The Collaborative International Dictionary of English v.0.48:

Phacops \Pha"cops\, n. [NL., fr. Gr. fako`s a lentil + 'w`ps,
   'wpo`s, the eye.] (Paleon.)
   A genus of trilobites found in the Silurian and Devonian
   formations. Phacops bufo is one of the most common species.
   [1913 Webster]