- caeca
- calanoida
- canine teeth
- caninelike
- capacious
- capape
- capsules
- carapace
- cardiform teeth
- Caribbean Sea
- carinate
- carmine
- carnivorous
- carrion
- cartilaginous
- CAS
- CAS(SU)
- Caspian Sea
- catadromous
- caudal
- cemiculus
- centroscyllium
- cephalic
- cephalopods
- ceratobranch
- ceratohyal
- cernium
- chaetognaths
- cheek
- chest
- chin
- chinchard
- chironomid
- chitons
- chordata
- chromatophore
- ciliata
- cimbrius
- circumglobal
- circumpolar
- circumtropical
- cirratum
- cirri
- cirriped
- cladocerans
- claspers
- cleft
- cleithral
- cline
- cloaca
- CLOFNAM
- CM
- CNHM
- coalesced
- coelenterates
- collar
- colonies
- commensalism
- commissure
- concave
- confluent
- conical teeth
- conspecific
- continental shelf
- copepod
- coralligenous
- coregonus
- cornubica
- corselet
- crab
- crangonidae
- crenulate
- crest
- cretense
- crevice
- crown
- crustacea
- ctenoid scale
- cuneiform
- cusp
- cutaneous fold
- cycloid scale
- Cyprus Island