446 



BULLETIN 56, UNITED STATES NATIONAL MUSEUM, 



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

 modon Mspidus) ranges west from tlie 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. rmininius) 



U is restricted to the Elevated Central Tract, 



whicli separates the two desert tracts and is 



/■^l- kno^vn only from the boundar}^ strip. 



?d,.^ 



/ 



0,0 



/i> 



m 



SIGMODON MINIMUS Mearns. 



MEARNS COTTON RAT. 



ih 



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

 XVIT, pp. 129, 130, Jul3^ 19, 1894 (original de- 

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

 VII, 1895, pp. 220, 221.— Miller and Rehn, 

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

 1901, p. 91 (Sy,st. Results Study N. Am. Mam. to 

 close of 1900) : XXXI, Aug. 27, 1903, p. 81 (Syst. 

 Results Study N. Am. Mam. during the years 

 1901 and 1902).— B.^iley, 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.). 



T)/j)e-localiti/.~ 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. Ulih U. S. National 

 ^luseuin.) 



Geographical range, — Elevated Central 

 Tract, along the Mexican Boundary, from 

 Monument No. 40 west to Momiment No. 

 11 1 in tlie I^pper Sonoran Life Zone. 



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

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

 and hispid; under fur, dark plumbeous; 

 Sigmodon mspiDus ARi- coarse outer coat quite bristly, especially on 

 6, forefoot, ^j^p sides of the head and neck; ears, feet, and 

 tail densely hairy, the latter not distinctly bi- 

 color; color of upper surface, grayish, 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; imder surface 

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



Fig. 109 



ZON^. a, ear; b, forefoot; 

 c, hindfoot; d, tail. 



