JAN., 1912. MAMMALS, VENEZUELA AND COLOMBIA OSGOOD. 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 sancta- 

 martce. The relation of this form to Z. thomasi is evidently very close, 

 sanctamarta 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. instans. 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 90, 86; tail vertebrae 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. i, 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 



