specimens from the nearby localities of 1 mi. S Pericos and 4 mi. N Terrero, although more grayish on the average than specimens from southern Sinaloa, are somewhat darker and distinctly larger than specimens of B. p. pallida from along the Río del Fuerte in northern Sinaloa. Specimens from southern Sinaloa average only slightly paler than typical plicata examined from southern México and Nicaragua.

Pteronotus psilotis (Dobson).—A total of six specimens from two localities in southern Sinaloa provide the first records from the state and are the northernmost records in western México. The two localities are: ½ mi. S Concepción, 250 ft. (84987-90); 1 mi. W Matatán (84985-86). The two individuals from the last-mentioned place extend the known range of the species approximately 275 miles north-northwest from a locality 7 mi. W, ½ mi. S Santiago, Colima (Anderson, 1956:349), and place the limit of the known distribution of P. psilotis farther to the north in western México than in the eastern part of the country. We follow Burt and Stirton (1961:24-25) in use of the generic name Pteronotus for this species.

The two specimens from 1 mi. W Matatán were shot at late dusk as they foraged with other bats, presumably of the same species, low over water at the place where the Río San Antonio joins the larger Río Baluarte. The four individuals from ½ mi. S Concepción were captured in mist nets stretched across the Río de las Cañas at the Sinaloa-Nayarit border, and were taken shortly after dark at heights of three feet or less above the water. Our six specimens all are males. Five are in the reddish color phase and one is in the brownish phase.

Average and extreme measurements of the six males, which average slightly smaller than specimens examined from Colima and Guerrero, are as follows: total length, 66.8 (65-69); length of tail, 16.3 (15-18); length of hind foot, 11.8 (11-12); length of ear from notch, 16.9 (16.5-17.0); length of forearm (dry), 41.5 (40.6-42.4); weight in grams, 8.3 (6.9-9.8); greatest length of skull, 15.4 (15.2-15.5); zygomatic breadth, 8.3 (8.2-8.4); interorbital constriction, 3.4 (3.3-3.6); mastoid breadth, 8.7 (8.6-8.8); length of maxillary tooth-row, 5.8 (5.8-5.9); breadth across M3, 5.4 (5.3-5.6).

Sturnira lilium parvidens Goldman.—The first specimens to be reported from Sinaloa are as follows: 32 mi. SSE Culiacán (61087); 1 mi. S El Dorado (75207); Pánuco, 22 km. NE Concordia (85648-50). The three bats from the last-mentioned locality were caught after midnight in a mist net stretched across a road adjacent to a nearly dry stream bed. The vegetation in the vicinity of the net consisted mostly of dry weeds and grass along with some low shrubs, but a tree-filled canyon was about one-fourth mile above the net. We lack details about the capture of the other two bats.

S. l. parvidens has been reported only once from farther north in western México than Sinaloa. Anderson (1960:7) recorded five specimens from along the Río Septentrión, 1½ mi. SW Tocuina, Chihuahua.

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.

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