I06 NELSON 



chest and inside of fore legs pale dull ferruginous, shading posteriorly 

 into dark brown, with only a slight wash of reddish along middle of 

 belly and inside of thighs ; tail at base like back ; remainder of tail all 

 around, grizzled dark reddish brown and black with fine yellowish 

 brown tips to hairs; hairs of extreme tip forming a black pencil. 

 Hairs on back black with narrow subterminal rings of rusty yel- 

 lowish. 



Variation. — Two adults, including the type and one partly grown 

 young, show but little variation except in color of underparts. The 

 immature specimen is slightly more reddish on back and tail; the 

 cheeks, chin, throat, chest and line down middle of abdomen are dark 

 dull ferruginous, and the sides of abdomen are similar to flanks. The 

 other adult is like the type except in the dull brownish buffy of the 

 underparts. 



Measurements. — Average of two adults (from dry skins) : total 

 length 251 ; tail vertebriE 109; hind foot 37. 



Cranial characters. — Premolars \. Skull (pi. I, fig. 6; pi. II, 

 fig. 2) short, broad, and much arched over top of braincase, the con- 

 vex outline descending in an almost unbroken curve to edge of occiput ; 

 rostrum short and broad, especially at base where the upper parts of 

 the premaxillaries are very broad and heavy; jugals very broad verti- 

 cally, much more so than in the other species examined in this sub- 

 genus. Measurements of type skull : basal length 29.5 ; palatal length 

 14.2; interorbital breadth 13; zygomatic breadth 22; length of upper 

 molar series 6. 



General notes. — Little is known about the interesting squirrels of 

 the subgenus Microsciurus., but, as suggested by Dr. Allen, further 

 work in Central and South America is revealing other species. Mr. 

 Cherrie collected the type in the forest on the slope of the Volcano of 

 Turrialba, near Jimenez, Costa Rica, and the species has been found 

 since in several other parts of the country. 



Specimens exatnined. — Three : from Jimenez, San Carlos, and Re- 

 ventazon, Costa Rica. 



