The presence or absence of the third molar tooth was recorded for 88 specimens (28 from Sonora, Sinaloa, and Chihuahua, and 60 from Guerrero and Jalisco). The third molar tooth is present on both sides of the lower jaw in all specimens except one (12413 Univ. Illinois) from Sonora which lacks both upper and lower third molars. The upper third molar is usually present on both sides. The exceptions are as follows: the above mentioned Sonoran specimen and one other Sonoran specimen, one specimen from La Bufa, Chihuahua, two from Jalisco, and five from Guerrero lack the tooth on both sides; two specimens from Guerrero and one from Sonora lack the tooth on only one side. Facial stripes are absent or present but inconspicuous in all specimens recorded here. The generally grayish hue, hairiness of interfemoral membrane, and configuration of skull described by Lukens and Davis (1957:7) for A. hirsutus are evident in all the specimens reported here. Skins of three adults from Sonora and Chihuahua are slightly browner and somewhat paler than skins of adults from Jalisco and Guerrero.
Reproductive data from Sonora and Chihuahua are as follows: of the five Chihuahuan specimens, two are immature (open epiphyseal sutures); the one adult female (79443) contained a single embryo 28 mm. in crown-rump length. Eight of 20 Sonoran specimens taken in May are females, each of which lacks epiphyseal sutures, and each contained one embryo. One embryo measured 8 mm. in length of uterine enlargement; all others are longer than 20 mm. from crown to rump, but vary in stage of development, some having no pigmentation in the membranes and others having pigmentation. The forearm is only 42 mm. long in one young male from Sonora. Three of 8 Sonoran specimens taken in July had open epiphyseal sutures but were of adult size. In summary of the reproductive data by states, Artibeus hirsutus is known to bear embryos in the following months: May in Sonora, July in Chihuahua, February in Jalisco, and May in Guerrero. These data, along with the presence of embryos and young of various ages among specimens taken at the same place and time, indicate that the species does not have a restricted breeding season.
A geographic overlap of the ranges of A. hirsutus and A. jamaicensis from Guerrero to central Sinaloa is now known. But the two species have not been taken at the same place within this region of overlap.
Other species.—At the locality on the Río Septentrión, 1500 feet, 1-1/2 mi. SW Tocuina, Chihuahua, from which specimens of A. hirsutus were obtained as mentioned previously, several other species of tropical bats were captured, including Desmodus rotundus murinus Wagner, Glossophaga soricina leachii (Gray), Chilonycteris parnellii mexicana Miller, Sturnira lilium parvidens Goldman, and Chiroderma (specimens not yet certainly identified to species). The canyon of the Río Septentrión is steep and rocky, the tropical vegetation occurs only in the bottom of the canyon, and unless construction of a railroad had been in progress the area could have been reached only after several days by means of a pack train. From a distributional standpoint the occurrence of Sturnira and Chiroderma 1-1/2 mi. SW of Tocuina is of unusual interest.
The published record of Sturnira lilium nearest to Tocuina is from 2 mi. N Ciudad Guzmán (19°43', 103°28'), Jalisco, and the nearest published record of the genus Chiroderma is of Chiroderma isthmicum from Presidio (18°37', 96°47'), Veracruz (Hall and Kelson, 1959:126, 134). The Chihuahuan specimens extend the known range of Sturnira lilium approximately 585 miles northwestward and that of the genus Chiroderma approximately 920 miles northwestward from the localities noted above. Five specimens (79434-79438) of Sturnira lilium, two adults and three immature individuals, were taken from July 18 to July 22, 1958, by the author and Kenneth E. Shain, as also were the two (79439-79440) Chiroderma.
To the list given by Koopman and Martin (1959:9) of neotropical genera known to range farther north on the west coast of North America than on the east coast there can now be added Artibeus, Sturnira and Chiroderma (as noted above), Anoura, Choeronycteris and Leptonycteris (Hall and Kelson, 1959:119, 120, 122; Hoffmeister, 1959:18), and Liomys (Hall and Kelson, 1959:536).
In view of these additional genera, and others that almost certainly remain to be discovered farther north on the west coast, the suggestion by Koopman and Martin (1959:11) that species inhabiting humid tropical habitats, in general extend farther north on the east coast of Mexico than on the west coast may need to be reconsidered. On the west coast, areas of more humid tropical vegetation and climate are more distant from the coastline as one proceeds northwestward from Nayarit to Sonora. The broad band of humid tropical vegetation along the coast is progressively reduced in width, and crowded back against the mountains, and still farther north consists of only small scattered remnants that are difficult to visit, in the bottoms of deep canyons.
LITERATURE CITED
Cockrum, E. L.
1955. Reproduction in North American Bats. Trans. Kansas Acad. Sci., 58:487-511.