MAMMALS OF Till! MEXICAN BOL'KDARY. 



297 



a Head and body, 180 mm. b Mammae, 4 pairs. o American Museum of Natural History. 

 Genus AMMOSPERMOPHILUS Merriam (1893), « 



Ammospermophilus Mebeiam, Proc. Biol. Soc. Washington, VII, p^ 27, 

 April 13, 1893. 



Type. — Tamias leucurus Merriam. 



Characters. — Dorsum with one longitudinal stripe on each side; 

 external ears considerably more developed than in Citellus citellus 

 (Linnaeus), but less so than in CallospermopMlus ; mammae, 5 pairs; 

 tail, cylindrical at base, flattened and bushy on terminal two-thirds.; 

 skull similar to that of Eutamias, but higher and more flattened 

 posteriorly, with relatively shorter and thicker rostrum, narrower 

 palate, heavier dentition, and larger audital bullae. The skull dif- 

 fers even more from Citellus in being relatively narrower, flattened 

 above and eleviited posteriorly, with audital bullae high and com- 

 pressed laterally, and in having the first premolar a much smaller, 

 simple, peg-like tooth. 



o The generic name SpermopMlus, so long in general use for the ground-squir- 

 rels or Spermophiles, has given place to the older name Citellus, and three of 

 its subgenera have been raised to the rank of genera. 



