Lepiotas are another beautiful group of white spored mushrooms, known for their delicate scaliness. They used to have their own family, the Lepiotaceae, but have since been found to be closely related to Agaricus, the dark spored store bought mushroom, and are now considered to be part of the Agaricaceae. However, they are distinct enough that I think they still deserve their own family (but that's not up to me), or at least deserve their own page on this site (that is up to me).
The creation of Lepiota likely occurred when the pigment in the spores was lost, and they became white spored. It turns out that evolving pigments in spores is unusual, and may have only happened a few times, with all of the brown and darker spored mushrooms belonging to one giant clade. (The Pluteaceae and Entolomataceae evolved pink spores in separate events). However, losing your pigment may be easier, as that has happened more than once. (Laccaria is also a white spored mushroom evolved from dark spored ancestors).
They do not form mycorrhiza with trees, yet even though they appear to be mostly saprophytic they still generally grow on the ground but occasionally on wood. They range in size from very small to very large.
Some of the smaller mushrooms in Lepiota evolved the same deadly toxin as the deadly Amanita, unfortunately for those who like to go around sampling mushrooms without identifying them first. Others are edible and some are quite delicious.
Chlorophyllum (Macrolepiota) - the largest mushrooms, 15cm or more across. These are the shaggy parasols with scaly caps, of which we have three local species. Formerly the differences were not recognized and they were all just called Macrolepiota rachodes. Luckily, our climate is usually too cool for the very poisonous lookalike Chlorophyllum molybdites, with green spores (from where we get the genus name, which means "green gilled"). That species is mostly found south and east of us, but it has been found in Washington! Cutting into all of these mushrooms will turn the flesh bright orange! They have a well developed ring on the stem that can usually be moved up and down.
Do not confuse with Leucoagaricus americanus, with a spindle shaped stem, different looking scales and staining yellow, orange or red.
C. olivieri - the entire cap is brownish, without any bright white visible underneath the scales. More rural.
C. brunneum - Contrasting cap from the bright white under brown scales. Very abrupt bulb on the stem. More urban. May not have scales when young!
This is what young C. brunneum looks like before the scales develop on the cap. Note the crazy bulb.
Leucoagaricus - medium to large, 5-15cm across, caps not always scaly, usually with a well developed ring on the stem. Resembling Agaricus somewhat in stature. The scales are not granular nor cottony like Leucocoprinus and Cystolepiota. Most easily confused with Lepiota. In fact, the proper genera for mushrooms in Lepiota, Leucoagaricus and Leucocoprinus have not been settled on.
L. rubrotinctus grp (rubrotinctoides) - the reddish-brown scales radiate from the centre in streaks, instead of the usual pattern of concentric circles of scales. Smallish.
L. glabridiscus is similar but smaller and bitter.
L. flammeatincta (Lepiota flammeotincta) - touch the cap or stem of this small mushroom and it turns red so quickly I actually jumped backwards once thinking I saw a flash pot. The red soon darkens.
Lepiota castanescens - gills redden too, but the red doesn't darken as in the others. Turns red in KOH (the others turn green).
Lepiota - small (2.5-5cm) to medium (5-10cm) sized, the core genus of Lepiota. The ring is usually well developed if the stem is smooth, but some scaly-stalked species don't have a well developed ring. Scaly caps. Smooth stem unless specified (sometimes a scaly or shaggy stem). A few species are deadly poisonous! Easily confused with Leucoagaricus, so much so that species are still being moved back and forth between them, so check both places. The scales are not granular nor cottony like Leucocoprinus and Cystolepiota.
