Correct spelling for the English word "epistomeus" is [ɪpˈɪstə͡ʊmɪəs], [ɪpˈɪstəʊmɪəs], [ɪ_p_ˈɪ_s_t_əʊ_m_ɪ__ə_s] (IPA phonetic alphabet).
Spigot-shaped.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.