SQUIRRELS OF MEXICO AND CENTRAL AMERICA 6l 



Characters. — Crown, nape, and middle of back pale rusty yellow- 

 ish ; flanks, legs, and feet whitish. Tail long, bushy; ears thinly 

 haired ; pelage rather full and soft ; under fur long. Teats : p. \ a. | 



Color. — Winter pelage : Top of nose gray, shading on fore crown 

 into grizzled yellowish gray, rest of crown, nape, middle of shoulders 

 and rump pale rust}- yellow slightly grizzled with black ; sides of neck, 

 shoulders, costal area, lower flanks, legs and feet grayish white, palest 

 on feet; sides of nose and ring around eye dingy gray; cheeks pale 

 yellowish brown ; ears dull rusty yellow with small basal patch of 

 same; underparts white; tail above brownish yellow, lightly grizzled 

 with black and heavily washed with white ; below, a broad median 

 area brownish yellow (thinly grizzled with black and lightly washed 

 with white) narrowly bordered with black and edged with white. 

 Hairs on back black with sub-basal and subterminal rings of rusty. 



Variation. — Specimens of this squirrel from extreme southern 

 Sinaloa are a little darker than the type. 



Meas?crements of type. — Total length 524; tail vertebrae 255; hind 

 foot 62. 



Cranial characters. — Premolars \. Skull larger and more mas- 

 sive than in true collicei\ rostrum decidedly heavier than in collicei ox 

 truei^ and heavier even than in aureogaster\ nasals bi"oader and 

 more expanded anteriorly. The skull of the type measures : basal 

 length 53 ; palatal length 26.3 ; interorbital breadth 20 ; zygomatic 

 breadth 34; length of upper molar series 11. 



General notes. — This fine species belongs to the group of which 

 S. collicBi^ S. c. nuchalis., and 6". truei are the other members. It is 

 the most divergent of all and its rusty yellow back and hoary white 

 sides and tail render it easily recognizable. Specimens from near 

 Rosario, in extreme southern Sinaloa, are darker than those from 

 Mazatlan, and it is possible, notwithstanding its wide difference, that 

 sifialoensis may eventually prove to be a subspecies of collicei. 



Specimens exainined. — Four : from Mazatlan, Tatamales, and 

 Plomosas, Sinaloa. 



SCIURUS TRUEI sp. nov. Sonora Squirrel. 



Type from Camoa, Rio Mayo, Sonora, Mexico. No. 96229 $ ad. 

 U. S. Nat. Museum, Biological Survey Collection. Collected Jan- 

 uary 20, 1S99, by E. A. Goldman. 



Distribution. — Scrubby forests of Arid Lower Sonoran zone in 

 southwestern Sonora and northern Sinaloa, Mexico. 



