Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
collectānĕus (conl-), a, um, adj. [collaudo], gathered or collected together, collectaneous (very rare): aes, Plin. 34, 9, 20, § 97: Dicta collectanea, the title of a work of Cæsar, now lost, Suet. Caes. 56 (perh. his Ἀποφθέγματα, mentioned by Cic., Fam. 9, 16, 4).
Hence, subst.: Collectānĕa, ōrum, n., the title of the collected works of Jul. Solinus.