- P1
- paedophore
- Palaeocopida
- pallial canal
- Palmate
- Palp
- palpacle
- Palpode
- palpon
- Palps
- Papilla
- Papillae
- paragnaths
- Paramere
- Parapodial cirrus
- parapodial lobe
- Parapodial rami
- Parapodial trunks
- Parapodium
- Parapylae
- parasite
- parietal
- Parmal pores
- Paroral membrane
- pars incisiva
- parthenogenesis
- Patagium
- Pc
- Pd
- pectinate
- pectoral fin
- Pedal
- Pedalium
- Peduncle
- pelagic
- Pellicle
- pelvic fins
- Pen
- Peniculus
- Penile sucker
- pereion
- pereionite
- pereiopod
- Pereon
- Pereopods
- Pereopods III and IV
- Pereopods V-VII
- Peribuccal denticules
- Perioral kinety
- Periostracum
- peripharyngeal bands
- Peripheral canal system
- Periplasmic cortex
- Perisarc
- Peristome
- Peristomial cirri
- Peristomial collar
- Peristomial disc
- Peristomial field
- Peristomium
- peritrophic membrane
- Peronia
- Peronial canal
- Perradial
- Perradial canal
- Pexicyst
- Phacellus
- Phacoid shell
- Phaeodium
- Pharynx
- phorozooid
- Photophore
- phyllocyst
- phytoplankton
- pigment
- Pillar genital
- pilose
- Pinnules
- Pit sensory
- Planispiral
- planktivore
- plankton
- Planula
- pleon
- pleonite
- pleopod
- Pleopods
- pleosome
- pleotelson
- pleura
- pleuston
- pleustonic
- plumose
- pneumadenia
- pneumatophore
- podomere
- podoplean tagmosis
- Polar caps
- Polydisc scyphistoma
- polygastric stage
- polyhaline
- Polyp
- Pore
- Pore arrangement
- Pores
- Porous sieve-plate
- Porticus genital
- Post-abdominal
- post-antennal sinus
- post-flexion stage
- post-larvae
- post-orbital groove
- post-temporal
- Postcephalic lobe
- postchaetal
- posterior
- posterior fins
- Posterior footlobe
- postlarval
- Pr
- praniza
- pre-anal length
- pre-flexion larva
- pre-opercle
- pre-orbital
- prechaetal
- Primary canal
- Primary circular canal
- Primary lateral spines
- Primary mouth
- Primary organic membrane
- primary production
- Primary ring canal
- Primary shell
- Primary spicule
- Primary spines
- Proboscis
- processus mamillaris
- procoxale
- Proloculus
- propodus
- propus
- Prostomium
- protandrous
- Protective membrane
- Protoconch I
- protogynous
- Protopod
- protopodite
- proventriculus
- proximal
- Pseudoconch
- pterotic
- pterygial
- pterygostomian spine
- Pustule
- pustules
- pygidial cirri
- Pygidium
- Pylome
- pylopods
- Pyramid
- Pyramidal elevation
- Pyramidal tubes