32 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



genotype of Dirias. Evidently the dental characters are not corre- 

 lated with the length of the tibia and foot in any natural association of 

 species, and since it is difficult to see generic significance in the relative 

 shortness of the tibia and foot, the recognition of Dirias as a distinct 

 genus is open to serious question. 



Cebus apella leucocephalus Gray. 



Seven specimens, Orope, Zulia, Venezuela; collected by N. Dear- 

 born. One of these (No. 16,567) has been compared with the type of 

 Cebus leucocephalus in the British Museum. The type is somewhat 

 larger and its pelage slightly fuller and longer than in our specimen, 

 but the color is practically identical, the only difference being in the 

 color of the under side of the tail which is slightly darker in the type. 

 Comparison has not been made with Cebus albifrons and it is there- 

 fore somewhat of an assumption to use the name leucocephalus as that 

 may possibly prove to be a synonym of albifrons. However, the 

 belief that leucocephalus differs from albifrons is encouraged by the 

 original description* of albifrons, which states that the forehead is 

 black, -whereas in our specimens it is brown. Moreover, the face in our 

 specimens is scarcely white, but pale brown. The locality assigned 

 to leucocephalus by Gray is simply "Columbia"! but its agreement 

 with our specimens makes it probable that the exact locality was at 

 least in northeastern Colombia and probably in western Venezuela 

 near the coast. This is the more probable since a well-distinguished 

 form (malitiosus) inhabits the Santa Marta region. 



* As follows: " Sitnia albifrons, ex albo cinerascens, vertice nigro, facie caerulea, fronte et 

 orbitis niveis. cruribus et brachiis fuscentibus." 

 t P.Z.S., 1865, p. 827. 



