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222 



MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



The subjoined tal)le illustrates Hilly the size and proportions, and the 

 variation in these respects, of this species. It seldom reaches and very 

 rarely if ever exceeds 4.00 in length of trunk; adults do not apparently fall 

 below y.OO; the great majority range between 3.25 and 3.75, settling at 

 barely over .'3.50 on an average. The law of increase of size with increase 

 of latitude is well illustrated, specimens from New England and the Middle 

 States ranging over those from the South Atlantic and Gulf States; the 

 latter perhaps never quite reach 4.00. The short tail, a striking feature, 

 is not so long as the head ; its vertebrsE run but little over the length of the 

 hind i'ct't, usually, and sometimes are not appreciably longer. The pencil of 

 hairs is about 0.10-0.15 in length; the general liairiness is mediocre. The 

 fore feet are larger comparatively than in any species of other sections of 

 the genus, being broader than the hinder ones, and decidedly more than half 

 as long. Part of this is due to the length of the fore claws, which appre- 

 ciably exceeds that of the hinder and confers a noticeably " fossorial " char- 

 acter. The palm runs from 0.30 to 0.40 in length, resting at an average of 

 just about three-eighths of an inch. The palms show five callosities ; the 

 thumb and its nail is possibly a little larger than ordinary. The hind feet are 

 rather small, ranging from 0.57 to 0.70, and striking just five-eighths of an 

 inch average. Tiie soles are rather scant-haired, and only so to the posterior 

 tubercle ; there are only^ve plantar callosities : a posterior internal one, one 

 at base of first, second, and fifth toes respectively, and one at base of third 

 and fourth toes together. It appears from measurements not herewith pre- 

 sented that the ear is only a fourth of an inch (l).20-0.30) high ; it is fairly 

 hidden in the fur, is orbicular, and in greatest part flat; the edge is scarcely 

 or not inflected, and the anterior and posterior heels of the rim do not meet 

 in front of the meatus, where, consequently, the surface is plane (not ridged as 

 in 'JhUotm, which compare). The anlitragus stands out as an evident flange 

 with a slightly convex free edge ; but it is not so large and valvular as in 

 more aquatic species, nor does it seem capable of closiu ^ the meatus. There 

 is a great dift'erence in the hairiness of the auricle, perhaps dependent on 

 individual variability, but quite as likely owing to seasonal or other conditions 

 that equally affect the general pelage. In some specimens, the flat part of 

 the conch is nearly as naked interiorly as in Chilotun; in others, the same 

 part is well haired ; the scoo])ed-out portion is always nuked, and the back 

 of the ear always noticeably pilous. The whiskers are shorter than usual, 



