Xenophon, Symposium 4.14 [Tredennick and Waterfield, trs., Penguin (1990) p. 242]:
"What's this," said Socrates. "You're bragging as if you were more beautiful than I am."
"Of course," said Critobulus, "otherwise I should be uglier than any Silenus in the satyr-plays."
Plato, Symposium 215a-216e:
[Alcibiades:] And now, my boys, I shall praise Socrates in a figure which will appear to him to be a caricature, and yet I speak, not to make fun of him, but only for the truth's sake. I say, that he is exactly like the busts of Silenus, which are set up in the statuaries, shops, holding pipes and flutes in their mouths; and they are made to open in the middle, and have images of gods inside them. I say also that he is like Marsyas the satyr. You yourself will not deny, Socrates, that your face is like that of a satyr.