h ! 





538 



MONOGRAPHS OF NORTH AUBBIOAN BODENTIA. 



ui Kc^ogmpliicnl limitations; Cor the specimens which nrc nrrnnged in the 

 t;il)le with referoncc tu ul*Holuto Icnf^th of tuil vortebra; (with wliich iibHolutu 

 length of feet is uppnixiniotcly corrci)|M>ndcnt) sliuw complete intcrmixtiiro 

 of localities. Measurements of a hundred or a thousand specimens would, 

 of course, only tend to place these facts in stronger light. It may be safely 

 stated as a fact, then, that differences in absolute size, either of the body or 

 of any of its members, are not avalluldc for distinction of two s|)ecie8 ; and, 

 furthermore, that no set of absolute dimensions is correlated with geographi- 

 cal distribution. 



Nevertheless, one cannot fail to be struck, in examining the table, with 

 the extraordinary discreimncy in relative length of the btnly and tail. In No. 

 4871, for example, the tail (vertebrst) is only half an inch longer thon the 

 lintid and body (4.50-5.00); that is to say, it is but one-ninth of the head and 

 bmly length longer. In No. 2626, the tuil is two and three-quarter inches 

 longer than the head and b<Mly; that is to sny, almost twice as long. It would 

 apiicur improbable that such unusual difference as this should not signify 

 something more than mere individual variability. In order to discover 

 whether or not the proportionate (as distinguished from absolute) dimensions 

 of body and tail may not lead to some tangible result, the following table is 

 constructed, in which the same specimens are arranged geographically. It is 

 necessary to exclude four of them, however — Nos. if478, 734!>, from unknown 

 localities, together with the two respectively marked "California" and "Rocky 

 Mts.", as I have reason to believe that these indications of locality are not 

 reliable. 



Tablb VI.— jrMMrmnita ^ iUrtttn iftelment 1/ Dipodomyr. 



NOCKT MUUnAW UOtOII. 



ArlioDa 



no 



New Mexico... 

 l-l*U«Vall«7.. 



ATenigc* 



12 



4.1s 



4.M 



9.M 

 S.9S 



i.as 



I.M 

 LH 

 I.U 



»aric com uoioii. 



OHMSkLlKM.. 



do 



4o 



Fort Reidliii, 0*1.. 



do 



Moatarey 



Fort TrjoD.Cal.... 



HM 



3.79 

 *,» 

 *.» 



4.» 



».» 



II 



«.« 



&7S 

 t.1» 



xm 

 ■.w 



«.7S 

 TOO 



I 



r 



a 

 t.ia 



I.M 

 I.M 

 I.M 



l.tf 



1.60 

 I.M 

 1. 10 

 1.10 



„..,......._ MM. ijjp gjg 



