Correct spelling for the English word "mantellia" is [mˈantɪlˌɪə], [mˈantɪlˌɪə], [m_ˈa_n_t_ɪ_l_ˌɪ__ə] (IPA phonetic alphabet).
In geol., fossil stems of a sub-cylindrical shape, covered with rhomboidal leaf-scars-termed "crow's nests" by the quarrymen.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.