[Polychaeta] Collective term used for a structure formed by the fusion of peristomium, prostomium and in many cases, one or more cephalised segments (body plan pelagic polychaete).

[Pteropoda] In molluscs the head bears the buccal mass, eyes, and tentacles (Pneumodermopsis in ventral view).

[Pisces] Specialized anterior part of an animal on which the mouth and major sensory organs are located; part other than the body (snout to the posterior gill opening in fish).