Spinicharybdis boucoti (FOSSIL) Rohr & al., 2008 †
Straparollus brevis (FOSSIL) E.K. Yoo, 1994 †
Euomphalus brooksensis (FOSSIL) E.L. Yochelson & Dutro,1960 †
Amphiscapha browni (FOSSIL) (A. Thomas, 1930 †)
Euomphalus bundtzeni (FOSSIL) Blodgett, 1992 †
Nummocalcar bussoni (FOSSIL) Cox, 1969 †
Philoxene caementarius (FOSSIL) Blodgett & Johnson,1992 †
Amphiscapha calix (FOSSIL) W.J. Gordon& E.L. Yochelson, 1975 †
Schizostoma calyx (FOSSIL) (B. Phillips, 1836 †)
Spinicharybdis canteriata (FOSSIL) Rohr & A. Packard, 1982 †
Euomphalus carbonarius (FOSSIL) Sowerby, 1844 †
Euomphalus catilliformis (FOSSIL) de Koninck, 1881 †
Amphiscapha catilloides (FOSSIL) (T.A. Conrad, 1842 †)
Euomphalus catillus (FOSSIL) (Martin, 1793 †)
Euomphalus cera (FOSSIL) R. Etheridge jr., 1917 †
Goldfussoceras circinalis (FOSSIL) (G.A. Goldfuss, 1844 †)
Euomphalopterus cirrhosa (FOSSIL) (Lindström, 1884 †)
Schizostoma cirridioides (FOSSIL) E.A.L. Kittl, 1894 †
Straparollus clymenioides (FOSSIL) J.W. Hall, 1860 †
Straparollus complanans (FOSSIL) (J. Perner, 1903 †)
Poleumita conferta (FOSSIL) Lamont †
Pleuronotus confusus (FOSSIL) J. Perner, 1903 †
Euomphalus conradi (FOSSIL) J.W. Hall, 1861 †
Rhabdotocochlis conveximarginatus (FOSSIL) Zhu, 1995 †
Nevadaspira cooperi (FOSSIL) E.L. Yochelson, 1971 †
Euomphalus cornudanus (FOSSIL) Shumard, 1859 †
Euomphalus coroniferus (FOSSIL) de Koninck, 1881 †
Schizostoma costata (FOSSIL) Münster, 1841 †
Euomphalus costellatus (FOSSIL) (McCoy) †
Straparollus cottrelli (FOSSIL) P.D. Montfort 1810 †
Euomphalus crateriformis (FOSSIL) Koninck †
Poleumita crenulata (FOSSIL) (J.J.F. Whiteaves,1884 †)
Straparollus crenulata (FOSSIL) P.D. Montfort 1810 †
Alaionema crenulatum (FOSSIL) (F.B. Meek, 1871 †)
Phanerotinus cristatus (FOSSIL) (B. Phillips, 1836 †)