2 1 8 Bulletin American Museum of Natural History. [Vol. XIV. 



breadth for about 4 mm. beyond the point of greatest expansion, then taper 

 suddenly and end abruptly, instead of converging evenly to a slender point. 

 The palatal vacuities are also unusually developed, as much so as is ordinarily 

 the case in Didelphis. The skull is large for the size of the skin, which is 

 sexed by the collector as a female. Total length, 68 ; basal length, 62 ; length 

 of nasals, 33 ; zygomatic breadth, 36 ; postorbital processes, 15 ; postorbital 

 constriction, 9 ; mastoid breadth, 37.6 ; breadth across mm *, 19.5 ; length of 

 upper toothrow, 23 ; upper molar series, 13. 



This species is based on a single specimen from Rio Cauca, 

 Colombia, collected by Mr. J. H. Batty, June, 1899. It differs 

 from the Mexican and Central American forms in its very light 

 coloration and in the tail being uniformly blackish brown with- 

 out the usual light tip. The skull is peculiar for a member of 

 this genus in the large size of the palatal vacuities and in the 

 great breadth of the posterior third of the nasals, which have 

 more the form of the nasals in M. nudicaudatus . It differs, how- 

 ever, from this species through its much larger size and different 

 coloration, and in the basal two inches of the tail being furred. 



