1915.].. . . Allen, Review of the South American: Sciuride.- 303: 
The third or saltuensis group of Mesosciurus was formerly known only 
from the small physiographically isolated area of the Santa Marta district 
of northeastern Colombia, where it ranges from sea level to about 9000 
feet, with a lowland and a highland subspecies. The American Museum 
expeditions have now shown that a form of this group occurs on the lower 
Rio Cesar, the principal river draining the Sierra de Santa Marta region. 
Another widely isolated species occurs in central Peru, which so closely 
resembles the Santa Marta forms that, if their ranges were contiguous, 
it might perhaps be regarded as merely a subspecies of the Santa Marta 
group.. The members of the saltwensis group agree in size with the forms 
of the gerrardt group, but differ widely from them in color and in the charac- 
ter of the pelage, which is long, soft, and full in the saltuensis group and thin, 
short, and hispid in the gerrardi group, in accordance with the contrasted 
environment of the two groups — temperate and humid tropical, respec- 
tively. The contrast in color in the two groups is striking, the ventral 
surface being deep red in all the forms of the gerrardi group and white in 
the saltuensis group, except that in the Peruvian form (Sciurus pyrrhinus 
Thomas) it may be either white or red or mixed white and red. The 
coloration of the upperparts in the two groups is equally distinctive, yet | 
they are so closely related in all essential characters that the two groups 
must have had a common origin or have been derived the one from the 
other, with probably the saltuensis group as the older of the two. Both 
groups belong to the subgenus Histriosciurus. 
The genus Leptosciurus is a small group of squirrels but little exceeding 
in size the larger forms of the genus Microsciurus, two of the three known 
species greatly resembling the Microsciuri in external features, but differ- 
ing from them and from the Mesosciuri in the shape of the skull and in 
tooth structure. The range of Leptosciurus is discontinuous, occupying 
two, and perhaps three, separate areas; one in Colombia and one in the 
Andes of southern Peru and Bolivia. The northern area comprises nearly 
all of the Colombian Andes, where it is represented by four known forms, 
three of them closely related, the other possibly specifically separable. 
The genus is not known from Ecuador, and has not been met with in north- 
ern Peru, its known range in the south being an area in the high Andes of 
southern Peru and the adjoining Andean portion of Bolivia, trending 
northwest-southeast, about 500 miles long and approximately half as wide. 
Here it is represented by a single species, oes distinctly related to the 
forms of the Colombian Andes. 
Another area in eastern Bolivia is occupied by a species here referred to 
Leptosciurus (the Macroxus leucogaster Gray), found at much lower alti- 
tudes in the Santa Cruz de la Sierra region, from which only it is thus 
