Thanks for the link. Upon further examination of the shell, there was still part of the snail in the shell so I dunno why part of the snail came out but the rest was still in tact. Either way, there was a good chunk of dead snail in the shell and it rotted off and left a foul odor to my tank. I got the dead part out and tossed it and my carbon/chemipure seems to have helped clear the odors fast. Very very very foul odor. ack!