It is illustration to the ancient greek myth, that gave name to the constellation Capricorn.
Goat Amalhteia suckled her milk Zeus the Thunderer, head of Olympus. When Zeus grew up and became the supreme god, he took his gratitude to the nurse at the sky, and she became a star Capella in the constellation Auriga.
But on the way to heaven Amalhteia goat accidentally lost one horn. Zeus picked it up and gave the nymphs, wich also took part in his upbringing. The head of Olympus gave the horn a magical property that was worth only wish from the horn appeared a variety of dishes or delicious drink flowed. He was literally a cornucopia.