Phthongometer, b. [47].

Physical optics, b. [52].

Piston, a. [346].

Plagihedral faces, b. [82].

Plane of maximum areas, b. [380].

Pleiocene, b. [529].

Plesiomorphous, b. [335].

Plumb line, a. [164].

Pneumatic trough, b. [273].

Poikilite, b. [530].