| Chionopsis ornatissima (Broderip, 1835) |
| Choristodon Jonas, 1844 |
| Choristodon robustum (G. B. Sowerby I, 1834) |
| Choristodon robustus (G. B. Sowerby I, 1834) |
| Circe Schumacher, 1817 |
| Circe margarita P. P. Carpenter, 1857 |
| Circe subtrigona P. P. Carpenter, 1857 |
| Circomphalus Mörch, 1853 |
| Circomphalus strigillinus (Dall, 1902) |
| Clementia Gray, 1842 |
| Clementia (Egesta) Conrad, 1845 |
| Clementia (Egesta) solida Dall, 1902 |
| Clementia solida Dall, 1902 |
| Clementiinae Frizzell, 1936 |
| Cooperella P. P. Carpenter, 1864 |
| Cooperella atlantica Rehder, 1943 |
| Cooperella subdiaphana (P. P. Carpenter, 1864) |
| Cyclina Deshayes, 1850 |
| Cyclina producta P. P. Carpenter, 1856 |
| Cyclinella Dall, 1902 |