_Measurements._--A female from the Sierra de Tamaulipas affords the following measurements: Total length, 67; length of hind foot, 13; length of ear from notch, 15; length of forearm, 43.1; condylobasal length, 15.0; zygomatic breadth, 5.1; palatal length, 4.1; least interorbital constriction, 5.3; length of maxillary tooth-row, 5.1. _Records of occurrence._--Specimen examined, one from the Sierra de Tamaulipas, 3 mi. S, 14 mi. W Piedra, 1300 ft. Additional records: Rancho Pano Ayuctle (de la Torre, 1954:114); Aserradero del Infernillo (Goodwin, 1954:5). =Desmodus rotundus murinus= Wagner Vampire 1840. _D[esmodus]. murinus_ Wagner, _in_ Schreber, Die Säugthiere ..., Suppl., 1:337, type from México. 1912. _Desmodus rotundus murinus_, Osgood, Field Mus. Nat. Hist., Publ. 155, Zool. Ser., 10:63, January. _Distribution in Tamaulipas._--Southern part of state, north at least to vicinity of Jiménez. Hall and Kelson (1959:151) listed a place 12 kilometers west and 8 kilometers north of Ciudad Victoria as the northernmost locality of record for _Desmodus_, but three specimens from Cueva La Esperanza, 6 kilometers southwest of Rancho Santa Rosa, are from a site slightly to the northwestward (12 mi.) of the locality first mentioned and a specimen from 13 miles west and six and a half miles north of Jiménez represents the northeasternmost known occurrence of _Desmodus_ in eastern México. Most of the vampires examined in this study were taken in caves; those from four miles southwest of Padilla were obtained from a hollow tree. Nine specimens were collected in a small cave 70 kilometers south of Ciudad Victoria on January 18, when water on the floor of the cave was frozen; the bats were congregated on the ceiling at a height of 20 feet. In a cave in the Sierra de Tamaulipas, 16 miles west and three miles south of Piedra, females and young were found some 50 yards from the entrance; _Natalus stramineus_ and _Glossophaga soricina_ were obtained from the same cave. In another cave only half a kilometer distant, 12 males were collected. In Cueva La Mula, _Desmodus_ was found near the mouth, whereas _Choeronycteris mexicana_ and two _Tadarida brasiliensis_ were collected in the deepest part. At Cueva La Esperanza, 300 feet deep and on the east side of the Sierra Madre Oriental, four different congregations of vampires were found along with about 400 _Natalus_. A male _Desmodus_ obtained in a cave 13 miles west and six and a half miles north of Jiménez also was associated with _Natalus_.