The young specimen, no. 2102, [M], has the tail slender, resembling somewhat that of the _S. p. senex_ from the southward. The underparts of the female are Warm Buff, more clearly so on the underside of the legs. =Sciurus poliopus senex= Nelson Michoacán Squirrel; Spanish, Ardilla Arborícola; Tarascan, Uakuí (Wakqe) _Sciurus poliopus senex_ Nelson, Proc. Biol. Soc. Washington, 17:148, October 6, 1904, type from La Salada, 40 mi. S Uruapan. _Range._--Lowlands in southern part of state. _Specimens examined_, 3: nos. 52004, 52014, 52015, distributed by localities as follows: Tancítaro, 6,000 ft., 1; Apatzingan, 1,040 ft., 2. _Remarks._--Specimen number 52014, [M], represents the melanistic phase of this subspecies. The upper parts of the hind legs in this specimen are slightly grizzled. The upper side of the tail is vermiculated with whitish and the underside of the tail is black. =Thomomys umbrinus pullus= Hall and Villa Southern Pocket Gopher; Spanish, Tuza Serrana; Tarascan, Cúmu (Cŏmŏ) _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)