These cats were said to be found in the Scottish Highlands and to be of a wild breed as large as dogs, black in color, and with a white spot on the breast. They had arched backs and erect bristles. According to superstition, elfin cats were witches in disguise.
"Cats, Elfin." Encyclopedia of Occultism and Parapsychology. . Encyclopedia.com. (January 21, 2019). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/cats-elfin
"Cats, Elfin." Encyclopedia of Occultism and Parapsychology. . Retrieved January 21, 2019 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/cats-elfin