Basic Inky Cap ID for California
Out of the millions of different kinds of fungi out there, I think that Inky Caps are the coolest by far. They are called Inky Caps because they dissolve into black ink when they get old. They are also often misidentified, so I put together a list of the common Inky Caps and their differences. In general, there are four kinds of inky caps.
The first kind of inky cap is the genus Coprinus. People know this one pretty well, since this group contains the popular edible Shaggy Mane. (Coprinus comatus)
https://www.inaturalist.org/observations/4604947
Coprinus comatus is pretty much unmistakeable. It is big, white, has brown patches on the top, and is kind of shaggy looking. However, there is a close look-alike, Coprinus calyptratus.
https://www.inaturalist.org/observations/4463980
Coprinus calyptratus is similar in all respects to C. comatus, but with a star shaped brown patch on top. If you do find a Coprinus, chances are that it is Coprinus comatus, since C. calyptratus somewhat rare. I believe that both species are edible.
The next group, Coprinopsis, is also fairly easy to learn. There are two main species in this genus; Coprinopsis lagopus and Coprinopsis atramentaria. Coprinopsis lagopus is small, gray, and often grows in wood chips. It also has fluffy veil pieces on the cap.
https://www.inaturalist.org/observations/18934600
Coprinopsis atramentaria, also know as the Common Ink Cap, is much larger and stockier and lacks the veil pieces on the cap. Contrary to the “common” in its name, it is actually uncommon in California.
https://www.inaturalist.org/observations/9683482
Coprinellus, the third kind of inky cap, is a little harder than Coprinopsis. In general, Coprinellus species are distinguished from the other inky cap groups by their yellow to orange colors. The most common species, Coprinellus micaceus, is orange to brown, grows in clusters, and has little flecks on the cap. These white veil pieces gave C. micaceus the common name "Mica Cap".
https://www.inaturalist.org/observations/19224901
Another species, Coprinellus flocculosus, is similar to the Mica Cap, but it has much bigger veil pieces.
https://www.inaturalist.org/observations/8621460
There is an interesting species in California that doesn't quite have a name yet. It is like C. micaceus, but it has more veil tissue on the cap, and it is more gray than C. micaceus. It is also doesn't grow in clusters like the Mica Cap. I believe that the correct name for it is Coprinellus radians.
https://www.inaturalist.org/observations/19223036
The last species I will list in the Coprinellus genus is Coprinellus disseminatus. It is easily recognized by its growth in huge clusters, white color, and lack of deliquescence. (to deliquesce = to turn into ink)
https://www.inaturalist.org/observations/19299747
The last group of inky caps, Parasola, is the hardest to identify. They are usually small, fragile, and have lines that radiate out from a "sun" at the center.
https://www.inaturalist.org/observations/6862216
Most of the species of Parasola are hard to ID without using a microscope. But one species, Parasola auricoma, can be identified fairly easily without a microscope. It often starts out dark orange, and will sometimes carry orange-red tones on the cap even when it is old. It is one of the biggest and stockiest Parasola.
https://www.inaturalist.org/observations/34888554
Another species of Parasola you can ID with macroscopic features is Parasola conopilus. It looks just like Psathyrella corrugis, but there are some slight differences. Just ask me or Alan Rockefeller if you want to know the difference.
There are dozens of other species of Inky Caps out there, but those are harder to identify. For example, here is an observation of a tiny Coprinopsis that I will probably never learn to identify without a microscope.
https://www.inaturalist.org/observations/19035795
That's pretty much it. I hope you've learned something from this. :)