174 



MONt)OBAPn8 OP NORTH AMRRIOAN RODENTIA. 



jSii 



13ut since several iiuniinal sppcicH ure represented in tlie list, which inigiit 

 collectively strike a ji^ennrnl nvcriigc without being severally on an nverngn, it 

 becomes n(?crHaary to discuss the scries in detail. On running the eye over 

 the column of lengths ol Irunk of the adults, it will he seen that they are 

 imperceptibly graduated from 3.50 to 4.75, an«l that this graduation is inde- 

 pendent of geographical or other consideratiuns. We have only, then, to 

 discuss the relative length of tail and feet as coni|Nired with the body. 



Now, the specimens from Nebraska, Utah, and the upper and mountain- 

 ous parts of California do not differ in any way from the eastern in size or 

 8ha|)e (as will be seen by making a calculation from the figures). '1 hose 

 from \\\c. lower parts of California and the Pacific Coast itself (representing 

 "edax", "californicus", and "occidentalis") average a little less (3.92; that is, 

 O.IG less) than the average of the whole; while the tails average a little 

 more (1.3 '; that is, 0.15 more), giving a relative length of body an«l tail as 

 3.J)2 : 1.G8 :: 1.00 : 0.43; while that of the whol;; e.istern series is only 

 1.00 : 0.37. The feet are correspondingly enlarged, averaging 0.84 instead 

 of 0.79. We may say, therefore, that these specimens are a little smaller 

 than usual, with tail and feet both absolutely and relatively a little longer. 

 But we must remember that this is only one end of a very long series of 

 145 specimens, a great many of which shade up to this extreme, and some 

 of which overlap it, and that the utmost of variation in these 39 specimens 

 is fairly within the normal limits of variability we demonstrated for the 

 eastern series. We now propose to match several individual specimens out 

 of this series, as nearly as may prove possible, with eastern ones. 



No. 4318 (Nebraska) is 4.50X1-60X0.78, and No. 3-)25 (North 

 Carolina) is 4.75 X '-^OX 79; differing less than two specimens from 

 Nebraska. No. 3551, from Utah, is 4 75X2.10X0.78, and No. 857, 

 from New York City, is 4.75X2.00X0.80; difference much less than 

 that between the several Utah specimens. No. 3867 (Fort Crook) is 

 4 25X1-40X83; No. 4723, from Pennsylvania is 4.00X1-40X0.82; 

 the type of " longirostris" (No. 1268) is 4.50 X 1-«'>0X 0-73; a Philadelphia 

 skin is 4.25X1-40X0.70 (precisely the same proportions). A typical 

 specimen of "montana" is 4.50 X 1-55 X 0.81; a Philadelphia skin is 4.60 X 

 l..'iJX0.82. The type of "edax" is 4.00X1-^X0.90; No. 903, from 

 Nuntuckot. is 4.20 X 1-40 X 0.85; and No. 901 (type of rufidorsum) is 4.20 X 

 1..55 X 82. The type of " californicus " is 4.0d X 1-75 X 0.80 ; No. 1578, 



