Offuscated, darkened, clouded, dimmed.
Olivaceous, being of a greenish olive colour.
Operculum, a lid which closes the aperture of some turbinated univalves; and also some of the tops of multivalves.
Orbicular, spherical, circular, round.
Order, the second division of the animal kingdom. Orders are made up of a plurality of genera.
Orifice, an opening or perforation.
Ovate, shaped like the longitudinal section of an egg.
Ovoid, oval.
P.
Palmated, webbed, as in the feet of some water-birds.