108 



MONOGRAPHS OF NOlfTII AMERICAN PODENTIA. 



The large amount of material in this table gives the following results:- 



The average length of the trunk (head and body) is 4.4?, or .slightly less 

 than lour and a half inches. The minimum, of apparently adult animals, is 

 3.50, the maximum is 5.7f>, and so two inches and a quarter is the gross 

 amount of variation deduced from the figures as they stand. To make 

 allowance, however, for probable error, both from inaccuracy of measure- 

 ment and from imperfect preparation of the dried skins, from which most ol 

 the measurements are taken, and thus to keep largely within reasonable 

 bounds, we will add 0.25 to the minimum and subtract 0.25 from the maxi- 

 mum. With this very liberal allowance, it will be seen that we have proven 

 a net variation of one and three-quarters inches to occur in the sixty-three 

 specimens measured. 



The tail averages 1.59 in this series, with 1.10 and 2.00 as extremes. 

 Making a fair allowance for error, as before, its true variation may safely be 

 held at three-quarters of an inch. Its average length relative to the trunk 

 is as 4.43 to 1.59 :: 1 : 0.3G nearly, or a little over one-third the length of 

 the trunk. 



The average hind foot is here 0.80, with 0.72 and 0.92 as extremes. 

 Probably little or no allowance is here to be made for error, as the feet are 

 never skinned, shrink but little in drying, and can be measured to a nicety. 

 The hind foot, then, varies two-tenths of an inch in length. 



AVe tabulate a resume of the four preceding series, as far as the three 

 principal measurements, of head and body, tail vertebra 1 , and hind foot, are 

 concerned. 



Combining the results of the 1 14 specimens, we have an average length 

 of trunk of exactly four ami one-third inches; a length of tail of 1.59, or almost 



