- cadophore
- caecum
- calceolus
- calyptopis
- campanulate
- capillary chaetae
- Capitata
- capitate tentacle
- capitulum
- carina
- carinate
- cariniform
- carnivore
- carotenoid
- carpal suckers
- carpus
- cartilage
- caruncle
- caudal
- caudal fold
- caudal furca
- central organ
- cephalon
- cephalothorax
- cerebral ganglion
- chaetae
- chaetiger
- chela
- chelate
- chitin
- chitinophore
- chitinous
- chromatin
- chromatophore
- chrysomitra
- cilia
- ciliar band
- ciliated tufts
- cilium
- circum-oesophageal ganglion
- circumoral appendages
- circumpolar
- cirri
- cirrophore
- clasper
- clinal variation
- closing mechanism
- closing membrane
- clypeus
- cnida
- cnidocyst
- cnidocyte
- cnidome
- cnidophore
- coelenteron
- coelom
- coelomic fluid
- collarette
- columella
- comb-chaetae
- commensalism
- competition
- compound chaetae
- compound eyes
- conaria
- concave
- conspecific
- constricted eye
- constriction
- continental shelf
- continental slope
- convex
- copepodid
- copulatory appendage
- cordylus
- cormidum
- cosmopolitan
- coxal plates
- craspedote
- crest
- crystalline cone
- cuticle
- cuttlebone
- cyclops
- cypris
- cyrtopia
- cythozooid