A common mistake in identifying Psilocybe pelliculosa is confusing it with Psilocybe semilanceata (another species known as the “liberty cap”). The easiest way to identify these two psilocybin mushrooms is by the shape of their caps. The cap of Psilocybe pelliculosa is noticeably convex or even bulbous, while the cap of Psilocybe semilanceata is more flat and wavy. Another distinguishing characteristic between these two species is that the gills on Psilocybe pelliculosa are often not attached to the stem.
 
The Pacific Northwest of North America, as far south as Northern California, north into British Colombia, and east as far as Idaho.