- caliculate
- calthrops
- candelabra
- canonochela
- carbonate spherule
- centrangulate
- centrotriaene
- centrotylote
- chela
- chiactine
- chiaster
- chiastosigma
- choanochamber
- choanocyte
- choanocyte chamber
- choanosomal skeleton
- choanosome
- cinctoblastula
- clad
- cladome
- cladotylote
- clathrate
- clathriid
- clavate
- clavidisc
- cleistochela
- coeloblastula
- coelodischela
- collagen fascicle
- color variety
- columnar
- comma
- compressible
- confused skeleton
- conule
- cored fibre
- cormus
- corrugated
- cortex
- cortical skeleton
- crateriform
- croca
- cuticle
- cyrtancistra
- cystencyte