364 University of California Publications in Zoology [Vou.17 
While most of the skulls in the Museum of Vertebrate Zoology lack- 
ing the third incisor, show badly worn teeth, yet two with unworn 
teeth show no trace of the third incisor, indicating that the absence 
of this tooth is sometimes a matter of individual variation, as well as 
of age. 
Canines strong and well developed, with distinct cingula. First 
upper premolar minute; second well-developed. First lower premolar 
about half as high as second, but with base nearly as large. Molars 
normal, 
Measurements.—Average and extreme measurements in milli- 
meters of twenty examples of N. mexicanus in the Museum of Verte- 
brate Zoology are as follows: ten males: total length, 95.4 (90.0-99.0) ; 
tail vertebrae, 34.6 (32.0-88.0) ; tibia, 12.3 (11.6-13.0); foot, 10.1 
(8.0-12.0) ; forearm, 41.4 (40.7-44.0) ; greatest length of cranium, 
17.1 (16.6-17.5); zygomatic breadth, 10.0 (9.6-10.5); mastoid 
breadth, 9.4 (9.3-9.7) ; interorbital constriction, 3.9 (3.9-4.2); ten 
females: total length, 96.2 (91.0-103.0) ; tail vertebrae, 35.5 (31.0- 
40.0); tibia, 12.2 (11.5-13.8); foot, 9.8 (8.0-11.0); forearm, 41.2 
(39.0-43.0) ; greatest leneth of cranium, 16.9 (16.7-17.4) ; zygomatic 
breath, 9.8 (9.6-10.0); mastoid breadth, 9.2 (9.1-9.5); interorbital 
constriction, 3.9 (3.7-4.2). 
Synonymy and History—Nyctinomus mexicanus was described 
under the name Molossus mexicanus by Saussure (1860, p. 283) from 
material obtained at Ameca, Jalisco, Mexico (Miller, 1912, p. 70). 
Merriam (1889), p. 25) described a bat which appears to be identical 
with N. mexricanus, from Fort Mohave, Mohave County, Arizona, 
under the name Nyctinomus mohavensis. Harrison Allen (1894. 
p. 166) deseribed the same species from California under the name 
Nyctinomus brasiliensis californicus. The California bat, however, 
appears to be distinet from brasiliensis of South America. The 
writer has examined the five bats from Belmont, California, recorded 
by Rehn (in Stone, 19046, p. 587) under the name Nyctinomus cyno- 
cephalus californicus and finds them distinet from true cynocephalus 
and in no way different from examples of mecicanus from elsewhere 
in California. 
Distribution.—N yctinomus mexicanus has been recorded from the 
voleano Popoeatepetl, Mexico, northward through the United States 
to Neweastle, Garfield County, Colorado (Warren, 1910, p. 286), and 
eastward from the Pacifie to the middle of Texas where, according to 
Bailey (1905, p. 215) ‘‘its eastern limit of range, so far as known, 
agrees closely with the eastern limits of mesquite.’’ In California 
the species is abundant throughout the Upper and Lower Sonoran 
zones, from the southern border of the state northward at least to 
Marysville Buttes, Sutter County. Throughout the central valleys 
