186 Mr. 0. Thomas on Mammals from 



Skull : greatest length 45 ; basilar length 36*2 ; zygo- 

 matic breadth 24; nasals 17 - 7; interorbital breadth 7*4:; 

 palatilar length 20; palatal foramina 8'6; upper molar 

 series 6'2. 



Hab. (of type). Lower Essequibo River, 12 miles from 

 mouth. Alt. 40 feet. Other specimens from Supinaam 

 River and from Surinam. 



Type. Adult male. B.M. no. 6. 4. 8. 32. Original num- 

 ber 60. Collected 10th March, 1906, by S. B. Warren. 

 Presented by Oldfield Thomas. 



This is the Guianan representative of the Brazilian water- 

 rat, N. squamipes, but is distinguishable by its darker dorsal 

 colour and smaller skull and teeth. 



The Trinidad form, iV T . palmipes, is also nearly allied, but 

 its nasals are more abruptly narrowed posteriorly. 



The three specimens in the present collection are of a more 

 rufous colour than the three obtained in 1906 by Mr. Warren, 

 but this would appear to be merely due to bleaching. 



10. Oryzomys macconnelli, sp. n. 



Eight. 



A large rich rufous species, apparently allied to O. inter- 

 medins. 



Size comparatively large. Fur rich and sleek ; hairs of 

 back about 12 mm. in length. General colour above bright 

 rich tawny or tawny ochraceous, darkened along the middle 

 area of the back. Sides clearer "tawny ochraceous.'" Under 

 surface sharply defined white, the basal halves of the hairs 

 slaty. Head rather browner than back. Ears large, blackish 

 brown. Hands and feet silvery white. Tail long, very 

 finely scaled, short-haired, brown above, dull white below. 



Skull somewhat like that of O. intermedins. General 

 outline long and slender. Interorbital ridges well marked, 

 evenly divergent, but little overhanging. Palatal foramina 

 of medium length, slightly longer than the molar series. 



Dimensions of the type (measured in skin) : — 



Head and body (c.) 145 mm.; tail 159; hind foot 35; 

 ear 24. 



Skull : greatest length 36'3 ; basilar length 27*7 ; zygo- 

 matic breadth 17*3 ; nasals 14*6 ; interorbital breadth 5"7 ; 

 breadth of brain-case 13*7 ; palatilar length 16 ; diastema 9"8 ; 

 palatal foramina 6*1 ; length of upper molar series 5 '3. 



Type. Old female. B.M. no. 10. 5. 4. 34. 



This handsome species is readily distinguished from any of 



