548 Mr. O. Thomas on new 



riglit back across the parietals to the outer corners of the 

 interparietal, at which point they turn abruptly downwards 

 and outwards. Anterior palatine foramina rather small, 

 ending about 1*5 millim. in front of the level of m} Poste- 

 rior nares very broad, open and rounded. 



Teeth very stout and heavy. Incisors thick and strong. 

 Molars broad and rounded, twice the bulk of those of an 

 average Oryzomys of tiie same size, and but little smaller 

 than those of JSectomys sqaamipes. 



Dimensions of the type (an aged female, measured by 

 collector in the flesh) : — 



Head and body 150 millim. ; tail 180 ; liind foot 35 ; ear 19. 



Skull: greatest length o(), basilar length 29" 1 ; greatest 

 breadth I'd'!; nasals 14"6x4'5; interorbital breadth 6'6 ; 

 interparietal 3*8x8'5; length of zygoma-root -l"? ; palate 

 length from henselion 17 ; diastema 10*4 ; anterior palatine 

 foiamina 6x 2*G ; length of upper mular series 6 ; width of 

 posterior nares 3"2. 



Hab. Valdivia, Colombia, alt. 1200 metres. Coll. A. E. 

 Pratt, 7th July, 1897. 



This species bears much the same proportion to the other 

 members of Nectomys that the little Holochllus nanus does to 

 the large rats of that genus. It shows less obvious adapta- 

 tion to an aquatic life than its congeners, althougli its fur is 

 equally glossy, and there is a slight indication of webbing 

 to the hind feet. 



Oryzomys peninsulce, sp. n. 



A large species allied to 0. Couesi and 0. fulgens. Fur 

 thick, close and rather woolly, about 10 millim. in length on 

 the back. Colour of head and fore back pale greyish, gradu- 

 ally changing to dull fulvous on the rump, tiie latter colour 

 closely similar to the general colour of 0. Couesi. Darker 

 lining on back little conspicuous. Under surface dull white, 

 not sharply defined ; the hairs slaty basally. Ears thinly 

 hairy, pale brown. Hands and feet uniformly silvery white 

 above. Tail thinly haired, brown above, darkening terminally, 

 whitish below. Skull stout and heavy, with well-defined 

 supraorbital ridges. 



Dimensions of the type (an adult male, measured in the 

 flesh):— 



Head and body 148 millim.; tail 150; hind foot, with 

 claws, 34 ; ear 18. 



Skull: basilar length 27*3; greatest breadth 18'7j nasals 

 13x3-9; palatine foramina 7x3; length of upper molar 

 series 5. 



Hah. Santa Anita, Lower California. Six specimens ex- 

 amined. 



