The Danger of Misidentifying Mushrooms
Here are some relevant quotes from Paul Stamets in Psilocybe Mushrooms of the World regarding the dangers of misidentifying mushrooms;
pages 30-31 "If you have any uncertainty about a mushroom, do not eat it! We have learned which mushrooms are poisonous or nonpoisonous through the experiences of the unfortunate."
"As more people sought the psilocybin varieties, poisonings from mistaken identifications increased. The extreme foolhardiness of randomly collecting little brown mushrooms becomes terrifyingly real for those whose unreserved enthusiasm overrode admonitions for adequate preparation.
Some of the mushrooms belonging to the genus Galerina that resemble Psilocybes and can be deadly are G. autumnalis, G. marginata, and G. venenata. These contain amatoxins (cyclopeptides) similar to those found in the lethal species of Amanita, such as A. phalloides, A. bisporigera, and A. verna, the "destroying angels." Although Amanitas do not resemble Psilocybes, the general form of Galerinas closely parallels that of the Psilocybes, differing to the unaided eye only in the overall color of the spores and to a lesser degree in the color of the caps. Galerina spores are a rusty brown in deposit, while psilocybes are purplish brown. However, when the caps are dried and/or forozen, the color can be very similar. Another deadly rusty brown-spored mushroom, Pholiotina filaris (= Conocybe filaris) also contains these amatoxins. Learn how to identify these mushrooms and avoid them. (See Page 192). In addition to P. filaris and the Galerinas, there are probably more species containing amatoxins than we presently realize.
I often find Psilocybe growing within inches of G. autumnalis[/I and
P. filaris. In fact I look upon G. autumnalis as an indicator species - when this poisonous mushroom is present, I look in the surrounding habitat for the Psilocybe that are likely to be nearby. One dramatic example of this occurrence is illustrated below. Two colonies of mushrooms, one G. autumnalis and the other Psilocybe stuntzii, have overlapped! The stems of poisonous and psilocybin-producing varieties in this case were actually touching. I worry that amateur collectors would not be knowledgable enough to separate the deadly species from the psilocybin one. In their eagerness, how many would overlook this deadly dance of species? Would you? This chance find was one of the primary reasons that I was compelled to write this book."
Below this text is this photo of the two species growing side by side.

The following page (32) displays this photo of "Psilocybe pellicosa sharing the same habitat with deadly Galerinas."

Pages 32-33 "Beware of Galerina species and Pholiotina filaris, as accidental consumption can result in an agonizing death. Following is a description of the effects of eating Amanita phalloides. Since the deadly Amanitas, Galerinas, and Conocybes all produce cyclopeptide toxins, similar effects can be expected...
...'First symptoms come late - six to twenty-four hours (average ten to fourteen hours) after ingestion... ...Sharp abdominal pains are followed by violent vomiting and persistent choleralike diarrhea... ...three to four days the patients condition begins to worsen, with symptoms of liver and kidney failure leading to death in seven to ten days'... (quoted from "Mushroom Poisoning in the Pacific Northwest")
"This description should convince any hunter of psilocybin mushrooms that mushroom identification must be approached seriously, and with the utmost caution.
Other brown-spored genera that have an abundance of poisonous species are Inocybe, Cortinarius, Hebeloma, and Entoloma. By taking spore prints, paying attention to detail, and following the keys in this book, the possibility of ingesting poisonous mushrooms is minimized.
Several species in this book, such as the bluing species formerly belonging to the genus Stropharia (ex. Stropharia aeruginosa = Psilocybe aeruginosa), have not been fully tested. Bluing Inocybes, like I. aeruginascens, although psilocybin containing, should be treated with extreme caution, because their close relatives can be very poisonous. In general, members of the genera Psilocybe and Panaeolus seem quite safe - only psilocybin, psilocin and related compounds have been detected thus far."
On pages 192 to 197, Stamets elaborates on the dangers of mistaking Galerinas and Pholiotinas for Psilocybes. For example, on page 192 he writes;
"I worry that eager hunters will see the blackening reaction of some Galerina as a blueing reaction... ...Precise identification cannot be made without the use of a microscope. Learn to recognize Galerinas and avoid them."
He then gives a detailed taxonomic description of Galerinas and Pholiotinas (whereas the majority of the book gives detailed descriptions of psilocybin containing mushrooms).
Of course, unless you live in a civilized nation, all this is just academic because it is unlawful to pick or eat psilocybin containing mushrooms. Nobody should ever break a law, of course. Not only is it dangerous or deadly to pick and eat wild mushrooms, but it is unlawful as well.