New fossils referrable to the Cancridae Latreille, 1802 extend the known stratigraphic range of the family into the middle Eocene and the geographic range into South America. Each genus within the family has been reevaluated within the context of the new material. A suite of diagnostic characters for each cancrid genus makes it possible to assign both extant and fossil specimens to genera and the two cancrid subfamilies, the Cancrinae Latreille, 1802, and Lobocarcininae Beurlen, 1930, based solely upon dorsal carapace morphology. Cheliped morphology is useful in assigning genera to the family but is significantly less useful at the subfamily and generic level. Each of the four subgenera sensu Nations (1975), Cancer Linnaeus, 1758, Glebocarcinus Nations, 1975, Metacarcinus A. Milne Edwards, 1862, and Romaleon Gistl, 1848, are elevated to full generic status. Additionally, three new genera and three new species accommodate the new, as well as some previously described taxa, and include Anatolikos new genus, Anisospinos berglundi new genus and species, and Notocarcinus sulcatus new genus and species and several new combinations. Recognition of new genera and reassignment of several species within the Cancrinae indicates that that subfamily may have arisen in the southern hemisphere, contrary to the previous interpretation of the subfamily as a primarily North Pacific or Tethyan group. The Lobocarcininae was primarily a Tethyan group.