1895. _Pappogeomys_ Merriam, N. Amer. Fauna, 8:145, January 31. 1895. _Cratogeomys_ Merriam, N. Amer. Fauna, 8:150, January 31. Type: _Geomys merriami_ Thomas. 1895. _Platygeomys_ Merriam, N. Amer. Fauna, 8:162, January 31. Type: _Geomys gymnurus_ Merriam; Hooper, Jour. Mamm., 27:397, November 25, 1946. _Type._--_Geomys bulleri_ Thomas, 1892, from near Talpa, west slope Sierra de Mascota, 8500 ft. (actually about 5000 ft.), Jalisco. _Chronologic range._--Late Pliocene, from deposits of early Blancan age (Benson local fauna, Arizona) to the Recent. However in the Pleistocene, only late Pleistocene records are known, and _Pappogeomys_ has not been found in early (late Blancan) or middle (Irvingtonian) Pleistocene local faunas. Presumably the genus was restricted to México during the Pleistocene until post-Wisconsin time. _Description and discussion._--The size ranges from as little as in the smaller kinds of _Thomomys_ to the maximum attained in the subfamily and matched elsewhere perhaps in only a few of the larger subspecies of _Orthogeomys grandis_. Depending on the species and subgenus, the form of the skull varies from generalized to specialized. The generalized skulls are short and not especially narrow; the zygomatic arches are spread laterally so far that the breadth across them exceeds the breadth across the mastoid processes. The most specialized skulls are platycephalic and the breadth across the mastoid processes equals or exceeds the breadth across the zygomatic arches (even so, the zygomatic arches are still relatively widespread). In correlation with the great breadth of the posterior part of the cranium, the rami of the mandibles diverge widely posteriolaterally and the angular processes are remarkably elongated. The rostrum is moderately broad in most species, but not nearly so broad and heavy as in _Orthogeomys_. The single deep, median sulcus on the outer surface of the upper incisor is slightly displaced to the inner side of the tooth. The posterior surface of P4 lacks enamel (small vestige found on lingual end of posterior wall in only two adult individuals--UA 3260 and KU 100442, of the subgenus _Pappogeomys_); the other three plates are fully developed as usual. The p4 is provided with four fully developed enamel plates, in the pattern characteristic of the tribe Geomyini. In the p4 of the late Pliocene species (_P. bensoni_) the re-entrant angles are open (obtuse), a trait that is evidently primitive in the Geomyini.