Most likely you'll be searching for Psilocybe Cubensis. It is the most common visionary mushroom found on dung. It can appear in many different sizes and colors. It will usually have a purple-blackish ring around the stem. The stem will also bruise blue when handled or pinched. The caps will usually have a tan-white color, fading to a darker tan towards the center of the cap. The center of the cap will usually have a nipple also. To be abesolutly sure you have a Cubensis. Cut the cap of its stem, and lay the cap on a piece of paper for about 12-24 hours. It should drop most of its spores on the paper. The color of the spores should be somewhat purple, sometimes more of a brown.

The Pic above is of the common Cubensis growing on dung. I believe this pic was tooken by Mjshroomer, just trying to give credit where credits due

[This message has been edited by Lizard King (edited January 14, 2000).]