Short story, possibly from the 1970's, hidden creatures on a mountain

Question

In an anthology I read approximately 1980, various sci fi and fantasy stories, I think it was hardback, I got it from a UK library.

Only one short story I recall (I may have posted this question online a couple of years ago but I'm not sure)

A man in America returns to a small town near a mountain area, with I think an army buddy, I'm not too sure, it could be some adverse person.

They go up into the mountains, protagonist hadn't been for years, he tells his companion about the odd creatures up here, something called a flatter because it could lie spread out very flat and then take it's prey....think like the robot in T2 when it spread out on the checked floor.

Another creature he mentions is a behinder, so called because it, like a bogeyman, is always behind you.

I think the person with him thought he was fooling and started saying loud nasty things about the mountain, then these things appeared and got him. The protagonist was left trembling because he'd finally saw what a behinder looked like, and now he understood why they stayed out of sight.

The name Yando or Yandry is in my mind for the mountain name

Answer 1

The short story The Desrick on Yandro by Manly Wade Wellman has both Flatters and Behinders. It was latterly made into a long work called Voice of the Mountain

The Behinder is another creature which few if any can describe since only John has seen one and lived. He chose not to tell us more. “The Behinder flung itself on his shoulders. Then I knew why nobody’s supposed to see one. I wish I hadn’t. To this day I can see it, as plain as a fence at noon, and forever I will be able to see it …” Still, John gives his protection from a Behinder in The Voice of the Mountain. “I reckoned what to do, if it got close, would be all a sudden to whip round and look it betwixt the eyes (if a Behinder truly has what we understand eyes to be) and say, ‘All right, what the hell do you figure to do?'”

_{^{Creatures High and Low: The Monsters of Manly Wade Wellman}}

And a mountain called Yandro.

"Yes, sir. The song's mountainy, not too far from the Smokies. I heard it in a valley, and the highest peak over that valley's called Yandro. Now," I said, "I've had scholar-men argue me it really means yonder—yonder high hill. But the peak's called Yandro. Not a usual name."