Swamp-Rats of East Africa. 161 



Type. Adult male. B.M. no. 11. 12. 2. 4. Original 

 number 1918. Collected by Mr. Robin Kemp on February 

 loth, 1911. 



The very much darker-coloured pelage and less abruptly 

 narrowing nasals distinguish this form from elgonis and 

 tropicalis. 



In addition to the four specimens collected by Mr. Kemp 

 on the Jombeni Range, this form has also been obtained by 

 J\ir. Percival on the Larrogie Mountains (altitude 7700 feet) 

 north of the Northern Guaso Nyiro, and at Mweru (1500 

 feet), and on the Embu Road (4000 feet) . 



0, orestes dollmani, its near neighbour, is immediately 

 distinguished by tiie fact that there are only six laminse 

 in m-^, while the Jombeni race possesses the same lamina 

 formula as the tropicalis group, i. e. l^^^' 



Group 3. 



Nasals very broad anteriorly (more than 8 mm. in width), transition 



from broad to narrow region marked by a distinct angle, 



(12) Otomys ruhecidus, sp. n. 



A very large species related to tropicalis. 



Size considerably greater than in any otiier East African 

 species, head and body measuring 201 mm. in length and 

 the hind foot 34. 



General colour very much as in angoniensis, dull brown 

 lined with buff. Face and sides of head less richly tinted 

 with buff; orange rings around eyes absent. Ventral sur- 

 face of body much as in tropicalis. Tail very long, dull 

 brownish black above, dirty cream-coloured below. 



Skull very large and massive. Nasals very broad in front, 

 the transition to the narrow portion marked by a fairly 

 distinct angle, much more so than in angoniensis or nyihce. 

 Brain-case very broad ; general outline of cranium nearly 

 horizontal. Auditory bullte exceptionally prominent. Teeth 

 large ; ju^ with 7 lamin?e. 



Dimensions of the type (measured in the flesh) : — 



Head and body 201 mm. ; tail 112 j hind foot 34 ; 

 ear 25. 



Skull: greatest length 46*2; basilar length 37 ; zygomatic 

 breadth 22 ; breadth of brain-case 18'2 ; greatest width across 

 nasals 9 ; width at constriction behind anterior expansion ^'2 ; 

 depth from highest point of orbit to alveolar border at front 

 of m^ 15'3 ; palatilar length 21 ; length of palatal fora- 

 mina 9 ; length of upper molar series from front alveolar 

 border to back of m^ 11 ; crowns 9*3. 



Ann. & Mag. N. Hist. Ser. 8. Vol. xv. 11 



