- Corycaeus ovalis
- Corycaeus pacificus
- Corycaeus robustus
- Corycaeus speciosus
- Corycaeus typicus
- Corystoides chilensis
- Coscinaspis isopora
- Coscinaspis peripora
- Cosmetirella davisi
- Cosmocalanus darwinii
- Cranchia scabra
- Craniaspis parmipora
- Cranocephalus scleroticus
- Creseis acicula acicula
- Creseis acicula clava
- Creseis chierchiae
- Creseis virgula conica
- Creseis virgula constricta
- Creseis virgula virgula
- Cromyechinus antarctica
- Cromyechinus icosacanthus
- Cromyomma circumtextum
- Cronius ruber
- Cronius tumidulus
- Crossota alba
- Crossota brunnea
- Cryptodromiopsis antillensis
- Cryptopodia concava
- Crystallophyes amygdalina
- Ctenocalanus citer
- Ctenocalanus heronae
- Ctenocalanus vanus
- Ctenoscina brevicaudata
- Cubaia aphrodite
- Cubotholus spp.
- Cunina duplicata
- Cunina frugifera
- Cunina globosa
- Cunina octonaria
- Cunina peregrina
- Cuvierina columnella atlantica
- Cycladophora davisiana
- Cyclidium glaucoma
- Cyclodorippe angulata
- Cyclodorippe antennaria
- Cyclöes bairdii
- Cyclograpsus integer
- Cycloplax pinnotheroides
- Cyclosalpa affinis
- Cyclosalpa bakeri