From March 16 to 23 we collected in the territory 1 to 6 miles south of Tacámbaro, making our headquarters in the Europa Hotel, in the town. The steep main street of Tacámbaro with native pines at the upper end descends to plantings of bananas and sugar cane at the lower end. Our collecting all was done below (south of) the town in the semitropical country and none at all was done above (north of) the town. From March 24 to 27 (three night's trapping) we collected in the vicinity of Zamora, making our headquarters in rooms diagonally across the street intersection from the Hotel Fenix. The resulting specimens, approximately 650 in number, were deposited in the Museum of Vertebrate Zoölogy at the University of California at Berkeley. A noteworthy coincidence is that on the very day, February 26, on which we crossed the international border into México at Laredo, the beginning of the new volcano, Paricutín, was announced in the daily press. Our collecting of mammals in Michoacán was nearly all done in sight of the towering white plume of this rapidly heightening volcanic cone and frequently our traps were thickly dusted with its wind-borne ash. Our eagerness at that time to have stations established for observing the effects on vertebrates of the deposition of ash, was gratified in that Dr. Robert T. Hatt independently had the same idea and such observations at appropriate places and times were begun by him and staff members of the Museum of Zoölogy of the University of Michigan. One of us, Villa, was privileged to share in these observations in the spring of 1947. This continuing interest in the mammals of Michoacán has made it seem, to us, the more desirable to place on record our findings as to kinds and occurrence of species. In doing this we have examined the collections made previously on Cerro Tancítaro and vicinity by the field party led by Mr. Harry Hoogstraal from the University of Illinois and the Chicago Natural History Museum. The specimens of mammals collected by this field party are in the Chicago Natural History Museum and we are obliged to Mr. Karl P. Schmidt, Mr. Colin C. Sanborn and the late Dr. Wilfred H. Osgood for the privilege of studying this material. Drs. William H. Burt and Emmet T. Hooper, of the Museum of Zoölogy of the University of Michigan, lent to us for examination five specimens of bats, of as many species, which they had taken in Michoacán. Drs. Remington Kellogg and Henry W. Setzer have provided us with data on specimens of deer and peccary from Michoacán which are in the United States National Museum. Specimens in the Institute of Biology of the University of México have been used. Financial provision by the Kansas University Endowment Association has enabled us to obtain specimens needed for comparison from other parts of México.