_Remarks._--When the present account first was prepared our specimen from six and a half miles west of Zamora was tentatively referred to _S. h. mascotensis_. Subsequently a second specimen, from Zamora, was found. It agreed with the specimen from six and a half miles west of Zamora. Inasmuch as the second specimen agrees with the first and since each of the two differs from any previously described kind, a name and description were published in time to be inserted in the present account. From _S. h. mascotensis_, _S. h. atratus_ differs in shorter hind foot, darker upper parts, more densely haired tail, shorter skull, more convex dorsal longitudinal outline of skull, posteriorly constricted anterior palatine foramina instead of parallel-sided foramina, and shorter and less decurved anterior process of maxillary arm of zygoma. =Neotomodon alstoni alstoni= Merriam Volcano Mouse; Spanish, Ratón de Los Volcanes _Neotomodon alstoni_ Merriam, Proc. Biol. Soc. Washington, 12:128, April 30, 1898, type from Nahuatzin, 8,500 ft., Michoacán. _Range._--Higher mountains of state. _Specimens examined_, 22: nos. 52179-52184, 52186, 52193-52196, 52199, 52200, 52204-52212, all from Mount Tancítaro, distributed by localities as follows: 7,800 ft., 5; 7,850 ft., 3; 10,000 ft., 4; 10,200 ft., 5; 10,500 ft., 1; 10,800 ft., 1; 11,000 ft., 2; 11,400 ft., 1. _Remarks._--The taking of specimens on Mount Tancítaro extends the known geographic range of _Neotomodon_ approximately 75 kilometers to the southwestward; the westernmost locality previously known was Nahuatzin, the type locality. =Nelsonia goldmani= Merriam Dwarf Wood Rat; Spanish, Rata Montera Minúscula _Nelsonia goldmani_ Merriam, Proc. Biol. Soc. Washington, 16:80, May 29, 1903, type from Mount Tancítaro, Michoacán. _Range._--Known only from the type locality. _Remarks._--In the original description three specimens are recorded from the type locality. =Neotoma latifrons= Merriam White-throated Wood Rat; Spanish, Rata Montera Frentuda _Neotoma latifrons_ Merriam, Proc. Biol. Soc. Washington, 9:121, July 2, 1894, type from Queréndaro, Michoacán. _Range._--Known only from the type locality. =Neotoma ferruginea tenuicauda= Merriam Ferruginous Wood Rat; Spanish, Rata Ferruginosa _Neotoma tenuicauda_ Merriam, Proc. Biol. Soc. Washington, 7:169, September 29, 1892, type from north slope of Sierra Nevada de Colima, 12,000 ft., Colima. _Neotoma ferruginea tenuicauda_, Howell, N. Amer. Fauna, 31:73, October 19, 1910. _Range._--Probably all but southern tropical part of state. _Specimens examined_, 4: nos. 100633 from 9 mi. SE Pátzcuaro, 8,000 ft., and 52177, 51390, 51391, from Tancítaro, the elevation being given as 7,850 ft. on no. 52177. _Remarks._--Our one specimen from 9 miles southeast of Pátzcuaro was caught in a small steel trap set at a meat bait. =Microtus mexicanus salvus= Hall