1906.] Allen, Mammals from Western Mexico. 245 



18; Garabatos, Tepic, 2 specimens, March 20; (all of these localities 

 are within a few miles of the boundary line between Tepic and Ja- 

 lisco;) Tuxpan, i specimen, June 24; Las Canoas (near Zapotlan), 16 

 specimens, Aug. 10-23 and Oct. i. 



The series consists largely of adults but includes 4 specimens 

 (Ojo de Agua, Feb. 15) about one-quarter grown, and 4 (Las Canoas, 

 Oct. i) nurslings. The latter, all from apparently the same litter, 

 are thinly haired, clear gray above, darker on the head, nape, shoulders, 

 and anterior half of the back, and faintly suffused with brownish 

 over the lower back and rump, and everywhere minutely necked 

 with black. 



The collector's measurements of 9 adult males from the Tepic- 

 Jalisco boundary are as follows: Total length, 545 (505-573) ; "head 

 and body, 308 (305-323, with one at 270) ; tail vertebrae, 235 (210-254), 

 hind foot without claws, 61 (57-69); ear from notch, 24 (23-25). 

 Four females: Total length, 493 (463-534); head and body, 272 

 (250-305); tail vertebrae, 222 (213-229); hind foot, 55; ear, 24. 



The Las Canoas specimens are younger and smaller, but are other- 

 wise similar. Specimens from Zapotlan, collected many years ago 

 by Dr. Buller, are among the largest of the series, an old male skull 

 measuring 68 mm. in total length by 42 in zygomatic breadth. 



Very few of the Tepic and Jalisco specimens show any tendency 

 to -a blackish area on the head, as do specimens from the Valley of 

 Mexico (the assumed type locality of variegatus) and Puebla. In 

 northern Durango and thence northeastward into Coahuila, speci- 

 mens (C. v. rupestris) without a conspicuous black cap are exceptional; 

 further to the eastward and northward this form passes into the 

 melanistic C. v. conchi. The form in western Mexico, ranging from 

 Tepic and Jalisco into Michoacan, is almost uniformly gray-headed 

 and very large. Unfortunately the form to which the name varie- 

 gatus has now become restricted, is an intermediate phase between 

 the small, light-colored, black-headed form of north-central Mexico 

 and the large, dark-colored, gray -headed form of the south. As, how- 

 ever, the Tepic-Jalisco gray-headed form is very constant in its 

 characters over a wide range, it seems as fairly entitled to a distinctive 

 name as many other geographical forms now currently recognized. 



9. Citellus (Xerospermophilus) mexicanus mexicanus (Erxlebcn). 

 Twenty-eight specimens, nearly all adult: Zapotlan, i specimen, 

 July 25; Las Canoas, 27 specimens, Aug. 5-25. 



Two phases of coloration are represented: most of the specimens 



