The Collaborative International Dictionary of English v.0.48:

Grivet \Griv"et\ (gr[i^]v"[e^]t), n. [Cf. F. grivet.] (Zool.)
   A monkey of the upper Nile and Abyssinia (Cercopithecus
   griseo-viridis), having the upper parts dull green, the
   lower parts white, the hands, ears, and face black. It was
   known to the ancient Egyptians. Called also tota.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Guenon \Guenon"\, n. [F.] (Zool.)
   Any of several long-tailed arboreal African monkeys, of the
   genera Cercopithecus and Erythrocebus (formerly
   classified as Cercocebus), such as as the green monkey
   (Cercopithecus callitrichus) and grivet (Cercopithecus
   griseo-viridis).
   [1913 Webster +PJC]