Origin of the Dufflepuds

Much unpacking has been going on in BiblioLand. My husband's science books made it onto the shelves yesterday. Now the center island of bookcases is full. I also discovered an overlooked box of books which had to be interfiled with the history section. Much book shifting ensued.

The very last book to come out of the box was Pliny's Natural History, edited by Loyd Haberly. Opening the book at random, my eye fell on the following:

[Ctesias] also speaks of another race of men who are known as Monocoli who have only one leg but are able to leap with surprising agility. The same people are also called Sciapodae because they are in the habit of lying on their backs during the time of the extreme heat, and protect themselves from the sun by the shade of their feet.

Well! I hadn't realized that the Dufflepuds were another one of C.S. Lewis' borrowings. But I'm an ignorant wight, so I won't be surprised if everyone else already knows this. As you can tell, I've never sat down and read all the way through even this condesed version of the Historia Naturalis.