260 



bicolor, to correspond with the body-areas — dark-brown above, whitisb 

 below. The ears have a light-colored rim» The whiskers are mostly- 

 black. The basal part of the fur, in the colored areas, is gray or plum- 

 beous, excepting just along the line of junction of the tawny of the 

 sides with the white of the belly, where the hairs are white to the roots, 

 like those of the belly. To this absence of dark bases of the hairs is 

 due the appearance of a fulvous stripe along the sides, sometimes quite 

 strongly marked, much as in species of Perognatlms or Oricetodipus. In 

 these cases there are thus four styles of coloration from back to belly:: 

 the dark dorsal area, mixed blackish and sandy, with plumbeous roots; 

 sandy, with little or no blackish, but still with gray roots ; sandy, 

 with white roots; and finally pure white. The variations to which the 

 species is subject .lie in the brightness or dullness of the tawny, and its 

 lining with a varying amount of blackish ; the degree of distinctness 

 of the dorsal area from that of the sides, and of this from the white of 

 the belly ; and in the sharpness or indistinctness of the tawny lateral 

 stripe along which the hairs are white at the roots. The line of the 

 belly-white is pretty constantly sharp, as in IIesj>eroinys ; but there is 

 often a very gradual shading from the dark dorsal area to the tawny of 

 the sides, and the latter is sometimes very pale yellowish-gray, &c. I 

 have observed no plumbeous or entirely gray stage like that of young 

 Sesperomys in general ; and I have failed to determine what definite 

 relation, if au\, the oliservable differences in coloration bear to sex 

 or age. 



The animal varies much in size, and to some extent in proportions, 

 especially the length of the tail. This is the most variable dimension, 

 as usual in all such cases of high development of parts. A tendency to 

 superior size in specimens from the Eocky Mountains and westward has 

 been noted. The following table of measurements of an alcoholic series. 

 indicates very fairly the dimensions^ and, to some extent, the variations^ 

 in size and proportions : 



Measurements of twenty-one alcoholic specimens (EngUsli inch and decimals J. 





2592 

 2393 

 2395 

 2396 

 2397 

 2398 

 2594 

 2599 

 2600 

 2605 

 2606 

 2607 

 2608 

 2604 

 2601 

 2602 

 2603 

 2611 

 2610 

 1929 

 2609 



Locality. 



Halifax, K S 



Middleboro', Mass 

 do 



do 



do 



do 



Bmlingtou, Vt 



Wetbersfield, Conn 



do 



Waterville, N. Y... 



do 



do 



do 



Pliiladelpliia, Pa ... 



Carlisle, Pa 



-do.... 



do 



West Nortbfield, 111 



Upper Missouri 



Platte Ptiver.Nebr.. 

 Sceilacoom, \V. T ... 



Averao-e 0.44 0.86 0.99 2, 



From tip of nose to — 



Eye. 



Ear. 



0.80 

 0.75 

 0.90 

 0.80 

 0.80 

 0.85 

 0.90 

 0.90 

 0.80 

 0.90 

 0.95 

 0.85 

 0.90 

 0. 85 

 0. 85 

 0.85 

 0.80 

 0.80 

 1.00 

 0.80 

 1.00 



Occi- 

 put. 



1.00 

 1.00 

 1.00 

 0.95 

 0.95 

 1.00 

 1.00 

 1.00 

 1.00 

 1.10 

 1.00 

 1.00 

 1.00 

 1.00 

 1.00 

 1.00 

 0.95 

 0.90 

 1.15 

 0.95 



Tail. 



2.75 

 2.90 

 3.00 

 2.75 

 3.00 

 2.75 



30 



3.10 

 3.25 



2.85 

 3.00 

 2.90 

 2.85 

 2.85 

 2.60 

 2.80 

 3.00 

 2.75 



Tail— 



Verte- 

 brae. 



5.00 

 5.25 

 .5.00 

 4.50 

 5.30 

 4.75 

 5.35 

 4.80 

 4.35 

 4.95 

 5.00 

 4.90 

 5.00 

 4.65 

 4.50 

 4.75 

 4.40 

 4.70 

 5.10 

 4.50 

 6.10 



90 



Length of- 



Fore 

 foot. 



0.40 

 0. 35 

 0.37 

 0.45 



0.35 

 0.40 

 0.40 

 0.35 

 0.45 



0.40 

 0.40 

 0.45 

 0.45 

 0.45 

 0.40 

 0.40 

 0.48 

 0.45 

 0. 50 



0.42 



Hind 

 foot. 



1.20 

 1.18 

 1.20 

 1.18 



1.15 

 1.18 

 1.10 

 1.15 

 1.15 



1.15 

 1.15 

 1.13 

 1.15 

 1.15 

 1.05 

 1.10 

 ].15 

 1.12 

 1.35 



1.15 



Skulls measure from 0.90 to 1.00 by 0.45 to 0.50. 



