1. Open one of the messages.
2. Find the "More" button (there are two, you want the one just over the message, not the one above it on the toolbar.
3. From the More menu, select "Filter messages like these".
4. If the filter is OK, then click create filter.
5. Click delete
6. Select the "apply filter to ____ messages like this".
This will continue deleting any similar message that comes in the future.