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1(52 



MONfKlUAlMia OF NORTH AMEUICAN IJODENTIA. 



It appears from this tabic that the average length is 4.3.1, and, hi the 

 best of our judgment, no allowance for shrinkage in the dimension is to be 

 made. The extremes are from 4.00 to 4.75, a variation of three-fourtiis of 

 an inch, or about 17 per cent, of the mean. The average of the tail, without 

 its hairs, being 1.4i, we may simihirly set its true average length at an inch 

 and a half; its variation amounts to 0..'17, about the same percentage. The 

 fore foot, averaging 0.35 in its present state, ranges from 0.30 to 0.38, that 

 is, a variatiim of over 20 per cent.; but from the sniallncss of the measure- 

 ment, the difficulty of placing the calipers upon exactly the same spot in the 

 several specimens, and an actual difTercnce in the ])osition of the ball of the 

 thumb when this is dried, the true percentage of variation would probably 

 fall below 0.20, and thus be nearly the same as in the cases of tiie head and 

 body and tail. The average dimension of the fore foot in life may be set at 

 three-twelfths of an inch, or three lines. The hind foot, from the tuberosity 

 of the heel to the end of the longest claw, can be measured with great exact- 

 ness; it averages 0.77, and so may be fixed at 0.80, or four-fifths of an inch, 

 in life; it varies 0.12, or very nearly 17 per cent., as before. With these 

 calculations for absolute dimensions and variation, we may further consider 



