Ob, prefixed to words, is used for inversely or inverted; as
_obconic_, inversely conic; _obcordate_, inversely heart-shaped.
Oblong-ovate, egg-shaped or oval.
Obsolete, indistinct, not well defined.
Ocellated, applied to eyelike spots.
Ochreous, of the colour of yellow ochre.
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.