An early Welsh Arthurian poem says that,

On the mount of Eidyn [Edinburgh], they [Arthur and presumably Cei] found with Dog-heads; by the hundred they fell.

Opponents of Arthur, fought by Arthur or Kay in Pa gur.

They are not necessarily monsters. H. Butler has advanced the theory that they were related to the Conchind (Dog-heads), a legendary people who ruled Ireland. There may be some connection with the Cunesioi, a tribe whom Herodotus places beyond the Celts in the Iberian Peninsula, and the Concani who, according to Horace, lived in Spain.