Ami ver. Ese día estaban en la orilla eran demasiados. Y pienso que estaban teniendo sus bebes..
I think these are Fissurella microtrema - I don't see any submissions of this species alive though...
There are lots of oyster species reporeted on iNat for this area, but I do not know how to distinguish them. This one is very fresh as there is still soft tissue attached.