Frick : New Abyssinian Rodents, 27 



the color of the back, which becomes lighter and more pronouncedly 

 fawn with age. The very young are mouse-gray, with only a slight 

 suggestion of drab on lower flanks. The spines are also undeveloped 

 in the young, and the tails are smooth and mouse-gray above, con- 

 trasting with the roughened and fawn-colored tails of adults. 



The nineteen specimens of a blue form taken at Gardula and the 

 Abai Lakes, which agree in coloration and measurements with the 

 series of A. percivali Dollman, in the U. S. National Museum, especially 

 that part of the series from the Lololokui Hills (north of the Northern 

 Guaso Nyiro River), appear to be identical with Dr. A. Donaldson 

 Smith's alcoholic specimens from Lake Abai and eastward, ^^ and differ 

 from A. kempi Dollman: 



1. By the blue instead of strongly fawn tone of the dorsal coloration; 



2. By the coarser and less brilliant under parts, with a tendency to 

 gray at the throat; 



3. By the less distinct demarcation between the sides and upper 

 parts; 



4. By the longer spines (maximum length 15.5 mm. versus 12.5 

 mm.); 



5. By the fact that skulls with well-worn molars average slightly 

 larger than skulls of A. kempi of the same age. But both forms are 

 somewhat variable. 



EXPLANATION OF PLATES. 



Plate L 



Fig. I. Slenocephalemys alhocaudala Frick. Adult. (Type No. 11.) Lateral 

 view of skull and mandible, y. 



Fig. 2. Do. Superior view of skull. 



Fig. 3. Do. Inferior view of mandible. 



Fig. 4. Do. Inferior view of skull. 



Fig. 5. Do. Superior view of mandible. 



Fig. 6. Dasymys sp. (U. S. Nat. Mus., No. 165237.) Lateral view of skull and 



mandible, j-. 



Fig. 7. Do. Superior view of skull. 



Fig. 8. Do. Inferior view of mandible. 



Fig. 9. Do. Inferior view of skull. 



Fig. 10. Do. Superior view of mandible. 



■^ In the collection of the Academy of Natural Sciences of Philadelphia marked 

 *' spinosissimus Peters," for the privilege of examining which the author is indebted -'■' 

 to Mr. Witmer Stone, the Curator in charge. 



