Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
massālis, e, adj. [1. massa], of or belonging to a mass, that constitutes a mass (eccl. Lat.): massalis moles, i. e. chaos, Tert. adv. Hermog. 30: summa, the All-embracer, i. e. Christ, id. adv. Marc. 4, 18.
Hence, adv.: massālĭter, in a mass, all together (eccl. Lat.), Tert. adv. Valent. 16.