Having a shape or cross-section like the cross-section of a bell.(adjective)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "bell-shaped" in a sentence
"I bid a few hundreds dollars on a pink and white decoupage cake platter with a bell-shaped top."
"The rate with which these ideas came followed a kind of a bell-shaped curve."
"Month after month this process continued until new memories were gradually harder to come by -- descending on the bell-shaped curve until they stopped altogether."