MAMMALS 329 



is covei-ed with a ttiick coat of soft fur beneath a layer of 

 longer coarse hair. The hind feet are webbed for swimming, 

 but the fore feet are fitted for digging. 



Moreover, the l^eaver is one of the greatest gnawers of 

 the whole group. It lives in colonies and is very indus- 

 trious ; but most of its work is done at night. The houses, 

 or " lodges," of the beaver are built on the edge of the water, 

 are dome-shaped, and some four or five feet high. They 

 are built of stones, sticks, and mud, and are finally plastered 

 over in the autunni with mud, which freezes, thus forming a 

 hard impenetrable shell. The opening into the lodge is 

 beneath the water. The living ajjartment is at the top, 

 al.iove the water line ; l)ut near by are stored branches of 

 trees, the bark of which serves for the winter food. In 

 order to maintain the water at the desired height about 

 their lodges, the beavers build dams of considerate length 

 (perhaps the longest ever noted Iieing three hundred yards) 

 across streams, with the con\'ex side upstream, to with- 

 stand the pressure. The dam is built of sticks, stones, and 

 mud, not in regular fashion, j-et forming a water-tight and 

 very firm barrier. 



Insect-eating M.a.mm.'Vls (Insectivora) 



The order, Insectivora, contains only very small mammals 

 with a thick, furry {sometimes spiny), covering. The muczle 

 is short and soft and the molars are Jilted for crushiruj the 

 bodies of insects. They live mostly on insects and the order 

 includes the shrew, moles, hedgehogs, and some other little- 

 known mammals. 



Shrews. — These are the smallest of rnanunals. One 

 species known as the lecLst shrew, which measures only a 



