Abstract
Karyotypes and Gimsa-banding patterns of Clethrionomys montanus and C. rufocanus bedfordiae are examined. The two have the same diploid number (56) and FN (58), and similar G-bands. The autosomes consist of 26 pairs of acrocentrics decreasing gradually in size and 1 pair of the smallest metacentrics. The X chromo-somes are the 4th acrocentrics, and the Ys the smallest acrocentrics. Chromosome variations explained by pericentric inversion are found on the pairs of No. 18 chromosome of C. montanus and No. 5 chromosome of C. r. bedfordiae. A close relation between the two species is suggested on the basis of the chromosomal survey and the intraspecific variation of the enamel patterns of molars found in some Clethrionomys species.
