Odd critter attached to Frogspawn??

[jiggysmb]

I have had a purple fuzz growing on the hard base of my frogspawn for a couple months. Initially I thought it was the old soft tissue that had not decay away. Today I was scratching it off and noticed 4 of these flat shells hidden in the soft fuzz up close to the soft tissue. Can someone help ID?

 

[Projects with Sam]

Limpet?

 

[jiggysmb]

Limpet?

The lower shell is what faces out, and does not look like other limpets I have seen. The upper pic is the flipped side with a little black head.

 

[bradleym]

It looks like some kind of bivalve, similar to a mollusks. Probably not anything to worry about.

 

[Ricox]

It looks like some kind of bivalve, similar to a mollusks. Probably not anything to worry about

I agree, it shouldn't be a problem.