174 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



But since several nominal species lire represented in the list, which might 

 collectively strike a general average without being severally on an average, it 

 becomes necessary to discuss the series in detail. On running the eye over 

 the column of lengths of trunk of the adults, it will be seen that they are 

 imperceptibly graduated from 3;50 to 4.7f>, and thai this graduation is inde- 

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

 discuss the relative length of tail and feet as compared 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 

 shape (as will be seen by making a calculation from the figures). Those 

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

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

 0.16 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 and tail as 

 3.92 : 1.68 :: 1.00 : 0.43; while that of the whoh' eastern 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 matcli 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. 3o25 (North 

 Carolina) is 4.75X1-60X0.79; differing less than two specimens from 

 Nebraska. No. 3551, from Utah, is 475X2.10X0.78, and No. 857, 

 from New York City, is 4.75 X -- () X 0.80 ; difference much less than 

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

 4 25X 1 -40X' s; '>: No. 4723, from Pennsylvania, is 4 00 X 1-40 X 0.82 ; 

 the type of " longirostris " (No. 1268) is 4.50X1-50X0.73: a Philadelphia 

 skin is 4.25 X 1-40X0-70 (precisely the same, proportions). A typical 

 specimen of "montana" is 4.50 X 1.55X0.81; a Philadelphia skin is 4.60 X 

 L.55X0.82. The type of "edax" is 4.00 X 1-55 X 0.90 ; No. 903, from 

 Nantucket, is 4.20 X 1-40X0.85; and No. 901 (type of rufidorsum) is 4.20 X 

 1.55X0 82. The type of "californicus" is 4.00X1-75X0.80; No. 1578, 



