Move the cursor over the top left corner of the tab.
"Tabbed browsing bar – Shows webpages in tabs. To close a tab, click the button that appears in the left of the tab when the cursor hovers over it."
The problem was that nothing appeared when the cursor hovered over the left side of the tab. However, when all else fails, reboot. Now the little closing buttons are back.
I appreciate that you answered my question, but I am not a newbie and have been opening & closing tabs for as long as they've been in existence. The copy you sent me out of the instruction manual was nothing new and did not solve my problem. But it did make me think, so my next thought was that something is hung up. The reboot solved the problem.