(Stolas, from Collin de Plancy's Dictionnaire Infernal, 1863)

"Stolas is a great prince, appearing in the forme of a nightraven, before the exorcist, he taketh the image and shape of a man, and teacheth astronomie, absolutelie understanding the vertues of herbes and pretious stones; there are under him twentie six legions." (Scot, Discoverie of Witchcraft, page 225)

As Collin de Plancy correctly illustrates, "nightraven" is another term for owl. The version of the Goetia used by Mathers reduces this to just "raven," in the process destroying the sense of the text.