JAN., 1912. MAMMALS, VENEZUELA AND COLOMBIA — Oscoop. 53 
heavy. It may represent a separable form, but for the present it seems 
best to regard it as an exceptionally large and aged male of sancte- 
marte. ‘The relation of this form to Z. thomasi is evidently very close, 
sanctemarte being characterized only by slightly larger size and somewhat 
more elongated skull. For the privilege of examining topotypes of both 
forms, I am indebted to Dr. J. A. Allen of the American Museum of 
Natural History. ; 
Chilomys fumeus sp. nov. Smoky Chilomys. 
Type from Paramo de Tama, head of Tachira River, Santander, 
Colombia. Alt. 6,000-7,000 ft. No. 18690 Field Museum of Natural 
History. Male adult. Collected Feb. 18, 1911, by W. H. Osgood 
and S. G. Jewett. 
Characters. Similar to Chilomys instans as described, but end of 
tail, digits of front feet, and distal phalanges of digits of hind feet white; 
size slightly smaller. Skull differing in slight details of measurement 
but in general similar to that of C. imstans. Color of upper and under 
parts practically uniform, the hairs dark slate color except for a narrow 
tipping of silvery hair brown or broccoli brown; face between nose and 
eyes blackish; feet brownish; toes, at least the distal phalanges, white; 
tail brownish above and below except the terminal inch which is white 
with a few irregular underlying blotches of brownish; a bright buff 
pectoral spot (in one specimen) continuous with a white line from throat 
to middle of belly. 
Measurements. Type and topotype, respectively: Total length 
211, 206; head and body go, 86; tail vertebra 121, 120; hind foot (c. u.) 
22, 23. Skulls of same: Greatest length 23.8, 23.4; basilar length 19.1, 
18.9; postpalatal length 8.8, 8.4; zygomatic breadth 13.2, 12.8; braincase 
12.8 X II.1, 12.5 X 11.4; interorbital constriction 4.6, 4.8; width of zygo- 
matic plate 2.1, 2; diastema 6.7, 6.5; maxillary toothrow 3.1, 3.15. 
- Remarks. Only two specimens of this peculiar mouse were obtained 
during some twenty days’ trapping in the forests about the head of the 
Tachira. It inhabits the same dark damp depths of the forest as 
Thomasomy shylophilus,and from its peculiar plumbeous color, white- 
tipped tail, and slender form was at first believed to represent the im- 
mature of that species. 
Material is not at hand for satisfactory discussion of the generic 
characters of Chilomys from a comparative standpoint, but several 
peculiarities not mentioned heretofore may be noted. The pollex is 
extremely rudimentary, and the soles of the hind feet lack imbrications, 
the subdigital pads being relatively large and the interspaces smooth and 
