476 



MONOGRAPHS OF NOItTII AMERICAN RODEFHA. 



of (lie sides, ami the latter is sometimes very pale yellowish-gray, &c. I 

 have observed no plumbeous or entirely gray stage like that frequently or 

 usually seen in young Hesperomys; and 1 have failed to determine what defi- 

 nite relation, if any, the observable differences in coloration bear to sex 

 or age. 



The animal varies much ill 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 Rocky 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 pro- 

 portions : — 



Table I. — Measurements of twenty-one alcoholic specimens o/Zapvs hudsonius. 



Skulls measure from 0*10 tu 1.00 by 0.45 to 0.50. 



"All measurements are in English inches and decimals. 

 GEOGRAPHICAL DISTRIBUTION. 



The dispersion of Znpus hudsonius in North America can at present be 

 given only in somewhat general terms, pending precise information respect- 



