From WordNet (r) 3.0 (2006) [wn]:
silenus
n 1: any of the minor woodland deities who were companions of
Dionysus (similar to the satyrs)
2: the chief satyr in the service of Bacchus; father of
Dionysus; usually depicted as drunk and jolly and riding a
donkey
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Silenus \Si*le"nus\, n. [L. Silenus the tutor and attendant of
Bacchus.] (Zool.)
See Wanderoo.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Wanderoo \Wan`der*oo"\, n. [Cingalese wanderu a monkey.] (Zool.)
A large monkey (Macacus silenus) native of Malabar. It is
black, or nearly so, but has a long white or gray beard
encircling the face. Called also maha, silenus,
neelbhunder, lion-tailed baboon, and great wanderoo.
[Written also ouanderoo.]
[1913 Webster]
Note: The name is sometimes applied also to other allied
species.
[1913 Webster]