28 



NOETH AMERICAN- FAUKA* 



[No. 36. 



winter pelage, but colors less strongly contrasted and black variations 

 of upperparts much reduced. Worn spring and summer pelage: Gen- 

 eral tone browner and colors less contrasted than in the winter 

 pelage, the buff on sides less pronounced and often lacking. 



SlcuU. — ^Larger than that of montanuSj with broader, flatter brain- 

 case. Compared with, fulvescens and tenuis: Slightly smaller, with 

 longer palatal foramina and narrower interpterygoid fossa. 



Measurements. — Average of 6 adults from type region (Casas 

 Grandes, Chihuahua; Mexican boundary, 50 to 100 miles west of 

 El Paso; and Organ Mountains, N". Mex.): Total length, 140 (128- 

 145); tail vertebrae, 71 (65-77); hind foot, 17.6 (17-18.5); ear from 

 notch, 12.5 (12-13.2). Average of 12 adults from Lone Pine, Cal.: 

 139; 70; 17.5; of 10 adults from Oasis Valley, Nev. (measured to 

 end of tail hairs) : 139; 72; 18.4. Skull: (See table, p. 81). 



Remarlcs. — This subspecies has the widest range of any of the forms 

 of megalotis and is subject to considerable individual variation, both 

 in color and in size of skull. It intergrades with aztecus in central 

 New Mexico, with longicaudus in California, with nigrescens in south- 

 ern Idaho, and with cinereus in central Mexico. The present writer 

 is in accord with Dr. J. A. Allen, who revised the group in 1895, in 

 his failure to find any constant color differences between the series 

 from the deserts of Nevada and California and that from the type 

 region (southern New Mexico and northern Chihuahua), individuals 

 in comparable pelage from the two regions being practically indis- 

 tinguishable. Specimens from the Death Valley region of southern 

 Cahfornia and Nevada have slightly larger skulls than those of the 

 typical form from Chihuahua and southern New Mexico but smaller 

 than those of aztecus. These have been separated as a subspecies, 

 ^'deserti by Dr. Allen on the basis of an alleged difference in the rel- 

 ative length of body and tail. A careful comparison of measurements 

 of adult specimens from the two regions, however, fails to show any 

 appreciable differences in proportion. The apparent differences 

 shown in Dr. Allen's published measurements probably are due in 

 part to differences in methods of measurement and in part to the inclu- 

 sion of a greater number of immature examples in the series from 

 New Mexico and Utah. The cranial differences are considered too 

 slight and inconstant to warrant recognition of the form by name. 



A large series from the Colorado River, Sonora, at Monument No. 

 204, Mexican boundary, are practically typical megalotis. Two in- 

 dividuals from Volcano Lake, head of Hardy River, Lower California, 

 are very small, but no smaller than an individual in the series from 

 Casas Grandes, Chihuahua, quite close to the type locality. 



A large series from various places in northwestern Nevada and a 

 small series from Salt Lake Valley, Utah, are fairly typical megalotis, 

 having sHghtly smaller skulls than the Death Valley series and thus 

 showing no approach to aztecus. 



