548 Mr. O. Thomas on new 
right 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.1 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 the same size, and but little smaller 
than those of Nectomys squamipes. 
Dimensions of the type (an aged female, measured by 
collector in the flesh) :— 
Head and body 150 millim. ; tail 180; hind foot 35; ear 19. 
Skull: greatest length 36, basilar length 29°15; greatest 
breadth 19°7; nasals 14°6x 4°53 interorbital breadth 6°6 ; 
interparietal 3°8 x85; length of zygoma-root 4:7; palate 
length from henselion 17; diastema 10°4; anterior palatine 
foramina 6 x 2°6; length of upper molar 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 Holochilus nanus does to 
the large rats of that genus. It shows less obvious adapta- 
tion to an aquatic life than its congeners, although its fur is 
equally glossy, and there is a slight indication of webbing 
to the hind feet. 
Oryzomys peninsule, sp. n. 
A large species allied to O. Cowest and O. 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, the latter colour 
closely similar to the general colour of O. Cowest. Darker 
lining on back little conspicuous. Under surface dull white, 
not sharply defined; the hairs slaty basally. Lars thinly 
hairy, pale brown. Hands and feet uniformly silvery white 
above. ail 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, 84; ear 18. 
Skull: basilar length 27°3; greatest breadth 18°7; nasals 
13x3°9; palatine foramina 7X3; length of upper molar 
serles 0. 
Hab. Santa Anita, Lower California. Six specimens ex- 
amined, 
