_=Myotis occultus=_ Hollister.--A single specimen of this species (67491) from 1 mi. N, ½ mi. E San Miguel provides the first certain record from Sinaloa, and is indistinguishable from specimens from Alamos, Sonora, that were referred to _occultus_ by Hall and Dalquest (1950:587). Miller and Allen (1928:100) identified a skin alone from Escuinapa as _occultus_, but Hall and Dalquest (_loc. cit._) later assigned this specimen provisionally to _M. fortidens_ on geographic grounds and because it agreed in color with undoubted specimens of the latter from Guerrero. Specimens from south of San Miguel and north of the undoubted range of _fortidens_ are needed in order to ascertain whether the two kinds are distinct species or instead only subspecies of a single species. The Sinaloan bat was taken in a mist net stretched over a drainage ditch adjacent to the Río del Fuerte on the night of June 19-20, 1955, by R. H. Baker. Several other kinds of bats were obtained (shot or netted) at the same place, among which was one specimen of _Myotis velifer_. The specimens studied of _occultus_ from Sinaloa and Sonora are clearly separable from specimens of _velifer_ from the same region (Sonora and northern Sinaloa) in having paler (more reddish) pelage, shorter forearm, smaller skull, relatively broader rostrum, and four fewer teeth. _=Myotis velifer velifer=_ (J. A. Allen).--Three specimens from the following localities in northern Sinaloa provide the first records of the species from the state: El Fuerte (75234); Río del Fuerte, 1 mi. N, ½ mi. E San Miguel (67490); Río del Fuerte, 10 mi. NNW Los Mochis (61149). The subspecies _M. v. velifer_ has been reported previously from the adjacent states of Chihuahua, Durango, and Sonora. A female (61149) obtained on June 8, 1954, carried a single embryo that measured 3 mm. in crown-rump length. _=Lasiurus borealis teliotis=_ (H. Allen).--A female from 10 mi. NNW Los Mochis (61172), obtained on June 8, 1954, represents the first record of the species from Sinaloa, and is tentatively referred to this subspecies. It resembles cranially, but is paler than, Californian specimens seen of _teliotis_. _=Molossus ater nigricans=_ Miller.--This large free-tailed bat previously has been reported no farther north in western México than the type locality, Acaponeta, Nayarit. Nineteen specimens from four different localities in Sinaloa are as follows: 1 mi. SE Camino Reál, 400 ft. (85093-99); 32 mi. SSE Culiacán (61279-87); 1 mi. S Pericos (61277-78); ½ mi. E Piaxtla (61288). The specimens labeled with reference to Camino Reál and Piaxtla were obtained along the Río Piaxtla at approximately the same place. Those from 1 mi. S Pericos extend the known range of the species approximately 225 miles northwestward.