Placosmilia, [401]

Placospongia, spicules of, [233]

Plakina, [212], [213];

P. monolopha, [210], [212], [213]

Plankton, Protozoa of, [48];

Foraminifera of, [61];

Radiolaria of, [75]

Planorbulina, [59], [63]

Plant(s), definition, [39];

Animals and, discussion on, [35] f.;