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PROCEEDINGS OF THE NATIONAL MUSEUM 



The difference between the color groups are slight and in any 

 large series completely intergrading. Extreme examples of the bright 

 color group are nearly erytliristic. On the other hand, no specimen 

 of the dark group even remotely suggests melanism. 



There are some examples in present material of adults molting 

 from one color group to another. 



The color of nestling young is like that of adults. As the juvenal 

 coat of cover hairs on upperparts and sides becomes worn, the dark 

 gray basal portions of the hairs show through. Adult pelage begins 

 to replace juvenal pelage on the lower parts of the sides of the body 

 and on the shoulders. Adult pelage appears next on head, nape, and 

 shoulders, respectively. Evidently, the short, wholly slate colored 

 pelage characteristic of most newborn terrestrial species of Oryzomys 

 is either absent or ephemeral in 0. bicolor. 



The Subspecies 



Four subspecies of Oryzomys bicolor are recognized, two of them 

 provisionally. The first, bicolor Tomes, occupies most of the range 

 of the species east of the Andes. The second, phaeotis Thomas of 

 southeastern Peru and northern Bolivia, averages larger in size than 

 the others. 0. b. trabeatus G. M. Allen and Barbour is the Central 

 American representative. It appears to be completely isolated 



Table 4. — Oryzomys (Oryzomys) laticeps Lund: External measurements {in 

 millimeters) of a series of adults from the Rio Caquetd region, eastern Colombia. 

 Specimens were collected and measured in the flesh by the author. Note tail length 

 and proportional length of hind feet and compare with table 3. 



