590 
The mamme are six in number. The posterior pair are in the 
usual pelvic position, but the middle pair are so situated that the 
teats are near the knees. The front pair also are in an unusual 
position, being toward the back, and on the side, back of the fore 
leg. It is evident that if the mammze were in the usual place 
beneath the body they could not be reached by the young, owing 
to the short legs of the dam and the projecting snout of the young 
moles. 
The fur, except on the snout and extremities, is dense, fine, and 
silky, with but very little slope, so that it offers little resistance to 
rubbing in any direction. The general color is hair-brown, some- 
times grayish, sometimes warmed to bister or sepia, but is always 
obscured by a shifting, sheeny luster. The base of the hairs is 
plumbeous. The chin, throat, upper surface of fore paws, and the 
wrists are much lighter in color, and often suffused with shades 
varying from ochraceous to ferruginous or, in spots, even to orange. 
The tail is whitish at base, nearly naked, and pinkish at the tip, as 
are also the tip of the snout and the toes. 
The moles are almost unique among vertebrates in leading a 
truly subterranean life in burrows of their own construction, not 
only finding a refuge in them, like so many other animals, but also 
seeking their food by plowing their way through the ground as a 
fish seeks its food in the water. Their burrows are made, for the 
most part, by simply pushing the earth aside, and not by loosening 
the dirt and bringing it to the surface as is the habit with most 
burrowing animals. This necessitates enormous strength in the 
fore limbs and shoulders. Moreover there is need that these limbs 
be able to work in as small a space as possible. If we estimate the 
average diameter of a mole-run as two and a half inches, a simple 
computation will show that if the working distance of each fore 
limb were increased a quarter of an inch it would add at least 40 
per cent. to the energy required for excavating every unit length of 
burrow. This ability to economize in working room is secured by 
the shortness of the fore limbs and still more by their position. 
Instead of being attached, as usual, on the side of the thorax, the 
whole pectoral girdle is brought forward around the neck. This is 
accomplished in the following manner: the sternum is produced 
forward in a separate keel-shaped bone, and the ventral attachment 
of the clavicle is to the front end of this. 
