96 SCIURUS. 
b. Back dark eray, top of ‘head 
iron eTtay or blackish: saa. < S.a.hypopyrrhus 
b.* Ribs and shoulders not rufous. 
a.” Back dingy whitish; nape patch 
PUSTYR a cetha 3 ne ced bee ee oe S. soctalts 
b.2 Back bluish gray in middle, re- 
mainder sooty brownish......... S. 1. hirtus 
b.’’’ Feet. white. 
a.‘ Back whitish, rump and nape 
patches Very Drie hiten: ola) eee S. 5) Goeas 
b.* Back gray. 
a. Nape patch strongly marked, 
darke rCtOus! aan teak ety ieee S. p. effugius 
b.’? Nape patch not strongly marked, 
Pusty. yellommSh ayy seu eese ae .... S. polropus 
b.’ Nape and rump patches absent or not 
well defined. 
a.” Nape and 1ump patches not well defined. 
a.’”’ Back dark gray, sparingly or not at 
all mixed with yellowish hairs. 
a. Back and under side of tail dark 
ILOM Pray 4 tee hr rane sea eevee S. p. cervicalis 
b.* Back and under side of tail paler 
gray. leet swhiter ie. pels tenes oe S. p. nemoralis 
b.’’” Back pale gray mixed with yellowish 
hairs; feet white. 
a’ Belly white: taser es aeeee S. p. hernandez’ 
b> Bellyarutotiss 2 Ape) os eit ae eee S. poliopus 
b.’’ Nape and rump patches absent. 
a.’’’ Back with broad median band of 
blackish; rest of body whitish.....: S. a. dorsalis 
b.’”” Back without broad median band 
of blackish. 
a.* Belly pale gray; back coarsely griz- 
zled gray or yellowish grav...... S. yucatanensis 
b.* Belly dark iron gray; back blackish 
gray suffused with§buff..........-. S. y. baliolus 
ce.’ Belly bright ferrugineous; back yel- 
low ferrugineous or blackish brown. .S. v. morulus 
d.* Belly blackish or white. 
e.’ Belly blackish. 
a.” Back sooty blackish grizzled 
with yellowish oray.:.. <2: says S.nelsona 
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