90 



NELSON 



Distribution. — Pine and oak forests of Transition and Boreal zones 

 on tableland slope of the Sierra Madre in the vState of Mexico, from 

 the Volcano of Toluca north to border of Michoacan ; also arid moun- 

 tains of southern and western Queretaro, central and eastern Guana- 

 juato, and southern San Luis Potosi, Mexico (alt. 7500— 12,060 feet) . 



Characters. — Paler than S. oculattis, with a wash of blackish, or 

 blackish brown along middle of back ; underparts dingy whitish, with 

 only a faint suffusion of buffy. Pelage and teats as in S. oculatus. 



Color, — Top of head and broad median line down back to base of 

 tail, gray with a faint blackish or dull brownish wash shading laterally 

 into clearer grizzled gray ; latter color, however, with slight shading of 

 yellowish on subterminal rings of some hairs ; ring around eye grayish 

 white with pale buffy shade ; rest of sides of head dingy gray suffused 

 with dull buffy or pale brownish ; ears dull gray shaded with buffy ; 

 patch behind ear dingy whitish ; feet grayish white with buffy wash, 

 usually deeper than on underparts ; outside of fore legs and thighs like 

 flanks ; thighs near feet suffused with yellowish brown ; tail above 

 black, heavily washed with white ; below, along median line grizzled 

 yellowish gray or pale yellowish brown, bordered with black and 

 broadly edged with white. Hairs of back black with one or two i-ings 

 of gray, yellowish or brownish gray, mixed with other hairs wholly 

 black. 



Variation. — A single melanistic specimen from the type locality is 

 the only one seen. The four normal specimens show little variation, 

 and this mainly in the amount of buffy on the feet and in the intensity 

 of the dark wash along middle of back. 



Measurements. — Average of four adults from type locality : total 

 length 531 ; tail vertebrae 263 ; hind foot 68. 7. 



Cranial characters. — Premolars \. Skull much like that of S. 

 oczdatus., but in nearly all of the specimens examined the nasals are 

 much narrower posteriorly with a corresponding increase in breadth of 

 the premaxillaries. Two adult skulls from type locality average as 

 follows : basilar length 54 ; palatal length 29 ; interorbital breadth 30.5 ; 

 zygomatic breadth 36.7; length of upper molar series 11. 



Ge7teral notes. — This form resembles specimens of S. oculatus 

 from Pinal de Amoles very closely in the color of the back, but may 

 be distinguished at once by the whitish ear patches and whitish ven- 

 tral surface. It was named for the Volcano of Toluca, the type 

 locality. » 



Specimens exa?ni?ied. — Seven: from Volcano of Toluca, Mexico; 

 Tequisquiapan, Qiieretaro ; mountains north of Guanajuato city, 

 Guanajuato, Mexico. 



