184 PROCEEDINGS OF THE ACADEMY OF [1896. 



ancestry. On cutting away the premaxillary the exposed base of 

 the incisor shows a constant increase in the development of the 

 lateral sulcus, so that at its root the tooth may be said to be almost 

 as characteristically grooved as in the adult. In the half-grown 

 skull the cutting edges of the upper incisors are oblique, forming 

 an acute angle in each at their median line ; in the adult skull this 

 obliquity is reversed, the outer sides of the teeth being longer than 

 the inner. In the young, the alveolar breadth of the incisor ex- 

 ceeds its terminal breadth ; in the old these dimensions are equal. 

 The incisive foramina are wider and shorter, and the upper molar 

 series more widely separated by the bony palate and maxillaries, 

 than in old adults. The crown structure of the molars in young 

 and old is identical, their only difference being due to the amount 

 of wear, shown most conspicuously in the posterior upper molar, 

 which has not protruded sufficiently to bring its posterior loop down 

 to the triturating plane, and in consequence, that section retains its 

 original cuspidate form. 



All of the five young have white-tipped hind feet almost precisely 

 like the young Evotomys taken in the same locality. This peculiar- 

 ity, is not confined to the young of these genera. An examination of 

 my series from the United States and Canada shows that several 

 young and some of the old among four species have the hind feet 

 so marked. In an adult Evotomys gapperi from Pennsylvania', both 

 fore and hind feet are nearly pure white and in E. g. saturatiis from 

 Mt. Baker, B. C, all four feet, and the throat and the breast are 

 similarly pied. Such cases are rare in my very large series of M. 

 pennsylvanicus. It is an interesting question why Synaptomys and 

 Evotomys should show this tendency to pedal albinism, while in 

 Peromyscus and Zapus the same kind of variation seems confined 

 to the tail. Indeed, in some of these instances this feature has 

 almost assumed the dignity of a diagnostic if not specific charac- 

 ter, and it may even be conjectured whether these white-footed 

 voles do not foreshadow color patterns, which are destined to figure 

 in the days to come. On the other hand it may indicate their past 

 connection with some harlequin ancestry, such as has given us 

 the variegated pelage of the Arctic Lemmings. 



Specimens — Roan Mt., Mitchell Co., N. C. 1 ad. ; 5juv. 



Genus MICROTUS Schrank. 

 8. Microtus pennsylvanicus (Ord). Wilson's Meadow Vole. 



The most careful search and systematic trapping failed to reveal 

 the presence of this common eastern and northern quadruped in any 



