Species such as the bighorn and the marmot that are rare within the Park, or those such as the chickaree, the prairie dog, the wandering shrew, the montane vole, and the long-tailed vole that occupy only small areas of suitable habitat within the Park are the species most likely to be eliminated by natural changes, or through the activities of man. For example parasites introduced through domestic sheep that wander into the range of bighorns within the Park might endanger the bighorn population. An increase in grazing activity, road building, and camping in Prater and Morfield canyons might eliminate the small areas of habitat occupied by the montane vole and the wandering shrew. Fire in Chickaree Draw could destroy all the Douglas fir there, and consequently much of the habitat occupied by the chickaree. Probably some species inhabit the Mesa that have not yet been found, but they are probably few, and their discovery will not alter the faunal pattern in which the few boreal species occupy restricted habitats in the higher parts of the Mesa, and a preponderance of geographically wide-spread species occupy all or most of the Mesa, and surrounding areas. Additional bats are the species most likely to be added to the list. 28-7577 LITERATURE CITED ANDERSON, S. 1959. Mammals of the Grand Mesa, Colorado. Univ. Kansas Publ., Mus. Nat. Hist, 9(16):405-414, 1 fig. in text. CAHALANE, V.H. 1948. The status of mammals in the U.S. National Park System, 1947. Jour. Mamm., 29(3):247-259. CARY, M. 1911. A biological survey of Colorado. N. Amer. Fauna, 33:1-256, 39 figs., frontispiece (map). FINDLEY, J.S. 1955. Speciation of the Wandering Shrew. Univ. Kansas Publ., Mus. Nat. Hist., 9(1):1-68, figs. 1-18. FINDLEY, J.S. and ANDERSON, S. 1956. Zoogeography of the montane mammals of Colorado. Jour. Mamm., 37(1):80-82,1 fig. in text. FINLEY, R.B. 1958. The wood rats of Colorado, distribution and ecology. Univ. Kansas Publ., Mus. Nat. Hist., 10(6):213-552, 34 plates, 8 figs., 35 tables in text. GETTY, H.T. 1935. New dates from Mesa Verde. Tree-ring Bulletin, 1(3):21-23. HOFFMEISTER, D.F. 1951. A taxonomic and evolutionary study of the piñon mouse, Peromyscus truei. Illinois Biol. Monogr., vol. XXI(4), pp. ix + 104, 24 figs., 4 tables and 5 plates in text. RODECK, H.G. and ANDERSON, S. 1956. _Sorex merriami_ and _Microtus mexicanus_ in Colorado. Jour. Mamm., 37(3):436. SCHULMAN, E. 1946. Dendrochronology at Mesa Verde National Park. Tree-ring Bulletin, 12(3):18-24, 2 figs., 1 table in text. YOUNGMAN, P.M. 1958. Geographic variation in the pocket gopher, Thomomys bottae, in Colorado. Univ. Kansas Publ., Mus. Nat. Hist., 9(12):363-387, 7 figs. in text. _Transmitted April 11, 1961._ UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATIONAL HISTORY