THE BLUE-GRASS MOUSE. 



513 



signed to the subspecies auricularis rather than scalopsoides, be- 

 cause their colors are darker and richer and the ears more promi- 

 nent than on specimens from Maryland, which are assumed to be 

 fairly typical of scalopsoides. Bailey in his revision of the genus 

 has assigned some Brookville specimens to each form. 



Measurements. — ^^Full grown specimens from Mitchell vary 17 

 mm. in total length and 2 mm. in length of hind foot. The average 

 of five specimens from this locality is: Total length, 119.2 mm. 

 (413/16 in.); tail 18.6 mm. (12/16 in.); hind foot, 15.8 mm. 

 (10/16 in.). Five from Bascom are slightly larger. Cranial meas- 

 urements of four from IMitchell : Greatest length of skull, 25.8 

 mm. (1 in.) ; basilar length, 21.2 mm. (14/16 in.) ; palatilar length, 

 12.8 mm. ("(/> in.) ; greatest width of braincase, 12.2 mm. (i/o in.) ; 

 depth of braincase over audital bullae, 15.5 mm. (7/16 in.) ; max- 

 illary tooth row, 6 mm. (14 in.)- 



Skull and teeth. — As compared with other species of Microtus 

 the skulls of pinetorum (fig. 11) and its subspecies are flat and 



a b 



Fig. 11. — Skull of Microtus pinetorum: a, dorsal view; b, ventral view. After 

 Bailey. N. Am. Fauna No. 17, Bureau of the Biol. Sur., U, S. Dept. of Agrri. 



wide, with a quadranguar braincase, wide interorbital space and 

 short rostrum. The molars are narrow, the loops and triangles 

 are essentially as in Microtus ochrogaster, although they differ in 

 proportions, the most apparent difference being in the posterior 

 upper one. (See fig. 8b.) 



Range. — The bluegrass vole occupies the region between the 

 Allegheny IMountains and the Mississippi River south of the Ohio 

 River, and extending north of the latter into southern Indiana 

 and Illinois. Other subspecies are found to the north and east. 

 Indiana records are Brookville, Bascom, Mitchell and Bicknell. 



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