Catathelasma evanescens

Catathelasma evanescens is a species of fungus in the family Tricholomataceae, and the type species of the genus "Catathelasma". The species was described by Ruth Ellen Harrison Lovejoy in 1910.
Description and Distribution.
The genus includes the commoner "C. imperiale" and "C. ventricosum", but the type species, "C. evanescens", seems extremely rare. In 1914 it was only known from the location of the initial find, which is at an altitude of 3500 m. in the Medicine Bow Mountains of Wyoming. It is distinguished from the other species because the gills are fairly distant ("subdistant") and because it has a large persistent volva around the base of the stipe.
The species name may refer to the ring.
The following summary is taken from Mrs. Lovejoy's original description.