We have also collected this species on Mauna Kea, Hawai`i and in the cow
pastures of West Maui.  In the field, it is distinguished from A. sepulchralis  by a
campanulate pileus that is tan to dingy yellowish buff, and by the presence of an
annulus.  It differs from Copelandia cyanescens  in lacking a blue staining reaction
when bruised, and from Panaeolus sphinctrinus  by having the partial veil remain
as a thin ring around the stipe instead of as a fringe on the pileus margin.  A good
description of A. semiovata  (as Panaeolus semiovatus ) may be found in Olah, Le
Genre Panaeolus  (Rev. Mycol. Ser. 10: 1-274. 1969).