mytiliteGeol.|ˈmɪtɪlaɪt| Also 8 mytul-. [f. Mytil-us: see -ite.] A fossil mussel-shell. 1794Kirwan Elem.Min. (ed. 2) I. 81 Compact Limestone..frequently abounds with..pectinites, gryphites, mytulites, &c.1811Pinkerton Petral. I. 254 In a specimen [of argillite] from Hessia, mytilites occur.