What is a double thiophene nucleus, C6H4S2, analogous to thionaphthene, and the base of a large series of compounds. [Written also thiophtene.] called?

thiophthene — A double thiophene nucleus, C6H4S2, analogous to thionaphthene, and the base of a large series of compounds. [Written also thiophtene.]. (Webster's 1913.)

Sources