Dalmanites is a genus of trilobite in the order Phacopida. They lived from the Late Ordovician to Middle Devonian. It was named for the Swedish naturalist Johan Wilhelm Dalman. The trilobites of this genus have slightly convex exoskeletons with an average length of 4–7 cm (1.5–3 in). The cephalon is semicircular or parabolic. The glabella (center portion of the head) is often pear-shaped, and tapers outward toward the front. The glabella also always contains three pairs of obvious glabellar furrows. Also prominent are the large mosaic (schizochroal) eyes. The thorax is composed of eleven segments, with the relatively large pygidium with a slender axis of 11 to 16 rings and 6 or 7 pleural ribs. The pygidium ends in a striking tail spike.