Sir John Williams, Bart, now of Aberystwyth, informed me that when a boy in the neighbourhood of Gwynfi, Carmarthenshire, he often heard some of the old people speak of a ghost which haunted the road in that part of the country in former times. This ghost was known as "Bwci," and always assumed the form of a horse. It is an old belief of the Celts that demons assumed the form of horses, and one of these mythic beings was the Water Horse, so well-known in North Scotland. It was also known in Wales once. THE GWYLLGI, OR DOG OF DARKNESS. The Gwyllgi was a frightful apparition of a mastiff with baleful breath and blazing red eyes. In former times, an apparition in this shape haunted Pant y Madog, in the neighbourhood of Laugharne, Carmarthenshire. A woman named Rebecca Adams, passing this spot late one night, fell down in a swoon, when she saw the spectral dog coming towards her. When within a few yards of her it stopped, squatted on its hounchers, "and set up such a scream, so loud, so horrible, and so strong, that she thought the earth moved under her." I was informed at Llangynog five years ago, that Spectral Dogs still haunt that part of Carmarthenshire; and more than one of my informants had seen such apparitions themselves. A spirit in animal form was not always a demon; sometimes the Spirit of a mortal was doomed to wear this shape for some offence. It was once believed that the Evil One, either from lust, or from nefarious designs, assumed the form of a young man or a young woman. The following two stories, the first from South Pembrokeshire, and the other from Gower, have reference to this belief. "A DEMON STEWARD." Giraldus Cambrensis in his Itinerary through Wales (Bohn's edition, page 110) says:--