450 On new Sigmodon, Oryzomys, Se. from Ecuador. 
Allen’s O. barbacoas, with the typical series of which Mr. H. E. 
Anthony has been so kind as to compare it for me. He 
reports that, in his opinion, it might be referred to that 
species, but is evidently distinct as a subspecies on account 
of its much more ochraceous-buffy colour, true O. barbacoas 
being of a more chestnut hue. 
Echimys occasius, sp. n. 
Very similar to Z. armatus. Tail naked. Incisors white. 
Size, Judging from a young specimen, about as in 2. ar- 
matus or a little smaller. Pelage profusely spinous, the 
admixture of hair about as in armatus; longest spines of 
back about 25 mm. in length by 1°5 in. breadth. General 
colour above darker than in armatus, near “ buffy brown,” 
the hairs dark ochraceous, the spines black, many with 
prominent pale buffy tips. Under surface strong buffy, the 
chest and inguinal region whiter. Head darker brown, with 
scarcely any of the rufous tinge on muzzle and cheeks usually 
so marked in armatus. Ears comparatively small. Hands 
and feet grizzled brownish, the digits lighter. Tail practically 
naked, prominently scaly, the rings of scales about ten to the 
centimetre, 
Skull and dentition essentially as in armatus, with the 
exception that the incisors are quite white in front and are 
distinctly more slender than in specimens of armatus of 
corresponding age. 
Dimensions of the type (immature), taken on the skin :— 
Head and body 180 mm.; tail 180; hind foot 31°5. 
Skull: greatest length 45; condylo-incisive length 39 ; 
zygomatic breadth 21; nasals 13:3; interorbital 8x 12:3; 
palatilar length 16; front of p* to back of m? (little worn) 8 ; 
antero-posterior diameter of incisors 16. 
Hab. Gualea, Ecuador, west of Pichincha. Alt. 4000’. 
Type. Immature female. B.M.no. 21. 2.15.6. Collected 
for Mr. L. Séderstré6m, of Quito. Received in exchange 
from the Stockholm Museum. 
This species may be distinguished from the 2. armatus of 
Guiana and the Lower Amazon by its darker colour, naked 
tail, more prominently light-spotted coloration, and white 
incisors. In the last two characters it shows an approach to 
the EH. punctatus group, but is differently coloured, and the 
tail in that group is even more thickly hairy-than in armatus. 
No member of the restricted genus Mchimys appears to- 
have been previously recorded from Ecuador. 
