The baculum in the Microtinae more closely resembles the baculum in the Cricetinae of the Old World than in the Murinae, or than in any other rodents known to me. This resemblance suggests relationship between Microtinae and Cricetinae. LITERATURE CITED ARGYROPULO, A. I. 1933a. Die Gattungen und Arten der Hamster (_Cricetinae_ Murray, 1866) der Paläarktik. Zeitschr. f. Säugetierkunde, 8:129-149, 27 figs. in text. 1933b. Über zwei neue paläarktische Wühlmäuse. Zeitschr. f. Säugetierkunde, 8:180-183, 3 figs. in text. CALLERY, R. 1951. Development of the os genitale in the golden hamster, _Mesocricetus (Cricetus) auratus_. Jour. Mamm., 32:204-207, 1 fig. in text. CHAMBERLAIN, J. L. 1954. The Block Island meadow mouse, _Microtus provectus_. Jour. Mamm., 35:587-589, 2 tables in text. DEARDEN, L. C. 1958. The baculum in _Lagurus_ and related microtines. Jour. Mamm., 39:541-553, 1 fig. in text. DIDIER, R. 1943. L'os pénien des Campagnols de France du Genre _Arvicola_. Mammalia, 7:74-79, 10 figs. in text. 1954. Etude systématique de l'os pénien des Mammifères (suite), Rongeurs: Muridés. Mammalia, 18:237-256, 14 figs. in text. ELLERMAN, J. R. 1941. The families and genera of living rodents. Vol. II. Family Muridae. The British Museum (Natural History), London, pp. xii + 690, 50 figs. FRILEY, CHARLES E. 1947. Preparation and preservation of the baculum of mammals. Jour. Mamm., 28:395-397, 1 fig. in text. HALL, E. R., and E. L. COCKRUM. 1953. A synopsis of the North American microtine rodents. Univ. Kansas Publ., Mus. Nat. Hist., 5:373-498, 149 figs. in text. HAMILTON, W. J., JR. 1946. A study of the baculum in some North American Microtinae. Jour. Mamm., 27:378-387, 3 figs. in text. HIBBARD, C. W., and G. C. RINKER. 1942. A new bog-lemming (Synaptomys) from Meade County, Kansas. Univ. Kansas Sci. Bull., 28:25-35, 3 figs. in text. 1943. A new meadow mouse (_Microtus ochrogaster taylori_) from Meade County, Kansas. Univ. Kansas Sci. Bull., 29:255-268, 5 figs. in text. HINTON, M. A. C. 1926. Monograph of the voles and lemmings (Microtinae), living and extinct, Vol. I. British Museum (Natural History), London, pp. xvi + 488, plus 15 plates, 110 figs. in text. MATTHEY, R. 1953. Les Chromosomes des Muridae. Revue Suisse de Zoologie, 60:225-283, avec les planches 1 à 4 groupant 84 photomicrographies, 98 figures et 5 schemas dans le texte. 1955. Nouveaux documents sur les chromosomes des Muridae. Problèmes de cytologie comparée et de taxonomie chez les Microtinae. Revue Suisse de Zoologie, 62:163-206, avec 114 figures. MILLER, G. S. 1896. Genera and subgenera of voles and lemmings. North American Fauna No. 12, pp. 1-85, 40 figs. and 3 plates in text. OGNEV, S. I.