48 THE CANADIAN NATURALIST. [Feb. 



of the feet is black, wrinkled, perfectly naked, and keenly sensitive 

 to tactile impressions. A distinct web joins the digits for about 

 half their length ; the upper parts of the feet are clothed with 

 short lustrous hairs, terminating at the sides in a fringe of stiff 

 bristles, which increase the surface, and give additional force in 

 swimming. Tail nearly as long as the body without the head, 

 cylindrical at the base, then flattened to the point. The tail 

 curves somewhat to a sickle shape ; being readily bendable towards 

 the belly, its point can be made to touch the inferior surface of 

 its base ; in this position it is almost circular, like a hoop. This 

 is a highly important arrangement, indispensable to the musk-rat. 

 A more perfect rudder was never designed than is this flexible 

 tail. If swimming when freighted, and a stiff breeze curls the 

 water into miniature waves, the musk-rat drops its tail, and bend- 

 ing it more or less according as it needs extra steering power, 

 guides itself straight for the desired haven. In calm weather and 

 smooth water the rudder is carried horizontally, and a slight 

 lateral motion close to the surface, suffices to guide the living ship. 

 It is worth while to note, en passant, how differently the beaver's 

 rudder is built, as compared with that of the musk-rat's — a differ- 

 ence easily accounted for when we know their respective habits. 

 The beaver never uses its tail as a trowel, and has no more idea 

 of ' lath and plaster ' than a hippopotamus has of a polka. This 

 story is a myth, and the sooner the absurd fables of plastering, 

 and " using the wondrous tail as a trowel," are sponged from out 

 all books on natural history the better. 



The beaver, with a heavy log of green timber (that would sink 

 like a stone if free) clasped between its fore-legs, swims for its 

 house. The counterpoise to this overweight at the bows is the 

 downward pressure of the flat tail on the water, flattened more 

 horizontally than the musk-rat's. Indeed, the tail of the beaver 

 is much like an ox- tongue in shape. The musk-rat, conveying 

 such materials through the water as are light, needs only powerful 

 rudder-power, having no forward weight to counterbalance. The 

 tail is covered by small hexagonal scales, with a few long, coarse 

 hairs irregularly scattered over it. The skull differs from Fiber 

 zibethicus in being much smaller, 2 J inches in length, If inch in 

 width, very much shorter from the anterior molar to incisors ; 

 nasal bones much more rounded at their posterior ends, the superior 

 outline less curved ; postorbital process not nearly so much devel- 

 oped ; the cranial portion of the skull in its upper outline is much 



