phacopIdæ

pl. [Mod. Latin phacop (s); Lat. fem. pl. adj. suff. -idæ.] Palæont.: A family of Trilobites. Head well developed, the globella broadest in front, with three lateral grooves; eyes large, and having facets; four instead of the three normal pairs of grooves; body-rings eleven. Lower Silurian to the Devonian inclusive. phalænopsis notched, nostrils partly closed by a membrane; two middle feathers of the tail very long and narrow. Three species are known, all from tropical seas.