_Cratogeomys zinseri_ occurs over the same general area as _C. gymnurus_ in central Jalisco, although these two species seemingly do not share the same local habitat. _C. zinseri_ differs from _C. gymnurus_ as follows: Tail relatively longer; skull wider across zygomatic arches than across mastoid processes of squamosal (reverse true in _C. gymnurus_); zygomata strongly bowed outward anteriorly; maxillary arm of zygomata almost touching squamosal arm (instead of widely separated from each other) above jugal; rostrum relatively narrower, less massive; border of nasals parallel or laterally swollen instead of gradually tapering. _Specimens examined._--Four, N end of Lago Sayula, 9 mi. N and 2 mi. E Atoyac. _Museum of Natural History, University of Kansas, Lawrence. Transmitted June 12, 1953._ 24-8662 * * * * * Transcriber's Notes: Page 538: Changed lead to led (conditions have lead to a high degree). Bold text is shown within =equal signs=. Italicized text is shown within _underscores_.