ALLEN: MAMMALS FROM THE BLUE NILE VALLEY. Pay 
or frequently coming boldly out several feet from the entrance, where 
perched on a boulder they look about or give a characteristic sharp 
bark of two syllables at short intervals for some minutes at a time. 
Apparently they are much preyed upon by leopards and no doubt by 
other smaller Carnivora or predacious birds. Their habit of throwing 
aside all caution and bounding a few paces from their holes of a sudden 
is thus rather the more remarkable. At times, however, they show 
more concern for their safety, and if alarmed, will sit motionless at the 
opening of the den for many minutes at a time. Again they may be 
seen to run a long distance from rock to rock, and then dive into a 
erevice. When convinced that no danger is near they delight to 
bask in the sun during the early forenoon, but commonly retire at 
about 9:30 or 10 o’clock in the morning. On one occasion, however, 
I saw three running rapidly among the loose boulders at 1 p.m. On 
the rocks where they are accustomed to bask and particularly at the 
- entrance to their dens, are usually to be seen large accumulations of 
their droppings. In addition to those from Gehel Fazogli, I found a 
| considerable colony on a large isolated rock peak, Gebel Okalma. 
This is in appearance an old volcanic neck, projecting steeply and 
abruptly from the plain, several days’ march from the nearest of the 
Abyssinian foothills from which it is separated by many miles of low 
country that would be utterly impassable for a Hyrax. The presence 
of these isolated colonies must therefore indicate that they have been 
long in the land, probably before the deposition of the loess that now 
covers the country. I could, nevertheless, detect no single character 
by which the Okalma specimens differed from those of Fazogli. No 
| trace of these animals was to be found on a neighboring hill (Gebel 
| Maba), which, however, was much less rocky, and afforded no suitable 
_ boulder heaps. 
ARVICANTHIS TESTICULARIS (Sundevall). 
Field Rat. 
| Isomys testicularis Sundevall, Kongl. Svenska vet.-acad. Handl., for 1842, 
1848, p. 221. 
This is the common Field Rat of the Blue Nile valley in the Sudan, 
_ and occurs generally throughout the country traversed from Sennar to 
_ Fazogli. Its favorite haunts are grassy fields, the borders of culti- 
| vated grounds, or the open scrub of bushes, weeds, and small palms. 
| It is practically a diurnal species, and was several times seen running 
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