Standard karyotypes of two species of the genus Scincella , S. assata and S. cherriei , both from Chiapas State, Mexico, were described for the first time. The diploid chromosome number was 28 in S. assata , whereas 30 in S. cherriei . The karyotypes of the two species, while differing in the number of microchromosomes, 14-15 in S. assata and 16-17 in S. cherriei, share four pairs of large metacentric, two pairs of medium-sized metacentric, and one particular pair (number 7) of chromosomes. Female S. assata carries chromosome pair 7 composed of two identical medium-sized subtelocentric chromosomes. This chromosome pair is heteromorphic in males of both species, i.e., one component of the pair is similar to the homomorphic chromosomes 7 of the S. assata female, while the other is nearly one-half the size of its counterpart and resembles a microchromosome. The homology of such externally different elements is deducted from the presence of an asymmetric bivalent in spermatocytes at diplotene-diakinesis. Female S. cherriei was not available. We suspect that the two Scincella species possess an XY sex determination system, as previously reported for the North American congeneric species, S. lateralis . ; SeriesInformation ; Acta Herpetologica, Vol 8, No 1 (2013)