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THE AMERICAN XATURALIST [Vou XLI 



the surface, rising as abruptly at one end as they had descended 

 at the other. The two openings of a single burrow were never 

 found closer together than a meter, and they were occasionally 

 four meters apart. This fact gives another means of distinguish- 

 ing the burrows of Blarina from those of ^licrotus. As far as I 

 have observed, the openings of an individual underground burrow 

 of Microtus were never as far apart as a meter, usually not more 

 than 35 or 40 cm. Microtus burrows, moreover, were not found 

 to extend as deep into the soil as those of Blarina. 



Nests and the Burrows Near Them.— Nests are found along the 

 course of the burrows. In digging out the burrows some sixteen 

 nests were unearthed. Some of these were along ditch banks where 

 the groundwater level was lower than elsewhere. All the others 

 were in small (>levations such as mounds where celery had been 

 burinl or l.ills thrown uy) by roots of fallen trees. The' nests were 

 t'ouiui at depths of 15 to 40 cm. They were 

 , \ \ . 12 to 15 cm. in diameter, and slightly de- 

 ^ ^'-^^ ^ pressed from the spherical form. They were 

 BiarlnalirciicM usually made of grass, sedge, and leaves of 



nettle, goldenrod or ash, arranged in the form 

 of a hollow ball, the shell of which was 1 to 3 cm. thick. One 

 was composed entirely of hair which mi(Toscopic examination 

 showed to be that of the meadow vole. When plant materials 

 were used, the plants furnishing them were invariably found 

 inniiediately adjoining the nest. If grass was near the nest, it 

 was used almost to the exclusion of other leaves. Coarse mate- 

 rials were used without being shredded or torn into smaller 

 pieces. This constitutes an easy distinction between the nests 

 of Blarina and such nests of Microtus as are constructed of any- 

 thing larger than grass. In all the nests of Microtus wliich I 

 observed, coarse materials were torn apart; sedge leaves 6 to 8 

 mm. wide were shredded into three or four strips, and corn blades 



than about 2 cm. Wlien the same kinds of material were used in 



