South Dakota. Buffalo County: 2 mi. S, 3 mi. E Ft. Thompson, 1370 ft., 4. Clay County: 2½ mi. N, ½ mi. W Vermillion, 1. Pennington County: 2 mi. S, 3 mi. W Scenic, 1. Stanley County: 1.2 mi. S, 4 mi. W Ft. Pierre, 1484 ft., 1.
Wyoming. Albany County: 27 mi. N, 8 mi. E Laramie, 6420 ft., 2. Big Horn County: 7½ mi. E Graybull, 4050 ft., 1; 7 mi. S, ½ mi. E Basin, 3900 ft., 1. Campbell County: 4 mi. N, 3 mi. E Rockypoint, 3800 ft., 3; 13⁄5 mi. N, ¾ mi. E Rockypoint, 2; Rockypoint, 5; 5 mi. S, 4 mi. W Rockypoint, 1; Ivy Creek, 5 mi. N, 8 mi. W Spotted Horse, 2. Crook County: 1½ mi. NW Sundance, 5000 ft., 3. Fremont County: 2 mi. N, 3 mi. W Shoshoni, 4650 ft., 1; 3⁄10 mi. NW Milford, 5357 ft., 1; Milford, 5400 ft., 1. Hot Springs County: 3 mi. N, 10 mi. W Thermopolis, 4900-4950 ft., 7. Johnson County: 1 mi. W, 8⁄10 mi. S Buffalo, 4800 ft., 5; 6½ mi. W, 2 mi. S Buffalo, 5620 ft., 4; 1 mi. WSW Kaycee, 4700 ft., 8. Laramie County: Horse Creek, 5000 ft., 3 mi. W Meriden, 1; 1 mi. N, ½ mi. W Pine Bluffs, 5040 ft., 4; 1 mi. S Pine Bluffs, 5100 ft., 1; 2 mi. S Pine Bluffs, 5200 ft., 2. Natrona County: 1 mi. NE Casper, 5150 ft., 1; 2¼ mi. W Casper, 5250 ft., 1; 7 mi. S, 2 mi. W Casper, 6370 ft., 1. Niobrara County: 2 mi. S, ½ mi. E Lusk, 5000 ft., 1. Park County: 4 mi. N Garland, 2; 13 mi. N, 1 mi. E Cody, 5200 ft., 2; 6⁄10 mi. S, 32⁄10 mi. E Cody, 5020 ft., 1. Platte County: 2½ mi. S Chugwater, 5300 ft., 4. Sheridan County: 3 mi. WNW Monarch, 3800 ft., 4; 5 mi. NE Clearmont, 3900 ft., 6. Washakie County: 1 mi. N, 3 mi. E Tensleep, 4350 ft., 5.
Table 2. Cranial Measurements of Two Subspecies of Reithrodontomys megalotis.
| Number Averaged and Sex | Greatest length of skull | Zygomatic breadth | Breadth of braincase | Interorbital breadth | Depth of cranium | Length of rostrum | Breadth of rostrum | Length of incisive foramen | Length of palate | Alveolar length of maxillary tooth-row |
| R. m. dychei, Douglas County, Kansas | ||||||||||
| Av. 17 (11 ♂, 6 ♀) | 20.9 | 10.5 | 10.1 | 3.1 | 7.9 | 7.2 | 3.8 | 4.3 | 3.5 | 3.3 |
| Minimum | 20.4 | 10.0 | 9.8 | 3.0 | 7.7 | 6.8 | 3.6 | 4.0 | 3.2 | 3.1 |
| Maximum | 21.9 | 10.9 | 10.3 | 3.3 | 8.2 | 7.9 | 4.0 | 4.5 | 3.9 | 3.4 |
| Cherry County, Nebraska | ||||||||||
| Av. 20 (14 ♂, 6 ♀) | 21.0 | 10.9 | 10.3 | 3.1 | 7.9 | 7.3 | 3.8 | 4.4 | 3.6 | 3.5 |
| Minimum | 20.4 | 10.0 | 9.8 | 2.9 | 7.5 | 6.8 | 3.5 | 4.3 | 3.4 | 3.2 |
| Maximum | 22.1 | 11.3 | 10.7 | 3.3 | 8.4 | 7.8 | 4.1 | 4.7 | 3.9 | 3.7 |
| R. m. aztecus, San Juan County, New Mexico, and Montezuma County, Colorado | ||||||||||
| Av. 10 (6 ♂, 4 ♀) | 21.5 | 10.8 | 10.2 | 3.1 | 8.1 | 7.7 | 3.7 | 4.5 | 3.4 | 3.5 |
| Minimum | 20.5 | 10.4 | 9.9 | 2.9 | 7.9 | 7.2 | 3.5 | 3.9 | 3.1 | 3.2 |
| Maximum | 22.7 | 11.1 | 10.6 | 3.3 | 8.4 | 8.2 | 3.9 | 4.8 | 3.7 | 3.7 |
LITERATURE CITED
Allen, J. A.
| 1893. | List of mammals collected by Mr. Charles P. Rowley in the San Juan region of Colorado, New Mexico and Utah, with descriptions of new species. Bull. Amer. Mus. Nat. Hist, 5:69-84, April 28. |
| 1895. | On the species of the genus Reithrodontomys. Bull. Amer. Mus. Nat. Hist, 7:107-143, May 21. |
Benson, S. B.
| 1935. | The status of Reithrodontomys montanus (Baird). Jour. Mamm., 16:139-142, 1 fig., May 15. |
Blair, W. F.