Don't want the thumbnail at the 'door' of the gallerie

Hi. I need that thumbnail on the 'door' of each gallerie to disappear.
When we look at a gallerie we see it´s name, "there are x images in this gallerie" and a thumbnail (when we have content inside). I want that thumbnail to disappear, and to see only thumbnails when entering inside the gallerie.
What lines should I delete?
Thank you.