Cacospongia schmidtii – synonym of Spongionella pulchella
Caminus osculosus – synonym of Pachymatisma johnstonia
Chalina arbuscula – synonym of Haliclona oculata
Chalina cervicornis – synonym of Haliclona oculata
Chalina flemingii – synonym of Haliclona cinerea
Chalina gracilenta – synonym of Acervochalina limbata
Chalina grantii – synonym of Haliclona oculata
Chalina limbata – synonym of Acervochalina limbata
Chalina montagui – synonym of Haliclona cinerea
Chalina oculata – synonym of Haliclona oculata
Chalina pulcherrima – synonym of Haliclona urceolus
Chalina seriata – synonym of Clathria seriata
Chalina simulans – synonym of Haliclona simulans
Chalina zostericola – synonym of Acervochalina limbata
Chalinula densa – synonym of Haliclona simulans
Chalinula fertilis – synonym of Acervochalina fertilis
Chalinula fertilis – synonym of Acervochalina loosanoffi
Chalinula limbata – synonym of Acervochalina limbata
Chalinula mcandrewii – synonym of Haliclona fistulosa
Chalinula montagui – synonym of Haliclona cinerea
Chalinula oculata – synonym of Haliclona oculata
Chalinula pallida – synonym of Haliclona simulans
Chalinula robustior – synonym of Haliclona urceolus
Ciocalypta leei – synonym of Ciocalypta penicillus
Clathria (Microciona) armata – synonym of Clathria armata
Clathria (Microciona) basifixa – synonym of Clathria basifixa
Clathria (Microciona) ctenichela – synonym of Clathria ctenichela
Clathria abyssorum – synonym of Antho dichotoma
Clathria beani – synonym of Antho involvens
Clathria cantabrica – synonym of Clathria barleei
Clathria dichotoma – synonym of Antho dichotoma
Clathria laciniosa – synonym of Clathria barleei
Clathria morisca – synonym of Antho involvens
Clathria pelligera – synonym of Dictyonella pelligera
Clathrina coriacea rubra – synonym of Clathrina rubra
Clathrina lacunosa – synonym of Guancha lacunosa
Clathrina spinosa – synonym of Clathrina contorta
Cliona corallinoides – synonym of Cliona vastifica
Cliona coralliophaga – synonym of Aka infesta
Cliona gorgonioides – synonym of Cliona celata
Cliona gracilis – synonym of Cliona vastifica
Cliona howsei – synonym of Cliona lobata
Cliona labyrinthica – synonym of Aka infesta
Cliona northumbrica – synonym of Cliona vastifica
Collingsia schmidti – synonym of Stelletta grubii
Collospongelia dendyi – synonym of Hyrtios dendyi
Cometella pyrula – synonym of Crella pyrula
Cometella spermatozoon – synonym of Suberites virgultosus
Cornulum ascidioides – synonym of Coelosphaera physa
Craniella cranium – synonym of Tetilla cranium
Crella inflata – synonym of Halicnemia patera
Crellomima derma – synonym of Crella derma
Cribrella elegans – synonym of Crella elegans
Cribrochalina calyciformis – synonym of Axinella infundibuliformis
Cribrochalina sluiteri – synonym of Stylissa cribrosa
Cydonium barretti – synonym of Geodia barretti
Cydonium conchilegum – synonym of Geodia conchilega