. Bulletin of the British Museum (Natural History), Geology. OF BRITISH ISLES 99. Fig. 18. Distribution of remains of Mimowys savini Hinton in the British Isles. Systematic remarks. M. savini was described by Newton (1881) from the Upper Freshwater Bed of *West Runton under the name of Arvicola intermedia. Hinton (1910b) described two further species of the same genus, M. majori and M. savini, from the same deposit. According to him, they differed from M. intermedius only in sUght differences in the pattern of M^, the dimensions of all the molars and the patterns of all other teeth being ident
. Bulletin of the British Museum (Natural History), Geology. OF BRITISH ISLES 99. Fig. 18. Distribution of remains of Mimowys savini Hinton in the British Isles. Systematic remarks. M. savini was described by Newton (1881) from the Upper Freshwater Bed of *West Runton under the name of Arvicola intermedia. Hinton (1910b) described two further species of the same genus, M. majori and M. savini, from the same deposit. According to him, they differed from M. intermedius only in sUght differences in the pattern of M^, the dimensions of all the molars and the patterns of all other teeth being identical. Kretzoi (1958) found that A. inter- media is a junior homonym and must therefore be replaced by the name Mimomys milleri Kretzoi; in a later paper (1965) he showed that the three species M. inter- medius, M. savini and M. majori really represent only one variable species. The name of it must therefore be Mimomys savini Hinton, which is the oldest valid name. In fact all possible intermediate forms between typical M. intermedius, M. savini and M. majori are present in the abundant material from the Upper Freshwater Bed (Pasquier 1972). The presence of three species of one genus with identical dimensions in one and the same layer is also scarcely imaginable from the ecological point of view. Specimens determined as 'M. majori and 'M. savini' have also been found in some Czechoslovak and German fossil localities, always associated with M. intermedius. Genus ARVICOLA Lacepede 1799 The systematic study of even the living representatives of this genus presents many difficulties to zoologists. Miller (1912) divided living populations of water voles from western Europe into seven species but later investigators (for bibliography see Reichstein 1963) have demonstrated that nearly all the characters which were used for the diagnosis of these species lie within the limits of individual variation. Variations occur principally in the dimensions and in some proportions of the skull, pr
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