98 SCIURUS. 
a.” Top of head paler than back. 
a.’ All of back blackish brown; PAGE 
feet, legs, lower flanks, and 
belly dull chestnut rufous..... S.adolpheit 126 
b.' Middle of back blackish or 
dark yellowish brown or gray- 
ish yellow; rest of bodyrufous.S.a.dorsalis 127 
b.° Top of head not paler than back. 
a.’ Back heavily washed with black. 
a.’ Belly rusty ruieuse se ae S.b. beltt 128 
b.* Belly rich dark ferrugineous.S. thomasi 126 
b.’ Back not washed with black. 
a.” Back pale gray or sooty 
blackish. 
a.” Back pale gray. 
a.’° Feet dark gray or 
blackish; rufous of 
belly sometimes ex- 
tending up on ribs. ..S. aureigaster 115 
b.” Feet pale gray; rufous 
of belly not extending 
(0 Bp ig la ea gh S.g.chiapensis 125 
b.” Back sooty blackish with 
thin wash of yellowish 
gray. 
a. Back unitormys.) 0055. § S.nelsont 120 
b.” Back with area of 
bluish gray across the 
MULES arene apa a venient S.n,. hirtus 121 
b.* Back not pale gray or sooty 
blackish. 
a.” Back yellowish brown, 
sometimes thinly washed 
TEE STAY: © Lutncih ahaa . grisetflavus 124 
b.” Back blackish, grizzled 
with gray or yellowish; 
under parts and costal 
area rufous.......S.a.hypopyrrhus 116 
S) 
A. Microsciurus, Allen. 
‘‘Size small; ear short, rounded; tail shorter than body, slender, 
rounded. Premolars, =. Skull short, broad, and deep at base; 
nasals narrow and shorter than interorbital breadth, upper end of 
