SQUIRRELS OF IMEXICO AND CENTRAL AMERICA 43 



jacent parts of extreme southeastern Oaxaca, Tabasco, eastern Chia- 

 pas, and perhaps extreme northwestern Guatemala (below 4000 feet). 



Characters. — This form is much darker than true 6". aureogaster\ 

 the intense, almost chestnut rufous of underparts usually extends as a 

 broad band over the costal area and top of shoulders; the pelage is 

 thinner, with much stiffer and more shining dorsal hairs, and the tail 

 slenderer with black predominating. Teats: p. \ a. \ i. \. 



Color. — Top of nose and fore part of crown d#rk iron gray; lum- 

 bar region, rump, outside of thighs and base of tail finely grizzled 

 with black, grayish white, and dull rusty or yellowish brown ; nape 

 patch indistinct, dull yellowish brown or dingy rufous, often grizzled 

 with black and gray ; ears like nape, grizzled gray or reddish brown, 

 sometimes bordered with black ; a thin basal patch of dingy grayish 

 white in winter; ring around eyes reddish or dark buffy brown, 

 confluent with area of same color extending back on sides of head 

 below ears; sides of nose, chin, and most of cheeks dingy gray; rest 

 of underparts deep, almost chestnut ferruginous, the same color 

 usually covering all of fore legs and extendmg up as a broad band 

 over costal area and shoulders ; fore and hind feet black, sometimes 

 minutely grizzled with gray ; tail above, black thinly washed with 

 white ; below, usually with a narrow median line of rich ferruginous, 

 heavily bordered with black and thinly edged with white, the median 

 rufous line frequently absent and replaced by black. Hairs on 

 back (except rufous area) black, with fine tips of white or some- 

 times narrow subterminal rings of yellowish brown. 



Variation. — Black squirrels of this form are very common at 

 Minatitlan and in Tabasco. A curious specimen from Minatitlan is 

 uniformly black except on sides of nose, cheeks and chin which are 

 dark gray; flanks and hips thinly grizzled with yellowish gray; upper 

 surface of tail thinly grizzled with gray ; underparts, including inside 

 of legs, dark reddish brown. The nuchal patch is sometimes 

 confluent with the rufous area on shoulders, though usually lighter. 

 An immature specimen from the vicinity of Santo Domingo, Oaxaca, 

 is dingy reddish brown above, grizzled with black and gray. The 

 area covered by rufous on sides and across shoulders varies, and 

 the color also varies in intensity. The forelegs are sometimes grizzled 

 iron gray with or without mixture of reddish. 



Measurements. — Average of 5 adults from Minatitlan : total 

 length, 522.8; tail vertebras, 266.8; hind foot, 67.3. 



Cranial characters. — Premolars f . Skull similar to that of typi- 

 cal aureogaster but larger and proportionately narrower, with audital 



