Copelcmd and Church — MammaU of Grand Manan. 123 



Twenty-three adult topotypes show no appreciable variation from the 

 type. 



The younger ppecimens differ only slightly from the old, — their general 

 color is a little more gray owing to the presence of but few russet hairs. 

 No very small young were obtained. 



Measurements. — Type: Total length, 179.5; tail vertebrae, 87 ; hind foot, 



21.5 ; ear, 17.5 mm. 



Skull: Greatest length, 26.4; basilar length, 20; palatilar length, 11; 

 zj'gomatic breadth, IS. 7 ; mastoid breadth, 11.1; interorbital breadth, 4 ; 

 length of nasals, 10. S ; length of upper molar series, 3 ; length of lower 

 molar series, 3.4 ; length of single half of mandible, 16.4 mm. 



Average measurements of twenty-three adult topotypes : Total length, 

 179.9 (171-194) ; tail vertebrae, 87.8 (82-93) ; hind foot, 21.2 (20-22). 



Average cranial measurements often adult topotypes : Greatest* length, 



25.6 (25.1-26.5) ; basilar* length, 19.4 (19-20.1); palatilar* length, 10.8 (10.5- 

 11.2); zygomatic breadth, 13 (12.7-13.4) ; interorbital breadth, 3.9 (3.7-4) ; 

 length of nasals, 10 (9.0-10.4). 



Average measurements of twelve adult topotypes of both sexes of 

 Peromyscus canadensis abietorum from collection of E. A. and 0. Bangs : 

 Total length, 172.7 ; tail vertebrae, 87 ; hind foot, 19.9 mm. 



Average cranial measurements of eight of the same : Greatest length, 24.7 

 basilar length, 18.8; palatilar length, 10.2; zygomatic breadth (seven speci- 

 mens), 12.2 ; interorbital breadth, 3.8 ; length of nasals, 9.7 mm. 



From the above it may be seen that argentatus averages slightly larger 

 than abielorum in body and foot measurements, and in all cranial measure- 

 ments. 



Re-marks. — This beautiful silvery gray deer mouse, so strikingly different 

 in color from its relatives of the coast, is a typical example of an insular 

 race which, through isolation and close interbreeding, has developed char- 

 acters quite its own. It inhabits the dark thick growths of spruce and fii-, 

 the more open mixed woods of conifers, birch, and beech, or some wooded 

 hillside strewn with numerous decaying stamps and prostrate trunks. 

 Here it makes its home in the underground passages beneath stumps and 

 the moss covered roots of trees, and runs through the rich carpet of moist 

 sphagnum so characteristic of the northern woods. 



The mouse is common about Grand Harbor and we took forty in our 

 traps, — baited with rolled oats, — all of which were preserved and examined. 



Microtus pennsylvanicus (Ord). 



MEADOW MOUSE. 



The meadow mouse proved to be a common species in the vicinity of 

 Grand Harbor, and we took over seventy in our traps. They inhabited 

 almost all the localities in which we trapped, and were equally abundant 

 in the wet meadows and dry fields, or with the white-footed mice in the 

 moist evergreen woods and along the edges of the heavier timber. 



♦ Thomas, O., Proc. Biol. Soc. Wash., XVIII, pp. 191-196, Sept. 2, 190.5. 



