Calycidion formosum – synonym of Podocoryne carnea
Campanularia caliculata – synonym of Orthopyxis integra
Campanularia clausa – synonym of Lovenella clausa
Campanularia integra – synonym of Orthopyxis integra
Campanularia johnstoni – synonym of Clytia hemisphaerica
Campanulina acuminata – synonym of Aequorea vitrina
Campanulina hincksi – synonym of Eucheilota maculata
Campanulina paracuminata – synonym of Aequorea forskalea
Campanulina repens – synonym of Phialella quadrata
Campanulina tenuis – synonym of Aequorea vitrina
Cancer (Astacus) scorpioides – synonym of Bodotria scorpioides
Cancer crangon – synonym of Crangon crangon
Cancer flexuosus – synonym of Praunus flexuosus
Cancer gammarus – synonym of Homarus gammarus
Cancer gammarus galba – synonym of Hyperia galba
Cancer maxillaris – synonym of Gnathia maxillaris
Cancer medusarum – synonym of Hyperia medusarum
Cancer scorpioides – synonym of Bodotria arenosa
Cancer sedentarius – synonym of Phronima sedentaria
Cancer spinus – synonym of Spirontocaris spinus
Cancer squilla – synonym of Palaemon adspersus
Carinaria atlantica – synonym of Carinaria lamarckii
Carinaria cymbium – synonym of Carinaria lamarckii
Carinaria fragilis – synonym of Carinaria lamarckii
Carinaria gaudichaudi – synonym of Carinaria lamarckii
Carinaria lamarcki – synonym of Carinaria lamarckii
Carinaria lamarcki forma lamarcki: Van der Spoel, 1972 – synonym of Carinaria lamarckii
Carinaria mediterranea – synonym of Carinaria lamarckii
Carinaria punctata – synonym of Carinaria lamarckii
Carinaria vitrea – synonym of Carinaria lamarckii
Catablema campanula – synonym of Catablema vesicarium
Catablema eurystoma – synonym of Catablema vesicarium
Cerithium perversum – synonym of Cheirodonta pallescens
Cerithium perversum var. pallescens – synonym of Cheirodonta pallescens
Chelophyes appendiculata – synonym of Chelophyes appendiculata
Cirolana borealis – synonym of Natatolana borealis
Cirolana spinipes – synonym of Natatolana borealis
Cirolana truncata – synonym of Eurydice truncata
Cirroteuthis mülleri – synonym of Cirroteuthis muelleri
Clavula gossii – synonym of Turritopsis nutricula
Cleodora (Creseis) spinifera – synonym of Styliola subula
Cleodora (Creseis) subula – synonym of Styliola subula
Cleodora andreae – synonym of Clio andreae
Cleodora falcata – synonym of Clio andreae
Cleodora lessonii – synonym of Clio cuspidata
Cleodora quadrispinosa – synonym of Clio cuspidata
Cleodora subula – synonym of Styliola subula
Clio caudata – synonym of Clio pyramidata
Clio limacina – synonym of Clio pyramidata
Clio limacina – synonym of Clione limacina limacina
Clio retusa – synonym of Clio pyramidata
Clione borealis – synonym of Clione limacina gracilis
Clione filifera – synonym of Clione limacina filifera
Clione gracilis – synonym of Clione limacina gracilis
Clione minuta – synonym of Clione limacina minuta
Conchoecia borealis – synonym of Boroecia borealis
Conchoecia curta – synonym of Mikroconchoecia curta
Conchoecia daphnoides – synonym of Conchoecilla daphnoides
Conchoecia echinulata – synonym of Mikroconchoecia echinulata
Conchoecia elegans – synonym of Discoconchoecia elegans
Conchoecia haddoni – synonym of Orthoconchoecia haddoni
Conchoecia imbricata – synonym of Conchoecissa imbricata
Conchoecia maxima – synonym of Boroecia maxima
Conchoecia obtusata – synonym of Obtusoecia obtusata
Conchoecia spinifera – synonym of Paraconchoecia spinifera
Conchoecia teretivalvata – synonym of Metaconchoecia teretivalvata
Corymorpha annulicornis – synonym of Euphysa aurata
Corymorpha aurata – synonym of Euphysa aurata
Coryne gravata – synonym of Sarsia lovenii
Coryne implexa – synonym of Zanclea costata
Coryne mirabilis – synonym of Sarsia tubulosa
Coryne stauridia – synonym of Cladonema radiatum
Cranchia megalops – synonym of Teuthowenia megalops
Crangon nanus – synonym of Philocheras bispinosus
Crangon septemcarinata – synonym of Sabinea septemcarinata
Crangon spinosus – synonym of Pontophilus spinosus
Ctenomysis alata – synonym of Lophogaster typicus
Cubogaster gemmascens – synonym of Lizzia blondina
Cuma cornuta – synonym of Diastylis cornuta
Cuma edwardsii – synonym of Bodotria scorpioides
Cuma nasica – synonym of Leucon nasica
Cuma resima – synonym of Brachydiastylis resima
Cuma rubicuna – synonym of Campylaspis rubicunda
Cuma scorpioides – synonym of Bodotria arenosa
Cuma trispinosa – synonym of Iphinoe trispinosa
Cupulita cara – synonym of Nanomia cara
Cupulita sarsii – synonym of Nanomia cara
Cuspidella humilis – synonym of Staurophora mertensii
Cyanaea bougainvillii – synonym of Bougainvillia macloviana
Cymothoa chelipes – synonym of Idotea chelipes
Cymothoa emarginata – synonym of Idotea emarginata
Cynthia flemingii – synonym of Siriella armata
Cynthilia armata – synonym of Siriella armata
Cynthilia clausii – synonym of Siriella clausii
Cynthilia flemengii – synonym of Siriella armata
Cynthilia frontalis – synonym of Siriella armata
Cynthilia jaltensis – synonym of Siriella jaltensis
Cynthilia norvegica – synonym of Siriella norvegica
Cynthis armata – synonym of Siriella armata
Cyrianassa elegans – synonym of Hemilamprops rosea
Cytaeis octopunctata – synonym of Rathkea octopunctata