Thomomys umbrinus pullus Hall and Villa, Univ. Kansas Publ., Mus. Nat. Hist., 1:251, July 26, 1948, type from 5 miles south Pátzcuaro, 7,800 ft., Michoacán.
Range.—Known only from pine-covered rolling land three to five miles south of Pátzcuaro.
Specimens examined, 17: nos. 100136-100152, distributed by localities as follows: 3 mi. S Pátzcuaro, 7,800 ft., 1; 4 mi. S Pátzcuaro, 7,800 ft., 10; 5 mi. S Pátzcuaro, 7,800 ft., 6.
Remarks.—Most of these pocket gophers were caught in areas supporting a good growth of pine trees in the same places where the much larger pocket gopher, Cratogeomys gymnurus, lived. Concerning the individual designated as the type specimen, H. H. Hall (field notes) writes that when he was making an excavation to reveal the gopher's burrow (5 inches below the surface), he dug deeper than was necessary and broke into the burrow of a Cratogeomys directly below. Another of us (E. R. Hall) had the same experience where the burrow of a Thomomys was approximately six inches below ground and that of a Cratogeomys approximately 16 inches below the surface of the ground. At the time this arrangement led us to wonder if Thomomys was in some sense a "parasite" on the larger Cratogeomys by levying on food stores, if Cratogeomys has any, but we found no evidence that such was the case and from our subsequent trapping concluded that the two-story arrangement was accidental and not the rule. The habit of burrowing at different levels probably was one factor which permitted the two kinds of pocket gophers to live in the same area. The average weight of these gophers was 86 grams in males and 74 grams in females, or only an eighth as much as in Cratogeomys.
Cratogeomys gymnurus imparilis (Goldman)
Plains Pocket Gopher; Spanish, Tuza Llanera; Tarascan, Cúmu (Cŏmŏ)
Platygeomys gymnurus imparilis, Goldman, Jour. Mamm., 20:89, February 14, 1939, type from Pátzcuaro, 7,000 ft., Michoacán.
Platygeomys tylorhinus Merriam, N. Amer. Fauna, 8:167, pl. 13, fig. 1, January 31, 1895.
Range.—Pátzcuaro and Tacámbaro, as now known.
Specimens examined, 14: nos. 100153-100166, distributed by localities as follows: 2 mi. W Pátzcuaro, 7,700 ft., 2; 3 mi. S Pátzcuaro, 7,800 ft., 1; 4 mi. S Pátzcuaro, 7,800 ft., 1; 5 mi. S. Pátzcuaro, 7,800 ft., 6; 9 mi. SE Pátzcuaro, 8,000 ft., 1; 1¾ mi. S Tacámbaro, 5,700 ft., 1; 1½ mi. S Tacámbaro, 5,700 ft., 2.
Remarks.—Burrows were common in cultivated fields and along the roads and trails on the southern and southeastern side of Lake Pátzcuaro. In the vicinity of Tacámbaro we noted burrows only in the area between one and a half and two miles south of town where two specimens were taken. As mentioned in the immediately preceding account, the small Thomomys umbrinus pullus and the large Cratogeomys were found in the same area. The color of our specimens varies from Cinnamon-Brown through Prouts Brown and in some specimens is Fuscous Black.