502 ZOOLOGICAL EESULTS OF THE RUWENZOEI EXPEDITION. 



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



Head and body 150 mm. ; tail 93 ; hind foot 26'5 ; ear 25. 



Skull: greatest length 37'5 ; basilar length 30'3 ; zygomatic breadth 19'5; nasals 

 16'5x6"7; interorbital breadth 4'2 ; palatilar length 17; palatal foramina 7; length 

 of upper molar series (grinding-surface) 7'3. 



Type. Male. B.M. no. 6.7.1.54. Original number 653. Collected 18th February, 

 1906, by Mr. E. B. Woosnam. 



This animal is related to the corresponding mountain-form from Mt. Elgon, Otomys 

 jacJcsoni, from 13,200 ft., but differs by its larger size, more uniform coloration, and 

 the possession of only six laminae on the last upper molar. 



[It is impossible to say which of the two Swamp-Rats, 0. dartmouthi or Basymys 

 montanus, is the most numerous, as they frequent the same ground and have exactly 

 similar habits (see under the latter species, p. 514). — R. B. W.] 



52. Otomys denti Thos. 

 ? . 14, 56, 645. 6 in spirits. Mubuku Valley, E. Ruwenzori. 6000-10,000 ft. 



Incisive grooves as in 0. irroratiis, but m^ with five laminee only. Colour very 

 dark. 



Size rather smaller than in 0. irroratus. Fur long and fine ; ordinary hairs of 

 back about 20 mm. in length. General colour dark blackish-brown (darker than 

 "bistre") with a coppery tinge, the rump almost black, the light rings on the hairs 

 dark tawny. Under surface and inner aspect of limbs slaty black, a few only of the 

 belly-hairs tipped with dull buffy. Upper surface of hands and feet uniformly 

 brownish-black. Tail black throughout, above and below. 



Skull smaller than that of 0. irroratus, more flattened above, its proflle not so convex 

 above the orbits, the height from tooth-row to supraorbital ridge markedly less. 



Incisive grooves as in 0. irroratus. Molar laminae ^ _2_2 - 



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



Head and body 157 mm. ; tail 89 ; hind foot 27 ; ear 21. 



Skull: greatest length 36-6; basilar length 30'3 ; zygomatic breadth 18-6; nasals 

 14-7 X6"8; interorbital breadth 4*5; height from alveolus of m^ to supraorbital 

 ridge 10*8 ; palatilar length 17 ; palatal foramina 7 '2 ; upper molar series (grinding- 

 surface) 7. 



Type. Female. B.M. no. 6.7.1.69. Original number 56. Collected 27th January, 

 1906, by Mr. E. E. Dent. 



This striking Swamp-Eat is readily distinguishable by its dark coppery colour, flat 

 skull, and the presence of only five laminae on the last upper molar. 



[Rather an uncommon species, obtained at 6000 and 10,000 ft. They inhabit the 

 swampy ground and banks of streams. — R. B. W.] 



