The cosmopolitan lizard genus Eumeces was first revised in 1936 and consisted of 15 species-groups comprising a total of 50 species. Nine species in North America were later recognized as belonging to the genus Plestiodon and all contained the diploid chromosome number of 26. Modern cladistic techniques indicated that Plestiodon anthracinus (Coal Skink) was near the ancestral form for the fasciatus group. We employed the hypotonic citrate method to study chromosomes of 5 Coal Skink specimens from Louisiana and Arkansas and found them to have a diploid number of 24 (12 macrochromosomes, 12 distinctly smaller chromosomes, all biarmed) and a fundamental number of 48. The diploid number of 24 is probably derived by some chromosome rearrangements in the evolution of Plestiodon and of the Plestiodon anthracinus group.