■146 



BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Remarks. — Two species occur on the Mexican Border: One (Sig- 

 raodon Jiispidus) ranges west from the Atlantic and Gulf coasts to the 

 western waters of the Colorado Basin, but does not reach the Pacific 

 Coast Tract, though its range crosses four differentiation tracts, and 

 it has become differentiated into a corresponding number of excellent 



subspecies. The other species (S. minimus) 

 is restricted to the Elevated Central Tract, 

 which separates the two desert tracts and is 

 known only from the bound ary strip. 



1 





SIGMODON MINIMUS Mearns. 



MEARNS COTTON RAT. 



Sigmodon minimus Mearns, Proc. U. S. Nat. Mus., 

 XVII, pp. 120, 130, July 19, 1894 (original de- 

 scription). — Allen, Bull. Am. Mus. Nat. Hist., 

 VII, 189.5, pp. 220, 221.— Millek and Rehn, 

 Proc. Bost. Soc. Nat. Hist., XXX, No. 1, Dec. 27, 

 1901, p. 91 (Syst. Results Study X. Am. Mam. to 

 close of 19(H)): XXXI, Aug. 27,1903, p. 81 (Syst. 

 Results Study X. Am. Mam. during the years 

 1901 and 1902 (.-Bailey, Proc. Biol. Soc. Wash- 

 ington, XV, p. 114, June 2, 1902 (Synopsis of the 

 North American species of Sigmodon). 



[Sigmodon] minimus, Elliot, Field Col. Mus., Zool. 

 Ser., II, 1901, p. 146 (Synop. Mam. N. Am.); 

 IV, 1904, p. 230 (Mam. Mid. Am.). 



Type-locality. — Grassy hollows and flats 

 between the most southern spurs of the 

 Apache Mountains, near Monument No. 40, 

 at an altitude of 1,500 meters. (Type, skin 

 and skull, Cat. No. fUf tj U. S. National 

 Museum.) 



Geographical range. — Elevated Central 

 Tract, along the Mexican Boundary, from 

 Monument No. 40 west to Monument No. 

 Ill in the Upper Sonoran Life Zone. 



Description. — Size, small; length, 240 nun. ; 

 tail, 100; ear, 14; hind foot, 28; coat, bushy 

 and hispid; tinder fur, dark plumbeous; 

 fig. 109.— sigmodon hispidus am- coarse outer coat quite bristly, especially on 



zon.s. a, ear; 6, forefoot; ^ [([ f t} j | d k f(l(>( J 



c, hindfoot; d, tail. . } m ' 



tail densely hairy, the latter not distinctly bi- 

 color; color of upper surface, gray isl i, the individual hairs being ringed 

 with gray and brown, the brown annuli being blackish in their middle 

 portion, fading to light-yellowish brown on their edges; under surface 

 of bod}^ clayey buff; feet yellowish gray; ears densely clothed with 



