*doublure*

‖n. [ F. ] 1. (Bookbinding) The lining of a book cover, esp. one of unusual sort, as of tooled leather, painted vellum, rich brocade, or the like. [ Webster 1913 Suppl. ]

2. (Paleon.) The reflexed margin of the trilobite carapace. [ Webster 1913 Suppl. ]