On-y-choph´o-ra [Gr. onyx, claw; pherein, bear.] Arthropods including only a single genus, the curious caterpillar-like Peripatus.
Oösperm [Gr. oon, egg; sperma, semen.] A fertilized ovum. The first stage in the existence of a human being is called oösperm.
O-per´cu-lum [Lat. lid.] The gill-cover.
O-phid´i-a [Gr. ophis, serpent.] Serpents; snakes.
Op-po´nens Hal-lu´cis [Lat. ob, pono, to place over against; hallux, great toe.] The name of a muscle in the foot.
Or-do-vi´cian [ordovices, ancient Celtic tribe in Wales.]
Or-nith-o-del´phi-a [Gr. ornis, bird; delphys, womb.] A sub-class of oviparous mammals.
Or-o-hip´pus [Gr. oros, mountain; hippos, horse.]
Or-tho-cer´a-tites [Gr. orthos, straight; keras, horn.]
Os´te-o-blasts [Gr. osteon, bone; blastano, sprout.]