Yellow patch on Nassirus snail

[DEL 707]

Rarly see the little guy out, but today I noticed a kind of yellow patch on his tail.
I mean it could always have been there, is this normal?

 

[tzabor10]

Snails are remarkably clean. I doubt it is anything to worry about. Great pictures!

 

[ROB2005]

That’s normal, he’ll use it at times to seal off the entrance to his shell of if a small crab or fish is trying to get at it.

Really cool how they bury themselves and leave their snout sticking out the sand waiting to erupt at the first whiff of food!

 

[ISpeakForTheSeas]

Yeah, that's normal - it's called the operculum, and, as mentioned, it's used to "close the door" behind the snail when the snail retracts into its shell.