Ciona fascicularis Hancock, 1870 – synonym of Ciona intestinalis
Circinalium concrescens Giard, 1872 – synonym of Sidnyum turbinatum
Cynthia claudicans Savigny, 1816 – synonym of Microcosmus claudicans
Cynthia comata Alder, 1863 – synonym of Polycarpa fibrosa
Cynthia coriacea Alder & Hancock, 1848 – synonym of Styela coriacea
Cynthia pomaria Savigny, 1816 – synonym of Polycarpa pomaria
Cynthia quadrangularis Appellöf & Grieg, 1890 – synonym of Polycarpa pomaria
Cynthia rosea Alder & Hancock, 1912 – synonym of Microcosmus claudicans
Cynthia vestita Alder, 1860 – synonym of Cnemidocarpa mollis
Cyntia echinata Alder, 1850 – synonym of Boltenia echinata