1.18.94-95 (tr. H. Rushton Fairclough):
Take the cloud from your brow; shyness oft gets the look of secrecy, silence of sour temper.
deme supercilio nubem: plerumque modestus
occupat obscuri speciem, taciturnus acerbi.
Margaret B. Fergusson, "Quo Sensu Credis et Ore? A Study of Facial Expression in Greek and Latin Literature," Greece & Rome
, Vol. 9, No. 26 (Feb., 1940) 102-116 (at 104, on the eyebrows):
In Greek and Latin, to draw them together is to frown—ὀφρῦς ἀνασπᾶν, συνέλκειν, frontem contrahere: to become calm and cheerful again is λύειν, μεθιέναι τὰς ὀφρῦς. In the Lysistrata τοξοποιεῖν τὰς ὀφρῦς is to arch them in superciliousness. A clouded brow is quite literally in Euripides
στυγνὸν ὀφρύων νέφος: Horace has deme supercilio nubem.