88 



MONOGRAMS OF NORTH AMERICAN RODKNTIA. 



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 leucopus, 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 Hespeijomys sonoriensis /re?n South- 

 ern Arizona. 



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 bieolor, 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 leucopus in its length of tail, exceptional in this series; while the 

 shade of its coloration is almost exactly as in typical eremicus. No. 8874 is 

 a precise duplicate of H. gossypinus in coloration. 



HESPEROMYS LEUCOPUS EREMICUS (Baird). 



Desert Mouse. 



Resperomys eremicus, Baird, M. N. A. 1857, 479. — Couks, Quad, of Arizona, Am. Nat. i, 308 (in part). 

 Sesperomys ( Vesperimus) leucopus eremicus, Coues, Proc. Acad. Nat. Sci. Pliila. 1874, 180. 



Diagnosis. — Hesp. leucopi staturd, caudd elongatd, truncum cum capite 

 subcequan/c, sparse pilosd, auriculis majusculis, subnudis, plan/is palmisque 



