Permian—seventh and last [period] of the [Paleozoic].
Permineralization—that process by which mineral matter has been added to the original shell material by precipitation in the interstices rather than replacing the original shell material.
Phosphatic—containing or pertaining to phosphate minerals.
Phylum—one of the primary divisions of the animal or vegetable kingdoms.
Planispiral—shell coiled in one plane.
Pleistocene—earliest epoch of [Quaternary] [period], [Cenozoic] era; follows [Pliocene] epoch of [Tertiary] period, precedes Recent epoch of Quaternary.
Pleural—referring to the side or ribs; in trilobites, refers to [lateral] portions of [thorax] and pygidium.
Pliocene—latest epoch of [Tertiary] [period] of [Cenozoic] era; follows [Miocene] epoch and precedes [Pleistocene] epoch of [Quaternary] period.
Polygonal—many sided or having many-sided plates.
Polyp—a many-tentacled aquatic [coelenterate] animal, typically cylindrical or cup-shaped, as in corals.