EAST AFRICAN MAMMALS IN NATIONAL. MUSEUM. 41 



of conspicuous concavity, or a sharply marked reentrant curve on the 

 outer lateral margin is purely individual and is not even an average 

 character of value in differentiating forms. 



Skins of females average darker than those of males in all species 

 of mole-rats represented in the United States National Museum col- 

 lection except Tachyoryctes spalacinus. 



In the table of measurements of specimens of this genus, dimen- 

 sions of old adult examples only are given, the oldest animals in each 

 series having been'selected for this purpose. The majority of speci- 

 mens in collections are rather j^oung. 



TACHYORYCTES RIIDDI Thomas. 



1909. Tachyoryctes rurWi Thomas, Ann. and Mag. Nat. Hist., ser. 8, vol. 4, p. 546. 



December. (Kiriii, Mt. Elgon, British East Africa; type in British 

 Museum.) 



Specimens. — Thirty-seven, as follows: 



British East Africa : Kaimosi, 2 in alcohol (Heller) ; Kakumega^ 

 32 (Heller) ; Lukosa River, 3 (Heller). 



This is the darkest species of Tachyoi^yctes in the collection. All of 

 the young examples are intense black and a large proportion of the 

 fully adult specimens are very dark blackish-brown or nearly black. 

 As with other forms the females average darker than the males. 

 Two nursing young were collected at Kakumega, February 16. Two 

 adult females from the same place, February 15 and 16, each con- 

 tained one embryo. 



TACHYORYCTES REX HeUer. 



Plate 15. 



1910. Tachyoryctes rex Heller, Smithsonian Misc. Coll., vol. 56, No. 9, p. 4. July 



22. (Western slope of Mount Kenia, 10,000 feet: type in U. S. Nat. Mus.) 

 1910. Tachyoryctes rex Roosevelt, African Game Trails, Amer. ed., pp. 473, 

 485; London ed., pp. 485, 496. 



Specimens. — Forty-nine, as follows: 



British East Africa: Mount Kenia, west side, 49, including 2 in 

 alcohol (Loring, Mearns) . 



These specimens were all collected at an altitude of from 9,000 

 to 10,700 feet. Mr. Heller says: 



This is an extremely abundant species on Mount Kenia, whefe it inhabits a narrow 

 zone at the upper edge of the bamboo forest where the moorland country first makes 

 its appearance. The species is not found immediately below this area in the bamboo 

 or yew forests, but another species appears on the grassy plains at the base of the 

 mountain.' 



Mr. Loring, who collected most of the specimens, has the following 

 note on TacJiyoryctes in Colonel Roosevelt's African Game Trails:^ 



Mole-rat mounds Avere common about the West Kenia Forest Station, but none were 

 seen between 7,500 and 8,500 feet, and from this altitude they ranged to 11,000 feet. 



1 Smithsonian Misc. Coll., vol. 56, No. 9, p. 4. July 22, 1910. 



2 AppendLxC, pp. 485, 486. 1910. 



