Orr, Henry B., [69].

Osborn, Prof. H. F., [33].

Owen, Richard, [11].

Paleontology, [31], [73], [75], [76].

Palms from Cordilleras, [82].

Pangenes, [40].

Panmixia, [15], [39], [42], [43], [64].

Papilio, [16], [52].

Parallecta, [23].

Parts, struggling of the, [29], [39], [66]-[67].