Cap 3-12 mm broad, hemispherical, and covered with tall, white, conical spines in primordia, convex to campanulate at maturity, spines readily falling off or remaining only on the center, striate, glabrous or minutely granulose, white. Gillss adnexed, close, narrow, white. Stem 5 15 x 0.5-1 mm, cylindrical, fragile, pruinose to hispid overall, white; lacking a basal disc. Spore Deposit white. Edibility: unknown.
Mycena spinossisima is certainly one of the most striking Mycena species. The primordia are covered with white, conical spines that eventually fall off as the fruiting body matures. M. spinosissima is widespread in Central and South America and was probably introduced to Hawai‘i from these areas. Is: HA, KA.