SCIUUIDzE— SPERMOmiLUS MEXICANUS. 869 



the sides; ring surrounding the eye and lower edge of cheeks white; head 

 above finely mixed white, black, and yellowish ; tail above varied centrally 

 with black and yellowish-white, with an indistinct black border broadly edged 

 with yellowish-white ; below, brownish-white centrally, with a distinct sub- 

 terminal band of black and a broad edging of brownish-white. The hairs 

 individually have a narrow black bar at the base, followed by alternate bars of 

 brownish-white and black, three of each, the terminal one being whitish. 



This species varies as usual more or less in respect to general color, that 

 of the dorsal surface ranging from dull ashy-brown to chestnut. The num- 

 ber of rows of white spots varies from nine to thirteen, but either nine or 

 eleven is the more common number, the two or three central ones on either 

 side of the median line being generally much more distinct than the outer 

 ones. In the latter, the white spots are longer and nearer together, forming 

 sometimes an almost uninterrupted line. The ears are very small, but dis- 

 tinct. The tail-vertebrse alone are rather more than half the length of the 

 head and body ; claws long, that of the thumb quite large. Soles nearly 

 naked. Pelage coarse and stifF, the hairs mostly grooved above. 



In size and proportions, as well as in the pattern of coloration, this 

 species more resembles S. tridecemlineatus than any other, but differs from 

 it quite markedly in many details. The tail is longer and more bushy, with 

 three narrow longitudinal lines of black beneath instead of one very broad 

 one (in addition, there is, however, in S. tridecemlineatus, a narrow basal 

 one) ; the general color above is much lighter and of a quite different shade, 

 with interrupted lines of whitish spots instead of six or more narrow, contin- 

 uous, yellowish-white stripes, with a similar number of interrupted ones be- 

 tween them ; there are also well-marked differences in the skull. In respect 

 to cranial characters, however, 8. mexicanus finds also its nearest ally in S. 

 tridecemlineatus. 



In respect to coloration, there is considerable resemblance between S. 

 mexicanus and S. spilosoma ; but, in other features, the two species differ 

 widely, as already noticed in the account of S. spilosoma. 



This species was first recognizably described and figured by Lichtenstein, 

 about 1830, from a specimen collected by Herr F. Deppe, in July, 1826, in 

 the neighborhood of Toluca, Mexico. Erxleben, in 1777, characterized a 

 " Sciurus mexicanus'", based on Fernandez's description of his " Tlamototli", 



