114 .On new South- American Mammals. 



Teeth about as in M. cerastes, tlie canines longer and 

 heavier. 



Dimensions of the type (measured in skin) : — 



Forearm 49 mm.; third finger, metacarpus 49, first 

 phalanx 20; fifth finger, metacarpus 26, first phalanx 11'5. 



Skull: greatest length, gnathion to tip of occipital crest 

 23*8; condylo-basal length 22-3; zygomatic breadth 16'5 ; 

 breadth of muzzle 11 ; interorbital breadth 5'5 ; mastoid 

 breadth 15"5 ; height of canine 4*8 ; front of canine to back 

 of w' 8*8. Height of lower jaw below m-i 3*5. 



Hah. Demerara. Type from Bartica Grove, Lower 

 Essequibo. 



Type. Old male. B.M. no. 10. 11. 10. 3. Collected by 

 Cozier and presented by F. V. McConnell, Esq. 



Related to M. brachym.eles of Peru and M. cerastes of 

 Paraguay and S. Brazil, but markedly larger than either. 



Rhipidomys bovallii, sp. n. 



A very large species, with grey-based belly-hairs. 



Size, as judged by the length of the tooth-row, larger than 

 in any other species. Fur long and thick, hairs o£ back 

 about 11 mm. in length, the long bristle-hairs surpassing 

 them by 4-5 mm. General colour above tiie usual dull 

 fulvous grey, darker along the median dorsal area^ clearer on 

 sides. Under surface dull creamy, the hairs slaty for rather 

 more than half their length; lateral line of demarcation little 

 marked. Hands and feet dark, the hallucal edges whitish. 

 Tail dark brown as usual, very heavily haired, especially at 

 the tip, where the hairs attain a length of 25 mm. 



Skull with rather narrow nasals and narrow interorbital 

 space. Palate much less broad than in M/i. lucullus. 



Dimensions of the type (measured on the skin) : — 



Head and body 180 ram.; tail 198 ; hind foot 33. 



Skull : nasals 15 ; interorbital breadth 5*6 ; diastema 11'2 ; 

 palatal foramina 8*6; breadth across outside 7?i^8'2; length 

 of upper molar series 6'8. 



Eah. Potaro Highlands, towards Mt. Roraima, British 

 Guiana. Alt. 2000'. 



Type. Adult. B.M. no. 7. 6. 10. 3. Collected 10th 

 November, 1905, and presented by Dr. Carl Bovallius. 



This fine species appears to be a Guianan representative of 

 the lih. Jeucodactylus group of Peru. From Rh. sclateri, the 

 only other Guianan species at all allied to it, it differs by its 

 larger size, longer coarser fur. 



