Description: Left arm extends into apical spur producing a triangular apical area. Right arm longer than left.

Remarks:

Original description:

Variants:

C. acutus Gartner and Bukry, 1974 - C.armatus and C.acutus were both described in 1974 from Indian Ocean sediments of Early Pliocene age (zone NN12, Sites 242 and 214 respectively). The holotypes, and paratypes, of the two species are very similar. The C. armatus specimens have slightly longer arms and more distinct ornament, but this is almost certainly a result of the much better preservation at Site 242. They are clearly synonyms, and probably not worth distinguishing, even at varietal level. According to the publication dates C. armatus has two months priority (May 1974 vs. July 1974). Nonetheless, several authors use both species.

C. larrymayeri Backman & Raffi, 1998, in Raffi et al. 1998 - this is a delicate variant of C. acutus with elongate arms. It appears to me to be an extreme variant of C. acutus but may prove to be a separate species.