Look under the mushroom cap

These pictures demonstrate the importance of always looking at (and photographing, if possible) the underside of the cap on a mushroom.  From above, these three species look nearly identical, but a quick check under the cap gives you more information, and usually enough to at least categorize the mushroom by family.  From left to right we have: an agaric (a mushroom with gills), a bolete (a mushroom with pores under the cap), and a tooth fungus (a mushroom with tiny, soft spines hanging under the cap).