88 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
. 
of the sides, &c.; and, on the whole, it is rather referable to this variety, 
although the soles are distinctly hairy. So that in this series, impossible to 
consider as representing more than one species, we find the form and colora- 
tion of true deucopus, of sonoriensis, and of eremicus. Stronger proof of the 
position we have taken up could not be desired. 
‘We should remark that in some of these specimens, and various others 
from Arizona, there is a tendency, sometimes decided, to extension of the 
dusky on the base of the metatarsus, as in Mexican species. 
TaBLE XXIII.— Measurements of ten additional specimens of supposed HESPEROMYS SONORIENSIS from South- 
ern Arizona. 
= =< 
5 5 
= Date. Locality. Collector. rea ee Fy ‘ Remarks. 
Ey BeH Ie Web lie 
4 |n q a | a | a 
8884 | of | Feb. 10, 1867 3.40 | 3.10 | 0.37 | 0.86 | Dry; adult. 
8872 | 9 | Apr. 18, 1867 3.50 | 2.25 | 0.34 | 0.76 |... do. 
8883 | 9 | Feb. 20, 1867 3.C0 | 2.30 | 0.31 | 0.75 | Dry ; youngish. 
e885 | 9 | Feb. 10, 1867 3.00 | 2.25 | 0.31 | 0.78 - do. 
8888 |.-..| Feb. 20, 1867 040) 2 LON eno =: 0.75 | Dry; young. 
8878 | o | Apr. 14, 1&67 2.90 | 2.30 |..... 0.78 | Dry; youngish. 
3556s| b5c4| beso0ssnosecs 2.S0 } 2.50 }......] 0.72 |....do. 
e887 | 9 | Apr. 18, 1867 3.40 | 2.50 |...... 0.76 |....do. 
8879 | ¢ | Mar. 10, 1867 2.190) |e) eee 0.75 |...:do. 
Goren rod ec) Salita lel il eo sane oor Ssoosescraeeearec || Sanacc  Oleeesesocascatanlsscoas oat Oi eae 0.70 | Dry; adult. 
The foregoing specimens were taken at Camp Grant, near Tucson, Ariz., 
at the same time as Dr. Palmer’s examples of eremicus were collected, the two 
forms living side by side. As we say in another place, most of Dr. Palmer's 
specimens are true eremicus; but the above seem referable to the short- 
tailed, pale variety sonoriensis; the soles are all furred as in ordinary 
leucopus; the ears are short; and the distinctly bicolor, rather hairy, tail 
ranges much less than the head and body, while the nearly uniform pallor of 
the tints is much like that of prairie specimens. Only one, No. 8884, is more 
like true dewcopus in its length of tail, exceptional in this series; while the 
shade of ifs coloration is almost exactly as in typical eremicus. No. 8874 is 
a precise duplicate of H. gossypinus in coloration. z 
HESPEROMYS LEUCOPUS EREMICUS (Baird). 
Desert Mouse. 
Hesperomys eremicus, BAIRD, M. N. A. 1857, 479.—Couxs, Quad. of Arizona, Am. Nat. i, 398 (in part). 
Hesperomys (Vesperimus) leucopus eremicus, Cours, Proc. Acad. Nat. Sci. Phila. 1874, 180. 
Dracnosis.—Hesp. leucopi staturd, caudd elongatd, truncum cum capite 
subequante, sparse pilosa, auriculis majusculis, subnudis, plantis palmisque 
