. Fig. 64. Distribution of Reithrodontomys mon- tanus in Colorado. 1. R. m. albescens. 2. R. m. mon- tanus. For explanation of symbols, see p. 9. Measurements.—External measurements of three males from eastern Yuma County, three young adult males from southern Washington County, and a male from northern Las Animas County are, respectively: 136, 132, 127, 119, 121, 111, 128; 67, 59, 53, 52, 58, 52, 62; 16, 17, 15, 17, 17, —, 16; 14, 13, 12, 16, 16, 14, 15; weights, , , , , —, , —. Ex- ternal measurements of a female from north- em Logan County are: 122, 53, 16,14. Repre- senta
. Fig. 64. Distribution of Reithrodontomys mon- tanus in Colorado. 1. R. m. albescens. 2. R. m. mon- tanus. For explanation of symbols, see p. 9. Measurements.—External measurements of three males from eastern Yuma County, three young adult males from southern Washington County, and a male from northern Las Animas County are, respectively: 136, 132, 127, 119, 121, 111, 128; 67, 59, 53, 52, 58, 52, 62; 16, 17, 15, 17, 17, —, 16; 14, 13, 12, 16, 16, 14, 15; weights, , , , , —, , —. Ex- ternal measurements of a female from north- em Logan County are: 122, 53, 16,14. Repre- sentative cranial measurements are presented in table 18. Remarks.—Smith (1964: 19) tentatively maintained the subspecific status of R. m. albescens, but expressed the opinion that al- bescens and montanus may be found insepa- rable when adequate material is available from the western part of the range of the species. The pronounced differences between albescens and montanus noted by A. H. How- ell (1914:22, 24) are artifactual, resulting from identification of a series of specimens from Medano Ranch, near San Luis Lakes, with montanus. Renson (1935a: 141) correctly iden- tified these specimens as R. megalotis. The population subsequently was recognized as a distinct subspecies, Reithrodontomys mega- lotis caryi by Howell (1935:143), but Jones and Mursaloglu (1961:19) considered caryi to be a synonym of the earlier-named R. m. aztecus. Two males (skulls only, KU 116772-73) from Yuma County are larger externally and cranially than other specimens of montanus examined. The skulls are considerably shorter, however, than undoubted examples of mega- TABLE 18 Selected cranial measurements of two species of Reithrodontomys. Number aver- Greatest Condylo- Inter- Depth Length of aged (or catalog length of basal Zygomatic Cranial orbital of maxillary number), sex skull length breadth breadth constriction skull toothrow Reithrodontomys montanus albescens, eastern Yuma County KU 11677
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