212 BULLETIN NO. VJI. 



upper molar has an anterior, two interior and two exterior 

 triangles; second molar with an anterior, interior and two ex- 

 terior triangles; back molar with an anterior, interior, and 

 exterior triangle, and a posterior V-shaped treffle. 



The following notes derived from the Bulletin of Denison 

 University, vol. vi, were printed under the title Biological Notes 

 upon Fiber, Geomys and Erethyzon, by C. L. and C. Judson 

 Herrick: 



The muskrat, Fiber zibethicus, is sufficiently well-known to 

 every one, and yet perhaps few are aware of the extent to which 

 the animal adapts itself to the varying conditions of its envi- 

 ronment. One who casually learned to know the water rat in 

 one of our western states might pass many years in Ohio with- 

 out recognizing the fact that the same animal abounds in Ohio, 

 and under the changed conditions here prevailing adopts an 

 almost wholly different method of life. It would be more accu- 

 rate to say that in the cold Northwest, with its luxus of small 

 lakes and marshes, the monotonous career of the animal expands 

 in conformity with the greater variety of aquatic stations. 



The muskrat is a truly arvicoline rodent, that is, its affinities 

 are with the field mice rather than with ihe jumping mice 

 (Hesperomys) or oriental rats and mice (Mus). Though, at first 

 sight, very different from Arvicola, the chief differences in 

 Fiber are such as are obviously adapted to aquatic habit. 

 The long, laterally flattened, scaly and naked tail, small ears, 

 obliquely set and fringed hind feet with webbed toes are all 

 modifications induced by accommodation to aquatic habit. 

 The dark brown fur is long, with a liberal admixture of long, 

 stiff, glossy hairs of a darker color than the rest. The color 

 and texture varies with the season, and in early summer rats 

 may be found with a curiously tufted or mottled pelage. There 

 are six mammas and strongly-developed perineal glands which 

 are responsible for the peculiar musky odor implied by the 

 name. 'The secretion is often used by trappers for the more ex- 

 pensive castoreum in preparing "scent" used in baiting traps. 



As already indicated, the habits of the muskrat are subject 

 to considerable variation. Its usual home is a long burrow 

 opening beneath the surface of the water and passing many 

 yards into the bank, terminating in a cosy nest beneath the 

 protecting roots of a tree. It is here that young are reared and 

 from these burrows the entire family may be seen emerging at 

 twilight to engage in swimming races, games of tag and sport- 

 ive contests upon the surface of the stream. The head and 



