212 BULLETIN NO. VII. 
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 vosterior 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 the jumping mice 
(Hesperomys) or oriental rats and mice (Mus). Though, at first 
sight, very different from Avrvicola, 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 mamme 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 atree. 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 
