n. A genus of trilobites belonging to the family Olenidæ and characterized by possessing 10 free segments and a small unsegmented pygidium. It occurs in the Lower Cambrian rooks.n. In chem., one of the rare earths, found with yttria in gadolinite, and supposed to be the oxid of a distinct element, holmium: but it may be an as yet unseparated mixture.