The chromosome set of N. anomalus from Bulgaria was studied by means of C-, and NOR-banding. The diploid chromosome number of this species is known to be 2n=52 (NF = 98, NFa = 94). In all the studied individuals, the X chromosome appeared to be the second longest submetacentric chromosome, whereas the Y chromosome was a medium-sized submetacentric chromosome, consisting of heterochromatin. Such morphology of the Y chromosome was not described previously. The extent and localization of C-bands in the pericentromeric regions varied between the pairs of chromosomes. The nucleolar organizer regions (NOR’s) were observed in four pairs of autosomes.