- Ornithodoros moubata
- Orothamnus Zeyheri
- Osprey and Grakles
- Ostrich
- Otiobius (Ornithodoros) megnini, head of nymph
- Otiobius (Ornithodoros) megnini, male. (a) dorsal, (b) ventral aspect
- Outlines of Manilla Buffalo
- Owl
- Owl
- Owl
- Owl
- Owl 2
- Owl catching a rabbit
- Oxen bearing the Yoke. (Lam. iii. 27)
- Paca
- Pachypodium succulentum
- Painted Dog
- Painted Stork
- Palæolithic Men Attacking Cave Bear
- Pama
- Panther snake
- Paradise fish
- Partridges
- Parts of Birds
- Passage into trachea and esophagus; Pharynx
- Peach
- Peach cut in half lengthwise
- Peacock
- Pear
- Pear cut lengthwise
- Pearl lizard
- Pearly Natilus
- Pediculoides ventricosus, female
- Pediculus showing the blind sac (b) containing the mouth parts (a) beneath the alimentary canal (p)
- Pediculus vestimenti
- Pediculus vestimenti 2
- Pegasse
- Pekari
- Pelican
- Pentapterygium serpens
- Pentapterygium serpens (flowers deep crimson)
- Peregrine Falcon, and young ones
- Performing Elephant
- Persian Kitten 'Lambkin'
- Persian Lion from the frieze at Susa (Perrot & chipiez)
- Pete
- Pharyngeal syringe or salivary pump of Fulgora maculata
- Phronima colletti, Male. From a Specimen taken in Deep Water near the Canary Islands
- Pied-billed Grebe
- Pied-billed Grebe, Breeding Plumage
- Pigeon tick
- Pike
- pine cone
- pine cone on a branch
- Pine Siskin
- Piophila casei
- Plan of the foetal circulation
- Pleat Gecko
- Plum
- Podolian Cow, Galicia