ALLEN: MAMMALS FROM THE BLUE NILE VALLEY. 327 



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 juotionless 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 

 crevice. 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 Gebel 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 w'ould 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 w^as 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, 

 1843, 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 



