John A. White

“ A variation that does not readily fall in any one of the three categories mentioned above is the degree of development of the lambdoidal crest. The crest is least developed in the subgenus Neotamias and most developed in the genus Tamias. The larger the skull, the more the lambdoidal crest is developed; seemingly, therefore, the degree of development is an expression of size of the skull and may be determined by heterogonic growth. ”

“ The head of the malleus in Tamias is clearly more elongated than in Eutamias. The plane formed by the lamina in Eutamias makes an angle of approximately 90 degrees with the plane formed by the manubrium; in Tamias the two planes make an angle of approximately 60 degrees.
Examination of series of mallei of Eutamias and Tamias indicate that there is slight individual variation, slight variation with age, and no secondary sexual variation. Intraspecific variation in the subgenus Neotamias is slight, consisting of differences in size. ”

“ In Sciurus the baculum is semispoonshaped and asymmetrical. There is a winglike process on one side and a spine, which projects lateroventrally, on the other side of the tip. The base of the baculum is broad but not so broad as in most species of Spermophilus. ”