cit.:fig. 11) indicated that the localities mentioned above for S. f. mearnsi were within the geographic range of S. f. similis.

Our comparison of each of the Nebraskan specimens with specimens of S. f. mearnsi in comparable pelage from Iowa and with the type and topotypes of S. f. similis reveals that each of the specimens of which catalogue numbers are given above is clearly referable to Sylvilagus floridanus similis.

Because some mammalogists have suspected that intergradation between Sylvilagus floridanus similis and Sylvilagus nuttallii grangeri occurs along the eastern base of the Rocky Mountains, we have examined specimens which may throw light on this matter.

From S. f. similis (holotype and three topotypes), S. n. grangeri (eight practical topotypes from Redfern, South Dakota) differ as follows: Throat patch darker; hind foot shorter; ear (dry) from notch longer; rostrum narrower; posterior extension of supraorbital process enclosing a longer and wider space between it and the braincase; superior border of premaxilla straight in profile instead of convex dorsally; tympanic bullae more inflated; external auditory meatus larger (diameter of the meatus more, instead of less, than crown length of upper molars); posterior border of palate without, instead of with, spine.

Specimens of the two species from places as near each other as extreme southeastern Montana (S. f. similis from Boxelder Creek, Capitol and the Little Missouri River) and Devils Tower, Wyoming (S. n. grangeri), seem not to differ in the length of the hind foot and the ear and in the color of the spot on the chest. Also, the presence or absence of the spine on the posterior margin of the palate is subject to individual variation in these specimens but the other cranial differences, mentioned above, still are apparent. These same cranial differences are readily apparent between specimens of the two species taken only five miles apart in eastern Wyoming (for the precise localities, see the following paragraph). It is concluded, therefore, that S. f. similis and S. n. grangeri do not inter-grade along the eastern base of the Rocky Mountains.

Data on specimens from Laramie County in eastern Wyoming show that S. f. similis is a heavier animal than S. n. grangeri and also that similis molts earlier. For example, an adult female (K.U. No. 15936) taken on July 13, 1945, three miles east of Horse Creek P.O., 6400 ft., weighed 1374 grams and is in fresh pelage, whereas an adult female of S. n. grangeri (K.U. No. 15935), taken on July 17, 1945, two miles west of Horse Creek P.O., 6600 ft., weighed only 1149 grams, and still has some of the worn winter pelage on the upper parts.

Sylvilagus floridanus holzneri (Mearns)

Examination of cottontail rabbits from Arizona in the Biological Surveys Collection and the United States National Museum indicates that Sylvilagus audubonii can be distinguished from Sylvilagus nuttallii and Sylvilagus floridanus by the larger (more inflated) tympanic bullae. Topotypes of Sylvilagus nuttallii pinetis and other specimens from Alpine, Mt. Thomas, Springerville, the Prieto Plateau at 9000 feet on the south end of the Blue Range, and the Tunitcha Mountains are characterized by a posteriorly pointed supraoccipital shield and a long, wide space between the braincase and the posterior extension of the supraorbital process. The cottontails with equally small tympanic bullae from more western and more southern localities are referable to Sylvilagus floridanus holzneri on the basis of a posteriorly