Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
testūdĭnĕus, a, um, adj. [testudo, I. and-II.], of or belonging to a tortoise; made of tortoise-shell: gradus, a tortoise-pace, snail’s pace, Plaut. Aul. 1, 1, 10: lyra, made of or overlaid with tortoise-shell, Prop. 4 (5), 6, 32; Tib. 4, 2, 22: conopeum, Juv. 6, 80: hexaclinon, Mart. 9, 60, 9.
As subst.: cui testudinea legata essent, ei lectos testudineos pedibus inargentatos deberi, Dig. 32, 1, 100, § 4.