Examination was made of the frequency of 27 non-metric variants of skull and molar structure in Clethrionomys glareolus (Schreber, 1780), originating from four distant and three nearer situations. It was found that out of 351 calculated coefficients of correlation between all pairs of characters, 108% differed significantly from zero, the proportion for dental characters analysed separately being 20.6%, but only 4.4% for skull characters. ; Examination was made of the frequency of 27 non-metric variants of skull and molar structure in Clethrionomys glareolus (Schreber, 1780), originating from four distant and three nearer situations. It was found that out of 351 calculated coefficients of correlation between all pairs of characters, 108% differed significantly from zero, the proportion for dental characters analysed separately being 20.6%, but only 4.4% for skull characters.