Goetia – S. L. MacGregor Mathers (1904) (quoted)

The Fourth Spirit is Samigina, a Great Marquis. He appeareth in the form of a little Horse or Ass, and then into Human shape doth he change himself at the request of the Master. He speaketh with a hoarse voice. He ruleth over 30 Legions of Inferiors. He teaches all Liberal Sciences, and giveth account of Dead Souls that died in sin. And his Seal is this, which is to be worn before the Magician when he is Invocator, etc.
 

Pseudomonarchia daemonum – Johann Wier (1583) (quoted)
Gamigin is a great marquesse, and is seene in the forme of a little horsse, when he taketh humane shape he speaketh with a hoarse voice, disputing of all liberall sciences; he bringeth also to passe, that the soules, which are drowned in the sea, or which dwell in purgatorie (which is called Cartagra, that is, affliction of soules) shall take aierie bodies, and evidentlie appeare and answer to interrogatories at the conjurors commandement; he tarrieth with the exorcist, untill he have accomplished his desire, and hath thirtie legions under him.
In demonology Gamigin (also Gamygin, Gamigm or Samigina) is a Great Marquis of Hell who rules over thirty legions of demons. He teaches all liberal sciences and gives an account of the souls of those who died in sin and who drowned in the sea, speaking with a rough voice. He also answers what is asked about, and stays with the conjurer until he or she is satisfied.

Gamigin is depicted as a little horse or a donkey, which changes form into a man under the conjurer’s request.