1906.] Allen, Mammals from Western Mexico. 229 



Add to the length of the hind foot, as given above, about 8-10 mm. 

 for the length of the claws. The fore claws average about 22-24 

 mm. in length. 



"Frequently found in bands. Sleep and breed in hollow trees. 

 Tail carried vertically, with no curve at the end. Fight savagely 

 with claws and teeth." J. H. B. A number of the very old males 

 are entered in the collector's catalogue as ' Solitaries, ' implying that 

 here as elsewhere 1 the old' males separate themselves from the bands 

 and live alone. 



Individual Variation. The skulls present an unusually small range 

 of individual variation, although they vary greatly with age and sex 

 in a number of important characters. The amount of individual 

 variation in coloration, however, is rarely equalled in any wild species 

 of mammal known to me. 



A series of 32 specimens collected at or in the immediate vicinity 

 of Escuinapa in February, and another large series obtained at the 

 same place in April, may be taken in illustration. The gradations 

 between the extreme types of variation are so complete that it is 

 difficult to classify many of the specimens as belonging to any partic- 

 ular phase. Beginning with the darkest, which may be designated 

 as the black phase, the whole animal is black or deep brownish black, 

 except the ventral surface from the chin posteriorly to the breast, 

 which is, as usual, white or yellowish white. In some specimens, 

 however, there is also a broad blackish band across the upper part 

 of the throat, but this frequently occurs in the lighter phases. The 

 basal half of the pelage, including the underfur, is light grayish 

 brown, lightest at the extreme base. 



The opposite extreme, which may be designated as the light phase, 

 has the general color of the upper parts pale yellowish brown, or pale 

 reddish brown (in different specimens), with the basal portion of 

 the pelage much lighter than in the black phase, and the light portion 

 more extended apically, so that either only the tips of the hairs are 

 light brown, or there is a narrow subapical zone of a darker tint with 

 the tips of the hairs light gray or pale yellowish gray. In this phase 

 only the feet are blackish, which even in the lightest specimens are 

 usually quite black. 



The most marked feature in the intermediate phases is the color 

 of the top of the head, nape, and shoulders, which vary from blackish, 

 with the tips of the hairs yellowish or golden, to deep ochraceous. 



i See Allen, Bull. U. S. Geol. and Ge9gr. Surv. Territories (Hayden), Vol. V, No. 2, Sept. 6 

 1879, PP- 158-160, where the previous literature of the subject is summarized. 



