40 MONOGRAPHS OF NORTE AMERICAN RODENTIA. 



tin' same, and with nearly the same limits of variation that were found in the 

 Carolina scries (4.40 to 6.00), though none drop to 4.00. The same may be 

 said of the ears, fore t'eri, head, nose to ear, and nose to eye. The case is 

 different respecting the tail and hind feet, in which we get some new figures 

 requiring attention, as the dimensions of these parts have entered into the 

 specific diagnoses. 



For all the United States specimens, except three (Nos. 8820, 566, and 

 8), both the absolute and relative length of the tail is almost exactly as in 

 Carolina skins ; if anything, the tail is rather shorter than longer. In none 

 of the United States specimens do the feet differ appreciably from the Carolina 

 figures. In No. 8, the tail first touches 4 inches; the tail of 8820 is a little 

 longer (4.30); that of 566 (type of " berlandieri") is still longer (4.60). But 

 not one of these even equals, not to mention exceeding, the head and body, as 

 alleged for "berlandieri". In several Mexican skins, similarly, the tail sur- 

 passes 4.00 (Nos. 9385, 9508, 9509, 9510); and in two of these (9509, 9510) 

 it actually equals the trunk. These are the only instances of this occurrence 

 in the whole series; and that they fall in the category of individual variations 

 is proven by the following considerations : — First, these specimens are associ- 

 ated with others (Nos. 9534, 6995, G996, 7210) positively identical in every 

 respect, and in which the tails bear the ordinary positive and relative length 

 of Carolina skins ; secondly, the Texan and Mexican skins differ more inter 

 se in length of tail than they do from the Carolina ones ; thirdly, we can 

 form from our two tables the following graduated series of tails' lengths : 

 2.25, 2.40, 2.50, 2.70, 2.75, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.75, 

 3.90, 4.00, 4.30, 4.40, 4.60, 4.70, 5.00, 5.25 ! Where shall we make a break 

 in this chain to establish specific difference upon length of tail? It is hard 

 to admit a variation of two inches in the tail of an animal the tail of which only 

 averages three inches long; but we do not see how to get around the figures. 



We found the feet of Carolina specimens to range from 1.00 to 1.30. 

 Among the Southwestern United States and Mexican examples, we have a 

 slight widening of the limits— from 0.97 to 1.37 and 1.40. The foot of 4927 

 is indeed enormous, 0.10 longer than the maximum Carolina foot, and heavy 

 in proportion ; while that of 9384 is hardly less. But No. 9385 (a specimen 

 that might have been twin-brother to 9384, the two are so absolutely alike in 

 other respects) immediately sinks the figure to 1.30, which is at the Carolina 

 extreme; and No. 4927 bis (taken along with 4927) has the foot within ordinary 



