E. V. Miller 1940 Cynomys mexicanus May 28 San Juan Nepomuceno, 5 mi. N la Ventura, Coahuila A small prairie dog city, about 1 mi. wide and 3 miles or more long is located at this place. The country is a wide valley, mostly covered with brush, but here there is a grassy plain, dotted with the mounds of the 'dogs'. These mounds are scattered irregularly from 50 to 100 feet apart in most instances, and are from 1 to 2 feet in height, with the steeply slanting hole near the center of the mound. The mounds vary with the age of the occupants. Those of small dogs are 1 1/2 to 2 ft. wide, while those of older dogs are from 2 to 4 ft. wide. The ground, which is flat, light colored, and not hard, is sparsely covered with low grass and very small low weeds. The larger 'dogs' usually occur singly, but not always. The youngsters are often in twos, threes, or fours. As one approaches the 'city' dog' can be seen sitting upright from about 50 yds. on. When one approaches closer they drop to all four legs and jerk their short tails rapidly up and down. They then run into their burrows, but stick their heads up to observe your closer approach. They have two kinds of calls - a rough but sharp keek and a more drawn out yap. May 30 Saw 2 more prairie dog cities, at about 19 and 24 miles N la Ventura, Coahuila. They were both fairly small.