4 SCIURUS. 
Parasciurus Treuss., Le Nat., 11, 1880, p. 292. 
Echinosciurus Treuss., Le Nat., 11, 1880, p. 292. 
Tamiasciurus Treuss., Le Nat., 11, 1880, p. 292. 
Microsciurus Allen, Bull. Am. Mus. Nat. Hist., 1895, p. 332. 
Hesperosciurus, Nelson, Proc. Wash. Acad. Scien., 1, 1899, p. 27. 
Otosciurus, Nelson, Proc. Wash. Acad. Scien., 1, 1899, p. 28. 
Areosciurus Nelson, Proc. Wash. Acad. Scien., 1, 1899, p. 29. 
Baiosciurus Nelson, Proc. Wash. Acad. Scien., 1, 1899, p. 31. 
Tail broad long, bushy, hairs mostly directed laterally; ears 
moderate, hairy, sometimes with long tufts at tip; no cheek pouches. 
Skull rather short, broad; postorbital processes directed downward 
and backward and well developed; one upper premolar, sometimes 
two; in the latter case the first is always very small; antorbital 
foramen slit-like, placed anteriorly to the zygomatic process of the 
maxillary. 
KEY TO THE SPECIES AND SUBSPECIES., 
*A. Size small, total length under 450 mm., but above 300 mm, = PAS® 
a. Premolars *—; ears medium long, thinly haired. 
a.’ Tail washed with bright ferrugineous...S.@. hojf/manni 104 
b.’ Tail washed with tawny............S.@. chiriquensts 104 
c.’ Tail washed with yellowish.............. S. richmondt 105 
b. Premolars *—~*; 
a.’ Ears small or medium, not tufted. 
a.’ Ears short, rounded, thickly haired; 
total length under 300 mm. 
a.” Tail washed: with veqqish. A5 sees ve tues S. alfart 99 
b.’” Tail washed with grayish white....... S. brownt 100 
c./” Tail washed with tawny olive....S. boquetensis 100 
b.”’” Ears medium long, pointed, thinly 
haired; total length over 300 mm. 
a.’ Back grayish brown... scas fans x ks S. negligens 102 
b.’/” Back reddish or yellowish brown.......S. deppit 101 
G,!” Back rusty Tedqien cyc ye ch eng sce eee S. d. vivax 102 
c. Premolars = or =. 
a.’ Ears large, tufted. 
a./’ Back gray, belly white, lateral line 
Dlatle cai sans Sic rie eee ae S. d. mearnsi 133 
* The construction of an intelligible key for the endless variations displayed 
by the members of the genus Scrurus is an almost insuperable task, and may 
not be attempted unless specimens of all the species are available at one time. 
This not having been possible for the author to accomplish, the present key for 
the species, with some few additions, has been taken from E. W. Nelson's 
* Revision of the Squirrels of Mexico and Central America.” 
