eww weird snail/abalone id please...

[mr.clownfish]

i found this thing this morning it was half way out of my tank. what is it?

and here it is upside down. the bottom part

 

[keri]

limpet?

 

[mr.clownfish]

really? wat is that good or bad?
i threw it in my cycling 12gal....

 

[alix2.0]

weird lookin limpet

 

[mr.clownfish]

Well Is It Good Or Bad???