460 Bulletin American Museum of Natural History. [Vol. XX, 



A. seniculus rubiginosa differs from true A. seniculus of 

 Guiana in its much darker, richer coloration, and larger size. 

 In the absence of skulls of true seniculus it is impossible to 

 say whether or not they are also distinguished by cranial 

 characters, which seems probable in view of the sharp differ- 

 entiation in this respect of the red howler of the Cauca Valley 

 from that of the Santa Marta district. That the group is sub- 



Fig. i. A louatta seniculus rubiginosa. Type. nat. Fig. 2. Alouatta seniculus caucensi 

 size. nat. size. 



Type. 



ject to great local variation is abundantly shown by a fine 

 series of 9 specimens from the upper Cauca Valley, -collected 

 at altitudes of from 3000 to 6000 feet in May and June, 1898, 

 by Mr. J. H. Batty. These agree in pattern of coloration 

 with the Santa Marta series, but differ widely in color, being 

 many shades paler throughout, including the head, neck, 

 flanks, limbs, and tail, as well as the dorsal area, which latter 

 is deep straw yellow instead of reddish orange, while the 



