68 NELSON 



by a narrow black line, and thinly edged with white. Some hairs on 

 back entirely black, others black with white tip and either a sub- 

 basal ring or basal and median rings of brownish yellow. 



Variation. — The gray wash on the back varies greatly, sometimes 

 being entirely absent, especially in specimens from the humid forests 

 fronting the Pacific Ocean ; in others it is general over the dorsal sur- 

 face, and in others still is confined to a band across the back, leaving 

 poorly marked rusty or yellowish brown nuchal and rump patches of 

 varying size. In one specimen the nape patch is chestnut brown, the 

 middle of back washed with light gray and the rump yellowish brown. 

 In winter, the white wash on the back is most conspicuous, and the 

 underparts are duller and less strongly ferruginous. (They may be dark 

 ferruginous, or dark grizzled grayish washed with fulvous, or pale fer- 

 ruginous). The absence of white tips produces the yellowish brown 

 nape and rump areas, or wholly yellowish brown backs of specimens 

 from the humid forest fronting the Pacific. Such specimens have 

 many hairs with subterminal rings of rusty yellow. 



Measurements . — Average of two adults from central Guatemala, 

 from dried skins: total length 547.5 ; tail vertebrae 270; hind foot 6^. 



Cranial characters. — Premolars \. Skull a little longer than that 

 of S. aureogaster but otherwise very similar. Four adult skulls from 

 southwestern Guatemala average: basal length 51.8 ; palatal length 

 27.2 finterorbital breadth 19; zygomatic breadth 34.4; length of 

 upper molar series 1 1 .4. 



General notes. — A specimen from central Guatemala (No. 61226 

 U. S. Nat. Museum) sent to London for comparison with Gray's 

 type, was pronounced by Mr. Thomas to closely resemble the two 

 cotypes on the dorsal surface but is richer rufous below with less white 

 on the tail. These differences fall within the minor individual varia- 

 tions. 



Gray gave ' Guatemala' as the type locality for this species, and 

 specimens from near Duenas are typical. Specimens from the dense 

 humid forests near Guatemala City and thence along the slopes of the 

 mountains fronting the Pacific to Pinabete, Chiapas, are darker or 

 browner than those from the higher mountains of the interior. Those 

 from Calel are a little paler than typical specimens, and those from 

 the forest at the Hacienda Chancol are still grayer or nearer the form 

 from the mountains of central Chiapas. 



Habits. — We found these squirrels rather common in the dense oak 

 forests at about 7000 feet above sea level on the volcano of Santa 

 Maria, near Qyiezaltenango, but owing to the tangled undergrowth and 