L. 'eriophora' - medium, erect brown scales on a white background.
L. acutesquamosa (aspera) - brown cap with some white between scales. Both have a somewhat cobwebby veil.
L. fuscosquamea - small-med, veil fleeting, scales somewhat erect. Scales on stem like the smaller L. castanea grp. ~5cm
L. cortinarius - similar with scales not erect and a fleeting cobwebby veil. <10cm
L. fuscovinacea - beautiful purple scales, ~5cm
L. decorata - medium beautiful pink scaled species. Likely a Leucoagaricus. Also consider the deadly L. subincarnata.
L. atrodisca - black edged ring, small, but not as delicate as the more coarsely scaly Leucocoprinus brebissonii. Southern species. Likely a Leucoagaricus.
L. magnispora - a group of medium, shaggy-stemmed Lepiotas. Stem not smooth like above, nor with sharp scales like some below. DEADLY?
L. clypeolaria - similar, without the dark eye, but with the same poorly defined ring and large spores. Here most of the stem scales have rubbed off. DEADLY? Compare L. subincarnata.
L. alba - an albino L. clypeolaria, but with cap somewhat smooth. Smaller, less developed ring and a slightly shaggier stem than Leucoagaricus. Larger than other white ones.
L. felina - small, eye and scales are very dark brown, but not black like L. atrodisca. Stem has some scales and a ring. DO NOT EAT.
L. castanea - small, sharp scales on stems. DEADLY. Without ring.
L. subincarnata (josserandii) - pink hues, shaggy stem when fresh, not scaly like L. castanea, smaller than the L. clypeolaria group. Without ring. Stains slightly reddish. DEADLY.
L. cristata - the classic urban, small Lepiota. Orange-brown eye with concentric scales. An odd scent.
L. castaneidisca - southern species in the wild under Redwood, Monterey Cypress and Live Oak. Paler, subtler scaling.
Leucocoprinus - the smallest (<5cm across) and most delicate Lepiotas with a well developed ring and granular scales on the cap and somewhat on the stems. They have striate margins, resembling the smaller inky caps in stature. These are usually more tropical species, and found more often in greenhouses and potted plants than in the wild, although some species manage to grow wild in the summer months. Very closely related to Leucoagaricus and possibly not deserving a genus of their own, but they are distinctive.
L. brebissonii - with a black eye in the disc, in the wild in warmer weather. Lepiota atrodisca is similar but less delicate with a black edged ring and more fibrillose cap scales.
L. heinemanii is found in greenhouses.
L. cepistipes - white, eye never black. More delicate, granular-scaly
Lepiota pulcherrima - more reliably
Lepiota pulcherrima - more reliably bitter.
Cystolepiota - small (<5cm across), often more cottony overall than scaly with a poorly developed ring. The shagginess will wear off with age, however.
C. bucknallii - purple and shaggy! Smells badly of coal-tar!
C. moelleri - covered in pink warts.
Cystoderma fallax - the only species with a well developed sheathing ring.
C. carcharias - a rare albino version, probably the same species.
Floccularia - another genus with attached gills, these larger mushrooms (up to 15cm across) also have shaggy scales on the cap and on the stem. These are especially like the ringed Tricholomas, so look there too.
Tricholoma focale (zelleri) - bright orange colours, somewhat farinaceous. The most similar Tricholoma.
Lastly, possibly the oddest gilled mushrooms in the PNW. Both of these have attached gills. They are small (<5cm across).
Melanophyllum haematospermum is rare and has green or red spores and almost free red gills, a unique spore colour perhaps representing an intermediate stage between the dark brown of Agaricus and the white of Lepiota, as the former was losing its spore pigment.
Squamanita parasitizes other mushrooms, sometimes growing right through them. They are very rare, purple and scaly and I'm not sure what they are related to (one study suggested Phaeocollybia!) so I don't know what page to put them on, but some of them parasitize Cystoderma, which they resemble. Finding one would be quite an accomplishment.
Melanophyllum haematospermum - red gills when young, fading and then harder to ID. Well developed veil. Green or red spores depending on how fresh the mushroom is.
And that completes another of the most beautiful groups of mushrooms found around here. Unfortunately there is not recent specialized literature with colour photos and up to date information for the PNW.