- sanidaster
- sceptrum
- secondary fibre
- selenaster
- sieve plate
- sigma
- sigmancistra
- sigmaspire
- spatuliferous anchorate chela
- sphaerancora
- spheraster
- spheroxyaster
- spicule
- spiculoid
- spiny
- spiraster
- spirosigma
- spongin
- spurred anisochela
- sterraster
- sterrospheraster
- stipitate
- streptaster
- strongylaster
- strongyle
- strongylostyle
- strongyloxea
- style
- sublithistid skeleton
- subtylostyle
- sulcate
- syconoid aquiferous system
- syllebeid aquiferous system