Type Species. Paromalus opuntiae LeConte. Designated by Mazur (1984).

Diagnosis and Comparison with Relatives. Taxa of this subgenus are characterized by the formation of individual ground punctures by a cluster or row of 3–4 micropunctures (Fig. 6), a tristriate lateral disc of the first abdominal ventrite (Fig. 2E), the continuation of the fourth dorsal elytral stria to the base without strongly arching toward the sutural stria, and an unmodified pygidium. The state of the ground punctation is shared with at least some members of the paromaline genus Xestipyge Marseul, but the latter two characters serve to distinguish Carcinopsida from these. Wenzel (in an unpublished key) compared a “sp. # 46” to C. opuntiae, reporting that it has the same ground punctation as C. opuntiae but “different elytral striae [and] only two lateral abdominal striae...”. Unfortunately, specimens labeled with a “46” or matching this description could not be found among the histerids at the Field Museum, where Wenzel’ s unfinished projects are housed.

Geographic Distribution and Natural History. Two species are distributed from California, Arizona, and southern Texas to northern Mexico and the Baja California Peninsula. They are associated with the necroses of a diversity of cacti and the decaying basal stems of plants in the subfamilies Agavoideae and Nolinoideae.