_M. a. nigricans_ is characteristically an early flier. Along the Río Piaxtla, 1 mi. SE Camino Reál, where bats probably found daytime retreats in the rocky walls of the steep-sided valley of the river, individuals first appeared early in the evening when the sun was still on the western horizon, but were gone before other species of bats were seen. A female from 32 mi. SSE Culiacán, taken on June 18, 1954, contained one embryo that was 18 mm. in crown-rump length. Each of the color phases of the species, reddish (8) and black (11), are represented among our specimens. We follow Goodwin (1960) in the use of the specific name _ater_ for this bat. _=Dasypus novemcinctus mexicanus=_ Peters.--Two armadillos (85402-03) from the valley of the Río del Fuerte, 3 mi. NE San Miguel, 300 ft., are the first of the species to be reported from northern Sinaloa. They extend the known range northwestward in the state approximately 285 miles from Escuinapa (Russell, 1953:25) and signal the possible occurrence of _D. n. mexicanus_ in southern Sonora. Sign of the armadillo was abundant at the place where our two specimens were collected. Because it was felt that the species possibly had been introduced along the Río del Fuerte, a number of local residents were questioned on the point, but all insisted that armadillos were native to the area. External measurements of 85402 (female) and 85403 (male) are, respectively, as follows: total length, 725, 748; length of tail, 351, 357; length of hind foot, 87, 89; length of ear from notch, 39, 39. _=Sylvilagus audubonii goldmani=_ (Nelson).--This cottontail has been reported from Sinaloa only from Bacubirito, Culiacán (type locality), and Sinaloa (Nelson, 1909:226). Additional records are: 12 mi. N Culiacán (67561-62); 6 mi. N El Dorado (75263); 6 mi. N, 1½ mi. E El Dorado (75264-66); 7 mi. NE El Fuerte (81076-77); and 1 mi. S Pericos (61292-93). Specimens from the vicinity of El Dorado extend the known range some 30 miles southward from the type locality. A female from 1 mi. S Pericos that was taken on June 13, 1954, carried three embryos that measured 29 mm. in crown-rump length. _=Sciurus truei=_ Nelson.--Three specimens (61300-02) of this species collected by A. A. Alcorn on June 19, 1954, 32 mi. SSE Culiacán extend the known range approximately 210 miles south-southeast from Guirocoba, Sonora (Burt, 1938:38), and provide the first record from Sinaloa. Two of the specimens are females and each was pregnant, one with two embryos and the other with three.