• Caneosphaera K.R. Gaarder in K.R. Gaarder & B.R. Heimdal, 1977
• Cannosphaera Haeckel, 1879 (uncertain)
• Catenisphaera Kanno et al., 2015
• Cenosphaera Ehrenberg, 1854
• Centosphaera F.H. Wind & S.W. Wise in S.W. Wise & F.H. Wind in P.F. Barker et al., 1977 †
• Chinosphaera Attems, 1935 (uncertain)
• Cleosphaera Janofska, 1987 † (uncertain)
• Coelosphaera Thomson, 1873
• Coneosphaera Q.L. Luo, 1991 †
• Conosphaera Haeckel, 1881