It's over a year since my first (and last) shaggy mane post. They're back. These two are about four inches high.
Below you can see what happens if you wait too long to pick them. They turn inky. According to Tom Volk
Members of the genus Coprinus have been collectively known as the "inky caps" because of the curious character of autodeliquescence of their gills-- in other words self-digestion to release their basidiospores. Most of these species have gills that are very thin and very close to one another, which does not allow for easy release of the spores. . . After the spores have matured and been released, the gill tissue digests itself and begins to curl up, allowing easy release of the basidiospores above. In other words, the digestion opens up the fruiting body so that spores from further up the gills become exposed to the air and a clear path of spore release. The self-digestion continues until the entire fruiting body has turned to black ink. In the olden days this ink was actually used for writing.