...Then Beren answered: "By the ring of Felagund that he gave to Barahir my father on the battlefield of the North, my house has not earned such names from any Elf, be he king or no." His words were proud, and all eyes looked upon the ring; for he held it now aloft, and the green jewels gleamed there that the Noldor had devised in Valinor. For this ring was like two twin serpents, whose eyes were emeralds, and their heads met beneath a crown of golden flowers, that the one upheld and the other devoured; that was the badge of Finarfin and his house.

The Silmarillion, "Of Beren and Luthien"