216 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
was left of it but some comminuted fragments of the skull, some loose teeth, 
bones of the feet, and a few whiskers. Most fortunately, however, the back 
upper molar was not lost, and this furnished perfect identification. Accord- 
ing to Cope’s measurements, his animal was smaller than any others we have 
seen, but not much so; nor is there, in other respects, any discrepancy 
sufficient to cast suspicion on the identification we make. 
No. 4172—Very light gray, with a noticeable darker (brownish-black) 
dorsal area, so much restricted as to appear almost like a dorsal stripe. 
Below, nearly white, but little soiled, and the pale plumbeous bases of the 
hairs little apparent; tail short, light brown above, white below; feet above 
nearly white. (Dimensions as below.) 
No. 10268 (Great Plains, Washington Territory; type of pauperrima 
Cooper).—Identical with the last, but the dorsal darkness pretty uniformly 
distributed. (Dimensions as below.) ‘Tail very short. 
No. 3056.—One of the palest Arvicolas we ever saw except ‘‘brewer1”. 
Above, uniform dull pale gray, with scarcely a brown shade and no blackish; 
below, hoary white, almost as pure as in a Hesperomys on the ends of the 
hairs, but these are so short (the animal was killed in August, probably a 
young of the year) that their plumbeous bases give the predominant shade; 
tail and feet hoary whitish; tail extremely short. (Dimensions as below.) 
The pallor of this specimen is parallel with that of all the other Murid@ of 
the same region. 
No. 3241.—Upper parts an intimate grizzle of gray and brown in equal 
parts, little if any blackish; below of ordinary riparius color; feet and tail 
brown above; tail short, but its caliber as well as its length undue, because 
a stout peg has been thrust into its skin after removal of the vertebrae. 
Rather exceeding any of the foregoing in size (see below). Approximating 
in color to the next, viz:— 
No. 8055.—Rather larger than any of the foregoing, even allowing much 
for the evident overstuffing; but tail short. In color, almost exactly like the 
paler “haydeni” stripe of austerus; the hoary gray of the belly quite muddy. 
With only the type of curtatus before us, together with the Californian, 
Washington, and Utah specimens, we could not have hesitated in admitting 
the species. But the precisely intermediate Kansas and Nebraska speci- 
mens prove that a truer rendering of the facts in the case will be to hold 
curtatus for a geographical differentiation of austerus. It will be recollected 
