What are these on nerite's shell?

[mkunk1]

I just received these and quite a few other snails the other day and just noticed these on two of the 4 nerite shells.... what are they?

http://imgur.com/NBdAkIb

http://imgur.com/6vSE2VJ

 

[pugcrush]

I just received these and quite a few other snails the other day and just noticed these on two of the 4 nerite shells.... what are they?

http://imgur.com/NBdAkIb

http://imgur.com/6vSE2VJ

barnacles; wouldn't worry about it