- Rachis
- Radial beams
- Radial canal
- radial canals
- Radial sinus
- Radial spicule
- Radial spines
- Radial symmetry
- Radial tubes
- radioli
- Radius
- Radula
- Radula ctenodont
- Radula heterodont
- Radula homodont
- Radula plate
- Ramus
- range
- rataria
- rectum
- regeneration
- region
- Resting cyst
- rête
- reticulate
- Reticulopod
- Rhinocanna
- Rhinophore
- Rhizostomae
- Rhopalar
- Rhopalial canal
- Rhopalial cleft
- Rhopalial lappet
- Rhopalial pit
- Rhopalial sinus
- Rhopalium
- rib
- Ribs
- ridge
- Right coiling
- Ring canal
- Ring furrow
- Rosette gland
- Rosette-shaped
- rostral incisure
- Rostral spine
- Rostrum
- rudimentary
- Rudimentary bulb
- rugose