1900.] MAMMALS PROM MOUNT KENYA. 179 



The mammals obtained by Mr. Mackinder's party at Nairobi are 

 as follows : — 



1. Ceecopithecus albigulakis Sykes. 

 a, b. $ . Nairobi Forest, 14/7/99. 



2. Funisciubus jacksoni de Wint. 



a-e. 2 ■ Nairobi Forest, 5600 ft., 14-20/7/99. 



3. MPS HILDEBEANBTI Petei'S. 



a. 2 ■ Nairobi, 6000 ft., 12/7/99. 



This Mouse is determined on the authority of Mr. de Winton, 

 by whom the above name has been placed on Mr. Jackson';-; 

 examples of it from Ravine Statiou. 



4. Abvicanthis abyssinicus Eiipp. 

 a. <$ . Nairobi, 16 July, 1899. 



This specimen appears to be conspecific with Uganda specimens 

 of Arvicanthis determined by Mr. de Winton as A. abyssinicus. 



5. Tachyoeyctes splendens ibeanus, subsp. n. 

 a. 6 . Nairobi Forest, 20 July, 1899. 



Similar in all essential respects to the typical Abyssinian form, 

 but rather larger, and on the average rather darker in colour, 

 especially on the head. 



For some years I have known that my reference of the East 

 African Tacliyoryctes to T. splendens was very doubtful, and have 

 now taken the opportunity to investigate the question with such 

 further material as has come in up to the present time. 



On laying out the Museum series of skulls, 9 from East Africa 

 and 5 from Abyssinia (including one of RiippelPs co-types),, it is 

 at once evident that the former is a larger and more powerful 

 animal, but is in other respects very closely allied. Even as to its 

 greater size, although there is no doubt of the fact, there is some 

 difficulty in reducing it to measurement owing to the way these 

 animals go on increasing in size until a late period of life, so that 

 old specimens of the small form may overtop in most measurements 

 the nearly adult specimen of the larger. But taking only old 

 specimens, two of each form, with sagittal crests completely 

 developed, the following comparative measurements may be 

 given :— 



Basilar length. Greatest breadth. Diastema. 



T. s. typims ... . 37'5, 37-2 28, 30-5 16-7, 16-2 



T. s. ibeanus 43, 41-5 34, 325 18-3, 19 



In all adult skulls also a diagonal measurement across the 

 brain-case from the squamosal edge above the meatus of one side 

 to the most bulging antero-lateral corner of the brain-case on the 

 other will illustrate the difference between the two forms, this 



