Europe. The sea contained a remarkably diverse trilobite fauna. Over a dozen species of Asaphus developed in this sea, with many species, including unrelated species, developing long eyestalks (officially called "peduncles") in various lengths. That so many species of trilobite developed eyestalks suggests that they were trying to overcome increased turbidity, or there was some sort of massive selective pressure leading these trilobites to bury themselves in the substrate up to their eyes. These species may have lain in wait buried beneath a loose substrate with only the tips of their eyes protruding above, looking out for danger or prey.