_=Artibeus lituratus palmarum=_ Allen and Chapman.--This species has been reported once previously from Sinaloa (from 1 mi. S El Dorado by Anderson, 1960:3). Six specimens (85668-72, 85674), all males, collected on December 23 and 24, 1960, at Pánuco, 22 km. NE Concordia, provide the second known occurrence in the state. _=Artibeus toltecus=_ (Saussure).--A male (85666) from Pánuco, 22 km. NE Concordia, provides the first record of this species from Sinaloa and extends the known range northwestward approximately 182 miles from Ambas Aguas [= 6½ km. SW Amatlán de Jora], Nayarit (Andersen, 1908:300). Our specimen was taken on December 22, 1960, in a mist net placed across a road in an area where vegetation consisted mostly of weeds, grasses and shrubs. Two _Glossophaga soricina leachii_ and two _Choeronycteris mexicana_ were taken in the same net. Davis' (1958:165-166) key is useful in separating the small Mexican members of the genus _Artibeus_, but we have found some adults of _toltecus_ to be smaller than the key indicates. For example, in the 12 Mexican specimens (Oaxaca, 6, Tamaulipas, 3, Jalisco, 2, Sinaloa, 1) examined by us the total length of skull varies from 19.7 to 21.0 and the forearm from 36.3 to 42.6. Dalquest (1953) and more recently Koopman (1961) regarded _A. toltecus_ and the larger _A. aztecus_, which occurs in the same areas but at higher elevations than _toltecus_, as subspecies of the more southerly _A. cinereus_. Davis (_op. cit._), on the other hand, recognized _toltecus_, _aztecus_, and _cinereus_ as distinct species. More specimens of small and medium-sized _Artibeus_ are needed from México before this baffling complex can be studied adequately, but on the basis of specimens examined we are inclined to agree with Davis as concerns the specific distinctness of _toltecus_ and _aztecus_. In Tamaulipas (the mammalian fauna of which is currently under study by Alvarez) for example, _toltecus_ is known from Rancho Pano Ayuctle at an elevation of 300 feet in tropical deciduous forest, whereas _aztecus_ has been taken only four miles away at Rancho del Cielo, but at an elevation of 3000 feet in cloud forest. The altitudinal difference between ranges of the two kinds in Tamaulipas corresponds to that found in Sinaloa (see Koopman, _loc. cit._) and is of approximately the same magnitude found by Davis at higher elevations in Guerrero. This relationship suggests that the two kinds are neither subspecies of a single species, nor individual variants of a widespread, monotypic species, but probably are two different species. We agree that one, most likely the smaller _toltecus_, may eventually prove to be a northern subspecies of _cinereus_.